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The History Of Carbon

I. Introduction
A. The History of Carbon

II. Occurrences in Nature
A. Diamond B. Graphite C. Coal and Charcoal D. Amorphous Carbon

III. Carbon Compounds
A. Inorganic B. Organic

IV. The Carbon Cycle IV. Conclusion Carbon, an element discovered before history itself, is one of the most abundant elements in the universe. It can be found in the sun, the stars, comets, and the atmospheres of most planets. There are close to ten million known carbon compounds, many thousands of which are vital to the basis of life itself
(WWW 1).
Carbon occurs in many forms in nature. One of its purest forms is diamond. Diamond is the hardest substance known on earth.
Although diamonds found in nature are colorless and transparent, when combined with other elements its color can range from pastels to black. Diamond is a poor conductor of heat and electricity.
Until 1955 the only sources of diamond were found in deposits of volcanic origin. Since then scientists have found ways to make diamond from graphite and other synthetic materials. Diamonds of true gem quality are not made in this way (Beggott 3-4).
Graphite is another form of carbon. It occurs as a mineral in nature, but it can be made artificially from amorphous carbon. One of the main uses for graphite is for its lubricating qualities. Another is for the lead in pencils. Graphite is used as a heat resistant material and an electricity conductor. It is also used in nuclear reactors as a lubricator (Kino*censored*a 119-127).
Amorphous carbon is a deep black powder that occurs in nature as a component of coal. It may be obtained artificially from almost any organic substance by heating the substance to very high temperatures without air. Using this method, coke is produced from coal, and charcoal is produced from wood. Amorphous carbon is the most reactive form of carbon. Because amorphous carbon burns easily in air, it is used as a combustion fuel. The most important uses for amorphous carbon are as a filler for rubber and as a black pigment in paint (WWW 2).
There are two kinds of carbon compounds. The first is inorganic. Inorganic compounds are binary compounds of carbon with metals or metal carbides. They have properties ranging from reactive and saltlike; found in metals such as sodium, magnesium, and aluminum, to an unreactive and metallic, such as titanium and niobium (Beggott 4). Carbon compounds containing nonmetals are usually gases or liquids with low boiling points. Carbon monoxide, a gas, is odorless, colorless, and tasteless. It forms during the incomplete combustion of carbon (Kino*censored*a 215-223). It is highly toxic to animals because it inhibits the transport of oxygen in the blood by hemoglobin (WWW 2).
Carbon dioxide is a colorless, almost odorless gas that is formed by the combustion of carbon. It is a product that results from respiration in most living organisms and is used by plants as a source of carbon. Frozen carbon dioxide, known as dry ice, is used as a refrigerant. Fluorocarbons, such as Freon, are used as refrigerants (Kino*censored*a 225-226). Organic compounds are those compounds that occur in nature. The simplest organic compounds consist of only carbon and hydrogen, the hydrocarbons. The state of matter for organic compounds depends on how many carbons are contained in it. If a compound has up to four carbons it is a gas, if it has up to 20 carbons it is a liquid, and if it has more than 20 carbons it is a solid (Kino*censored*a 230-237). The carbon cycle is the system of biological and chemical processes that make carbon available to living things for use in tissue building and energy release (Kino*censored*a 242). All living cells are composed of proteins consisting of carbon, hydrogen, oxygen, and nitrogen in various combinations, and each living organism puts these elements together according to its own genetic code. To do this the organism must have these available in special compounds built around carbon. These special compounds are produced only by plants, by the process of photosynthesis. Photosynthesis is a process in which chlorophyll traps and uses energy from the sun in the form of light. Six molecules of carbon dioxide combine with six molecules of water to form one molecule of glucose (sugar). The glucose molecule consists of six atoms of carbon, twelve of hydrogen, and six of oxygen. Six oxygen molecules, consisting of two oxygen atoms each, are also produced and are discharged into the atmosphere unless the plant needs energy to live. In that case, the oxygen combines with the glucose immediately, releasing six molecules of carbon dioxide and six of water for each molecule of glucose (Beggott 25-32). The carbon cycle is then completed as the plant obtains the energy that was stored by the glucose. The length of time required to complete the cycle varies. In plants without an immediate need for energy, the chemical processes continue in a variety of ways. By reducing the hydrogen and oxygen content of most of the sugar molecules by one water molecule and combining them to form large molecules, plants produce substances such as starch, inulin , and fats and store them for future use. Regardless of whether the stored food is used later by the plant or consumed by some other organism, the molecules will ultimately be digested and oxidized, and carbon dioxide and water will be discharged. Other molecules of sugar undergo a series of chemical changes and are finally combined with nitrogen compounds to form protein substances, which are then used to build tissues (WWW 2). Although protein substances may pass from organism to organism, eventually these too are oxidized and form carbon dioxide and water as cells wear out and are broken down, or as the organisms die. In either case, a new set of organisms, ranging from fungi to the large scavengers, use the waste products or tissues for food, digesting and oxidizing the substances for energy release (WWW 1).
At various times in the Earth's history, some plant and animal tissues have been protected by erosion and sedimentation from the natural agents of decomposition and converted into substances such as peat, lignite, petroleum, and coal. The carbon cycle, temporarily interrupted in this manner, is completed as fuels are burned, and carbon dioxide and water are again added to the atmosphere for reuse by living things, and the solar energy stored by photosynthesis ages ago is released (Kino*censored*a 273-275). Almost everything around us today has some connection with carbon or a carbon compound. Carbon is in every living organism. Without carbon life would not exist as we know it.

White Blood Cells

White Blood Cells Bacteria exist everywhere in the environment and have continuous access to the body through the mouth, nose and pores of skin. Further more, many cells age and die daily and their remains must be removed, this is where the white blood cell plays its role. According to this quotation, without white blood cells, also known as leukocytes, we would not be able to survive. White blood cells are our body’s number one defense against infections. They help keep us clean from foreign bacteria that enter our bodies. Statistics show that there are five to ten thousand white blood cells per micro liter of blood, however this number will increase during an illness. White blood cells can differ in many ways, such as, size, shape and staining traits. There are five different kinds of white blood cells that fall into two separate categories. One category is called, granular leukocytes, and the other is called agranular white cells. There are three different types of granular leukocytes. Neutrophil is a phagocyte, produced in the bone marrow that ingests and destroys bacteria extremely fast. Neutrophil has a diameter, which is, about ten to twelve micrometers long. They make up about 60-70 percent of the total number of white blood cells in our body. Eosinphil is a type of white blood cell that secretes poisonous materials in order to kill parasites, allergies and phagocytosis of bacteria, which is when the cell takes in materials to eliminate them or move them from where they were. They make up about 2-4 percent of the total number of white blood cells in our body. These white blood cells are similar to Neutrophil because they attack bacteria by the immune system. This particular group of white blood cells is extremely important in my body, because they are prominent at sites of allergic reactions, such as anaphylaxis. The nucleus of Eosinphil is made of two lobes, and implanted in the cytoplasm are large, red-orange granules, and the diameter of them is on average about twelve to fifteen µm. The third type of granular leukocytes is called, basophil. Basophil’s major function is, secretion. They tend to have a diameter of 12-15 µm. These cells make up only about one percent of the total population of white blood cells, causing them to be much more difficult to detect. These cells secrete both histamine and heparin. Histamine draws blood into the damaged area, while heparin slows clotting so that more blood can enter the damaged area. There are two different kinds of agranular white cells. One is called monocyte, and the other is called lymphocyte. The major function of monocyte is, phagocytosis. These cells more very quickly and are therefore able to consume bacteria and dead tissue at a fast rate. Monocytes have an average diameter of, 12-17 µm, and they make up about 3-8 percent of our leukocyte’s population. Lymphocytes, major function are immunity. There are many different forms of lymphocytes, and all of the different forms have different functions. B-lymphocytes produce, plasma cells, which form antibodies to (humeral immune response), T-lymphocytes produce, suppressor cells, helper cells, and cytotoxic, killer cells. Lymphocytes have a diameter of about 8-18 µm. In general leukocytes, “either clear away dead cells from the body, or destroy specific bacteria, viruses, and other agents of disease.”

Acid Rain

Acid Rain Acid rain is a serious problem with disastrous effects. Each day this serious problem increases, many people believe that this issue is too small to deal with right now this issue should be met head on and solved before it is too late. In the following paragraphs I will be discussing the impact has on the wildlife and how our atmosphere is being destroyed by acid rain. CAUSES Acid rain is a cancer eating into the face of Eastern Canada and the North Eastern United States. In Canada, the main sulphuric acid sources are non©ferrous smelters and power generation. On both sides of the border, cars and trucks are the main sources for nitric acid(about 40% of the total), while power generating plants and industrial commercial and residential fuel combustion together contribute most of the rest. In the air, the sulphur dioxide and nitrogen oxides can be transformed into sulphuric acid and nitric acid, and air current can send them thousands of kilometres from the source.When the acids fall to the earth in any form it will have large impact on the growth or the preservation of certain wildlife. NO DEFENCE Areas in Ontario mainly southern regions that are near the Great Lakes, such substances as limestone or other known antacids can neutralize acids entering the body of water thereby protecting it. However, large areas of Ontario that are near the Pre©Cambrian Shield, with quartzite or granite based geology and little top soil, there is not enough buffering capacity to neutralize even small amounts of acid falling on the soil and the lakes. Therefore over time, the basic environment shifts from an alkaline to a acidic one. This is why many lakes in the Muskoka, Haliburton, Algonquin, Parry Sound and Manitoulin districts could lose their fisheries if sulphur emissions are not reduced substantially. ACID The average mean of pH rainfall in Ontario's Muskoka©Haliburton lake country ranges between 3.95 and 4.38 about 40 times more acidic than normal rainfall, while storms in Pennsilvania have rainfall pH at 2.8 it almost has the same rating for vinegar. Already 140 Ontario lakes are completely dead or dying. An additional 48 000 are sensitive and vulnerable to acid rain due to the surrounding concentrated acidic soils.Ô ACID RAIN CONSISTS OF....? Canada does not have as many people, power plants or automobiles as the United States, and yet acid rain there has become so severe that Canadian government officials called it the most pressing environmental issue facing the nation. But it is important to bear in mind that acid rain is only one segment, of the widespread pollution of the atmosphere facing the world. Each year the global atmosphere is on the receiving end of 20 billion tons of carbon dioxide, 130 million tons of suffer dioxide, 97 million tons of hydrocarbons, 53 million tons of nitrogen oxides, more than three million tons of arsenic, cadmium, lead, mercury, nickel, zinc and other toxic metals, and a host of synthetic organic compounds ranging from polychlorinated biphenyls(PCBs) to toxaphene and other pesticides, a number of which may be capable of causing cancer, birth defects, or genetic imbalances. COST OF ACID RAIN Interactions of pollutants can cause problems. In addition to contributing to acid rain, nitrogen oxides can react with hydrocarbons to produce ozone, a major air pollutant responsible in the United States for annual losses of $2 billion to 4.5 billion worth of wheat, corn, soyabeans, and peanuts. A wide range of interactions can occur many unknown with toxic metals. In Canada, Ontario alone has lost the fish in an estimated 4000 lakes and provincial authorities calculate that Ontario stands to lose the fish in 48 500 more lakes within the next twenty years if acid rain continues at the present rate.Ontario is not alone, on Nova Scotia's Eastern most shores, almost every river flowing to the Atlantic Ocean is poisoned with acid. Further threatening a $2 million a year fishing industry. Ô Acid rain is killing more than lakes. It can scar the leaves of hardwood forest, wither ferns and lichens, accelerate the death of coniferous needles, sterilize seeds, and weaken the forests to a state that is vulnerable to disease infestation and decay. In the soil the acid neutralizes chemicals vital for growth, strips others from the soil and carries them to the lakes and literally retards the respiration of the soil. The rate of forest growth in the White Mountains of New Hampshire has declined 18% between 1956 and 1965, time of increasingly intense acidic rainfall. Acid rain no longer falls exclusively on the lakes, forest, and thin soils of the Northeast it now covers half the continent. EFFECTS There is evidence that the rain is destroying the productivity of the once rich soils themselves, like an overdose of chemical fertilizer or a gigantic drenching of vinegar. The damage of such overdosing may not be repairable or reversible. On some croplands, tomatoes grow to only half their full weight, and the leaves of radishes wither. Naturally it rains on cities too, eating away stone monuments and concrete structures, and corroding the pipes which channel the water away to the lakes and the cycle is repeated. Paints and automobile paints have its life reduce due to the pollution in the atmosphere speeding up the corrosion process. In some communities the drinking water is laced with toxic metals freed from metal pipes by the acidity. As if urban skies were not already grey enough, typical visibility has declined from 10 to 4 miles, along the Eastern seaboard, as acid rain turns into smogs. Also, now there are indicators that the components of acid rain are a health risk, linked to human respiratory disease. PREVENTION However, the acidification of water supplies could result in increased concentrations of metals in plumbing such as lead, copper and zinc which could result in adverse health effects. After any period of non©use, water taps at summer cottages or ski chalets they should run the taps for at least 60 seconds to flush any excess debris. Ô STATISTICS Although there is very little data, the evidence indicates that in the last twenty to thirty years the acidity of rain has increased in many parts of the United States. Presently, the United States annually discharges more than 26 million tons of suffer dioxide into the atmosphere. Just three states, Ohio, Indiana, and Illinois are responsible for nearly a quarter of this total. Overall, twoªthirds of the suffer dioxide into the atmosphere over the United States comes from coal©fired and oil fired plants. Industrial boilers, smelters, and refineries contribute 26%; commercial institutions and residences 5%; and transportation 3%. The outlook for future emissions of suffer dioxide is not a bright one. Between now and the year 2000, United States utilities are expected to double the amount of coal they burn. The United States currently pumps some 23 million tons of nitrogen oxides into the atmosphere in the course of the year. Transportation sources account for 40%; power plants, 30%; industrial sources, 25%; and commercial institutions and residues, 5%. What makes these figures particularly distributing is that nitrogen oxide emissions have tripled in the last thirty years. FINAL THOUGHTS Acid rain is very real and a very threatening problem. Action by one government is not enough. In order for things to be done we need to find a way to work together on this for at least a reduction in the contaminates contributing to acid rain. Although there are right steps in the right directions but the government should be cracking down on factories not using the best filtering systems when incinerating or if the factory is giving off any other dangerous fumes. I would like to express this question to you, the public:WOULD YOU RATHER PAY A LITTLE NOW OR A LOT LATER?

What Is Science

define science as a system of knowledge about a specific topic. The systems come from systematic, or precise, observations of natural events; a random example would be the study of the movement of a caterpillar. This very fact would make one think that science encompasses every topic in the world. It amazingly does; from apples to zucchini (in the science called botany). Science is not just the “systems” of Chemistry, Physics, and Biology as traditionally known. It is the systems of our knowledge about everything on this planet, beyond, and even the human race. Science is an action word in most cases. I am witnessing the topics in the science of anatomy and physiology as type this home-lesson: the blood vessels supplying blood to my bones are allowing me to move my fingers and press the keys. Furthermore, science is a vehicle for change in our society today. The systems of knowledge are communicated by scientists through science media such as journals, web-sites (the internet), newspapers and through person-to-person interaction. At Tufts University a Ph.D. student may share his experiment on drug metabolism rates in the form of a presentation; moreover, someone in his same lab might use points from his research as a stepping stone or bridge leading and connecting, respectively their research to success. Science is what we are and what shapes our world.

Nanotechnology

The science of nanotechnology could lead to radical improvements for space exploration.

When it comes to taking the next "giant leap" in space exploration, NASA is thinking small - really small.

In laboratories around the country, NASA is supporting the burgeoning science of nanotechnology. The basic idea is to learn to deal with matter at the atomic scale - to be able to control individual atoms and molecules well enough to design molecule-size machines, advanced electronics and "smart" materials.

If visionaries are right, nanotechnology could lead to robots you can hold on your fingertip, self-healing spacesuits, space elevators and other fantastic devices. Some of these things may take 20+ years to fully develop; others are taking shape in the laboratory today.

Thinking small

Image by artist Pat Rawling. Nanotechnology could provide the very high-strength, low-weight fibers that would be needed to build the cable of a "space elevator."

Simply making things smaller has its advantages. Imagine, for example, if the Mars rovers Spirit and Opportunity could have been made as small as a beetle, and could scurry over rocks and gravel as a beetle can, sampling minerals and searching for clues to the history of water on Mars. Hundreds or thousands of these diminutive robots could have been sent in the same capsules that carried the two desk-size rovers, enabling scientists to explore much more of the planet's surface - and increasing the odds of stumbling across a fossilized Martian bacterium!

But nanotechnology is about more than just shrinking things. When scientists can deliberately order and structure matter at the molecular level, amazing new properties sometimes emerge.

An excellent example is that darling of the nanotechnology world, the carbon nanotube. Carbon occurs naturally as graphite - the soft, black material often used in pencil leads - and as diamond. The only difference between the two is the arrangement of the carbon atoms. When scientists arrange the same carbon atoms into a "chicken wire" pattern and roll them up into miniscule tubes only 10 atoms across, the resulting "nanotubes" acquire some rather extraordinary traits.

Nanotubes:

How Space Was Created?

When we look around us we take the space for granted. We know that space is the distance between tow objects. Or what lies between two objects. As things are scattered in the world there is space that occupies that. It is true for outer space that lies between tow stars. This space is three-dimensional. Was this space there since eternity? Who created the space? If no object is left in the cosmos what would happen to the space? Will it still remain? How Space Was Created?

We know that at the time of Big bang everything exploded out of a point called singularity. What most of us do not realize is that at that time there was no space. There was only this single point in the cosmos and nothing else. It is difficult to imagine and understand, isn't it?

As the mass and energy exploded out space was created. At this time there are billions of stars that are running away from us. The universe is expanding. This is creating more and more space. What lies beyond this space? Is there another cosmos/universe or more space? No body knows the answer to this question. According to Einstein one can never reach the edge of the space. This space is something like the surface of the earth. There are no edges. It folds on itself. So if you start looking or the edge of the space you will come back from where you began. Of course the distances are so vast that it is impossible for any mortal to think of doing this. Billions of light years make a very huge distance. This distance is unimaginable.

Next time you look at the sky begin thinking about the space, the stars and what lies beyond everything. You will forget your problems at home and work because you will feel you are so small compared to what is happening out there.

4 Simple Inventions That Changed the World

There are many conveniences that we take for granted these days. In fact, it's hard to imagine life without many things that were cutting edge long ago! Computers, vehicles, gas and electric ranges, sewing machines and ballpoint pens are just some of the innovations that influence daily life.

They say the simplest inventions are the cleverest. I agree. There is a recent story about a three-year old kid who invented a double-ended broom, one for a coarse brush and one for a fine brush. It's amazing that he's the first to patent that. Throughout history, such simple inventions changed the lives of people everywhere. What are these all-important devices?

1. The Wheel - one of the early inventions that changed the way humans lived. We see it everywhere; on cars, trucks, planes, ships, inside machines, toys, and much much more. Life wouldn't be the same without the wheel. It was said to be invented by the Mesopotamians in 4th century BC, eventually helping usher about the Bronze Age. Starting from wooden carts and wagons, the simple yet so very useful device evolved over time. With so many uses and applications, it is forever part of the human race, and one of the first steps to civilization. Can you imagine being unable to take a taxi to your hotel, instead footing several miles with tons of bags? Or spending an hour walking to get to the mall?

2. Tools - Yet another thing that set us on the path of civilization. Humans have opposable thumbs, which led to the creation of tools. Simple tools like sharp rocks used to cut turned into knives and spears. Large rock used as a hammer became actual hammers. We built our own houses, caught animals, made our own fields and improved our way of life with tools. Interestingly, some mammals and birds use tools too.

3. Sewers - Sanitation is important to civilized people. A system where waste is gathered and disposed of in once place rather than everywhere is indeed helpful. Ancient people saw this, and were among the first to invent the system. Today, we rarely think of the network of pipes running under our feet, making sure that our waste stays out of our sight, and out of our noses! I'm happy knowing that we're not defecating on the ground. Well, most of the time.

4. Roads - Along with the first wheeled inventions, roads came about. Dirt paths worn by hunters were common before vehicles, but it was only after the wheeled inventions were invented that there became a real need for better roads. Dirt-worn paths became wood, stone and brick roads. Because of the ease of transport roads offered, the world became prosperous. Today, they are the backbone of economy and society. Imagine life without roads now. We would be living in houses in a haphazard manner. Goods are transported slower. There would be more accidents

There you have it! These are, for me, the ones that truly shaped the world. Well, I guess money did, too. What inventions do you think changed the world?

Human Anatomy

I have studied and interviewed groups of medical and science students that have excelled in their course work. It is true that there are specific and detailed guidelines that these students adhere to and credit for their academic success. With some time and applying these study skills to your studies you can greatly improve your academic performance. The following are study strategies and tips from past honor students of Human Anatomy.

Study Skill #1 - It is NOT enough to simply read, re-read, and re-type up the notes. The goal in anatomy is to become a visual learner, so it is extremely important to keep pictures in front of you. Let's say you are studying the forearm for example. The best approach is three pronged. That is, to have three pictures out side-by-side, one of the superficial structures, one of the deep muscles and bone matrix, and a third of cross-sections. Now as you read each sentence of your text, the words will have graphic substance to support them. This allows your brain to start building the 3-D structure of the human body.

Study Skill #2 - Knowing the relationships is key. This means that if you are given a point anywhere in the human body, that you should be able to navigate your way to any other point by spatial relationships to landmark structures. The best way to accomplish this is by describing the path of a body part in relation to its surroundings. Let's take the Ulnar Nerve for example. Beginning in the axilla, it courses as the most medial branch of the brachial plexus. As it descends down the arm, it remains superficial to the triceps muscles, medial to the humerus, and maintains a tight medial position to the brachial artery. It continues this until the distal region of the arm, where it courses on the posterior aspect of the humerus, and then it makes a tight cross over the elbow joint posterior to the medial epicondyle. It continues between the heads of the flexor carpi ulnaris muscle and enters the anterior compartment of the forearm where it accompanies the ulnar artery. This will enhance your understanding of human anatomy because it forces your brain to travel through the mental images and describe it in your own words. This is a skill that will be necessary for nerve lesion questions.

Study Skill #3 - Make charts for the muscles. List the muscles in the rows on the left and then make columns on the right for Origin, Insertion, Action, and Innervation. Stare at pictures of the muscle under study and match the answers in the columns with the pictures.

Study Skill #4 - Memorize the boundaries and contents of specific compartments of the human body. For example, the Cubital Fossa is bounded: Laterally - medial border of brachioradialis, Medially - the lateral border of pronator teres, Floor - brachialis, Roof - skin and fascia, Contents - median nerve, brachial artery, tendon of biceps, radial nerve, & median cubital vein. Once these have been memorized they serve as valuable landmarks to navigate your way around the body.

Study Skill #5 - Understand the terminology. This is obvious, but if you do it from the very beginning of your human anatomy course it will save you a lot of time later on. Anatomists often sound like they are speaking a different language and it overwhelms students at first. But if you take the time, you will see that a name of a muscle or ligament will often tell of its origin, insertion, or action. Flexor Digitorum Profundus for example, is the major muscle that flexes the fingers. Therefore, you may already know what Flexor Digitorum Superficialis does, it's the same action, but this weaker muscle lies closer to the surface of the forearm. In addition, arteries tend to be named for their destination. The right coronary artery will supply blood to the right ventricle of the heart. Knowing the terminology breaks down the information in digestable pieces and makes it easier for you to remember where things are positioned.

Study Skill #6 - Photocopy the pictures from your anatomy book and white out the labels. In fact, make several copies of important diagrams without labels and use these to study and fill them in on your own. It is often helpful to use these same pictures to trace the pathways of the nerves and arteries with colored pencils. This will help to separate the structures in your mind and reinforce their routes.

Study Skill #7 - If you have access to a cadaver, give him/her a name, because the amount of time you spend with the cadaver is directly related to your grade. Identify the same structure on multiple cadavers. This exercise will prove that you can use different anatomical landmarks as a navigation system for the human body. This is also important to understand and identify regions of variation in the body, such as arterial branches of the subclavian. Keep in mind that arteries should be named based on where they are going, not where they branched from.

Jordan Castle is medical student and cognitive psychologist research assistant. His work spans many different aspects of the learning process and aims to help students excel in their individual courses. Detailed study strategies and practice exams can be found on his website at http://medstudysites.com Courses include: Physiology, Genetics, Histology, Neuroanatomy, and Histology.

About Gasifier

The first gasifiers were known as gasification retorts and they have been around for well over a century providing our town gas supplies from coal. In basic terms they involve a container in which combustible fuel is heated, driving off flammable hydrocarbon gases. These gases are then scrubbed in filters to remove particulate matter and any corrosive chemicals, before being plumbed into anything from the towns gas supply to a modified carburettor to fuel a standard internal combustion engine.

Gasifiers are available now. They are proven technology. They can and are helping in the war to reduce gas and electricity prices, and the magic thing is that the same principle can be applied to many fuels other than coal.

These systems are capable of producing electricity from any biomass source. They may use any fuel in some, such as coal, petroleum coke, residual oil, oil emulsions, tar sands, and/or other similar fuels. Gasifiers produce a gas which is commonly known as syngas. This gas is used mostly where it is created to power a gas turbine. Gasification uses chemistry and high temperature and pressures to change the way the coal or other form of solid carbonaceous (fossil) fuel produces heat. In other words instead of burning the fuel outright, a gasifier part burns the fuel due to the presence of only a limited amount of oxygen and creates a fuel gas.

One gasifier, for example, is a device that has been developed by TERI (The Tata Energy Research Institute in India) for use in the drying of cardamom. The gasifier uses briquettes that are made from firewood and other types of biomass and turns them into a gas that burns with a clean smokeless flame.

In another example a gasifier is the key component in the Ag Bio-Power Energy System, but it is not the only component. In the patented configuration of the system, solid wastes containing metals and other non-combustible materials are burned separately while a gasifier is used as a scrubber for the polluting emissions because gasification is so good at burning out these substances.

It is reported that Household and Commercial Waste can also be gasified. In this case combustible gases are used within the system for increased efficiency and high temperature combustion than is archived in an incinerator. After gasification the residue of thermal decomposition is cooled and rough particles such as metals and non-combustibles are separated by means of a vibrating sieve and magnetic separator. The separated fine particles are mostly ash and carbon content, and these particles can then be crushed and sent to the final furnace for vitrification, where they are turned into essentially a form of glass, safely binding in any toxic substances, out of harm's way, for ever.

Combustible waste from industrial production processes which is reported to be suitable for gasification includes textile waste, wood scrap/trimmings, plastic scrap, and non-reusable solvents. Textile waste can consist of excess yarn, thread, cloth, carpet, or any other fabric. Combustion temperatures of 1500-1600~F and heat release rates of about 400,000 Btu/cu ft/hr are possible and give heat transfer rates reported to be larger than those of conventional pulverized coal boilers.

Some of these technology providers are claiming cell microturbine combinations are possible which have the potential to achieve up to 60 percent efficiency and near-zero emissions. On top of that they say that fuel flexibility enables the use of low-cost indigenous fuels, renewables and waste materials. Even, for example, experts say briquettes produced from agricultural residues can be used in some gasifier models.

Some gasifier plant is now also being developed which is based on fluidized bed technology with the possibility of the common and low cost availability of practically zero emissions release systems achieving high efficiencies using a host cheap, locally produced, renewable fuel sources.

Now, we think that this is pretty cool, when at present all we can see is rapidly rising gas prices and practically no alternatives for me and you, but to pay them.

Reducing energy demand, especially in the sense of better insulation for heating homes and offices, is of course, more of a potential for saving CO2 emissions, but that's not what what we are discussing in this article.

We have been here before, as well, in that in the mid to late 1970s, when it was believed that there was going to be a shortfall of oil due to the formation of OPEC, fuel prices rose excessively. At that time also there was an expected decline in supplies, and considerable effort went into developing alternatives. But, those efforts came to very little, as in real terms the alternatives were still more expensive than the oil and coal based alternatives. This time around that is no longer the case, so expect to hear about more suddenly "cool" energy solutions, but which are also very "hot" indeed - at the same time!

Blood Vessels

STRUCTURE AND FUNCTION OF BLOOD VESSELS

INTRODUCTION

The main transport systems are the circulatory systems, in which substances are dissolved or suspended in liquid and carried from one part of the body to another in a system of tubes called vessels.

There are two main circulatory systems:

The blood circulatory system (sometimes called the cardiovascular system) and the LYMPHATIC SYSTEM.

The blood circulatory system is the main method of transporting oxygen, carbon dioxide, nutrients and metabolic breakdown products, cells of the immune and other defence systems, chemical messengers (hormones), other important substances (e.g. clotting factors).

The lymphatic system drains extra-cellular fluid from the tissues returning it to the blood circulatory system after passage through lymph nodes. This system is also involved in absorption of nutrients from the gut.

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THE BLOOD CIRCULATORY SYSTEM

There are three types of blood circulatory system, two of which (systemic circulation and pulmonary circulation) depend on a pump, the heart, to push the blood around. The third type of circulation is known as a portal system. These are specialised channels that connect one capillary bed site to another but do not depend directly on a central pump. The largest of these in the human is the hepatic portal system which connects the intestines to the liver.

The systemic circulation transfers oxygenated blood from a central pump (the heart) to all of the body tissues (systemic arterial system) and returns deoxygenated blood with a high carbon dioxide content from the tissues to the central pump (systemic venous system).

As briefly mentioned above the systemic circulation supplies all the body tissues, and is where exchange of nutrients and products of metabolism occurs. All the blood for the systemic circulation leaves the left side of the heart via the aorta.

This large artery then divides into smaller arteries and blood is delivered to all tissues and organs. These arteries divide into smaller and smaller vessels each with its own characteristic structure and function. The smallest branches are called arterioles.

The arterioles themselves branch into a number of very small thin vessels, the capillaries, and it is here that the exchange of gases, nutrients and waste products occurs.

Exchange occurs by diffusion of substances down concentration and pressure gradients.

The capillaries then unite to form larger vessels, venules, which in turn unite to form fewer and larger vessels, known as veins.

The veins from different organs and tissues unite to form two large veins. The inferior vena cava (from the lower portion of the body) and the superior vena cava (from the head and arms), which return blood to the right side of the heart. Thus there are a number of parallel circuits within the systemic circulation.

The pulmonary circulation is where oxygen and carbon dioxide exchange between the blood and alveolar air occurs. The blood leaves the right side of the heart through a single artery, the pulmonary artery, which divides into two - one branch supplying each LUNG. Within the lung, the arteries divide, ultimately forming arterioles and capillaries; venules and veins return blood to the left side of the heart.

Portal circulation. Normally there is only one capillary bed for each branch of a circuit; however, there are a few instances where there are two capillary beds, one after each other, in series. These are known as portal systems or portal circulations. One example of this is in the liver. Part of the blood supply to the liver is venous blood coming directly from the QASTROINTENTINAL tract and spleen via the hepatic portal vein. This arrangement enables the digested and absorbed substances from the gut to be transported directly to the liver, where many of the body's metabolic requirements are synthesised. Thus there are two micro-circulations in series, one in the gut and the other in the liver.

The force required to move the blood through the blood vessels in the two circulations is provided by the heart, which functions as two pumps, the left side of the heart supplying the systemic circulation and the right side the pulmonary circulation.

The systemic circulation is much larger than the pulmonary circulation and thus the force generated by the left side of the heart is much greater than that of the right side of the heart. However, as the circulatory system is a closed system, the volume of blood pumped through the pulmonary circulation in a given period of time must equal the volume pumped through the systemic circulation - that is, the right and left sides of the heart must pump the same amount of blood. In a normal resting adult, the average volume of blood pumped simultaneously is approximately 5 litres per min. As there are approximately 5 litres of blood in an adult, this means that the blood circulates around the body approximately once every minute. During heavy work or EXERCISE, the volume of blood pumped by the heart can increase up to 25 litres per min (or even 35 litres per min in top class athletes).

How the Lungs Work

The lungs provide a very large surface area (the size of a football field) for the exchange of oxygen and carbon dioxide between the body and the environment.

A slice of normal lung looks like a pink sponge filled with tiny bubbles or holes. These bubbles, surrounded by a fine network of tiny blood vessels, give the lungs a large surface to exchange oxygen (into the blood where it is carried throughout the body) and carbon dioxide (out of the blood). This process is called gas exchange. Healthy lungs do this very well.

Here is how normal breathing works:

• You breathe in air through your nose and mouth. The air travels down through your windpipe (trachea) then through large and small tubes in your lungs called bronchial (BRON-kee-ul) tubes. The larger tubes are bronchi (BRONK-eye), and the smaller tubes are bronchioles (BRON-kee-oles). Sometimes the word "airways" is used to refer to the various tubes or passages that air must travel through from the nose and mouth into the lungs. The airways in your lungs look something like an upside-down tree with many branches.
• At the ends of the small bronchial tubes, there are groups of tiny air sacs called alveoli. The air sacs have very thin walls, and small blood vessels called capillaries run in the walls. Oxygen passes from the air sacs into the blood in these small blood vessels. At the same time, carbon dioxide passes from the blood into the air sacs. Carbon dioxide, a normal byproduct of the body's metabolism, must be removed.

The airways and air sacs in the lung are normally elastic—that is, they try to spring back to their original shape after being stretched or filled with air, just the way a new rubber band or balloon would. This elastic quality helps retain the normal structure of the lung and helps to move the air quickly in and out. In COPD, much of the elastic quality is gone, and the airways and air sacs no longer bounce back to their original shape. This means that the airways collapse, like a floppy hose, and the air sacs tend to stay inflated. The floppy airways obstruct the airflow out of the lungs, leading to an abnormal increase in the lungs' size. In addition, the airways may become inflamed and thickened, and mucus-producing cells produce more mucus, further contributing to the difficulty of getting air out of the lungs.

Steam Engine

Steam

A scale model Allchin traction engine
– an example of a self-propelled steam engine

'Preserved' (but incomplete) portable engine, Tenterfield, NSW – an example of a mobile steam engine

A steam engine is a heat engine that performs mechanical work using steam as its working fluid.^[1]

Steam engines have a long history, going back almost two thousand years. Early devices were not practical power producers, but more advanced designs become a major source of mechanical power during the industrial revolution. Modern steam turbines generate about half of the electric power in the world.

Many steam engines are external combustion engines,^[2] although other sources of heat such as solar power, nuclear power or geothermal energy are often used. The heat cycle used is known as the Rankine cycle.

In general usage, the term 'steam engine' can refer to integrated steam plants such as railway steam locomotives and portable engines, or may refer to the motor unit alone, as in the beam engine and stationary steam engine. Specialized devices such as steam hammers and steam pile drivers are dependent on steam supplied from a separate, often remotely-located boiler.

Contents [hide] 1 Applications 1.1 Stationary applications 1.2 Transport applications 2 History 3 Basic operation of a simple steam engine 4 Components of steam engines 4.1 Heat source 4.2 Cold sink 4.3 Boilers 4.4 Motor units 4.4.1 Simple expansion 4.4.2 Compounding engines 4.4.3 Multiple expansion engines 4.4.4 Uniflow (or unaflow) engine 4.4.5 Turbine engines 4.4.6 Rotary steam engines 4.4.7 Jet type 4.4.8 Rocket type 5 Advantages 6 Safety 7 Efficiency 8 See also 8.1 Steam fairs 8.2 Steam museums 9 Notes 10 References 11 External links

[edit] Applications

Since the early 18th century steam power has been set to a variety of practical uses. At first it was applied to reciprocating pumps, but from the 1780s rotative engines (i.e. those converting reciprocating motion into rotary motion) began to appear, driving factory machinery. At the turn of the 19th century, steam-powered transport on both sea and land began to make its appearance becoming ever more predominant as the century progressed.

Steam engines can be said to have been the moving force behind the Industrial Revolution and saw widespread commercial use driving machinery in factories and mills, powering pumping stations and transport appliances such as locomotives, steam ship engines and road vehicles. Their use in agriculture led to an increase in the land available for cultivation.

Very low power engines are used to power models and speciality applications such as the steam clock.

The presence of several phases between heat source and power delivery has meant that it has always been difficult to obtain a power-to-weight ratio anywhere near that obtainable from internal combustion engines; notably this has made steam aircraft extremely rare. Similar considerations have meant that for small and medium-scale applications steam has been largely superseded by internal combustion engines or electric motors, which has given the steam engine an out-dated image. However it is important to remember that the power supplied to the electric grid is predominantly generated using steam turbine plant, so that indirectly the world's industry is still dependent on steam power. Recent concerns about fuel sources and pollution have incited a renewed interest in steam both as a component of cogeneration processes and as a prime mover. This is becoming known as the Advanced Steam movement.

Steam engines can be classified by their application:

[edit] Stationary applications

Stationary steam engines can be classified into two main types:

1. Winding engines, rolling mill engines, steam donkeys, marine engines, and similar applications which need to frequently stop and reverse.
2. Engines providing power, which stop rarely and do not need to reverse. These include engines used in thermal power stations and those that were used in pumping stations, mills, factories and to power cable railways and cable tramways before the widespread use of electric power.

The steam donkey is technically a stationary engine but is mounted on skids to be semi-portable. It is designed for logging use and can drag itself to a new location. Having secured the winch cable to a sturdy tree at the desired destination, the machine will move towards the anchor point as the cable is winched in.

A portable engine is a stationary engine mounted on wheels so that it may be towed to a work-site by horses or a traction engine, rather than being fixed in a single location.

[edit] Transport applications

Steam engines have been used to power a wide array of transport appliances:

• Marine: Steamboat, Steamship
• Rail: Steam locomotive, Fireless locomotive
• Agriculture: Traction engine, Steam tractor
• Road: Steam wagon, Steam bus, Steam tricycle, Steam car
• Construction: Steam roller, Steam shovel
• Military: Steam tank (tracked), Steam tank (wheeled)
• Space: Steam rocket

In many mobile applications internal combustion engines are more frequently used due to their higher power-to-weight ratio, steam engines are used when higher efficiency is needed and weight is less of an issue.

[edit] History

Main article: History of the steam engine

Aeolipile

The history of the steam engine stretches back as far as the first century AD; the first recorded use of steam being the aeolipile described by Hero of Alexandria. In the following centuries, the few engines known about were essentially experimental devices used by inventors to demonstrate the properties of steam.

The first practical steam-powered 'engine' was a water pump, developed in 1698 by Thomas Savery. It proved only to have a limited lift height and was prone to boiler explosions, but it still received some use for mines and pumping stations.

The first commercially-successful engine did not appear until 1712. Incorporating technologies discovered by Savery and Denis Papin, the atmospheric engine, invented by Thomas Newcomen, paved the way for the Industrial Revolution. Newcomen's engine was relatively inefficient, and in most cases was only used for pumping water. It was mainly employed for draining mine workings at depths hitherto impossible, but also for providing a reusable water supply for driving waterwheels at factories sited away from a suitable 'head'.

Early Watt pumping engine.

The next major step occurred when James Watt developed an improved version of Newcomen's engine. Watt's engine used 75% less coal than Newcomen's, and was hence much cheaper to run. Watt proceeded to develop his engine further, modifying it to provide a rotary motion suitable for driving factory machinery. This enabled factories to be sited away from rivers, and further accelerated the pace of the Industrial Revolution.

Around 1800, Richard Trevithick introduced engines using high-pressure steam. These were much more powerful than previous engines and could be made small enough for transport applications. Thereafter, technological developments and improvements in manufacturing techniques (partly brought about by the adoption of the steam engine as a power source) resulted in the design of more efficient engines that could be smaller, faster, or more powerful, depending on the intended application.

Steam engines remained the dominant source of power well into the 20th century, when advances in the design of electric motors and internal combustion engines gradually resulted in the vast majority of reciprocating steam engines being replaced in commercial usage, and the ascendency of steam turbines in power generation.

See also

The history of steam engine development is a vast subject. The following articles cover aspects of steam engine development in greater detail:

• Timeline of steam power – overview
• History of the steam engine – general history, concentrating on reciprocating engines
• Steam turbine – the parallel development of turbine-type engines
• Steam power during the Industrial Revolution
• History of steam road vehicles

[edit] Basic operation of a simple steam engine

• Heat is obtained from fuel burnt in a closed firebox
• The heat is transferred to the water in a pressurised boiler, ultimately boiling the water and transforming it into saturated steam. Steam in its saturated state is always produced at the temperature of the boiling water, which in turn depends on the steam pressure on the water surface within the boiler.
• The steam is transferred to the motor unit which uses it to push on pistons to power machinery.
• The used, cooler, lower pressure steam is dumped to the environment.

[edit] Components of steam engines

There are two fundamental components of a steam engine: the boiler or steam generator, and the motor unit, itself often referred to as a "steam engine". The two components can either be integrated into a single unit or can be placed at a distance from each other, in a variety of configurations.

Other components are often present; pumps to supply water to the boiler during operation, condensers to recirculate the water and recover the latent heat of vaporisation, and superheaters to raise the temperature of the steam above its saturated vapour point, and various mechanisms to increase the draft for fireboxes.

[edit] Heat source

The heat required for boiling the water and supplying the steam can be derived from various sources, most commonly from burning combustible materials with an appropriate supply of air in a closed space (called variously combustion chamber, firebox). In some cases the heat source is a nuclear reactor) or geothermal energy.

[edit] Cold sink

As with all heat engines, a considerable quantity of waste heat is produced at relatively low temperature. This must be disposed of.

The simplest cold sink is simply to vent the steam to the environment. This is often used on Steam locomotives, but is quite inefficient. Steam locomotive condensing apparatus can be employed to improve efficiency.

Steam turbines in power stations often use cooling towers which are essentially one form of condenser.

Sometimes the 'waste heat' is useful in and of itself, and in those cases very high overall efficiency can be obtained; for example combined heat and power uses the waste heat for district heating.

[edit] Boilers

Main article: boiler (steam generator)

Boilers are pressure vessels that contain water to be boiled, and some kind of mechanism for transferring the heat to the water so as to boil it.

The two most common methods of transferring heat to the water according are:

1. water tube boiler - water is contained in or run through one or several tubes surrounded by hot gases
2. firetube boiler - the water partially fills a vessel below or inside of which is a combustion chamber or furnace and fire tubes through which the hot gases flow

Once turned to steam, some boilers use superheating to raise the temperature of the steam further. This allows for greater efficiency.

[edit] Motor units

A motor unit takes a supply of steam at high pressure and temperature and gives out a supply of steam at lower pressure and temperature, using as much of the difference in steam energy as possible to do mechanical work.

A motor unit is often called 'steam engine' in its own right. They will also operate on compressed air or other gas.

[edit] Simple expansion

This means that a charge of steam works only once in the cylinder. It is then exhausted directly into the atmosphere or into a condenser, but remaining heat can be recuperated if needed to heat a living space, or to provide warm feedwater for the boiler.

Schematic Indicator diagram showing the four events in a double piston stroke

In most reciprocating piston engines the steam reverses its direction of flow at each stroke (counterflow), entering and exhausting from the cylinder by the same port. The complete engine cycle occupies one rotation of the crank and two piston strokes; the cycle also comprises four events — admission, expansion, exhaust, compression. These events are controlled by valves often working inside a steam chest adjacent to the cylinder; the valves distribute the steam by opening and closing steam ports communicating with the cylinder end(s) and are driven by valve gear, of which there are many types.

The simplest valve gears give events of fixed length during the engine cycle and often make the engine rotate in only one direction. Most however have a reversing mechanism which additionally can provide means for saving steam as speed and momentum are gained by gradually "shortening the cutoff" or rather, shortening the admission event; this in turn proportionately lengthens the expansion period. However, as one and the same valve usually controls both steam flows, a short cutoff at admission adversely affects the exhaust and compression periods which should ideally always be kept fairly constant; if the exhaust event is too brief, the totality of the exhaust steam cannot evacuate the cylinder, choking it and giving excessive compression ("kick back").

In the 1840s and 50s there were attempts to overcome this problem by means of various patent valve gears with separate variable cutoff valves riding on the back of the main slide valve; the latter usually had fixed or limited cutoff. The combined setup gave a fair approximation of the ideal events, at the expense of increased friction and wear, and the mechanism tended to be complicated. The usual compromise solution has been to provide lap by lengthening rubbing surfaces of the valve in such a way as to overlap the port on the admission side, with the effect that the exhaust side remains open for a longer period after cut-off on the admission side has occurred. This expedient has since been generally considered satisfactory for most purposes and makes possible the use of the simpler Stephenson, Joy and Walschaerts motions. Corliss, and later, poppet valve gears had separate admission and exhaust valves driven by trip mechanisms or cams profiled so as to give ideal events; most of these gears never succeeded outside of the stationary marketplace due to various other issues including leakage and more delicate mechanisms.^[3][4]

Compression

Before the exhaust phase is quite complete, the exhaust side of the valve closes, shutting a portion of the exhaust steam inside the cylinder. This determines the compression phase where a cushion of steam is formed against which the piston does work whilst its velocity is rapidly decreasing; it moreover obviates the pressure and temperature shock, which would otherwise be caused by the sudden admission of the high pressure steam at the beginning of the following cycle.

Lead

The above effects are further enhanced by providing lead: as was later discovered with the internal combustion engine, it has been found advantageous since the late 1830s to advance the admission phase, giving the valve lead so that admission occurs a little before the end of the exhaust stroke in order to fill the clearance volume comprising the ports and the cylinder ends (not part of the piston-swept volume) before the steam begins to exert effort on the piston. ^[5]

[edit] Compounding engines

Main article: Compound engine

As steam expands in a high pressure engine its temperature drops; because no heat is released from the system, this is known as adiabatic expansion and results in steam entering the cylinder at high temperature and leaving at low temperature. This causes a cycle of heating and cooling of the cylinder with every stroke which is a source of inefficiency.

A method to lessen the magnitude of this heating and cooling was invented in 1804 by British engineer Arthur Woolf, who patented his Woolf high pressure compound engine in 1805. In the compound engine, high pressure steam from the boiler expands in a high pressure (HP) cylinder and then enters one or more subsequent lower pressure (LP) cylinders. The complete expansion of the steam now occurs across multiple cylinders and as less expansion now occurs in each cylinder so less heat is lost by the steam in each. This reduces the magnitude of cylinder heating and cooling, increasing the efficiency of the engine. To derive equal work from lower pressure steam requires a larger cylinder volume as this steam occupies a greater volume. Therefore the bore, and often the stroke, are increased in low pressure cylinders resulting in larger cylinders.

Double expansion (usually known as compound) engines expanded the steam in two stages. The pairs may be duplicated or the work of the large LP cylinder can be split with one HP cylinder exhausting into one or the other, giving a 3-cylinder layout where cylinder and piston diameter are about the same making the reciprocating masses easier to balance.

Two-cylinder compounds can be arranged as:

• Cross compounds - The cylinders are side by side.
• Tandem compounds - The cylinders are end to end, driving a common connecting rod
• Angle compounds - The cylinders are arranged in a vee (usually at a 90° angle) and drive a common crank.

With two-cylinder compounds used in railway work, the pistons are connected to the cranks as with a two-cylinder simple at 90° out of phase with each other (quartered). When the double expansion group is duplicated, producing a 4-cylinder compound, the individual pistons within the group are usually balanced at 180°, the groups being set at 90° to each other. In one case (the first type of Vauclain compound), the pistons worked in the same phase driving a common crosshead and crank, again set at 90° as for a two-cylinder engine. With the 3-cylinder compound arrangement, the LP cranks were either set at 90° with the HP one at 135° to the other two, or in some cases all three cranks were set at 120°.

The adoption of compounding was common for industrial units, for road engines and almost universal for marine engines after 1880; it was not universally popular in railway locomotives where it was often perceived as complicated. This is partly due to the harsh railway operating environment and limited space afforded by the loading gauge (particularly in Britain, where compounding was never common and not employed after 1930). However although never in the majority it was popular in many other countries ^[6]

[edit] Multiple expansion engines

Main article: Compound_engine#Multiple_expansion_engines

An animation of a simplified triple-expansion engine.
High-pressure steam (red) enters from the boiler and passes through the engine, exhausting as low-pressure steam (blue) to the condenser.

1890s-vintage triple-expansion marine engine that powered the SS Christopher Columbus

Model of a triple expansion engine

SS Ukkopekka triple expansion steam engine

It is a logical extension of the compound engine (described above) to split the expansion into yet more stages to increase efficiency. The result is the multiple expansion engine. Such engines use either three or four expansion stages and are known as triple and quadruple expansion engines respectively. These engines use a series of double-acting cylinders of progressively increasing diameter and/or stroke and hence volume. These cylinders are designed to divide the work into three or four, as appropriate, equal portions for each expansion stage. As with the double expansion engine, where space is at a premium, two smaller cylinders of a large sum volume may be used for the low pressure stage. Multiple expansion engines typically had the cylinders arranged inline, but various other formations were used. In the late 19th century, the Yarrow-Schlick-Tweedy balancing 'system' was used on some marine triple expansion engines. Y-S-T engines divided the low pressure expansion stages between two cylinders, one at each end of the engine. This allowed the crankshaft to be better balanced, resulting in a smoother, faster-responding engine which ran with less vibration. This made the 4-cylinder triple-expansion engine popular with large passenger liners (such as the Olympic class), but was ultimately replaced by the virtually vibration-free turbine (see below).

The image to the right shows an animation of a triple expansion engine. The steam travels through the engine from left to right. The valve chest for each of the cylinders is to the left of the corresponding cylinder.

The development of this type of engine was important for its use in steamships as by exhausting to a condenser the water can be reclaimed to feed the boiler, which is unable to use seawater. Land-based steam engines could exhaust much of their steam, as feed water was usually readily available. Prior to and during World War II, the expansion engine dominated marine applications where high vessel speed was not essential. It was however superseded by the British invention steam turbine where speed was required, for instance in warships, such as the pre-dreadnought battleships, and ocean liners. HMS Dreadnought of 1905 was the first major warship to replace the proven technology of the reciprocating engine with the then-novel steam turbine.

[edit] Uniflow (or unaflow) engine

Main article: Uniflow steam engine

Schematic animation of a uniflow steam engine.
The poppet valves are controlled by the rotating camshaft at the top. High pressure steam enters, red, and exhausts, yellow.

This is intended to remedy the difficulties arising from the usual counterflow cycle mentioned above which means that at each stroke the port and the cylinder walls will be cooled by the passing exhaust steam, whilst the hotter incoming admission steam will waste some of its energy in restoring working temperature. The aim of the uniflow is to remedy this defect by providing an additional port uncovered by the piston at the end of its half-stroke making the steam flow only in one direction. By this means, thermal efficiency is improved by having a steady temperature gradient along the cylinder bore. The simple-expansion uniflow engine is reported to give efficiency equivalent to that of classic compound systems with the added advantage of superior part-load performance. It is also readily adaptable to high-speed uses and was a common way to drive electricity generators towards the end of the 19th century before the coming of the steam turbine.

Uniflow engines have been produced in single-acting, double-acting, simple, and compound versions. Skinner 4-crank 8-cylinder single-acting tandem compound [1] engines power two Great Lakes ships still trading today (2007). These are the Saint Marys Challenger,[2] that in 2005 completed 100 years of continuous operation as a powered carrier (the Skinner engine was fitted in 1950) and the car ferry, S. S. Badger.[3]

In the early 1950s the Ultimax engine, a 2-crank 4-cylinder arrangement similar to Skinner’s, was developed by Abner Doble for the Paxton car project with tandem opposed single-acting cylinders giving effective double-action. [4]

[edit] Turbine engines

A rotor of a modern steam turbine, used in a power plant

Main article: Steam turbine

A steam turbine consists of an alternating series of rotating discs mounted on a drive shaft, rotors, and static discs fixed to the turbine casing, stators. The rotors have a propeller-like arrangement of blades at the outer edge. Steam acts upon these blades, producing rotary motion. The stator consists of a similar, but fixed, series of blades that serve to redirect the steam flow onto the next rotor stage. A steam turbine often exhausts into a condenser that provides a vacuum. The stages of a steam turbine are typically arranged to extract the maximum potential work from a specific velocity and pressure of steam, giving rise to a series of variably sized high and low pressure stages. Turbines rotate at very high speed, therefore are usually connected to reduction gearing to drive another mechanism, such as a ship's propeller, at a lower speed. A turbine rotor is also capable of providing power when rotating in one direction only. Therefore a reversing stage or gearbox is usually required where power is required in the opposite direction.

Steam turbines provide direct rotational force and therefore do not require a linkage mechanism to convert reciprocating to rotary motion. Thus, they produce smoother rotational forces on the output shaft. This contributes to a lower maintenance requirement and less wear on the machinery they power than a comparable reciprocating engine.

The Turbinia - the first steam turbine-powered ship

The main use for steam turbines is in electricity generation (about 80% of the world's electric production is by use of steam turbines)^{[citation needed]} and to a lesser extent as marine prime movers. In the former, the high speed of rotation is an advantage, and in both cases the relative bulk is not a disadvantage; in the latter (pioneered on the Turbinia), the light weight, high efficiency and high power are highly desirable.

Virtually all nuclear power plants and some nuclear submarines, generate electricity by heating water to provide steam that drives a turbine connected to an electrical generator for main propulsion. A limited number of steam turbine railroad locomotives were manufactured. Some non-condensing direct-drive locomotives did meet with some success for long haul freight operations in Sweden, but were not repeated. Elsewhere, notably in the U.S.A., more advanced designs with electric transmission were built experimentally, but not reproduced. It was found that steam turbines were not ideally suited to the railroad environment and these locomotives failed to oust the classic reciprocating steam unit in the way that modern diesel and electric traction has done.

[edit] Rotary steam engines

It is possible to use a mechanism based on a pistonless rotary engine such as the Wankel engine in place of the cylinders and valve gear of a conventional reciprocating steam engine. Many such engines have been designed, from the time of James Watt to the present day, but relatively few were actually built and even fewer went into quantity production; see link at bottom of article for more details. The major problem is the difficulty of sealing the rotors to make them steam-tight in the face of wear and thermal expansion; the resulting leakage made them very inefficient. Lack of expansive working, or any means of control of the cutoff is also a serious problem with many such designs. By the 1840s it was clear that the concept had inherent problems and rotary engines were treated with some derision in the technical press. However, the arrival of electricity on the scene, and the obvious advantages of driving a dynamo directly from a high-speed engine, led to something of a revival in interest in the 1880s and 1890s, and a few designs had some limited success.

Of the few designs that were manufactured in quantity, those of the Hult Brothers Rotary Steam Engine Company of Stockholm, Sweden, and the spherical engine of Beauchamp Tower are notable. Tower's engines were used by the Great Eastern Railway to drive lighting dynamos on their locomotives, and by the Admiralty for driving dynamos on board the ships of the Royal Navy. They were eventually replaced in these niche applications by steam turbines.

[edit] Jet type

Invented by Australian engineer Alan Burns and developed in Britain by engineers at Pursuit Dynamics, this underwater jet engine uses high pressure steam to draw in water through an intake at the front and expel it at high speed through the rear. When steam condenses in water, a shock wave is created and is focused by the chamber to blast water out of the back. To improve the engine's efficiency, the engine draws in air through a vent ahead of the steam jet, which creates air bubbles and changes the way the steam mixes with the water.

Unlike in conventional steam engines, there are no moving parts to wear out, and the exhaust water is only several degrees warmer in tests. The engine can also serve as pump and mixer. This type of system is referred to as 'PDX Technology' by Pursuit Dynamics.

[edit] Rocket type

The aeolipile represents the use of steam by the rocket-reaction principle, although not for direct propulsion.

In more modern times there has been limited use of steam for rocketry—particularly for rocket cars. The technique is simple in concept, simply fill a pressure vessel with hot water at high pressure, and open a valve leading to a suitable nozzle. The drop in pressure immediately boils some of the water and the steam leaves through a nozzle, giving a significant propulsive force.

It might be expected that water in the pressure vessel should be at high pressure; but in practice the pressure vessel has considerable mass, which reduces the acceleration of the vehicle. Therefore a much lower pressure is used, which permits a lighter pressure vessel, which in turn gives the highest final speed.

There are even speculative plans for interplanetary use. Although steam rockets are relatively inefficient in their use of propellant, this very well may not matter as the solar system is believed to have extremely large stores of water ice which can be used as propellant. Extracting this water and using it in interplanetary rockets requires several orders of magnitude less equipment than breaking it down to hydrogen and oxygen for conventional rocketry.^[7]

[edit] Advantages

The strength of the steam engine for modern purposes is in its ability to convert heat from almost any source into mechanical work. Unlike the internal combustion engine, the steam engine is not particular about the source of heat. Most notably, without the use of a steam engine it would be more difficult to harness nuclear energy for useful work, as a nuclear reactor does not directly generate either mechanical work or electrical energy—the reactor itself simply heats or boils water. It is the steam engine which converts the heat energy into useful work. Steam may also be produced without combustion of fuel, through solar concentrators. A demonstration power plant has been built using a central heat collecting tower and a large number of solar tracking mirrors, (called heliostats). (see Whitecliffs Project[5])

Similar advantages are found in a different type of external combustion engine, the Stirling engine, which can offer efficient power (with advanced regenerators and large radiators) at the cost of a much lower power-to-size/weight ratio than even modern steam engines with compact boilers^{[citation needed]}. These Stirling engines are not commercially produced, although the concepts are promising.

Steam locomotives are especially advantageous at high elevations as they are not adversely affected by the lower atmospheric pressure. This was inadvertently discovered when steam locomotives operated at high altitudes in the mountains of South America were replaced by diesel-electric units of equivalent sea level power. These were quickly replaced by much more powerful locomotives capable of producing sufficient power at high altitude.

In Switzerland (Brienz Rothhorn) and Austria (Schafberg Bahn) new rack steam locomotives have proved very successful. They were designed based on a 1930s design of Swiss Locomotive and Machine Works (SLM) but with all of today's possible improvements like roller bearings, heat insulation, light-oil firing, improved inner streamlining, one-man-driving and so on. These resulted in 60 percent lower fuel consumption per passenger and massively reduced costs for maintenance and handling. Economics now are similar or better than with most advanced diesel or electric systems. Also a steam train with similar speed and capacity is 50 percent lighter than an electric or diesel train, thus, especially on rack railways, significantly reducing wear and tear on the track. Also, a new steam engine for a paddle steam ship on Lake Geneva, the Montreux, was designed and built, being the world's first full-size ship steam engine with an electronic remote control[6]. The steam group of SLM in 2000 created a wholly-owned company called DLM to design modern steam engines and steam locomotives.

[edit] Safety

Steam engines possess boilers and other components that are pressure vessels that contain a great deal of potential energy. Steam explosions can and have caused great loss of life in the past. While variations in standards may exist in different countries, stringent legal, testing, training, care with manufacture, operation and certification is applied to try to minimise or prevent such occurrences.

Failure modes include:

• overpressurisation of the boiler
• insufficient water in the boiler causing overheating and vessel failure
• pressure vessel failure of the boiler due to inadequate construction or maintenance.
• escape of steam from pipework/boiler causing scalding

[edit] Efficiency

Main article: thermodynamic efficiency

The efficiency of an engine can be calculated by dividing the number of joules of mechanical work that the engine produces by the number of joules of energy input to the engine by the burning fuel. The rest of the energy is dumped into the environment as heat.

No pure heat engine can be more efficient than the Carnot cycle, in which heat is moved from a high temperature reservoir to one at a low temperature, and the efficiency depends on the temperature difference. Hence, steam engines should ideally be operated at the highest steam temperature possible (superheated steam), and release the waste heat at the lowest temperature possible.

In practice, a steam engine exhausting the steam to atmosphere will have an efficiency (including the boiler) of 1% to 8%, but with the addition of a condenser and multiple expansion engines the efficiency may be greatly improved to 25% or better. A power station with steam reheat, etc. will achieve 30% to 42% efficiency. Combined cycle in which the burning material is first used to drive a gas turbine can produce 50% to 60% efficiency. It is also possible to capture the waste heat using cogeneration in which the residual steam is used for heating. It is therefore possible to use as much as 90% of the energy produced by burning fuel—only 10% of the energy produced by the combustion of the fuel goes wasted into the atmosphere.

The reason for varying efficiencies is because of the thermodynamic rule of the Carnot Cycle. The efficiency is the absolute temperature of the cold reservoir over the absolute temperature of the steam, subtracted from one. As the temperature changes in seasons, the efficiency changes with it, unless the cold reservoir is kept in an isothermal state. It should be noted that the Carnot Cycle calculations require absolute temperatures.

One source of inefficiency is that the condenser causes losses by being somewhat hotter than the outside world, although this can be mitigated by condensing the steam in a heat exchanger and using the recovered heat, for example to pre-heat the air being used in the burner of an external combustion engine.

The operation of the engine portion alone is not dependent upon steam; any pressurized gas may be used. Compressed air is sometimes used to test or demonstrate small model "steam" engines.