Hydroelectric Power - Water power - micro hydro systems

Micro hydro power is probably the least common of the three readily used renewable energy sources, but it has the potential to produce the most power, more reliably than solar or wind power if you have the right site. This means having access to a river or creek that has a high enough flow to produce useable power for a good part of the year.

Many creeks and rivers are permanent, ie, they never dry up, and these are the most suitable for micro-hydro power production.

A micro hydro turbine can take several forms, the most widely recognized of which would be the water wheel, used extensively for grain grinding up until this century. Waterwheels are still used in some situations that do not require a fast-spinning turbine, such as for pumping water. However, other type of turbines have become quite common.

Image provided by Bernard Bélisle of Electrovent

The most common of these newer turbines is the Pelton wheel, which is basically a series of cups attached to a hub. A jet of water is aimed at the cups, and the resulting force on the cups causes the turbine to spin.

Other types of turbines include the Turgo, Crossflow and various axial flow turbines, where the shaft through the center of the turbine runs in the same direction as the water flow, much like a boat propeller.

Water turbines have many advantages over solar panels or wind turbines, the most obvious of which is that they produce power continuously, 24 hours per day. However, they also have some associated problems or requirements. The most important of these is correct siting of the turbine and associated equipment so as to cause the least environmental damage as possible. Placing a large concrete dam across a creek or river can do considerable damage to the surrounding ecology. A general rule of thumb is to not divert more than 20% of the water flow of the creek through your turbine, and to return any diverted water back to the creek just below the turbine.

Other requirements that must be considered are flood protection for the turbine and how to transmit the power to the batteries, which may often be located a long way from the water source. http://www.ata.org.au/~ata/basics/bashydro.htm
Turning water's mechanical energy into electricity
Since the time of ancient Egypt, people have used the energy in flowing water to operate machinery and grind grain and corn. However, hydropower had a greater influence on people's lives during the 20th century than at any other time in history. Hydropower played a major role in making the wonders of electricity a part of everyday life and helped spur industrial development. Hydropower continues to produce 24 percent of the world's electricity and supply more than 1 billion people with power.

Evolution of Hydropower

The first hydroelectric power plant was built in 1882 in Appleton, Wisconsin to provide 12.5 kilowatts to light two paper mills and a home. Today's hydropower plants generally range in size from several hundred kilowatts to several hundred megawatts, but a few mammoth plants have capacities up to 10,000 megawatts and supply electricity to millions of people.

Worldwide, hydropower plants have acombined capacity of 675,000 megawatts and annually produce over 2.3 trillion kilowatt-hours of electricity, the energy equivalent of 3.6 billion barrels of oil.

Hydropower in the U.S.

With a capacity of more than 92,000 mega-watts— enough electricity to meet the energy needs of 28 million households—the U.S. is the world's leading hydropower producer. Hydropower supplies 9 percent of the country's electricity and accounts for 49 percent of all renewable energy used in the U.S.

The nation's largest hydropower plant is the 7,600 megawatt Grand Coulee power station on the Columbia River in Washington State. The plant is being upscaled to 10,080 megawatts, which will place it second in the world behind a colossal 13,320 megawatt plant in Brazil.


How Hydropower Works

Hydropower converts the energy in flowing water into electricity. The quantity of electricity generated is determined by the volume of water flow and the amount of "head" (the height from turbines in the power plant to the water surface) created by the dam. The greater the flow and head, the more electricity produced.

A typical hydropower plant includes a dam, reservoir, penstocks (pipes), a powerhouse and an electrical power substation. The dam stores water and creates the head; penstocks carry water from the reservoir to turbines inside the powerhouse; the water rotates the turbines, which drive generators that produce electricity. The electricity is then transmitted to a substation where transformers increase voltage to allow transmission to homes, businesses and factories.


Types of Hydropower Plants
Conventional

Most hydropower plants are conventional in design, meaning they use one-way water flow to generate electricity. There are two categories of conventional plants, run-of-river and storage plants.

Run-of-river plants—These plants use little, if any, stored water to provide water flow through the turbines. Although some plants store a day or week's worth of water, weather changes—especially seasonal changes—cause run-of-river plants to experience significant fluctuations in power output.

Storage plants—These plants have enough storage capacity to off-set seasonal fluctuations in water flow and provide a constant supply of electricity throughout the year. Large dams can store several years worth of water.

Pumped Storage

In contrast to conventional hydropower plants, pumped storage plants reuse water. After water initially produces electricity, it flows from the turbines into a lower reservoir located below the dam. During off-peak hours (periods of low energy demand), some of the water is pumped into an upper reservoir and reused during periods of peak-demand.


Building Hydropower Plants

Most hydropower plants are built through federal or local agencies as part of a multipurpose project. In addition to generating electricity, dams and reservoirs provide flood control, water supply, irrigation, transportation, recreation and refuges for fish and birds. Private utilities also build hydropower plants, although not as many as government agencies.


Benefits

Hydropower is a clean, domestic and renewable source of energy. Hydropower plants provide inexpensive electricity and produce no pollution. And, unlike other energy sources such as fossil fuels, water is not destroyed during the production of electricity—it can be reused for other purposes.


Obstacles

Hydropower plants can significantly impact the surrounding area—reservoirs can cover towns, scenic locations and farmland, as well as affect fish and wildlife habitat. To mitigate impact on migration patterns and wildlife habitats, dams maintain a steady stream flow and can be designed or retrofitted with fish ladders and fishways to help fish migrate upstream to spawn.


Potential

The best sites for hydroelectric plants are swift-flowing rivers or steams, mountainous regions and areas with heavy rainfall. Only 20 percent of potential U.S. hydro-power has been developed, but unfavorable terrain and environmental concerns make many sites unsuitable for

hydropower plants.

However, since only 2,400 of the nation's 80,000 dams are currently used for hydropower, new projects do not necessarily require building new dams—many existing dams can be retrofitted to produce electricity. At existing hydropower plants, advanced technologies can be installed to increase efficiently and energy production.

The Future of Ford's EcoBoost Engine

Ford’s new twin-turbo gasoline direct-injection EcoBoost engines pack plenty of punch for their size. The 2010 Ford Flex with the 3.5-liter EcoBoost V-6 is rated at 355 hp and 350 pounds-feet of torque. That’s an increase of 35% horsepower and 41% more torque than the Flex’s standard 3.5-liter V-6, while returning the same 16/22 mpg city/highway gas mileage (all-wheel drive model). It's also available in the new Ford Taurus SHO, Lincoln MKS sedan and upcoming MKT crossover.

Brett Hinds, Ford’s advance engine design and development manager, said it will only get better from here.

“The [Flex’s] EcoBoost [engine] is the foundation for us,” Hinds said. “It’s a six-cylinder engine that performs like an eight-cylinder, but we’re looking at many ways to make EcoBoost even more efficient so it can meet future fuel economy and CO2 standards.”

Here are three improvements to EcoBoost that Hinds said Ford is studying:

* Ethanol compatibility: Today’s EcoBoost engines can’t use E85, which has several properties that make it better to use in an EcoBoost engine than in a conventional non-turbo engine. Ethanol has a higher octane and heat-of-vaporization point than gasoline, meaning it combusts at a higher temperature and with greater force (higher compression) than gasoline, while also having a greater capacity to cool the fuel/air mix in the cylinder before combustion. This allows a larger charge to be drawn into the cylinder before ignition.

What it means: An EcoBoost engine running on E85 could produce the same power as the Flex’s 3.5-liter V-6 but with even smaller displacement. This could also improve E85 fuel economy, which is typically less on a per-gallon basis than a gallon of gasoline because of E85's lower energy content.

* Start-stop: Without changing the engine, EcoBoost could share start-stop technology originally developed for hybrid vehicles. Start-stop would automatically shut the engine down when the vehicle is stopped, running accessories like the radio and air conditioning off an upgraded starter motor and bigger battery. Hit the gas pedal, and the EcoBoost engine would fire right back up.

What it means: Idling burns fuel and emits CO2 without helping you reach your destination. Start-stop would reduce both.

* Homogeneous charge compression ignition: The only thing larger than HCCI’s spelled-out name is the technical challenge of making it work in a gas engine. HCCI enables a normally spark-ignited gasoline engine to operate similar to a compression-ignited diesel engine, but only in certain driving conditions.

What it means: Shifting on the fly from spark to compression ignition could yield another 10% to 15% improvement in fuel economy.

The Future of the Gasoline Engine

Don't count out the petrol engine just yet according to motoring giant Mercedes-Benz, which has unveiled a new gasoline engine offering the high torque and fuel economy of a diesel together with extremely clean emissions. The company is highly optimistic, calling it "the future of the gasoline engine." The Mercedes-Benz DiesOtto powertrain is a further development of the spark-ignition engine and includes features such as direct gasoline injection, turbocharging, variable valve timing and variable compression and it will be used in conjunction with a hybrid integrated starter/generator module. At its core lies the controlled auto ignition, a highly efficient combustion process similar to that of a diesel. The result is an 1800cc four-cylinder motor producing 238 bhp (175 kW) with torque of 400 nm while delivering 6 l/100 km (47 UK mpg, 40 US mpg) in an S-class.

Optimising the internal combustion engine is one of the milestones on the Mercedes-Benz roadmap for sustainable mobility.

The company's powerful and economical BLUETEC diesel engine diesel has already been available in the US in the E-Class since 2006, and it will also become available in Europe from the end of this year.

The E 300 BLUETEC will be by far the cleanest diesel in its class, and will meet the requirements of the EU5 exhaust emission standards in full.

"Our next goal will now be to make the gasoline engine as economical as a diesel. All the preconditions for this are provided by our DiesOtto concept, which incorporates the foremost strengths of both the gasoline engine and diesel engine," says Prof. Dr. Herbert Kohler, Head of Group Research & Advanced Engineering Vehicle and Powertrain; Chief Environmental Officer of DaimlerChrysler.

The result of this "marriage" is a four-cylinder unit with a displacement of just 1.8 litres, which combines the strengths of the low-emission gasoline engine with the fuel economy of a diesel.

Despite its considerably reduced displacement -- downsizing is one of the major factors for achieving a lower fuel consumption -- this compact power unit delivers superior performance together with refinement at the level of the luxury class.

An output of 175 kW/238 hp and a maximum torque of 400 newton metres are achieved together with the hybridisation a fuel consumption of less than six litres of gasoline per 100 kilometres. This figure by no means relates to a small or compact car, but to a vehicle the size of the current S-Class, with the level of comfort and safety that is typical of a Mercedes.

"In line with the worldwide success of today's diesel engine, vehicles equipped with gasoline engines will continue to have a long-term attraction for many customers and in many markets. Accordingly we are giving our attention to both engine types -- including a full hybrid option for diesel and gasoline vehicles," says Prof. Kohler. Mercedes-Benz is working on its DiesOtto concept with corresponding emphasis.

Its key technological features are as follows:

* Downsizing with fewer cylinders and a smaller displacement * Turbocharging for superior performance * Direct gasoline injection as a further fuel economy measure * Controlled auto ignition, a combustion process similar to that of a diesel * Variable valve control * A variable compression ratio leading to even better fuel economy and, depending on customer needs and the type of operation, * A hybrid module with an integrated starter/generator, which makes the drive unit even more economical.

When starting and under full load, the fuel/air mixture is ignited by a spark plug, as in a conventional spark-ignition engine (homogeneous combustion). The controlled auto ignition to which the DiesOtto automatically reverts within its working cycle occurs under partial load conditions, i.e. at low and medium engine speeds. The result is the very low nitrogen oxide emissions of homogeneous combustion at reduced reaction temperatures. All further emissions control in the DiesOtto engine is by means of a standard three-way catalytic converter. A highly efficient engine management and control system has also been realised to combine the individual sub-systems into a drive concept.

The current prospects for the future of the internal combustion engine reveal its great potential, and show that the new drive concept is a feasible proposition in the mid-term according to Benz. Some of the intermediate solutions incorporated, e.g. direct gasoline injection, are already in series production at Mercedes-Benz. Others will be gradually integrated into series-production engines until the overall solution has been realised

Internal combustion engine

The internal combustion engine is a heat engine in which combustion occurs in a confined space called a combustion chamber.

Combustion of a fuel creates high temperature/pressure gases, which are permitted to expand.

The expanding gases are used to directly move a piston, turbine blades, rotor(s), or the engine itself thus doing useful work.

Internal combustion engines can be powered by any fuel that can be combined with an oxidizer in the chamber..

For more information about the topic Internal combustion engine, read the full article at Wikipedia.org, or see the following related articles:
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Low-emission, High-performance Engine For Future Hybrids

toward introduction of an amazing new kind of internal combustion engine, researchers in China are reporting development and use of a new and more accurate computer model to assess performance of the so-called free-piston linear alternator (FPLA).
Their study of the FPLA, which could provide a low-emission, fuel efficient engine for future hybrid electric vehicles, is scheduled for the Sept. 17 issue of ACS' Energy & Fuels, a bi-monthly journal.

Qingfeng Li and colleagues point out that the FPLA has only one moving part and is an engine designed to generate electricity. In the device, a piston in a cylinder shuttles between two combustion chambers. Permanent magnets on the piston generate electricity by passing through the coils of an alternator centered on the cylinder. The engine can burn a variety of fuels, including natural gas and hydrogen, and seems ideal use in a future world of climate change and possible fossil fuel shortages, they suggest.

Their report describes development of a better computer model to evaluate performance of the FPLA and guide engineers in construction of the engine. Results of their initial simulations showed that the FPLA could accelerate three times faster than other internal combustion engines and burns fuel in ways that minimize air pollution. "It is an environmentally friendly power source for the future," the report concludes.

Engine

the internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidiser (usually air) in a combustion chamber. In an internal combustion engine the expansion of the high temperature and pressure gases, that are produced by the combustion, directly apply force to a movable component of the engine, such as the pistons or turbine blades and by moving it over a distance, generate useful mechanical energy

The term internal combustion engine usually refers to an engine in which combustion is intermittent, such as the more familiar four-stroke and two-stroke piston engines, along with variants, such as the Wankel rotary engine. A second class of internal combustion engines use continuous combustion: gas turbines, jet engines and most rocket engines, each of which are internal combustion engines on the same principle as previously described.
The internal combustion engine (or ICE) is quite different from external combustion engines, such as steam or Stirling engines, in which the energy is delivered to a working fluid not consisting of, mixed with or contaminated by combustion products. Working fluids can be air, hot water, pressurised water or even liquid sodium, heated in some kind of boiler by fossil fuel, wood-burning, nuclear, solar etc.

A large number of different designs for ICEs have been developed and built, with a variety of different strengths and weaknesses. While there have been and still are many stationary applications, the real strength of internal combustion engines is in mobile applications and they completely dominate as a power supply for cars, aircraft, and boats, from the smallest to the biggest. Only for hand-held power tools do they share part of the market with battery powered devices. Powered by an energy-dense fuel (nearly always liquid, derived from fossil fuels) the ICE delivers an excellent power-to-weight ratio with few safety or other disadvantages.

Internal combustion engines are most commonly used for mobile propulsion in vehicles and portable machinery. In mobile equipment, internal combustion is advantageous since it can provide high power-to-weight ratios together with excellent fuel energy density. Generally using fossil fuel (mainly petroleum), these engines have appeared in transport in almost all vehicles (automobiles, trucks, motorcycles, boats, and in a wide variety of aircraft and locomotives).

Internal combustion engines appear in the form of gas turbines as well where a very high power is required, such as in jet aircraft, helicopters, and large ships. They are also frequently used for electric generators and by industry.

The History of the Automobile

the First Mass Producers of Cars - The Assembly Line


By the early 1900s, gasoline cars started to outsell all other types of motor vehicles. The market was growing for economical automobiles and the need for industrial production was pressing.

The first car manufacturers in the world were French: Panhard & Levassor (1889) and Peugeot (1891). By car manufacturer we mean builders of entire motor vehicles for sale and not just engine inventors who experimented with car design to test their engines - Daimler and Benz began as the latter before becoming full car manufacturers and made their early money by licensing their patents and selling their engines to car manufacturers.

Rene Panhard and Emile Levassor

Rene Panhard and Emile Levassor were partners in a woodworking machinery business, when they decided to become car manufacturers. They built their first car in 1890 using a Daimler engine. Edouard Sarazin, who held the license rights to the Daimler patent for France, commissioned the team. (Licensing a patent means that you pay a fee and then you have the right to build and use someone's invention for profit - in this case Sarazin had the right to build and sell Daimler engines in France.) The partners not only manufactured cars, they made improvements to the automotive body design.

Panhard-Levassor made vehicles with a pedal-operated clutch, a chain transmission leading to a change-speed gearbox, and a front radiator. Levassor was the first designer to move the engine to the front of the car and use a rear-wheel drive layout. This design was known as the Systeme Panhard and quickly became the standard for all cars because it gave a better balance and improved steering. Panhard and Levassor are also credited with the invention of the modern transmission - installed in their 1895 Panhard.

Panhard and Levassor also shared the licensing rights to Daimler motors with Armand Peugot. A Peugot car went on to win the first car race held in France, which gained Peugot publicity and boosted car sales. Ironically, the "Paris to Marseille" race of 1897 resulted in a fatal auto accident, killing Emile Levassor. (Learn more about Panhard and Levassor)

Early on, French manufacturers did not standardize car models - each car was different from the other. The first standardized car was the 1894, Benz Velo. One hundred and thirty four identical Velos were manufactured in 1895.

Charles and Frank Duryea

America's first gasoline-powered commercial car manufacturers were Charles and Frank Duryea. The brothers were bicycle makers who became interested in gasoline engines and automobiles and built their first motor vehicle in 1893, in Springfield, Massachusetts. By 1896, the Duryea Motor Wagon Company had sold thirteen models of the Duryea, an expensive limousine, which remained in production into the 1920s. (Learn more about Charles and Frank Duryea)

Ransome Eli Olds

The first automobile to be mass produced in the United States was the 1901, Curved Dash Oldsmobile, built by the American car manufacturer Ransome Eli Olds (1864-1950). Olds invented the basic concept of the assembly line and started the Detroit area automobile industry. He first began making steam and gasoline engines with his father, Pliny Fisk Olds, in Lansing, Michigan in 1885. Olds designed his first steam-powered car in 1887. In 1899, with a growing experience of gasoline engines, Olds moved to Detroit to start the Olds Motor Works, and produce low-priced cars. He produced 425 "Curved Dash Olds" in 1901, and was America's leading auto manufacturer from 1901 to 1904.

Henry Ford

American car manufacturer, Henry Ford (1863-1947) invented an improved assembly line and installed the first conveyor belt-based assembly line in his car factory in Ford's Highland Park, Michigan plant, around 1913-14. The assembly line reduced production costs for cars by reducing assembly time. Ford's famous Model T was assembled in ninety-three minutes. Ford made his first car, called the "Quadricycle," in June, 1896. However, success came after he formed the Ford Motor Company in 1903. This was the third car manufacturing company formed to produce the cars he designed. He introduced the Model T in 1908 and it was a success. After installing the moving assembly lines in his factory in 1913, Ford became the world's biggest car manufacturer. By 1927, 15 million Model Ts had been manufactured.

Another victory won by Henry Ford was patent battle with George B. Selden. Selden, who had never built an automobile, held a patent on a "road engine", on that basis Selden was paid royalties by all American car manufacturers. Ford overturned Selden's patent and opened the American car market for the building of inexpensive cars. (Learn more about Henry Ford)

Pump Style Espresso Machines:

you don’t need to be an expert to brew a great shot of espresso. Pump espresso machines take most of the guesswork out of the brewing equation.

Early espresso machines, which are still popular today in homes and on camping trips, use a very simple system for brewing coffee: ground coffee beans are placed in a small filter area above a filled water receptacle. When the water is brought to a boil, the pressure forces it up through the beans and into a spout, where it is then dispensed into a cup. Voila!

The problem some users run into with these machines is quality. Through no fault of the machine, it’s sometimes tricky to get just the right ratio of beans, water volume and temperature, and brewing time. Some users would rather jump right into the process and get things right on the first try. That’s where pump-style machines come in.


Pump-Style Espresso Machines
A pump espresso machine works much like the earlier version mentioned above, with a little more automation. How much automation depends on the machine; there are semi-automatics that still require some skill on the part of the user. There are also super-automatics that even grind the beans themselves – and everything in between. The common characteristic of these machines is that the water is pumped from the reservoir into an electric heating chamber, and then passed through the grinds and into one or more cups waiting below.


How to Use a Pump-Style Machine

1. Fill the machine’s reservoir with cold water, and turn on the power.

2. Grind your beans and place them in the machine’s portable filter basket.

3. When the water is heated, twist the portable filter into place.

4. Place an espresso cup beneath each spout on the bottom of the filter.

When you start the brewing process, usually by turning a valve to the ‘espresso’ setting, the hot water in the reservoir is pressurized just enough to send it through the grinds and out into the waiting cups. This usually takes 25 seconds for a typical serving. Some machines also contain automatic milk steamers and frothers to whip up more gourmet espresso drinks like lattes and cappuccinos.

Pump-style espresso machines are the best espresso machines for new users. Unlike their earlier counterparts, these machines are more forgiving of small errors in measurement. The fancier ones even do all of the measuring themselves! Thanks to new advances, an espresso machine commercial or residential can brew up a wonderful cup of coffee with a minimal amount of guidance from the user. Great taste has never been easier!

Who is the inventor of television?

Who is the inventor of television? You have really opened up a can of worms with that question! Probably no other invention in history has been so hotly disputed as the prestigious claim to the invention of 'Tele-vision or 'long-distance sight' by wireless.”

Since Marconi’s invention of wireless telegraphy in 1897, the imagination of many inventors have been sparked with the notion of sending images as well as sound, wirelessly. The first documented notion of sending components of pictures over a series of multiple circuits is credited to George Carey. Another inventor, W. E. Sawyer, suggested the possibility of sending an image over a single wire by rapidly scanning parts of the picture in succession.

On December 2, 1922, in Sorbonne, France, Edwin Belin, an Englishman, who held the patent for the transmission of photographs by wire as well as fiber optics and radar, demonstrated a mechanical scanning device that was an early precursor to modern television. Belin’s machine took flashes of light and directed them at a selenium element connected to an electronic device that produced sound waves. These sound waves could be received in another location and remodulated into flashes of light on a mirror.

Up until this point, the concept behind television was established, but it wasn’t until electronic scanning of imagery (the breaking up of images into tiny points of light for transmission over radio waves), was invented, that modern television received its start. But here is where the controversy really heats up.


he credit as to who was the inventor of modern television really comes down to two different people in two different places both working on the same problem at about the same time: Vladimir Kosma Zworykin, a Russian-born American inventor working for Westinghouse, and Philo Taylor Farnsworth, a privately backed farm boy from the state of Utah.

“Zworykin had a patent, but Farnsworth had a picture…”

Zworykin is usually credited as being the father of modern television. This was because the patent for the heart of the TV, the electron scanning tube, was first applied for by Zworykin in 1923, under the name of an iconoscope. The iconoscope was an electronic image scanner - essentially a primitive television camera. Farnsworth was the first of the two inventors to successfully demonstrate the transmission of television signals, which he did on September 7, 1927, using a scanning tube of his own design. Farnsworth received a patent for his electron scanning tube in 1930. Zworykin was not able to duplicate Farnsworth’s achievements until 1934 and his patent for a scanning tube was not issued until 1938. The truth of the matter is this, that while Zworykin applied for the patent for his iconoscope in 1923, the invention was not functional until some years later and all earlier efforts were of such poor quality that Westinghouse officials ordered him to work on something “more useful.”



Another player of the times was John Logie Baird, a Scottish engineer and entrepreneur who 'achieved his first transmissions of simple face shapes in 1924 using mechanical television. On March 25, 1925, Baird held his first public demonstration of 'television' at the London department store Selfridges on Oxford Street in London. In this demonstration, he had not yet obtained adequate half-tones in the moving pictures, and only silhouettes were visible.' - MZTV

In the late thirties, when RCA and Zworykin, who was now working for RCA, tried to claim rights to the essence of television, it became evident that Farnsworth held the priority patent in the technology. The president of RCA sought to control television the same way that they controlled radio and vowed that, “RCA earns royalties, it does not pay them,” and a 50 million dollar legal battle subsequently ensued.

n the height of the legal battle for patent priority, Farnsworth’s high school science teacher was subpoenaed and traveled to Washington to testify that as a 14 year old, Farnsworth had shared his ideas of his television scanning tube with his teacher.

With patent priority status ruled in favor of Farnsworth, RCA for the first time in its history, began paying royalties for television in 1939.

Philo Farnsworth was recently named one of TIME Magazine's 100 Greatest Scientists and Thinkers of the 20th Century.

How Television Works – Lights, Camera, Action

Many people simply take their television for granted. They just assume that when they turn it on, picture and sound appear like magic. When the channel gets snowy, they hit the side of the television to get it working again.

Amazingly, sometimes, it does.

But have you ever wondered how your favorite television program gets to your house from a broadcast station thousands of miles away? How about from a satellite dish? Just what is this technology that spends so much time entertaining and enlightening us that it could be considered a part of the family?

Take a minute to read this article, and what you find out about your television may surprise you

The Heart and Soul of Your Television

At the center of the standard projection-style television set is the all-important Cathode Ray Tube (CRT). You may have heard of a CRT before, but what exactly does it do? The answer to that is surprisingly simple and amazingly complex at the same time.

In science, the term “cathode” means a negative terminal. The opposite of a cathode is an “anode”, which means negative terminal.

In a CRT, the Cathode is a heated filament that creates electrons. The Ray is the stream of electrons that emanate from the cathode filament, and the Tube is the large glass vacuum (otherwise known as your picture screen) that houses the entire thing. It’s that simple.

Now it’s time for the complicated part.

The cathode, or negative-charged heated filament, creates negative charged electrons in a stream (the Ray part of the CRT, remember?). These electrons are compacted by a focusing anode terminal and an accelerating anode terminal, which causes the electron stream to be compacted into a tight beam travelling at a high rate of speed.

This electron beam is then directed at the inside of the flat screen (your viewing screen) at the opposite end of the tube. The flat area is coated in a thin layer of phosphor, a substance that lights up when it is struck by the electron stream.

The inside of the picture tube is also given a thin coating of conductive material, ensuring that all those electrons have somewhere to go after they hit the phosphors.

Now, if this was all there was to your CRT, all you would see when you turned the television on would be a tiny little circle of light, much like that tiny light in the center of old television sets when you turn them on or off. The electron beam needs to cross every pixel of phosphor on the screen to show an effective picture, and it does this with the help of steering coils.

A steering coil is a series of copper wires wrapped around the CRT to make an electromagnet. These electromagnets can create two separate electromagnetic fields within the CRT, one vertical and the other horizontal.

The electrode beam can be manipulated by changing the strength of these electromagnetic fields because it carries a negative charge. Using an X and Y axis style grid, the beam can be moved to point at any part of the picture screen.

Monochrome

For the first 50 years of television, the most common television sets in people’s homes were black and white sets. This was because black and white was the technology standard of the day, while colour sets were unreliable at best. During the 1940s and 1950s, even if one could afford a colour television, it was disheartening to turn it on and realize that most broadcasts were black and white transmissions only.

This is not the case today. In the age of High Definition Television (like Sony HDTV) and digital broadcasting, black and white television screens have been relegated to mostly cheap security video monitors and camping televisions.

There may always be a market for black and white or monochrome television technology simply because it is so easy use (by television standards, at any rate).

The CRT in a monochrome television is pretty much the same as a colour television, but with a few important exceptions. Where the phosphors of a colour set are bunched in groups of blue, green, and red, the phosphors in a monochrome set are all white. That means that when an electron beam is directed at them they give off white light. To get black, the phosphors are simply switched off.

This balance of white phosphors and black ones are able to create the many soft “greys” of a monochrome set. By manipulating the amount of light the white phosphors give off and which phosphors are turned off, a monochrome CRT can reproduce a perfect black and white version of any image.

Colour

In a colour CRT, things work just a little differently. Instead of a single electron beam, as in a monochrome CRT, there are actually three beams. Since the phosphors are grouped into blue, green, and red pixels (take a close up look at your television screen and you can see them), the colour CRT is constructed to direct beams at each group.

By varying the intensity of the three beams or turning one or more of them off completely, thousands of colour schemes can be achieved. When all three of the pixels are struck simultaneously with the same level of power, then the pixels mix to form white light. When they are all shut off, a black effect is achieved.

In both colour and monochrome CRTs, the phosphor pixels are separated by a device known as a shadow mask. A shadow mask is simply a filter devised to keep the electron beams from spilling into other pixel groups. A shadow mask is like a metal plate covered with rows of tiny holes. Each tiny hole lines up with a pixel grouping.

And They’re Off!

In standard televisions, these beams race across the picture screen, lighting up and combining phosphor colours as they go. They travel in a straight line from the left side of the screen to the right side of the screen, and when they reach the end they race back to the left side. Only this time they start at a slightly lower position, right underneath the original line.

This is known as a “Raster Scan”, and it continues in this pattern all the way down to the bottom of the screen. Then it goes back to the top left corner and starts again. When the beam is activating phosphors in a line it is on, and it switches off when it starts a new line or begins another pattern. The left to right movement is known as “horizontal retrace”, while the movement from the bottom to the top of the screen is known as “vertical retrace.”

Because these lines are tiny and spaced so close together, your brain blurs them into a single image.

The average television uses an interlacing technique where every other line is painted first, and then the remaining unpainted lines are completed on a second sweep. In this way the entire screen is covered in two sweeps and is completed 30 times a second.

Another pattern, known as a “Progressive Scan”, paints each line one after the other with no spaces, and completes the screen 60 times a second. At these speeds, your brain doesn’t see a series of still images spaced fractions of a second apart.

It sees a uniform, moving image.

As a side note, that high pitched whine that some people hear coming from their television is actually the broadcast signal, moving the electron beam across the screen at over 15,000 times a second!

Tune in and Drop Out

so you see how a picture is recreated in a Cathode Ray Tube, but how does it get to your television set?

Television broadcasting is based on a signal, much like radio. However, a monochrome television signal is comprised of three pieces, and a colour signal is comprised of four.


The different pieces of a television signal are:

* Intensity Information
Intensity information is used to tell the television how bright or dark the phosphors need to be at a given point.
* Horizontal Retrace Signals
Horizontal retrace signals tell the television when it is time to move back to the left side of the screen after is has completed a line.
* Vertical Retrace Signals
Vertical retrace signals occur in the broadcast signal 60 times per second, and tell the television to move the beam back from the bottom-right side to the top-left side so it can paint a new image.
* Chrominance Signal
A Chrominance Signal is added to a monochrome signal to add colour to the image. Essentially, it is a separate frequency that tells the television how to modulate the electron beams so that they will produce the right colour combination for each pixel grouping. This part of the signal is ignored by old monochrome televisions.


So, if you take these four parts, add another frequency modulation for sound, and a vestigial sideband, and you have a full television signal. Your television takes in all that information, interprets it, and turns it into your favourite programs. Sounds like a lot of work, right?

Now think about that effort going into all those annoying commercials you see on television. Sheesh!

This is the basic principle behind image reception for televisions, and all the signals you receive basically operate in this same fashion, from using an antenna to pick up the Saturday night hockey game to receiving satellite broadcasts on your high-definition widescreen television set.

A High Definition Future

The television industry has been lit up in the past few years with a growth of new broadcast and reception ideas. As we speak, high definition television and digital surround sound technology are quickly becoming the norm. With every passing day new markets and broadcast opportunities are opening up across the globe.

The advent of the internet is also doing for television what it has done for computers. It is a very real possibility that one day soon you will use your television set to watch sitcoms, rent movies or sporting events, do your groceries, check your mail, do on-line banking or surf the internet, or even order a pizza for supper.

The possibilities are endless. That may be the ultimate genius of television. More than just a tool for couch potatoes, it could one day be an integral part of how society runs.

How Television Works – Lights, Camera, Action

Many people simply take their television for granted. They just assume that when they turn it on, picture and sound appear like magic. When the channel gets snowy, they hit the side of the television to get it working again.

Amazingly, sometimes, it does.

But have you ever wondered how your favorite television program gets to your house from a broadcast station thousands of miles away? How about from a satellite dish? Just what is this technology that spends so much time entertaining and enlightening us that it could be considered a part of the family?

Take a minute to read this article, and what you find out about your television may surprise you.

How Does a Television Work

just as a radio and a telephone are devices for converting acoustic energy into electrical and vice versa, the television receives wirelessly transmitted electromagnetic waves and converts them into acoustic and light energy for viewing. Although the initial inspiration for the television existed as early as the 1830s, when inventor Michael Faraday demonstrated the relationship between light and electricity, the television did not become practical for mass-production until more than a century later - in the 1940s. The history of the television is marked by a series of devices that were progressively more effective at sending or receiving wireless electronic patterns containing light and sound information.

The first "televisions", like the first computers, made use of mechanical media to store information. In 1883, German engineer Paul Nipkow introduced a device using a rotating scanning disk that was perforated with small holes in a spiral pattern. Images could be "broken down" through the use of a sensitize photocell placed behind the spinning disk. The photocell then transmitted the image as a series of electrical impulses to a receiver, where the electricity could again be converted into light and shined through an identical spinning disk, which reconstituted the initial image - but at a very poor level of resolution. Many variants and imitations of this mechanical TV system were invented and used by hobbyists and electronics enthusiasts throughout the next quarter-century. Incremental improvements occurred, but the mechanical television primarily remained a curiosity impractical for mass use.

The modern television was only made possible with the scientific advances of the early 1900s, which included significant developments in radio, x-rays, and physics. Wireless transmission of sound became possible with the invention of the radio at the turn of the century. But the critical component necessary for the high-fidelity projection of reconstituted light information was the cathode-ray tube, originally used to produce x-rays for medical purposes. In 1906, Karl Braun found that manipulating the electron stream of the cathode-ray tube with a magnetic field was possible. Less than a year later, it was suggested that the cathode-ray tube be used as a receiving device for images. Russian scientist Boris Rosing quickly created such a cathode-ray tube and encouraged further development of the technology.

Rosing's student, Vladimir K. Zworykin, migrated to the United States after WWI and created the "iconoscope", a device that scanned an image with an electron beam and converted it into electronic signals for transmission. To minimize the amount of data needing to be sent, he fed the image through a "mosaic" - a plate covered with microscopic photosensitive dots we now know as "pixels". The information was then broadcasted and received by a device that ran the process in reverse, using the cathode-ray tube to project images far more quickly and effectively than the mechanical televisions of the past. The first incarnation of the modern TV was born. It was successfully demonstrated in a public context in 1929.

The next two decades saw a series of advances that made TV easy and practical. Televisions did not begin to enter the family home until the late 40s and early 50s. NBC of New York was the first broadcaster to utilize the new technology. Technological improvements in 1945 resulted in the familiar black-and-white television. Color television arrived in 1953. Basic television technology has not changed substantially until recently, with the introduction of HDTV (High Definition Television). Today the average American watches between two and six hours of television per day.

It has probably washed your clothes hundreds of times, but have you ever wondered what's inside that trusty washing machine?
How does it spin the clothes so fast without leaking water? Why is it so heavy? How does the agitator switch directions? In this edition of HowStuffWorks, we'll venture inside a washing machine to answer all of these

questions and more.

We'll start by explaining how the washing machine cleans clothes, then we'll take a look at how ­the machine is put together. We'll look at the plumbing, the drive mechanism and the controls.

Cleaning Clothes

­Operating a washing machine is pretty simple:

* There are a few things to decide before you start your load of clothes, such as how big the load is (small, medium, large, extra large), what temperature the water will be for the wash and rinse cycles (cold/cold, warm/cold, warm/warm, hot/cold), how the machine should agitate (delicate, knit, permanent press, heavy), and how long the cycles should last (number of minutes, based on how soiled your clothes are).

* After you fill the tub with clothes, the machine fills the tub with water, and then stirs the clothes around using an agitator.

* After some time agitating, the washer drains the water and then spins the clothes to remove most of the water. Then, it refills, and agitates the clothes some more to rinse out the soap. Then it drains and spins again.

inside a Washing Machine

If we take a look under the washing machine, you'll see what makes it so heavy

Yes, that is in fact a block of concrete in the picture above. The concrete is there to balance the equally heavy electric motor, which drives a very heavy gearbox that is attached to the steel inner tub. There are lots of heavy components in a washing machine.

The washing machine has two steel tubs. The inner tub is the one that holds the clothes. It has an agitator in the middle of it, and the sides are perforated with holes so that when the tub spins, the water can leave.

The outer tub, which seals in all the water, is bolted to the body of the washer. Because the inner tub vibrates and shakes during the wash cycle, it has to be mounted in a way that lets it move around without banging into other parts of the machine.

The inner tub is attached to the gearbox, which is attached to the black metal frame you see in the picture above. This frame holds the motor, gearbox and the concrete weight.

The picture above shows just the black metal frame, without the tub or gearbox. The cable that you see on the left side of the picture is the other end of the same cable that you see on the right side. There are a total of three pulleys, so that if one side of the frame moves up, the other side moves down. This system supports the weight of the heavy components, letting them move in such a way as not to shake the entire machine.

But, if all of these parts are just hanging by cables, why don't they swing around all the time?

A laundry machine has a damping system that uses friction to absorb some of the force from the vibrations.
In each of the four corners of the machine is a mechanism that works a little like a disc brake. The part attached to the washer frame is a spring. It squeezes two pads against the metal plate that is attached to the black frame. You can see where the pads have polished the plate from movement during vibration.

Plumbing

The plumbing on the washing machine has several jobs:

* It fills the washing machine with the correct temperature of water.
* It recirculates the wash water from the bottom of the wash tub back to the top (during the wash cycle).
* It pumps water out the drain (during the spin cycle).

The washing machine has hookups for two water lines on the back, one for hot water and one for cold. These lines are hooked up to the body of a solenoid valve.

The image above shows the back and front of the solenoid valve. You can see that there are two valves, but they feed into a single hose. So depending on the temperature selected, either the hot valve, the cold valve or both valves will open.

Before the hose releases water into the wash tub, it sends it through an anti-siphon device.


This device prevents wash water from being sucked back into the water supply lines, possibly contaminating the water for your house or even your neighborhood. You can see that the white, plastic device has a big opening that allows air in. The water from the hose shoots into the device and turns downward, exiting through the tube on the other end. But while it is inside the device, it is open to the atmosphere. This means that if there were suction on the water supply line, it could not possibly suck any water in from the washing machine; it would get only air.


The picture above shows the inlet through which water enters the washing machine. The nozzle to the right is an overflow port, which is connected to a pipe that dumps water out the bottom of the washing machine (onto your floor), instead of letting it overflow the tub and possibly get the motor wet.

pump

The rest of the plumbing system, the part that recirculates the water and the part that drains it, involves the pump.


In the picture above, you can see how the pump is hooked up. This pump is actually two separate pumps in one: The bottom half of the pump is hooked up to the drain line, while the top half recirculates the wash water. So how does the pump decide whether to pump the water out the drain line or back into the wash tub?

This is where one of the neat tricks of the washing machine comes in: The motor that drives the pump can reverse direction. It spins one way when the washer is running a wash cycle and recirculating the water; and it spins the other way when the washer is doing a spin cycle and draining the water.

Let's take a closer look at the pump:

If you look carefully, you can see the vanes of the bottom layer of the pump. When water enters the pump's inlet, these vanes, or fins, push the water around and force it back out of the pump by way of the outlet. This type of pump can operate in both directions -- which port is the inlet and which is the outlet depends on which direction the pump is spinning in.

Take another look at the pump. If the pump spins clockwise, the bottom pump sucks water from the bottom of the wash tub and forces it out the drain hose, and the top pump tries to suck air from the top of the wash tub and force it back up through the bottom, so that no water recirculation takes place.

If the pump spins counter-clockwise, the top pump sucks water from the bottom of the tub and pumps it back up to the top, and the bottom pump tries to pump water from the drain hose back into the bottom of the tub. There is actually a little bit of water in the drain hose, but the pump doesn't have the power to force much of it back into the tub.

Take another look at the drain hose in the picture above -- notice how it loops all the way to the top of the machine before heading back down to the drain. Because one end of the hose is hooked up to the bottom of the tub and the other is open to the atmosphere, the level of water inside the drain hose will be the same as the level inside the tub. If the drain hose didn't go all the way up to the top of the machine, then the tub could never fill all the way. As soon as the water reaches the bend in the hose, it goes out the drain.

There are also times when the pump does not spin at all. The washer just churns the water that is in the tub without recirculating it. For this situation, the pump is hooked up to the motor by way of a clutch

In this picture, you see the flexible coupling that hooks the clutch up to the pump. The coupling is needed because the motor and clutch are mounted to the frame, which can move freely with the inner tub, whereas the pump is mounted to the stationary outer tub.

On the bottom of the clutch is a set of four teeth. When the electromagnet engages, it raises an arm up into these teeth, which stops them from rotating. Once the teeth are stopped, the clutch starts to engage. After a couple of revolutions, it locks up to the motor shaft and the pump starts to turn with the motor.

Drive Mechanism

The drive mechanism on a washing machine has two jobs:

* To agitate the clothes, moving them back and forth inside the wash tub.
* To spin the entire wash tub, forcing the water out.

There is a really cool gearbox that handles these two jobs, and it uses the same trick as the pump does. If the motor spins in one direction, the gearbox agitates; if it spins the other way, the gearbox goes into spin cycle.

First, let's see how everything is hooked up:

In this picture, the frame has been removed. You can see the pump mounted to the outer tub, and the gearbox, which holds the inner tub. A piece of rubber seals the outer tub to the gearbox. The inner tub is mounted to the gearbox on the other side of the seal.

The inner tub has been removed from the outer tub in the picture above. It is resting on the gearbox, and the plastic agitator is visible in the center of the tub.


Here you can see the top side of the gearbox with the seal cut and the inner tub removed. The inner tub bolts to the three holes in the flange of the gearbox. You can see from the buildup of crud on top of the gearbox that it has been exposed to wash water for many years. A hollow tube extends from the center of the gearbox. Inside this tube is a splined shaft -- the spline on top of the shaft hooks into the plastic agitator.

How does a jet engine work

Jet engines move the airplane forward with a great force that is produced by a tremendous thrust and causes the plane to fly very fast.

All jet engines, which are also called gas turbines, work on the same principle. The engine sucks air in at the front with a fan. A compressor raises the pressure of the air. The compressor is made up of fans with many blades and attached to a shaft. The blades compress the air. The compressed air is then sprayed with fuel and an electric spark lights the mixture. The burning gases expand and blast out through the nozzle, at the back of the engine. As the jets of gas shoot backward, the engine and the aircraft are thrust forward.

The image below shows how the air flows through the engine. The air goes through the core of the engine as well as around the core. This causes some of the air to be very hot and some to be cooler. The cooler air then mixes with the hot air at the engine exit area.

What is Thrust?

Thrust is the forward force that pushes the engine and, therefore, the airplane forward. Sir Isaac Newton discovered that for "every action there is an equal and opposite reaction." An engine uses this principle. The engine takes in a large volume of air. The air is heated and compressed and slowed down. The air is forced through many spinning blades. By mixing this air with jet fuel, the temperature of the air can be as high as three thousand degrees. The power of the air is used to turn the turbine. Finally, when the air leaves, it pushes backward out of the engine. This causes the plane to move forward.

Parts of a Jet Engine

an - The fan is the first component in a turbofan. The large spinning fan sucks in large quantities of air. Most blades of the fan are made of titanium. It then speeds this air up and splits it into two parts. One part continues through the "core" or center of the engine, where it is acted upon by the other engine components.

The second part "bypasses" the core of the engine. It goes through a duct that surrounds the core to the back of the engine where it produces much of the force that propels the airplane forward. This cooler air helps to quiet the engine as well as adding thrust to the engine.

Compressor - The compressor is the first component in the engine core. The compressor is made up of fans with many blades and attached to a shaft. The compressor squeezes the air that enters it into progressively smaller areas, resulting in an increase in the air pressure. This results in an increase in the energy potential of the air. The squashed air is forced into the combustion chamber.

Combustor - In the combustor the air is mixed with fuel and then ignited. There are as many as 20 nozzles to spray fuel into the airstream. The mixture of air and fuel catches fire. This provides a high temperature, high-energy airflow. The fuel burns with the oxygen in the compressed air, producing hot expanding gases. The inside of the combustor is often made of ceramic materials to provide a heat-resistant chamber. The heat can reach 2700°.

Turbine - The high-energy airflow coming out of the combustor goes into the turbine, causing the turbine blades to rotate. The turbines are linked by a shaft to turn the blades in the compressor and to spin the intake fan at the front. This rotation takes some energy from the high-energy flow that is used to drive the fan and the compressor. The gases produced in the combustion chamber move through the turbine and spin its blades. The turbines of the jet spin around thousands of times. They are fixed on shafts which have several sets of ball-bearing in between them.

Nozzle - The nozzle is the exhaust duct of the engine. This is the engine part which actually produces the thrust for the plane. The energy depleted airflow that passed the turbine, in addition to the colder air that bypassed the engine core, produces a force when exiting the nozzle that acts to propel the engine, and therefore the airplane, forward. The combination of the hot air and cold air are expelled and produce an exhaust, which causes a forward thrust. The nozzle may be preceded by a mixer, which combines the high temperature air coming from the engine core with the lower temperature air that was bypassed in the fan. The mixer helps to make the engine quieter.

The First Jet Engine - A Short History of Early Engines

Sir Isaac Newton in the 18th century was the first to theorize that a rearward-channeled explosion could propel a machine forward at a great rate of speed. This theory was based on his third law of motion. As the hot air blasts backwards through the nozzle the plane moves forward.

Henri Giffard built an airship which was powered by the first aircraft engine, a three-horse power steam engine. It was very heavy, too heavy to fly.

In 1874, Felix de Temple, built a monoplane that flew just a short hop down a hill with the help of a coal fired steam engine.

Otto Daimler, in the late 1800's invented the first gasoline engine.

In 1894, American Hiram Maxim tried to power his triple biplane with two coal fired steam engines. It only flew for a few seconds.

The early steam engines were powered by heated coal and were generally much too heavy for flight.

American Samuel Langley made a model airplanes that were powered by steam engines. In 1896, he was successful in flying an unmanned airplane with a steam-powered engine, called the Aerodrome. It flew about 1 mile before it ran out of steam. He then tried to build a full sized plane, the Aerodrome A, with a gas powered engine. In 1903, it crashed immediately after being launched from a house boat.

In 1903, the Wright Brothers flew, The Flyer, with a 12 horse power gas powered engine.

From 1903, the year of the Wright Brothers first flight, to the late 1930s the gas powered reciprocating internal-combustion engine with a propeller was the sole means used to propel aircraft.

It was Frank Whittle, a British pilot, who designed the first turbo jet engine in 1930. The first Whittle engine successfully flew in April, 1937. This engine featured a multistage compressor, and a combustion chamber, a single stage turbine and a nozzle.

The first jet airplane to successfully use this type of engine was the German Heinkel He 178. It was the world's first turbojet powered flight. General Electric for the US Army Air Force built the first American jet plane. It was the XP-59A experimental aircraft.

Types of Jet Engines

Turbojets

The basic idea of the turbojet engine is simple. Air taken in from an opening in the front of the engine is compressed to 3 to 12 times its original pressure in compressor. Fuel is added to the air and burned in a combustion chamber to raise the temperature of the fluid mixture to about 1,100°F to 1,300° F. The resulting hot air is passed through a turbine, which drives the compressor. If the turbine and compressor are efficient, the pressure at the turbine discharge will be nearly twice the atmospheric pressure, and this excess pressure is sent to the nozzle to produce a high-velocity stream of gas which produces a thrust. Substantial increases in thrust can be obtained by employing an afterburner. It is a second combustion chamber positioned after the turbine and before the nozzle. The afterburner increases the temperature of the gas ahead of the nozzle. The result of this increase in temperature is an increase of about 40 percent in thrust at takeoff and a much larger percentage at high speeds once the plane is in the air.

The turbojet engine is a reaction engine. In a reaction engine, expanding gases push hard against the front of the engine. The turbojet sucks in air and compresses or squeezes it. The gases flow through the turbine and make it spin. These gases bounce back and shoot out of the rear of the exhaust, pushing the plane forward.

Turboprops

A turboprop engine is a jet engine attached to a propeller. The turbine at the back is turned by the hot gases, and this turns a shaft that drives the propeller. Some small airliners and transport aircraft are powered by turboprops.

Like the turbojet, the turboprop engine consists of a compressor, combustion chamber, and turbine, the air and gas pressure is used to run the turbine, which then creates power to drive the compressor. Compared with a turbojet engine, the turboprop has better propulsion efficiency at flight speeds below about 500 miles per hour. Modern turboprop engines are equipped with propellers that have a smaller diameter but a larger number of blades for efficient operation at much higher flight speeds. To accommodate the higher flight speeds, the blades are scimitar-shaped with swept-back leading edges at the blade tips. Engines featuring such propellers are called propfans.

Turbofans

A turbofan engine has a large fan at the front, which sucks in air. Most of the air flows around the outside of the engine, making it quieter and giving more thrust at low speeds. Most of today's airliners are powered by turbofans. In a turbojet all the air entering the intake passes through the gas generator, which is composed of the compressor, combustion chamber, and turbine. In a turbofan engine only a portion of the incoming air goes into the combustion chamber. The remainder passes through a fan, or low-pressure compressor, and is ejected directly as a "cold" jet or mixed with the gas-generator exhaust to produce a "hot" jet. The objective of this sort of bypass system is to increase thrust without increasing fuel consumption. It achieves this by increasing the total air-mass flow and reducing the velocity within the same total energy supply.

Turboshafts

This is another form of gas-turbine engine that operates much like a turboprop system. It does not drive a propellor. Instead, it provides power for a helicopter rotor. The turboshaft engine is designed so that the speed of the helicopter rotor is independent of the rotating speed of the gas generator. This permits the rotor speed to be kept constant even when the speed of the generator is varied to modulate the amount of power produced.

Ramjets

The most simple jet engine has no moving parts. The speed of the jet "rams" or forces air into the engine. It is essentially a turbojet in which rotating machinery has been omitted. Its application is restricted by the fact that its compression ratio depends wholly on forward speed. The ramjet develops no static thrust and very little thrust in general below the speed of sound. As a consequence, a ramjet vehicle requires some form of assisted takeoff, such as another aircraft. It has been used primarily in guided-missile systems. Space vehicles use this type of jet.