|MadSci Network: Engineering|
Greetings: There are many types of engines for doing work and they all have one thing in common, they convert high temperature liquid, solid or gas materials into low temperature liquid, solid or gas materials and they extract power to they do useful work in the process. These processes are based in the laws of THERMODYNAMICS. Generally, the greater the difference between the high and low temperatures, the greater will be the useful power output and efficiency of the engine. Engines that run on gasoline, methanol and diesel fuels are called internal combustion engines (ICE) and they use the rapid explosion, heating and expansion of a compressed fuel air mixture in an enclosed cylinder to drive a piston downward during the power stroke. Currently internal combustion engines have a number of advantages over external combustion engines with the explosive fuel being part of the heating process being a major advantage. Steam engines are external combustion engines (ECE) and they use an external fuel combustion process to convert liquid water to high-pressure, high-temperature steam in a boiler. The high-pressure, high temperature steam is then transferred into the cylinder to drive the piston during the power stroke. However, a steam-generating boiler and heater also have to be added to the vehicle to run an ECE engine. Because steam engines run at lower pressure and temperature differences than ICEs, they must use larger diameter pistons (greater volumes of gas) to produce the same amount of drive power and thus they are less efficient. The inability to rapidly build up steam pressure from a cold start has always been one of the drawbacks of steam engines and a number of flash heating concepts have been tried and proposed. See the laser flash heater proposal in the Mad Science archives (Rick Hall, Wed Aug 18 12:56:52 1999. Engineering: Re: Use laser(s) to flash heat water in a small tube(s) to power a car? ) As you suggest, fixed rate of combustion processes for steam boilers and also for hybrid electric vehicles can be designed to generate far less pollution that current ICEs. Here in California, to reduce air pollution, a number of manufacturing plants now use pure oxygen instead of air with petroleum based fuels for their ICEs and heating systems. This combustion process eliminates the harmful nitrogen compounds released when using air as an oxidizer. However, the oxygen must be stored in large cryogenic tanks. The hydrogen/oxygen fueled engine and or boiler would be one of the cleanest engines with water and steam being the residue from the process. One of the problems with these engines is to safely store hydrogen fuel and oxygen oxidizer. In California we have a number of hydrogen fueled busses operating which use the oxygen in air as an oxidizer. They are very clean but do produce some nitrogen compounds. The busses use large hydrogn fuel tanks filled with hydrogen absorbing materials such as nickle hydride to reduce the pressure in the fuel tanks. Hydrogen/oxygen fuel cells that can generate electricity in a clean process is another concept being studied for electric vehicles. Currently, cost effectively generating, storing and delivering hydrogen gas is an important part of the fuel cell concept being studied. A search of the Mad Science archives for fuel cells and hydrogen will return a large number of questions and answers that address the problems and potential of using these environmentally clean processes for motor vehicles, spacecraft and for aircraft. Currently, research on fuel cells, new batteries and hybrid vehicles are the concepts most favored by the world’s automotive industry for future clean vehicles. The infrastructure to deliver the fuel to the consumer is also an important part of the process. Best regards, Your Mad Scientist Adrian Popa
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