An internal-combustion engine goes through four strokes: intake, compression, combustion (power), and exhaust. As the piston moves during each stroke, it turns the crankshaft. Of the different techniques for recovering the power from the combustion process, the most important so far has been the four-stroke cycle, a conception first developed in the late 19th century. The four-stroke cycle is illustrated in the . With the inlet valve open, the piston first descends on … How stuff works.com Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle , in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated in Figure 1 . They are: Intake stroke Compression stroke Combustion stroke Exhaust stroke You can see in the figure that a device called a piston replaces the potato in the potato cannon . The piston is connected to the crankshaft by a connecting rod . As the crankshaft revolves, it has the effect of &quot;resetting the cannon.&quot; Here's what happens as the engine goes through its cycle: The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work. (Part 1 of the figure) Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. (Part 2 of the figure) When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down. (Part 3 of the figure) Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. (Part 4 of the figure) The potato cannon uses the basic principle behind any reciprocating internal combustion engine: If you put a tiny amount of high-energy fuel (like gasoline) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. You can use that energy to propel a potato 500 feet. In this case, the energy is translated into potato motion. You can also use it for more interesting purposes. For example, if you can create a cycle that allows you to set off explosions like this hundreds of times per minute, and if you can harness that energy in a useful way, what you have is the core of a car engine! Now the engine is ready for the next cycle, so it intakes another charge of air and gas. Notice that the motion that comes out of an internal combustion engine is rotational , while the motion produced by a potato cannon is linear (straight line). In an engine the linear motion of the pistons is converted into rotational motion by the crankshaft. The rotational motion is nice because we plan to turn (rotate) the car's wheels with it anyway. Now let's look at all the parts that work together to make this happen, starting with the cylinders.
Scuderi Split-Cycle Hybrid Engine First a recap of the basics: The engine employs pistons and connecting rods turning a crankshaft, just like 99.9 percent of the engines on the road, but here half of them breathe in and compress the air, while the other pistons combust and exhaust the mixture. The basic engine's overall efficiency is estimated at 43 percent (up from about 33 percent for ordinary engines), with a compressed-air hyrbrid system boosting that to over 50 percent. Why split the cycles? The primary benefit is that now the cylinder designs can be optimized for the two fairly different tasks of compressing and combusting. Intake stroke How do the compression and combustion cylinders differ? By altering the bore and stroke slightly, it's possible to have very different compression and expansion ratios--one of the holy grails of engine performance and efficiency. The compression cylinders can have very high compression, because there is never any fuel in them to detonate. A larger bore also permits a natural supercharging effect of compressing a larger volume of air than the combustion chamber displaces. (Air pressures of up to 725 psi have been suggested.) A longer stroke on the combustion cylinder extracts more power from the charge. In this way, the Split-Cycle concept mimics the Miller-cycle. How does the air get from one cylinder to the other? There's a short passageway connecting the cylinders. A conventional cam-actuated valve admits air to the combustion chamber, but a pressure-activated disk-type valve (picture a heavy-duty version of the reed-valves in your Briggs & Stratton) admits air into the passageway from the compression chamber and prevents it from leaking back into the intake cylinder. Compression stroke When and where is the fuel injected? Fuel is injected directly into the cylinder just as the valve opens. The highly-compressed air whooshes in so quickly and atomizes the injected fuel so thoroughly that the spark is fired to ignite it 11 to 15 degrees after top-dead-center, even when running lean mixtures for increased efficiency. How on earth can the flame burn completely with such late ignition? Conventional wisdom holds that, particularly at higher engine speeds, the spark must be advanced to light the mixture well in advance of top-dead-center in order to have enough time to fully burn the mixture before the bottom of the piston's stroke. Scuderi's modeling suggests that the high air pressures and turbulence serve to atomize the fuel so thoroughly that the mixture burns in about half the time it takes in a conventional engine. Start Combustion What about emissions? Lighting the mixture while the piston is still compressing it creates extreme heat and pressures that cause the formation of NOx, which ordinary engines combat by recirculating exhaust gasses and using a three-way catalyst. By lighting the mixture when the piston is already moving down, the flame front actually cools as it propagates, reducing the production of NOx in the cylinder by a claimed 80%. It's not low enough to meet current standards, but it requires less aftertreatment and no exhaust-gas recirculation is needed.
How are Cars Powered? How do we get from the gas pump to ...
How are Cars Powered?
How do we get from the gas pump to driving down the highway…
Gasoline & Internal Combustion Engines http://www.britannica.com/eb/art-89315/An-internal-combustion-engine-goes-through-four-strokes-intake-compression Put high energy fuel in a small area and ignite it.
BioDiesel <ul><li>Biodiesel is usually made from plant oils or animal fat through a series of chemical reactions. It is both non-toxic and renewable. Because biodiesel essentially comes from plants and animals, the sources can be replenished through farming and recycling. </li></ul><ul><li>Biodiesel is safe and can be used in diesel engines with little or no modification needed. Although biodiesel can be used in its pure form, it is usually blended with standard diesel fuel. Blends are indicated by the abbreviation Bxx, where xx is the percentage of biodiesel in the mixture. For example, the most common blend is B20, or 20 percent biodiesel to 80 percent standard. So, B100 refers to pure biodiesel. </li></ul>http://auto.howstuffworks.com/biodiesel.htm
E85 <ul><li>The number of models that can run on the E85 ethanol is at an all time high. Choices include cars, minivans, SUVs, and pickup trucks. General Motors leads the industry in E85 ethanol-capable vehicles, with more than a dozen models for 2007. Chrysler, Dodge, Jeep and Ford also field a selection, with Mercedes-Benz and Nissan represented as well. </li></ul><ul><li>It's this flexibility that gives them the nickname, flex-fuel vehicles. E85 ethanol fuel costs about the same per gallon as conventional 87-octane gasoline. </li></ul><ul><li>E85 is shorthand for a blend of combustible motor-vehicle fuel that's 85 percent ethanol and 15 percent conventional unleaded gasoline. Ethanol is derived from plant material, corn mostly. Because its raw materials come mostly from U.S. farms and are distilled in U.S. refineries, ethanol is touted as a renewable energy source that has the potential to reduce America's dependence on foreign oil. </li></ul>
Hydrogen Powered <ul><li>It's sleek. It's aerodynamic. It's environmentally friendly. BMW's H2R (Hydrogen Record Car) is powered entirely by the clean-burning process of liquid-hydrogen combustion, and this next-generation racecar has already set speed records in its class. </li></ul>
How does H 2 power a car? <ul><li>A Hydrogen-Fueled Car </li></ul><ul><li>The use of hydrogen as a fuel in motor vehicles offers several advantages over traditional fossil fuels: </li></ul><ul><li>There exists an unlimited supply of hydrogen -- hydrogen is the most abundant element in the universe and the tenth most abundant element on Earth. </li></ul><ul><li>Hydrogen is renewable -- When hydrogen reacts with oxygen, the by-product is water (H2O), which can then be hydrolyzed (broken up into its component parts) to yield more hydrogen. </li></ul><ul><li>Hydrogen is clean-burning -- Unlike the burning of fossil fuels, hydrogen combustion does not produce any destructive environmental pollutants. </li></ul><ul><li>Hydrogen weighs less and generates more power than hydrocarbon-based fuels. </li></ul><ul><li>Hydrogen burns faster (and at a lower temperature) than conventional gasoline. </li></ul>http://auto.howstuffworks.com/bmw-h2r1.htm