uses of diesel engines
Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. By compressing air rather than using an air-fuel mixture, the diesel engine is not limited by the preignition problems that plague high-compression spark-ignition engines. Thus, higher compression ratios can be achieved with diesel engines than with the spark-ignition variety; commensurately, higher theoretical cycle efficiencies, when compared with the latter, can often be realized. If you’re considering buying a new automobile, compare the pros and cons of diesel-powered vehicles. At first the fuel is burned in a nearly constant-volume process while the piston is near top dead centre. There are, however, a few higher-pressure systems. Black Friday Sale! PRO: Diesel engines are built more ruggedly to withstand the rigors of higher compression. The fuel is introduced under high pressure either into a precombustion chamber or directly into the piston-cylinder combustion chamber. The typical sequence of cycle events in a four-stroke diesel engine involves a single intake valve, fuel-injection nozzle, and exhaust valve, as shown here. The power stroke includes both the constant-pressure process during combustion and the expansion of the hot products of combustion after fuel injection ceases. Diesel technology is constantly being improved. CON: Although diesel fuel is considered more efficient because it converts heat into energy rather … Both two-stroke and four-stroke engine designs can be found among engines with bores (cylinder diameters) less than 600 mm (24 inches). Government pressure to produce low-emission diesel engines for passenger vehicles, trucks, buses, and farm and construction equipment has resulted not only in low-sulfur diesel fuels but also specialized catalytic converters, advanced filters, and other devices to cut down or destroy toxic emissions. As the piston moves away from this position, fuel injection is continued, and the combustion process then appears as a nearly constant-pressure process. The most outstanding feature of the diesel engine is its efficiency. It is preferable to use a liquid-cooled generator as it is quiet in operation and has evenly controlled temperature. The U.S. military uses diesel fuel in tanks and trucks because diesel fuel is less flammable and less explosive than other fuels. Diesel engine, any internal-combustion engine in which air is compressed to a sufficiently high temperature to ignite diesel fuel injected into the cylinder, where combustion and expansion actuate a piston. The combustion process in a diesel engine is heterogeneous—that is, the fuel and air are not premixed prior to initiation of combustion. Since the entire combustion process is controlled by fuel injection, injection must begin at the correct piston position (i.e., crank angle). Engine work is obtained during the power stroke. Fuel sprayed into air that has a temperature higher than the “auto-ignition” temperature of the fuel spontaneously reacts with the oxygen in the air and burns. Diesels also can deliver as much or more fuel economy than traditional gasoline-electric hybrids, depending on the models involved and whatever rapidly developing automotive technology achieves. Even if the price goes up, diesel fuel would have to be 25 to 30 percent more expensive than gas to erase the cost advantage of a diesel engine’s greater fuel efficiency. Engines with bores of greater than 600 mm are almost exclusively two-stroke cycle systems. Diesel engines can either be two cycle or four cycle and are chosen depending on mode of operation. Cleaner diesel fuels no longer require you to bleed excess water out of the system, but many vehicles still have water separators that need to be emptied manually. CON: Although diesel fuel is considered more efficient because it converts heat into energy rather than sending the heat out the tailpipe as gas-powered vehicles do, it doesn’t result in flashy high-speed performance. What’s more, diesel-powered trucks, SUVs, and cars also can out-tow gas-powered vehicles while still delivering that improved fuel economy. Mercedes-Benz holds the longevity record with several vehicles clocking more than 900,000 miles on their original engines! It should be noted that for a given compression ratio the theoretical efficiency of the spark-ignition engine is greater than that of the compression-ignition engine; however, in practice it is possible to operate compression-ignition engines at compression ratios high enough to produce efficiencies greater than those attainable with spark-ignition systems. CON: Diesels still need regular maintenance to keep them running. Consider these facts to help you decide between an engine powered by diesel fuel and a gasoline-powered one: PRO: Diesels get great mileage. Updates? Consequently, in the small-engine category, consumer acceptance is low. Consequently, they usually go much longer than gas-powered vehicles before they require major repairs. Coauthor of. Diesel engines are also less likely to stall than gasoline-fueled engines. The principal drawback of diesel engines is their emission of air pollutants. Let us know if you have suggestions to improve this article (requires login). The compressed air becomes heated sufficiently to ignite the fuel. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. Diesel fuel is also used in diesel engine generators to generate electricity. The diesel engine gains its energy by burning fuel injected or sprayed into the compressed, hot air charge within the cylinder. Furthermore, diesel engines do not rely on throttling the intake mixture to control power. A diesel engine is started by driving it from some external power source until conditions have been established under which the engine can run by its own power. A pplication of Diesel Engines. It converts the chemical energy stored in the fuel into mechanical energy, which can be used to power freight trucks, large tractors, locomotives, and marine vessels. This places much emphasis on injector nozzle design, especially in direct-injection engines. Diesel fuel is also used for commercial trucks, home and industrial generators, and heating oil, so as demand for diesel passenger vehicles grows, the price of diesel fuel is likely to continue to rise because of competition from those other users. In some ways, a gasoline-powered engine is like a racehorse — high-strung, fiery, and fast — whereas a diesel engine is more like a workhorse — slower, stronger, and more enduring.
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