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diesel engine

diesel engine, type of internal-combustion engine invented by the German engineer Rudolf Diesel and patented by him in 1892. Although his engine was designed to use coal dust as fuel, the diesel engine now burns fuel oil.

The diesel engine does not require a large water supply or a long warming-up period and is highly efficient in converting heat energy into work. Diesels are widely used in both stationary and mobile installations where the power required is between that furnished by the gasoline engine and that of the steam turbine and where the relatively high initial cost can be written off over a long period. For example, diesels having capacities of 100 to 5,000 hp are employed on industrial and municipal electric generators and on continuously operating pumps (e.g., on oil pipelines). Moreover, they occupy relatively little space compared with steam units, since no boiler is needed—a factor of importance aboard ships.

The diesel engine differs from the gasoline engine in that the ignition of fuel is caused by compression of air in its cylinders instead of by a spark: the high compression ratio allows the air in the cylinder to become hot enough to ignite the fuel. Because of the high temperatures of operation, a diesel engine must be water-cooled. The construction of the diesel engine is heavier than that of the gasoline engine; there are usually three or more cylinders (supported on a framework and bedplate) and a heavy flywheel. The cylinders are set to work alternately to give a smooth-turning effect, and the flywheel contributes further to smooth action.

There are two classes of diesel engines. In the two-stroke, or two-cycle, type there is a complete cycle of operation in every two strokes of a piston. This type of engine requires a supply of compressed air for operating and for starting. In the four-stroke, or four-cycle, type the first downstroke of the piston draws in air, which is compressed on the upstroke to about 500 lb per sq in. (35 kg per sq cm). At the top of the stroke a jet of oil is sprayed in through a fuel injector. The oil is ignited and the rapid expansion of the gas created by the explosion forces the piston down in the working, or firing, stroke. The next upstroke drives the waste gases out through the exhaust valve, and the cycle is complete.

The speed and power of the diesel are controlled by varying the amount of fuel injected into the cylinder, not the amount of air admitted as in the gasoline engine. Small and medium-size ships may have several diesels producing as much as 50,000 hp. Heavy-duty land transports such as trains, trucks, buses, and tractors are often diesel-powered. Some automobiles—in Europe, roughly half—use diesel engines, and even some airplanes have had diesel engines.

Diesel engines, although more fuel efficient than gasoline engines, have in the past generated more smog-producing combustion products (although they produce less greenhouse gases). This has restricted the sale of diesel-powered automobiles in states such as California where smog has been a significant problem. The introduction of ultra-low-sulfur diesel fuel in 2006, undertaken in part to encourage the development of improved emission control technology for diesel engines, has spurred the development of cleaner burning diesel engines for automobiles. New rules for diesel engines in 2009 required them to match the emissions standards set for gasoline engines.

See W. R. Nitske and C. M. Wilson, Rudolf Diesel (1965); A. W. Judge, High Speed Diesel Engine (1967); S. D. Haddad and N. Watson, ed., Design and Applications in Diesel Engineering (1984); L. R. Lilly, Diesel Engine Reference Book (1984).

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Diesel Engine

Diesel engine

A diesel engine is a type of internal-combustion engine developed by German engineer Rudolf Diesel (18581913) in the late nineteenth century. His original design called for the use of coal dust as fuel, but most modern diesel engines burn low-cost fuel oil. Whereas gasoline engines (found in the majority of present-day automobiles) use an electric spark to ignite the premixed fuel-air blend, diesel engines use compressed air to ignite the fuel.

In both gasoline and diesel engines, fuel is ignited in a cylinder, or chamber. Inside the sealed, hollow cylinder is a piston (a solid cylinder) that is attached at the bottom to a crankshaft. The movement of the piston up and down turns the crankshaft, which transfers that movement through various gears to the drive wheels in an automobile.

In a diesel engine cylinder, the piston completes one up-and-down cycle in four strokes: intake, compression, power, and exhaust. During the intake stroke, the piston moves downward, sucking air into the cylinder through an open intake valve. On the compression stroke, the intake valve closes and the piston rises, compressing the air in the cylinder and causing it to become heated. While the air is being compressed, a fuel pump sprays fuel into the cylinder to mix with the air. When the compressed, hot air reaches the right temperature, it ignites the fuel, driving the piston down on the power stroke. As the piston rises on the exhaust stroke, the exhaust valve opens and the gases created by explosion of the fuel (exhaust) pass out of the cylinder. Then the cycle repeats.

The entire combustion cycle takes but a fraction of a second. Diesel engines can operate from several hundred up to almost one thousand revolutions per minute. The high pressure created in the cylinders during compression requires diesel engines to be strongly constructed and, thus, much heavier than gasoline engines. This weight cuts into their fuel efficiency. Diesel engines also emit high levels of foul-smelling exhaust.

However, diesel engines are more powerful than conventional gasoline engines and run on a less costly fuel. First installed on a ship in 1910 and in an automobile in 1922, they are generally used in large vehicles such as locomotives, trucks, and buses, and in heavy construction and agricultural machinery. Because of their ability to burn crude fuels while delivering an efficient amount of the fuel's energy as usable power, diesel engines are almost the only choice for industrial power throughout the world.

[See also Internal-combustion engine ]

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Diesel

Diesel


Rudolf Christian Karl Diesel (18581913), a German thermal engineer, invented the diesel engine and patented it in 1893. Unlike their gasoline counterparts, which ignite an air/fuel mixture using spark plugs, diesel engines compress air to a very high pressure and then inject the fuel. The fuel then ignites due to the high temperature of the compressed air. Diesel engines are relatively fuel-efficient engines commonly used in heavy construction equipment, ships, locomotives, commercial trucks, and some large pickups, as well as in the production of electricity at some power plants or in factories.

Diesel-powered automobiles gained popularity in the United States during the oil crisis of the 1970s because they tend to result in better fuel economy than their gasoline counterparts. But diesel-powered cars have declined in popularity with American drivers since their peak in the mid-1970s because of quality-related problems in early models and because earlier diesel engines did not accelerate as quickly as those powered by gasoline. Diesel passenger cars have also declined in popularity because they are more expensive and they emit more smog-forming pollutants and toxic soot than other conventional internal-combustion engines. For eighteen-wheel trucks and other large vehicles, however, diesel engines are currently the standard.

see also Vehicular Pollution.

Internet Resource

"How Diesel Engines Work." Available at http://auto.howstuffworks.com/diesel1.htm.

David Friedman

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diesel

die·sel / ˈdēzəl; -səl/ • n. (also diesel engine) an internal combustion engine in which heat produced by the compression of air in the cylinder is used to ignite the fuel: [as adj.] a diesel locomotive. ∎  a heavy petroleum fraction used as fuel in diesel engines: eleven liters of diesel. DERIVATIVES: die·sel·ize / -ˌlīz/ v.

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diesel engine

diesel engine Internal combustion engine, invented by Rudolf Diesel (1897). Heat for igniting the light fuel oil is produced by compressing air.

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diesel

dieselbasil, bedazzle, dazzle, frazzle, razzle •damsel • razzle-dazzle • Basel •bezel, embezzle •Denzil •appraisal, hazel, nasal, phrasal •wych hazel •diesel, easel, teasel, weasel •chisel, drizzle, fizzle, frizzle, grizzle, mizzle, pizzle, sizzle, swizzle, twizzle •reprisal, revisal •nozzle, shemozzle •acausal, causal, clausal, menopausal, monocausal •arousal, carousal, espousal, spousal, tousle •disposal, proposal •accusal, bamboozle, foozle, ouzel, perusal, refusal •guzzle, muzzle, nuzzle, puzzle •mangel-wurzel

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Diesel Engine

Diesel Engine

Resources

Diesel engines are a class of internal combustion engine in which the fuel is burned internally and the combustion products are used as the working fluid. Unlike the spark-ignited (SI) engines found in the majority of early twenty-first century automobiles in which the premixed fuel-air mixture is ignited by an electric spark, diesel engines are characterized by a spontaneously initiated combustion process where the ignition is brought about by very high temperature compressed air. A small amount of diesel fuel is injected at the end of the compression stroke into the cylinder where the fuel auto-ignites. Because of their higher actual operating efficiencies, as compared with SI engines that require pre-ignition, diesel engines are primarily used in heavy-duty vehicles such as trucks, ships, and locomotives.

Diesel engines were first developed by German inventor Rudolf Diesel (18581913) in the late nineteenth century. He patented his invention on February 23, 1893, and demonstrated it at the 1900 Worlds Fair using peanut oil. The original concept was to build a multifuel engine and to use coal as a primary fuel. However, for some reason, coal-fueled diesel engines so far have gained only occasional interest from the industry (e.g., when fuel-oil prices are high), most of the diesel engines currently being used rely on petroleum fuels. They are four-stroke cycle engines, and operate from several hundred up to around one thousand rpm (revolutions per minute). In addition to pistons, cylinders, crankshaft, and various valves, diesel engines are also equipped with controlled fuel injection systems, exhaust systems, cooling systems, and so on. Sufficient lubrication is required to prevent excessive wear of various parts in engines. Since pre-ignition is not required, the compression step can be continued to reach a higher pressure or a higher compression ratio than that in SI engines. This results in compressed air with a temperature exceeding the ignition point of the injected fuel for auto-ignition. To achieve high combustion efficiency, the fuel jets must draw in and mix well with air, ignite, and burn, all within less than one millisecond, when they impact on the cold

combustion chamber walls. Engine performance is closely related to compression ratio, piston speed, supercharging, turbo-charging, etc., and engine size is normally in terms of power rating (i.e., horsepower (hp); for instance, 20, 000 hp applicable for ship propulsion). In principle, the same engine frame can be designed for different output by varying the number of cylinders (10, 12, 16 cylinders, and so on) (Figure 1).

In reality, because the fuel-air mixture is burned and the products of combustion are emitted, the process for work production via combustion in diesel engines is complex and not cyclical. However, in order to analyze it, the actual operation is frequently represented approximately by a cyclical process, called Diesel cycle. From the point of view of thermodynamics, the working fluid is assumed to be air, the compression and expansion stages are assumed to be adiabatic (without the loss or gain of heat) and reversible, and the combustion and exhaust strokes are replaced by constant-pressure heat-absorption and constant-volume heat-rejection stages. As shown in Figure 1, a typical pressure-volume (P-V) diagram for air-standard diesel engine operation, after the intake, air is compressed adiabatically along the path 1-2 and its temperature is increased substantially. At point 2 where the piston begins to reverse its motion, the fuel is injected and added slowly so that combustion is initiated and sustained at constant pressure following the path 2-3. After completion of the combustion, there is the work stroke, i.e., along the path 3-4 where the high-temperature and high-pressure products of combustion are expanded to produce mechanical work. Then, the exhaust valve is opened, the spent combustion products and waste heat are exhausted, and the pressure is rapidly reduced as the path 4-1. This, therefore, completes typical four strokes in each cycle of engine operation. The thermal efficiency of the cycle can be obtained from the net work produced divided by the heat absorbed during the entire cyclical process.

Overall, diesel engines can be viewed as a piston-and-cylinder assembly and the work-producing machine. Their operation cycle is similar to that in SI engines that are based on the Otto (after German inventor Nikolaus August Otto [18321891] who invented the first internal-combustion engine produced in the mid 1860s) cycle. However, the latter require an external combustion initiator and have combustion occurring under an almost constant-volume condition, which is different from the path 2-3 as shown in Figure 1. In these engines, the chemical (molecular) energy of the fuel (hydrocarbons) is released by a combustion process. Energy is evolved as heat and part of the heat is subsequently converted into useful work or mechanical energy. Because of the loss of heat during the process, research and development efforts have been made constantly in chamber design, new coatings for rings and liner, emission control, alternative fuels, and associated compressor and turbine technologies to improve the conversion efficiency. As can be expected, diesel engines

KEY TERMS

Adiabatic A process during which no heat is transferred between the system and surroundings is described as adiabatic.

Heat engine A device converts heat to mechanical work in a periodic process.

Reversible A process occurs in such a way that both the system and its surroundings can be returned to their initial states.

Supercharging Methods to increase the inlet manifold air pressure above ambient pressure so that power output in engines is increased.

Thermal efficiency The ratio of net work to thermal energy input.

Turbocharging An approach to utilizing high-temperature exhaust gas by expanding it through a turbine for driving the supercharging compressor.

will continue finding a variety of applications in the future, such as power generation as well as land, marine, and aircraft transport.

Resources

BOOKS

Haddad, S.D. ed. Advanced Diesel Engineering and Application. New York: John Wiley & Sons, 1988.

Norman, Andrew. Diesel Technology: Fundamentals, Service, Repair. Tinley Park, IL: Goodheart-Willcox, 2001.

PERIODICALS

Rutland, Christopher. Probability Density Function Combustion Modeling of Diesel Engine. Combustion Science and Technology 174, no. 10 (2002): 19-54.

OTHER

Combustion Modelling For Direct Injection Diesel Engines. Proceedings Of The Institution Of Mechanical Engineers 215, no. 5 (2001): 651-663.

Pang-Jen Kung

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Diesel Engine

Diesel engine

Diesel engines are a class of internal combustion engine in which the fuel is burned internally and the combustion products are used as the working fluid. Unlike the spark-ignited (SI) engines found in the majority of today's automobiles in which the premixed fuel-air mixture is ignited by an electric spark, diesel engines are characterized by a spontaneously initiated combustion process where the ignition is brought about by very high temperature compressed air. A small amount of diesel fuel is injected at the end of the compression stroke into the cylinder where the fuel auto-ignites. Because of their higher actual operating efficiencies, as compared with SI engines that require pre-ignition, diesel engines are primarily used in heavy-duty vehicles such as trucks, ships, locomotives, etc.

Diesel engines were first developed by Rudolf Diesel (1858-1913) in the late nineteenth century. The original concept was to build a multifuel engine and to use coal as a primary fuel. However, for some reason, coal-fueled diesel engines so far have gained only occasional interest from the industry (e.g., when fuel-oil prices are high), most of the diesel engines currently being used rely on petroleum fuels. They are four-stroke cycle engines, and operate from several hundred up to around one thousand rpm. In addition to pistons, cylinders, crankshaft, and various valves, diesel engines are also equipped with controlled fuel injection systems, exhaust systems, cooling systems, and so on. Sufficient lubrication is required to prevent excessive wear of various parts in engines. Since pre-ignition is not required, the compression step can be continued to reach a higher pressure or a higher compression ratio than that in SI engines. This results in compressed air with a temperature exceeding the ignition point of the injected fuel for auto-ignition. To achieve high combustion efficiency, the fuel jets must draw in and mix well with air, ignite, and burn, all within less than one millisecond, when they impact on the cold combustion chamber walls. Engine performance is closely related to compression ratio, piston speed, supercharging, turbo-charging, etc., and engine size is normally in terms of power rating (i.e., horsepower; for instance, 20,000 hp applicable for ship propulsion). In principle, the same engine frame can be designed for different output by varying the number of cylinders (10, 12, 16 cylinders, and so on).

In reality, because the fuel-air mixture is burned and the products of combustion are emitted, the process for work production via combustion in diesel engines is complex and not cyclical. However, in order to analyze it, the actual operation is frequently represented approximately by a cyclical process, called "Diesel cycle." From the point of view of thermodynamics , the working fluid is assumed to be air, the compression and expansion stages are assumed to be adiabatic (without the loss or gain of heat ) and reversible, and the combustion and exhaust strokes are replaced by constant-pressure heat-absorption and constant-volume heat-rejection stages. As shown in Figure 1, a typical pressure-volume (P-V) diagram for air-standard diesel engine operation, after the intake, air is compressed adiabatically along the path 1-2 and its temperature is increased substantially. At point 2 where the piston begins to reverse its motion , the fuel is injected and added slowly so that combustion is initiated and sustained at constant pressure following the path 2-3. After completion of the combustion, there is the work stroke, i.e., along the path 3-4 where the high-temperature and high-pressure products of combustion are expanded to produce mechanical work. Then the exhaust valve is opened, the spent combustion products and waste heat are exhausted, and the pressure is rapidly reduced as the path 4-1. This, therefore, completes typical four strokes in each cycle of engine operation. The thermal efficiency of the cycle can be obtained from the net work produced divided by the heat absorbed during the entire cyclical process.

Overall, diesel engines can be viewed as a piston-and-cylinder assembly and the work-producing machine. Their operation cycle is similar to that in SI engines which are based on the Otto (after the German inventor for the first internal-combustion engine produced in the mid 1860s) cycle; however, the latter require an external combustion initiator and have combustion occurring under an almost constant-volume condition, which is different from the path 2-3 as shown in Figure 1. In these engines, the chemical (molecular) energy of the fuel (hydrocarbons) is released by a combustion process. Energy is evolved as heat and part of the heat is subsequently converted into useful work or mechanical energy. Because of the loss of heat during the process, research and development efforts have been made constantly in chamber design, new coatings for rings and liner, emission control, alternative fuels, and associated compressor and turbine technologies to improve the conversion efficiency. As can be expected, diesel engines will continue finding a variety of applications in the future, such as power generation as well as land, marine, and aircraft transport.

Resources

books

Haddad, S.D., ed. Advanced Diesel Engineering and Application. New York: John Wiley & Sons, 1988.

periodicals

Rutland, Christopher. "Probability Density Function Combustion Modeling of Diesel Engine." Combustion Science and Technology 174, no. 10 (2002): 19-54.

Ryan III, T.W. " Coal-Fueled Diesel Development: A Technical Review." Journal of Engineering for Gas Turbines and Power (1994).

other

"Combustion Modelling For Direct Injection Diesel Engines." Proceedings Of The Institution Of Mechanical Engineers 215, no. 5 (2001): 651-663.


Pang-Jen Kung

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adiabatic

—A process during which no heat is transferred between the system and surroundings is described as "adiabatic."

Heat engine

—A device converts heat to mechanical work in a periodic process.

Reversible

—A process occurs in such a way that both the system and its surroundings can be returned to their initial states.

Supercharging

—Methods to increase the inlet manifold air pressure above ambient pressure so that power output in engines is increased.

Thermal efficiency

—The ratio of net work to thermal energy input.

Turbocharging

—An approach to utilizing high-temperature exhaust gas by expanding it through a turbine for driving the supercharging compressor.

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