STS, The Diesel Engine

8/4/2019 STS, The Diesel Engine

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The Diesel Engine

Richard Long

STS ProjectMr. Schuetz AM1 Physics


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About the Inventor In 1894, German inventor Rudolph Diesel

developed the first single-cylinder dieselengine.

He signed a multi-million dollar deal withAdolphus Busch, head of brewery empire,to manufacture the diesel engine.

However, he lost his fortune, and in 1913,

mysteriously was found dead after goingoverboard a boat. Suicide was onespeculation, but also assassination byKaiser Wilhelms agents, fearing thatDiesel, with WW I looming, would sell the

engine to England


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The Combustion Cycle The four-stroke combustion cycle of the diesel engine

is composed of the intake stroke, compression stroke,power stroke, and the exhaust stroke.

The diesel engine operates through the motion ofcompression pistons in inside the cylinders of theengine.

Pistons inside the cylinders are connected by rods to acrankshaft. As the pistons move up and down in their

cylinders, they cause the crankshaft to rotate. The crankshafts rotational force is carried by a

transmission to a drive shaft, which turns axles,causing the wheels to rotate.


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The Intake Stroke During the intake stroke, the intake

valve opens as the piston movesdown to allow air into the cylinder.

The air is pushed by atmosphericpressure into the cylinder throughthe intake valve port.


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The Compression Stroke After the piston reaches its lower

limit, it begins to move upward andas the piston moves up, the intake

valve closes. The exhaust valve is also closed, so

that at this point in the cycle, thecylinder is sealed.

As the piston moves upward, the airis compressed and the compressionof the air causes the pressure andthe temperature of the cylinder toincrease.


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The Power Stroke As the piston reaches maximum

compression of the air, diesel fuel isinjected to the combustion chamberfilled with compressed air.

The heat of the compressed air ignitesthe fuel spontaneously at the self-ignition temperature of the fuel.

As the cylinder pressure increases, the

piston is forced down into the cylinder. The power impulse is transmitted

down through the piston, through theconnecting rod, and to the crankshaft,which is rotated due to the force.


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The Exhaust Stroke As the piston reaches the bottom of

its stroke, the exhaust valve opens.

As the piston moves up on the

exhaust stroke, it forces the burnedgases out of the cylinder throughthe exhaust port.

Then as the piston reaches the top

of its stroke, the exhaust valvecloses, and the intake valve opens.

The cycle repeats again with theintake stroke.


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Efficiency One positive aspect of the diesel engine is that

they are thermally efficient.

The improved efficiency is caused by therelatively high compression ratios

The diesel engine is 54% thermally efficient,while gasoline engines are only 34%.

As a result of diesel engines thermally efficiency,they are able to achieve better gas mileagebecause they produce greater horsepower outputfor fuel intake.


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Fuel Economy One main reason for the diesel engines excellent fuel

economy is that it burns far more air than fuel.

In a gasoline engine, its air intake is carefullyrestricted and controlled by the carburetor for a 15:1air to fuel ratio.

However, in the diesel engine, the air intake isunrestricted.


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Durability Diesel engines are also capable of running high miles

without major engine work.

Truck diesel engines can run 250,000 or even 500,000miles without major engine work.

In 1978, Mercedes-Benz launched a Great DieselSearch to find the highest mileage diesel in the UnitedStates.

Robert OReilly drove his 1957 Mercedes-Benz 180D1,184,000 miles, 750,000 on its original engine.

Another owner drove his 1968 Mercedes-Benz 220 D912,000 miles, 902,000 miles on its original engine.


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Compression Ratio The diesel engine compresses at a very high ration of

14:1 to 25:1.

The higher the compression ratio, the more power is

generated. The main limiting factor to compression ratio is based

on the knock limits of the fuel.

Knock is the term used to describe the auto ignition

that occurs when a fuel ignites because the pressurein the cylinder is such that combustion occurs.

The knock limit of the fuel is determined by the pointat which the engine begins to shake.

The higher the knock limit, the higher thecompression ratio, the more power is generated.


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Advantages of a Diesel Engine Low maintenance, greater efficiency, high power

output, and better fuel economy under all types ofloads.

Does not require a spark plug to ignite fuel, it relieson the spontaneous combustion through the heat ofcompression to ignite the diesel fuel.

Because of this type of combustion, a diesel engine

are built more ruggedly and heavily built than the gasengine.

The ruggedness of the diesel engine gives a two tothree times longer life than the gas engine, whichhas a life of around 100,000 miles.


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Disadvantages Components of diesel engines are usually heavier

that those of gasoline engines because of theadditional structural strength needed to obtain the

higher compression ratio and power output. They can emit large amounts of ozone-forming

constituents and particulates.

Because of diesel engines weight and compression

ratio, they tend to have lower maximum RPMs thangasoline engines.

This makes diesel engines has high torque ratherthan high horsepower, and this tends to makecars with diesel engines slow in terms of

acceleration.


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Disadvantages (cont.) Diesel fuel is not as readily available at all locations

as gasoline tends to be.

Diesel engines are harder to start in cold weatherconditions, because it is difficult to get thetemperature inside the cylinder up to the self-ignition

temperature of the diesel fuel.


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Emissions The most harmful emission from diesel engines are

the nitrogen oxides.

The problem of nitrogen oxide (NO) production indiesel engines comes from the early rapid burning,which produces very high-temperature products.

As a result of the pollutants from diesel engines, theyare subject to increasingly stringent regulations thatrequire continual improvements in the combustionprocess.


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Main Differences of Gas and Diesel The main difference between a gasoline engine and a

diesel engine is that in a diesel engine, there is nospark plug to ignite the fuel.

Diesel fuel is injected into the cylinder, and it ignitesspontaneously as the heat and pressure of thecompression stroke cause the temperature inside thecylinder to increase.

The other major difference between the two types ofengines is in the gas mileage.

As a result of diesel fuel having a higher energydensity than gasoline, diesel engines get highergas mileage.

STS, The Diesel Engine

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