Classifications of Automobile Engines According to the Cycle of Operations

Classifications of automobile engines can be in different types. In an automobile vehicle, the Internal Combustion Engine(IC) is used to produce power. So, the classification will be on the IC engine only. In this article, I will discuss the classifications of automobile engines according to the cycle of operations.

classifications-of-automobile-engines

Classifications of Automobile Engines

An automobile vehicle depends on engine operations and engine power. The engine power develops inside the cylinder and powers the overall vehicle. So this power generation depends on various factors like engine size, displacement, metal quality, etc.

According to the engine burning fuel, this burning of gases depends on various factors like pressure and volume. If the volume rises in the cylinder then the pressure will decrease. This is called the Pressure-Volume formula and this formula creates the method of Adiabatic Cycle Operation in the cylinder.

To the adiabatic cycle of operations, automobile vehicle engines may be of the following three types-

  1. Otto cycle engine
  2. Diesel cycle engine
  3. Dual cycle engine

So, read the details of each of these cycles.

Otto Cycle or Constant Volume Cycle

Otto-Cycle-or-Constant-Volume-Cy

German scientist Otto, 1876, introduced the Otto cycle, although it was described by a French scientist Beaude Roches in 1862. The engines operating on these cycles are known as Otto cycle engines. The petrol-powered engine operates on this cycle.

An IC engine works on the principle of the air heating method. Also, this air is not first chemically charged. The air is heated first and also the air is cooled down for better cycle operation. Also, the automobile company has the ideal operation method that has to be followed. The Otto cycle consists of the operations-

  • 1-2 Adiabatic compression
  • 2-3 Heat addition at constant volume
  • 3-4 Adiabatic expansion
  • 4-1 Heat rejection at constant volume

At this point, the air in the cylinder initially corresponds to p1, v1, and T1(pressure, volume, and absolute temperature). The piston compresses the air adiabatically during the compression stroke and at point 2 lets the air condition be P2, V2, and T2.

The air now takes the place of the clearance volume of the cylinder. A hot body is then brought into contact with the cylinder so that the heat is supplied at constant volume. This increases the pressure and temperature of the air, corresponding to P3, T3, and Here V3=V2.

At point 3, the hot body is removed and the air is expanded adiabatically during the expansion stroke, up to point 4 corresponding to P4, V4, and T4. A cold body is then brought in contact with the cylinder end such that the pressure drops at constant volume, corresponding to the condition P1, V1, and T1. Here V4=V1.

In this process, the air finally returns to its original condition and the cycle is complete. For a specific compression ratio, the Otto cycle is far more efficient than the Diesel Cycle.

Diesel Cycle or Constant Pressure Cycle

Diesel-Cycle-or-Constant-Pressure-Cycle

The diesel cycle was introduced by Dr. Rudolph Diesel in 1897. The engines operating in this cycle are known as Diesel Cycle. This is the p-v diagram of the Diesel Engine. It consists of the following operations-

  • 1-2 Adiabatic compression
  • 2-3 Heat addition at constant pressure
  • 3-4 Adiabatic expansion
  • 4-1 Heat rejection at constant volume

The Diesel cycle is different from the Otto cycle. The heat is added at constant pressure instead of at constant volume, compared to the Otto cycle in the Diesel engine.

During the compression stroke, the air is compressed from 1 to 2. Now, heat is added at constant pressure from point 2 to 3, and then the air is expanded adiabatically from point 3 to 4. Finally, the heat is rejected at constant volume from point 4-1. The air returns to its original condition and the cycle is complete.

Dual Cycle(or Dual Combustion Cycle)

Dual-Cycle-or-Dual-Combustion-Cycle

The dual cycle is more efficient in that it has more burning efficiency than the Diesel Engine. The fuel is injected into the cylinder at a constant volume. This also helps to keep the property at constant pressure and the combustion occurs at constant volume. This dual cycle is used in modern cars as it serves several advantages to the vehicle. The Diesel engine uses this Dual cycle.

The diagram shows the dual cycle on the p-v diagram. It consists of the following operations-

  • 1-2 Adiabatic compression
  • 2-3 Heat addition at constant volume
  • 3-4 Heat addition at constant pressure
  • 4-5 Adiabatic expansion
  • 5-1 Heat rejection at constant volume

Because the fuel is injected into the cylinder before the end of the compression stroke in the dual cycle, it takes care of the ignition lag characteristics of the fuel.

Conclusion

The operation cycle of the automotive engines helps to gain knowledge of engine power and output performance. This ensures the pressure generated and the volume it covers during all the strokes. The measurement is done with the help of the count of the atmospheric pressure.


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