The diesel engine has the highest thermal efficiency (engine efficiency) of any practical internal or external combustion engine due to its very high expansion ratio and inherent lean burn which enables heat dissipation by the excess air.

1. Run the engine fuel-lean, that is, use excess air. It is well known that fuel-lean running improves the efficiency.
2. Higher compression ratio.
3. We need new cycles put into practical use.
4. Run the engine at optimum conditions, meaning low friction (modest engine speed) and low pumping work (air throttle more open).

Toyota has now developed a new gasoline engine which it claims has a maximum thermal efficiency of 38 percent–greater than any other mass-produced combustion engine.

as the air-fuel ratio is increased. It should be noted that, to compare the two cycles, efficiencies have been calculated for compression ratios and air-fuel ratios which are outside the normal operating values for one or the other of the cycles.

Diesel engines are designed with longer strokes in mind, as this produces more torque and more power. The more pressure built in the strokes and cylinders, the more torque the wheels will have. The combustion temperature of diesel fuel is also designed for higher torque.

3. 6 Diesel Cycle. Although for a given compression ratio the Otto cycle has higher efficiency, because the Diesel engine can be operated to higher compression ratio, the engine can actually have higher efficiency than an Otto cycle when both are operated at compression ratios that might be achieved in practice.

An Otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine. It is the thermodynamic cycle most commonly found in automobile engines.

An Otto cycle is an ideal thermodynamic cycle that describes the function of a spark ignition piston engine. A diesel cycle is an ideal-engine cycle during which the working substance successively undergoes adiabatic compression, constant-pressure heating, adiabatic expansion, and then constant-volume cooling.

In it, fuel is ignited by heat generated during the compression of air in the combustion chamber, into which fuel is then injected. This is in contrast to igniting the fuel-air mixture with a spark plug as in the Otto cycle (four-stroke/petrol) engine.

The Otto Cycle, describes how heat engines turn gasoline into motion. Like other thermodynamic cycles, this cycle turns chemical energy into thermal energy and then into motion. The Otto cycle describes how internal combustion engines (that use gasoline) work, like automobiles and lawn mowers.

Carnot cycle is an ideal cycle proposed by said carnot, ideal cycle. An Otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine. It is the thermodynamic cycle most commonly found in automobile engines.

In the diesel engine, air is compressed adiabatically with a compression ratio typically between 15 and 20. The ideal air-standard cycle is modeled as a reversible adiabatic compression followed by a constant pressure combustion process, then an adiabatic expansion as a power stroke and an isovolumetric exhaust.

The efficiency of the carnot engine is defined as the ratio of the energy output to the energy input. efficiency=net work done by heat engineheat absorbed by heat engine=−wsysqhigh=nRThighln(V2V1)+nRTlowln(V4V3)nRThighln(V2V1) Since processes II (2-3) and IV (4-1) are adiabatic, (T2T3)CV/R=V3V2. and.

: an ideal reversible closed thermodynamic cycle in which the working substance goes through the four successive operations of isothermal expansion to a desired point, adiabatic expansion to a desired point, isothermal compression, and adiabatic compression back to its initial state.

The Carnot heat-engine cycle described is a totally reversible cycle. Heat is absorbed from the low-temperature reservoir, heat is rejected to a high-temperature reservoir, and a work input is required to accomplish all this.

The Carnot cycle is composed of four reversible processes. Hence, it is a reversible heat transfer process. Gas in the cylinder expands slowly, does work to its surroundings, and remains at a constant temperature TH. The total amount of heat transferred to the gas during this process is QH.

In other words, no machine can be more than 100% efficient. Machines cannot multiply energy or work input. If a machine were 100% efficient then it can’t have any energy losses to friction, so no friction can be present.

Xenon is by far the most efficient of the gases, although krypton is more effective at a specific wavelength of light.

In order to achieve 100% efficiency (η=1), Q2 must be equal to 0 which means that all the heat form the source is converted to work. The temperature of sink means a negative temperature on the absolute scale at which the temperature is greater than unity.