Why is the thermal efficiency of the auto cycle higher than diesel engine What is the reason for increasing use of diesel cycle instead of Otto cycle?

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.

Why thermal efficiency of diesel engine is higher than petrol engine?

Because diesel has a higher compression resistance — because it is denser than light distillate fuels — engineers can design and develop diesel engines with higher compression ratios than gasoline engines. The higher the compression ratio of an engine, the greater the thermal efficiency.

Why the higher efficiency of the Otto cycle compared to the diesel cycle for the same compression ratio is not a result of practical importance?

The simple answer is ,In the otto the energy available is fully used to raise the pressure in the cylinder. Higher the pressure implies larger work done. But in diesel cycle, Part of the energy is added only during the expansion, So it does not contribute to the work. Hence Otto cycle is more efficient.

What is indicated thermal efficiency?

Indicated thermal efficiency is the ratio of indicated power (ip) and energy in fuel per second. η ith= ip (KJ/s)/ energy in fuel per second (KJ/s) Indicated power is defined as the sum of friction power and brake power.

Which engine has more efficiency diesel or petrol?

Per litre, diesel contains more energy than petrol and the vehicle’s engine combustion process is more efficient, adding up to higher fuel efficiency and lower CO2 emissions when using diesel.

What is thermal efficiency of diesel engine?

Current on-road diesel engines have approximately 42\% brake thermal efficiency at full load, with 28\% of fuel energy wasted in exhaust gas (including 4\% going to pumping loss), 28\% of fuel energy dissipating to cooling media as heat rejections to the ambient (including 4\% going to mechanical friction and parasitic …

How does compression ratio affect the thermal efficiency of combustion engine?

In the following section, it will be shown that the compression ratio determines the thermal efficiency of used thermodynamic cycle of the combustion engine. In general, it is desired to have a high compression ratio, because it allows an engine to reach higher thermal efficiency.

What is the difference between constant volume and constant pressure combustion?

As the constant volume combustion process provides higher adiabatic flame temperature, then the corresponding higher temperature reservoir will be increased over that provided by a constant pressure combustion process. This result is confirmed by the analysis of air standard cycles (Otto versus Diesel cycles) for the same compression ratio.

What is the fuel conversion efficiency of the constant volume cycle?

The net indicated fuel efficiency ( ηf,i) for the constant volume cycle is only a function of compression ratio and γ: At a compression ratio of 10 with γ = 1.35, the constant volume cycle fuel conversion efficiency is 55\%.

How does adiabatic compression affect fuel efficiency?

Simply, a compression engine converts a larger sum of the energy produced during combustion into kinetic energy than a spark-fired engine does because diesel engines can achieve higher compression ratios. The relationship between adiabatic compression and fuel efficiency has to do with thermal dynamics and physics.