How is heat rejected in an Otto cycle?

In the Otto cycle, there is no heat transfer during the process 1–2 and 3–4 as they are isentropic processes. Heat is supplied only during the constant volume processes 2–3 and heat is rejected only during the constant volume processes 4–1.

How is the heat rejected in the diesel cycle?

During process 2-3 the fuel is injected and combusted and this is represented by a constant pressure expansion process. Finally, process 4-1 represents the constant volume heat rejection process. In an actual Diesel engine the gas is simply exhausted from the cylinder and a fresh charge of air is introduced.

Why is there constant volume heat in Otto cycle?

When you add heat at constant volume, the pressure is allowed to rise, and all of the energy added can be expanded through the whole compression (you may call it expansion) ratio. Thus the last heat added is subjected to a smaller expansion ratio, producing less work, and giving a lower efficiency.

Why is Otto cycle more efficient than diesel cycle?

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 happens when a gas is heated at constant volume?

When the gas is heated at constant volume, the heat supplied increases the internal energy of the gas.

In which of the following cycle heat is added at constant volume?

Otto cycle
Explanation: Since, Dual Cycle is a combination of Otto cycle and Diesel cycle, so in Dual cycle, generally heat addition takes place first at constant volume then at constant pressure.

In which cycle does heat addition and heat rejection occur at constant pressure?

The Joule cycle is the air-standard cycle which describes the processes in the gas turbine. The Joule cycle has constant pressure combustion and constant pressure heat rejection.

Why does heat addition takes place at constant volume in engine?

When you add heat to a gas, it tries to expand due to increase in energy of the molecules and can be felt as increased pressure of the gas. In constant pressure heat addition process we adjust the volume of the gas in a way so that the pressure of the gas remains constant.

Why does during the ignition process volume remain constant in petrol engine and pressure remain constant in Diesel engine?

These gases originating from a liquid source occupy the void clearance volume of the cylinder. The pressure exerted against these gaseous expansion during the combustion process is constant throughout. Hence, the process is modeled as constant pressure.

Why is Otto cycle more efficient than Diesel cycle for the same compression ratio and heat input?

Explanation: Otto cycle is more efficient than Diesel cycle for a given compression ratio. For constant maximum pressure and heat input, the air standard efficiency of the gas power cycle is in the order.

What is the primary reason why an Otto cycle is less efficient than a Carnot cycle?

The cylinders are not perfectly insulated from the engine block, so heat energy is lost from each cylinder by conduction. This makes the engine less efficient that a Carnot engine, because heat is being discharged at a temperature that is not as cool as the environment.

What is the difference between Otto cycle and Diesel cycle?

In Otto cycle heat addition takes place at constant volume while in diesel cycle, heat addition at constant pressure takes place and Otto-cycle has lower compression ratio below 12 while, diesel cycle has higher compression ratio up to 22. Otto-cycle uses spark plug for ignition while diesel cycle needs no assistance for ignition.

Does heat addition or rejection occur at constant volume in Otto?

But for the sake of our convenience we consider heat addition or rejection to occur at constant volume in otto and diesel cycles.

What is the thermal efficiency of the ideal Otto cycle?

Under the cold air-standard assumption, the thermal efficiency of the ideal Otto cycle is Process 1-2 and process 3-4 are isentropic. Thus, where r is the compression ratio and k is the specific heat ratio.

What is the compression ratio of Otto cycle?

Compression ratio of Otto cycle is defined as the ratio of volume before expansion to volume after expansion In this cycle Compression ratio is generally 6 – 10. It is limited to 10 because of knocking in the engine.