03.1 Explain what is meant by an adiabatic change - AQA - A-Level Physics - Question 3 - 2022 - Paper 6

To calculate the compression ratio, we apply the formula derived from the adiabatic condition: $\frac{P2}{P1} = \frac{V1}{V2}^\frac{γ}{γ - 1}$ Here, substituting the given values: $P1 = 1.0 \times 10^5 \text{ Pa}$ $P2 = 67 \times 10^5 \text{ Pa}$ Thus, solving this equation provides the required compression ratio.

Diesel engines require a higher compression ratio to sufficiently increase the air temperature for ignition without the presence of a spark plug. The higher pressure in the combustion chamber helps to combust the fuel and air mixture at relatively lower pressures and temperatures, enhancing efficiency.

A typical indicator diagram will reflect a curved cycle consistent with the operations of a real four-stroke diesel engine, which often displays less sharp corners.

The X should be placed at the end of the compression stroke before the combustion starts.

The ideal cycle assumes constant volume processes, while real engines operate with variable volume processes. Additionally, ideal cycles assume no losses due to friction or heat dissipation, whereas real engines experience these losses, which affects their performance.