Otto cycle idealization — constant-volume heat addition in petrol engines In the idealized analysis of a petrol (spark ignition) engine, the spark initiates combustion that raises pressure and temperature while the piston is momentarily near top dead centre so that volume is assumed constant. Is this statement correct for the Otto cycle model?

Introduction / Context:
Thermodynamic cycle models help approximate the complex real processes inside engines. The Otto cycle is the canonical model for spark ignition engines and assumes heat addition at constant volume to simplify analysis and capture first-order behavior.

Given Data / Assumptions:

• Spark ignition near top dead centre.
• Very short combustion duration compared with piston motion near TDC in the ideal model.
• Neglect of heat losses and finite-rate effects in the ideal cycle.

Concept / Approach:
In the Otto cycle, heat addition is modeled as a constant-volume process. Because the piston displacement is minimal during the short ignition and early flame propagation period, the volume is approximated as fixed, so pressure and temperature rise sharply. This distinguishes the Otto cycle from the Diesel cycle, which assumes constant-pressure heat addition during part of combustion in a compression ignition engine.

Step-by-Step Solution:
Identify the model used for petrol engines: Otto cycle.Recognize the heat-addition idealization: constant volume.Therefore, the statement describing pressure and temperature rise at nearly constant volume is correct within the model.

Verification / Alternative check:
Real cycles show finite burn duration and some volume change during combustion, but the constant-volume approximation yields reasonable trends for efficiency and pressure ratios, supporting its educational value.

Why Other Options Are Wrong:
Answering No would conflate the Otto cycle with Diesel or dual cycles, which have different heat-addition assumptions.

Common Pitfalls:
Assuming that the idealization exactly matches reality. It is a simplifying model used for comparative and preliminary calculations.

Final Answer:
Yes