Cylinder conditions: I.C. engine vs. steam engine Compared to a steam engine, the working pressure and temperature inside the cylinder of an internal combustion engine are…

Introduction / Context:
Understanding relative operating conditions helps explain design choices such as materials, cooling, and lubrication. Internal combustion engines burn fuel directly inside the cylinder, while steam engines receive external heat in a boiler and expand steam at comparatively lower in-cylinder temperatures and pressures.

Given Data / Assumptions:

• I.C. engines: peak cylinder pressures often 4–7 MPa (or more) and high combustion temperatures.
• Steam engines: cylinder pressures typically limited to boiler pressure and expansion, generally lower than peak I.C. cylinder pressures.
• Direct in-cylinder combustion produces very high local temperatures.

Concept / Approach:

Because chemical energy converts to thermal energy directly within the I.C. engine cylinder during a very short interval, both temperature and pressure peaks are significantly higher than in reciprocating steam engines. This necessitates robust cooling and high-performance lubricants in I.C. engines.

Step-by-Step Solution:

Verification / Alternative check:

Empirical data from engine indicator diagrams show higher peak values in I.C. engines versus reciprocating steam engines operating at comparable mean effective pressures.

Why Other Options Are Wrong:

Choices indicating lower or similar values contradict the fundamental difference in heat addition and resulting thermodynamic states.

Common Pitfalls:

Confusing mean effective pressure with instantaneous peak pressure; the latter is the relevant comparison for material stress and temperature.

Final Answer:

very high