What is the approximate design-load thermal efficiency of a petrol engine_________________?
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Answer: D. 30%
Explanation
The design load thermal efficiency of a typical spark ignition petrol engine is generally around thirty percent. Thermodynamic losses through exhaust heat and engine cooling systems limit petrol engines from reaching higher efficiencies. This percentage reflects the fraction of chemical fuel energy successfully converted into useful mechanical shaft work. Thermal efficiency is calculated by dividing useful mechanical work output by the total chemical energy input of fuel. The Carnot cycle imposes an upper theoretical temperature limit on all internal combustion engine thermal efficiencies. Frictional losses within pistons, bearings, and valve trains further reduce the practical thermal efficiency achieved.
An efficiency of ninety percent violates basic thermodynamic laws regarding heat engine energy conversion limits. Fifty percent is exceptionally high and typically achievable only in large industrial diesel or combined cycle plants. Fifteen percent represents poor performance or extreme idling losses rather than standard design load efficiency.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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