Subtopic: Selection, operation, maintenance and repair of I.C. engines
Question Statement:
The effectiveness of the turbocharger of a diesel engine increases when
Options:
(A) the ambient temperature increases
(B) the pressure ratio across the compressor decreases
(C) the load on the engine increases
(D) the displacement volume of the engine decreases
Official Answer Key:
C
Step-by-Step Solution & Explanation
A turbocharger's turbine is driven by the energy in the exhaust gas stream. As engine load increases, fuel burnt and exhaust gas energy (mass flow and temperature) increase, driving the turbine harder and boosting compressor output — turbocharger effectiveness (boost pressure and hence volumetric efficiency gain) improves with load. (A) higher ambient temperature reduces intake air density and turbocharger effectiveness. (B) a lower pressure ratio across the compressor means LESS boost is being achieved — the opposite of increased effectiveness. (D) displacement volume is a fixed engine-design parameter, not something a turbocharger's own effectiveness depends on. Answer: (C).
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