Subtopic: I.C. engine systems – fuel, cooling, lubrication, ignition, electrical, intake and exhaust
Question Statement:
A fundamental thermodynamic distinction between a mechanically driven supercharger and an exhaust-gas turbocharger is that:
Options:
(A) A supercharger is driven by an exhaust turbine, while a turbocharger is driven by an electric motor
(B) A supercharger draws parasitic shaft power directly from the engine crankshaft, whereas a turbocharger utilizes waste enthalpy from exhaust gases
(C) Superchargers can only be installed on spark ignition engines
(D) Turbochargers operate with zero boost threshold lag
Answer Key:
B
Step-by-Step Solution & Explanation
- **Supercharger vs Turbocharger:**
- A supercharger is mechanically coupled (via belt or gears) directly to the crankshaft, consuming up to $10\text{--}15\%$ of engine shaft work as parasitic load.
- A turbocharger is completely uncoupled mechanically; its turbine recovers waste kinetic and heat energy from hot expanding exhaust gases, resulting in superior overall brake thermal efficiency.