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Thermodynamics and engines (A-level only)

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Question 4

During a test run of a prototype double-acting, two-stroke gas engine, the following data were recorded:

  • Rotational speed of the crankshaft: 150 rev min−1150 \text{ rev min}^{-1}150 rev min−1
  • Net area of the indicator diagram for each chamber: equivalent to a work done per cycle of 180 J180 \text{ J}180 J
  • Fuel gas consumption rate: 7.50×10−4 m3 s−17.50 \times 10^{-4} \text{ m}^3 \text{ s}^{-1}7.50×10−4 m3 s−1
  • Calorific value of the fuel gas: 20.0×106 J m−320.0 \times 10^6 \text{ J m}^{-3}20.0×106 J m−3
  • Measured torque at the crankshaft: 45.0 N m45.0 \text{ N m}45.0 N m

The indicator diagrams for the left and right chambers are identical, and each chamber completes one cycle per crankshaft revolution.

Calculate:

1.

The indicated power (PindP_{\text{ind}}Pind​) of the engine.

[3]
2.

The input thermal power (PinP_{\text{in}}Pin​) supplied by the fuel.

[2]
3.

The output (brake) power (PoutP_{\text{out}}Pout​) of the engine.

[3]
4.

The mechanical efficiency (ηmech\eta_{\text{mech}}ηmech​) of the engine.

[2]

Thermodynamics and engines (A-level only) Questions

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