Explain volumetric re-ignition as applied to S.I engine

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Two strokes Cl engine develops a break power of 386kW while its frictional power is 73.6 kW. Its fuel consumption is 180 kg/h and works with an air-fuel ratio of 20:1. The heating value of the fuel is 42000kJ/kg. solve the questions 26-30 Calculate air consumption per hour? a. 3600 kg/h O b. 5690 kg/h Oc. 3345 kg/h O d. 1209 kg/h Oe. All of the answers are false.