Engineering Thermodynamics
Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because in Otto cycle

Expansion and compression are isentropic
Combustion is at constant volume
Maximum temperature is higher
Heat rejection is lower

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Engineering Thermodynamics
The mass of flue gas per kg of fuel is the ratio of the

Mass of oxygen in 1 kg of fuel to the mass of oxygen in 1 kg of flue gas
Mass of oxygen in 1 kg of flue gas to the mass of oxygen in 1 kg of fuel
Mass of carbon in 1 kg of fuel to the mass of carbon in 1 kg of flue gas
Mass of carbon in 1 kg of flue gas to the mass of carbon in 1 kg of fuel

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