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The specific heat ratio used in heat release calculation plays an important role and the mass fraction burned is also a crucial parameter in thermodynamics analysis for engine combustion. A research of high methane fraction natural gas was investigated in a constant volume combustion vessel at different initial conditions. Results show that with the increase of the initial pressure, the specific heat ratio is decreased, and the time of the mixture burned up is postponed, while the peak heat release ratio is increased. With the increase of the methane fraction, the parameters have the opposite behavior. With the increase of the initial temperature, the specific heat ratio is decreased, and the time when the mixture is burned up is accelerated, and the peak heat release ratio has no obviously difference. With the increase of the dilution ratio or the CO2/N2 ratio, the specific heat ratio is decreased, and the peak heat release heat ratio is decreased.

Propanol isomers are oxygenated fuels and have higher octane number and energy density compared to methanol and ethanol. In recent years, with the development of fermentation method, propanol isomers have gained more attention as engine additive to reduce the emission and the consumption of traditional fossil fuels. In this study, Hydrocarbon (HC), carbon monoxide (CO) and particulate matter (PM) emission characteristic of propanol isomers/gasoline blends were comparatively investigated at different blending ratios (0, 10, 20, 40 and 100) combined with exhaust gas recirculation (EGR) in a spark-ignition engine. The number distribution of particulate matter emission is mainly studied in addition to the particulate matter mass distribution. Results show that pure propanol isomers yield significantly different emission characteristics compared to the other blends.