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A new model of gaseous fuel-air mixing that is based on the ideal gas law and the equation of continuity is applied to propane-air mixtures. The local degree of mixing and the rate of mixing are calculated using the mass fraction of fuel measured within an infinitesimal fluid element and the time rate of this mass fraction, respectively. According to the model, mixing is promoted by pressure, temperature and velocity gradients. High initial pressure reduces mixing caused by pressure gradients. Results presented here provide the isolated effects of pressure and velocity gradients on mixing. These results facilitate the development of high intensity and high efficiency combustors with special focus on reducing pollutants emission.

A mathematical model of combustion process in a diesel engine has been developed according to the theory of the chain reactions for the higher hydrocarbon compounds. The instantaneous rates of fuel vaporization and combustion are defined by the current values of temperature, pressure, concentration of fuel vapors, overall diffusion rate, fuel injection rate, and mean fuel droplet size in terms of the SMD. Numerical experiments have been carried out for investigating the interdependencies between various combustion-related parameters. Specifically, the effect of fuel droplet size (in terms of SMD) on the subsequent combustion parameters, such as, pressure, temperature, thermodynamic properties of air/gas mixture, heat transfer, fuel vaporization, combustion rate, current A/F ratio, gas mixture composition have been investigating. In addition, the integral indicator parameters of the engine, such as the mean indicated pressure, peak pressure, compression pressure have been analyzed.