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| Based on dimethyl ether(DME) engine experiments, a turbulent combustion model was developed to study the combustion characteristics of DME engine. It consisted of two sections. First, the correlation of DME thermal properties to temperature are required for numerical simulation of DME spray and combustion process, but cannot be obtained instantly through measurement. So molecule theory was applied here to estimate the correlation of the DME thermal properties to temperature, including latent enthalpy, surface tension, thermal conductivity and diffusion coefficient. And other DME thermal properties measured by experiments, including vapor pressure and viscosity coefficient, are also collected here. Then the combustion model was developed. The model took into account the influence of turbulence on combustion by coherent flamelet model(CFM) in addition to the original chemical kinetic model, so closer to the experiments and can be applied to the qualitative analysis of DME engine combustion. Numerical simulation indicated that, in engine condition DME spray has short tip penetration than diesel oil, with almost no wall impingement occurring. The upper edge of spray near the nozzle ignite first for the appropriate fuel concentration and higher temperature. In diffusion combustion the combustion is slow and lasts long for the slow air-fuel mixture formation. The results of numerical simulation are in good agreement with experiments. |
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| Keywords:dimethyl ether(DME); thermal properties, molecule theory, CFM model, combustion characteristics |
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