微型燃烧器内甲烷预混催化燃烧的数值研究
首发时间:2007-12-17
摘要:微尺度燃烧存在热量损失大、易熄火、燃烧不完全、转化效率不高等问题,因此对微型燃烧器内甲烷的燃烧采取预混催化燃烧方式,来提高燃烧的稳定性和转化效率,为微型发动机碳氢燃料燃烧技术奠定基础。采用连续介质层流有限速率模型和二阶离散方法对微型燃烧器微流道内的催化燃烧、流动和传热进行了详细的三维数值模拟。结果表明,随着甲烷质量流量的减小,催化转化效率相应增大。过量空气系数的增大使催化转化效率先增后减。当催化壁面温度增大和甲烷质量流量减小时,最佳过量空气系数增大。催化壁面温度是影响催化转化效率的主要因素,催化转化效率随催化壁面温度的升高而迅速增大。可根据催化温度来选取最佳过量空气系数,选择富燃料或富氧燃烧方式提高微尺度催化转化效率。在恒壁温边界条件下,催化燃烧主要发生在燃烧腔的下壁面。
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Numerical Investigation of Premixed Catalytic Combustion of Methane in Micro-combustor
Abstract:Considering that micro combustion is easy to flameout, great heat loss, incomplete combustion and low efficiency and so on. The premixed catalytic combustion of methane in micro-combustor to improve combustion stability and combustion efficiency is studied. It lays the foundation for the technology of hydrocarbon-fuel combustion in micro-engine. Numerical Investigation of catalytic combustion, flow and heat transfer in micro-channels of three-dimensional micro-combustor was done by using laminar finite-rate and second-order upwind discretization model. The numerical Investigation results show that catalytic combustion efficiency increases while mass flow rate of methane decreases. While coefficient of excess air increases, catalytic combustion efficiency firstly increases and then decreases. Optimal coefficient of excess air increases, while temperature of catalytic wall increases and mass flow rate of methane decreases. Temperature of catalytic wall is the primary influence factor of catalytic combustion efficiency. Catalytic combustion efficiency increases immediately, while temperature of catalytic wall increases. To improve micro catalytic combustion efficiency, the optimal coefficient of excess air and a proper of oxygen-enriched (or fuel-rich) combustion method should be selected according as temperature of catalytic wall. While temperature of wall is treated as constant thermal boundary condition, catalytic combustion is mostly happened on the downside wall of combustion-chamber.
Keywords: micro-combustor methane premix catalytic combustion numerical investigation
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No.1702617618611978****
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