不同外部风温对微尺度火焰的影响

Effect of external wind temperature to micro-scale flame

为了研究微尺度燃烧器由于散热造成燃烧稳定性差的问题,对微尺度燃烧器外部吹风控制表面散热,对比不同工况下燃烧器的工作性能.当燃料混合气体体积流量为0.12、0.24、0.36L/min时,风温分别为277.15、380.15、635.15、790.15、1 001.15K.实验结果表明,提高冷却风温或燃料流量可以抑制熄火.测量燃烧器壁面温度,结合数值模拟,研究内部燃烧过程.结果显示,随着冷却风温上升,反应区域峰值温度上升且向上游偏移.在0.24L/min,燃料气体当量配比下,当冷却风温由277.15K上升到1 001.15K时,峰值温度上升约165K,反应中心上移约5mm.证明高温冷却风通过减少散热,提升反应强度,抑制热熄火.当体积流量由0.12L/min上升到0.36L/min时,虽然壁面散热量上升,但占总能量的份额相对降低,因此提升燃料流量可以抑制热熄火.

The surface heat loss of a micro combustor was controlled by the external wind temperature and the performances of the combustor under different wind temperatures were compared in order to analyze the stability of micro combustor affected by the heat loss.The flow rates of fuel mixture were 0.12,0.24,0.36 L/min.The wind temperatures were adjusted to 277.15,380.15,635.15,790.15 and 1 001.15 K.Experimental results show that increasing the wind temperature or fuel-mixture flow rate can inhibit the extinction.The surface temperatures of the combustor at different conditions were measured.The numerical simulation was applied to investigate the internal combustion process.Results showed that the higher wind temperature made the reaction temperature increase and the reaction region shift upstream.At 0.24 L/min and stoichiometric condition,the peak temperature increased by 165 K and the reaction region shifted upstream by 5 mm while the wind temperature increased from 277.15 K to 1001.15 K.Accordingly,high wind temperature intensifies the reaction rate,thus inhibites extinction.The heat loss increased while the flow rate increased from 0.12 to 0.36 L/min.But the ratio of heat loss to total energy decreased,which indicated that increasing fuel-mixture flow rate can inhibit extinction.