雾化特性对喷雾燃烧点火过程的影响

Effects of Spray Characteristics on Ignition Process in Spray Combustion

关键词:  喷雾燃烧  雾化特性  点火过程

Key words:  Spray combustion  Spray characteristics  Ignition process

摘要:

为了研究雾化特性对喷雾燃烧点火过程的影响，用马尔文激光粒度分析仪等雾化测量系统，对离心喷嘴流量、喷雾锥角、周向不均匀度、液滴索太尔平均直径(SMD)、液滴尺寸分布指数(N)等雾化特性进行了测量；采用高速摄影机和热电偶测温系统，记录了燃烧室内点火过程和燃烧室出口温度变化历程，揭示了初始火焰形成及火焰传播过程，探讨了喷嘴雾化特性对燃烧室初始火焰形成、火焰发展、出口温升开始时间、最大温升时间以及温升率等点火过程和点火性能的影响规律。研究结果表明:随着供油压力的提高，离心喷嘴的燃油流量呈现二次曲线增加，SMD逐渐减小，N值呈现先下降后上升的趋势。在点火油气比为0.0078～0.0125时，随着供油压力的提高，初始火焰变长，火焰的发展先沿着靠近燃烧室上壁面部分向下游发展，再向燃烧室中下部分发展，火焰亮度增强，燃烧室出口温升开始时间缩短，最高温升时间增大，温升率提高，最大温度值上升。在相同的点火油气比下，距离燃烧室上壁面1/4燃烧室高度处热电偶(TC-1)温升值和温升率最高，温升开始时间最低；距离燃烧室上壁面3/4燃烧室高度处热电偶(TC-3)温升值和温升率最低，温升开始时间最高。

Abstract:

In order to study the effects of spray characteristics on ignition process in spray combustion，the variation of flow characteristics，spray cone angle，circumferential non-uniformity，sauter mean diameter(SMD)and droplet size distribution index(N)were measured by the Malvern laser particle size analyzer. The ignition process and?combustor outlet temperature were recorded by the high-speed camera and thermocouple temperature measurement system. The?initial flame formation and flame propagation processes were revealed. The effects of atomizer atomization characteristics on the initial flame formation，flame propagation processes，temperature rise rate，start and the maximum time of combustor outlet temperature rise were discussed. The results showed that with the increase of the fuel pressure，the flow rate of the pressure-swirl atomizer increased presenting a quadratic curve relationship，SMD?gradually reduced，and droplet size distribution index initially decreased and then increased. When the ignition fuel-air ratio was between 0.0078 and 0.0125，with the increase of fuel pressure，the flame initially propagated near the top of the combustor，afterwards it moved to the bottom of the combustor. The length of initial flame increased and flame became brighter. Also the start time of combustor outlet temperature rise was reduced，the maximum temperature rise time，temperature rise rate and the maximum temperature increased. For the same fuel-air ratio，the temperature rise and temperature rise rate of the TC-1 thermocouple were the highest and the start time of temperature rise was the minimum at the position of 1/4H from the upper wall of combustor. (H means height of combustor). Meanwhile the temperature rise and temperature rise rate of the TC-3 thermocouple were the lowest and the start time of temperature rise was the maximum at the position of 3/4H from the upper wall of combustor.