不同压力煤油气溶胶点火延时的测量研究

Study on ignition delay of kerosene aerosol in shock tube

研究不同压力(0.1,0.3,0.6MPa)的化学计量比煤油/空气溶胶点火延时.研制了新型两相激波管,采用室温He/N2为驱动气体和缝合接触面运行,反应区温度范围是1160～1650K,基于压电传感器和数据采集系统,测量了不同点压力时间曲线,以OH(波长约306nm)发射光作为点火指示信号,用ICCD拍摄反射激波后的燃烧流场.结果表明:当压力为0.1MPa、温度为1068K,可获得实验时间约19ms.本文条件下,测得煤油点火延时τig约0.1～6ms.与加热方式相比,煤油气溶胶在低温时点火延时偏大.不同初压的ln(τig)与10000/T均呈线性分布.压力测量显示:当压力为0.1MPa、温度大于1500K,点火过程中出现了当地爆燃,伴随明显的压力振荡,出现爆燃的当地温度随初压升高而降低.对低温自点火工况,煤油火焰面呈非平面结构.在反射激波后,出现随机分布的自点火区域.随着温度升高,自点火呈平面火焰结构.

The ignition delay of stochiometric kerosene aerosol was investigated over a temperature range of 1 160-1 650 K, at pressure of 0.1, 0.3 and 0.6 MPa. A two-phase shock tube was developea to provide an auto-ignition region behind reflected shock waves. He/N2 mixture at room temperature was used as a driver gas to get the tailor condition. Pressure time histories at different stations were measured by piezoelectric gauges and the data acquisition system. Using OH emission near 306 nm as an ignition indicator, the flame image behind reflected shock waves was captured by ICCD. The results indicate that test time up to 19 ms was achieved at the temperature of 1 068 K and pressure of 0. 1 MPa. The ignition delay in this paper ranges from 0. 1 to 6 ms, which is close to that of gasified kerosene at high temperature, but longer at low temperature, In（τig） almost depends on 10000/T linearly at a specified pressure. In the auto ignition region, the pressure histories show that local deflagration occur with subsequent pressure oscillation at temperature above 1 500 K and pressure 0.1 MPa. The critical temperature of local deflagration decreases as pressure increasing. ICCD images indicate the flame front is not exactly planar and auto-ignition occurs randomly behind reflected shock waves.