不同喷油压力RP-3航空煤油、柴油碰壁喷雾着火和燃烧特性的对比研究

利用直径0.22mm的单孔喷嘴高压共轨喷油器,以喷油器油量标定数据及控制参数为基础,采用高速相机成像技术在定容燃烧室内在等喷油量变喷油压力的前提下测量了着火点、着火滞燃期、燃烧持续期、火焰面积(AF)和火焰自然发光强度(SINL)的变化规律,对比研究了RP-3航空煤油、柴油碰壁喷雾的着火和燃烧特性。结果表明:在低喷油压力下着火点分布在离壁面较远的区域,在较高喷油压力下着火点位于壁面上,距喷油器中心线的距离随喷油压力的增加而增加,且RP-3航空煤油着火点距喷油器的距离比柴油更远。随着喷油压力的增加,RP-3航空煤油碰壁喷雾火焰的着火滞燃期先降低后增加,柴油碰壁喷雾火焰的着火滞燃期不断降低,且RP-3航空煤油具有更短的着火滞燃期。燃烧持续期随喷油压力的增加而降低,RP-3航空煤油的燃烧持续期比柴油短。喷油压力越高,火焰面积(AF)和自然发光强度(SINL)的变化速率越高,而AF和SINL的最大值及达到最大值所需的时间越小。与柴油相比,RP-3航空煤油的AF、SINL具有更高的变化速率,且AF、SINL的峰值更高,达到峰值的时间更短。

Comparative Investigation of Ignition and Combustion Characteristics of Wall-Impinged Kerosene(RP-3) and Diesel Sprays at Different Injection Pressures

The ignition and combustion characteristics of wall-impinged kerosene(RP-3) and diesel spray were comparatively investigated under the condition of a fixed injection mass and different injection pressures and based on calibrated fuel injection quantity data and corresponding control parameters. Adopting a common rail nozzle with single-hole of 0.22 mm, the experiments were conducted in a constant volume combustion vessel to simulate diesel engine condition. Flame images were captured using a high-speed camera, and then the behaviors of ignition and combustion were processed. The variation laws of ignition position, ignition delay time, combustion duration, flame area(AF) and spatially integrated natural luminosity(SINL) of both wall-impinged fuel sprays were determined by analyzing the flame images. The results show that at low injection pressures, the ignition positions of both fuels are in the region that is far from the wall surface. At high injection pressures, the ignition positions of both sprays are on the wall surface, and are pushed farther away from the injector center-line with the increase of the injection pressures. The ignition positions of the kerosene spray are farther away from the injector center-line than those of the diesel spray. The ignition delay of the wall-impinged kerosene flames shortens first and then prolongs with the increase in the injection pressure, and that of the diesel flames reduces with the increased injection pressure. The kerosene RP-3 spray has a shorter ignition delay than the diesel spray. The combustion durations of both sprays are shortened with the increased injection pressures, but that of the kerosene RP-3 spray is shorter. Increasing the injection pressures enhances the variation rates of AF and SINL of both sprays, but the maximum values of AF and SINL and the time to reach them decreases. The kerosene RP-3 spray has higher variation rates of AF and SINL, greater values of the maximum AF and SINL, and shorter time to reach the maximum AF and SINL compared to the diesel spray.