发动机进气道天然气/空气混合流场的纹影显示

研究天然气/空气在发动机进气道中的混合特征以及喷射压力、流速和喷嘴布置对混合效果的影响.采用抽吸式风洞进行实验研究.进气流量由矩形通道中的喉道(声速面)控制.采用纹影对天然气/空气流场进行光学显示,得到了不同喷射压力、喉道高度和喷嘴布置(单列6喷嘴和3列18喷嘴)条件下的流场纹影照片.结果表明对指定喷射压力、喷嘴布置压力工况,当喉道高度为7.1mm,节流阀角度小于64.87°,天然气/空气混合流场与节流阀开度无关;当喉道高度为16.4mm,节流阀角度小于51.38°,天然气/空气混合流场也与节流阀开度无关.喷射压力和喷孔数决定着天然气的流量.尽管支架会引起流动阻力,影响进气效率,但支架喷射的混合效果要比壁面喷射的效果好.天然气流量由喷射压力和喷孔数决定,未观察到天然气向支板上游的气流中扩散.

Experimental visualization on natural gas-air mixing in engine intake

This paper studies the natural gas(NG)-air mixing characteristics in engine intake and the effects of injection pressure, flow speed and injector alignment. The ejection-type wind tunnel was built as a test rig. The air mass flow rate was determined by sonic throat in the duct and schlieren photograph was used to visualize the mixing flow-field. The schlieren pictures were obtained at different injection pressure, sonic throat height and injector alignment. The results show that the NG-air mixing is independent of the throttle angle less than its critical value at the specified flow speed as well as the NG injection pressure. When the values of throat height are respectively 16.4mm and 7. 1mm, the corresponding values of critical throttle angle with respective to the stream-wise direction are 51.38° and 64.87°. In contrast to wall injection, the strut injection can enhance NG-air mixing and avoid NG penetration difficulties, although the drag of strut is large. The mass flow rate of NG depends on the injection pressure and injector numbers. Upstream or the strut within the duct flow, no NG diffuses adversely.