Experimental Investigation On The Spray Characteristics Of Varaible Pintle Injectors

Based on the throttling liquid rocket engine,the flow and spray characteristics of the adjustable pintle injector were studied by theoretical analysis and experimental research.The effects of the blockage factor,the sleeve expansion angle,the orifice type and the momentum ratio on the flow and spray characteristics were analyzed.The research could inspire the design of the throttling pintle engine to some extent.Firstly,the law of mass flow rate characteristics with structure parameters and operating conditions was obtained with experimental methods.The results indicate that structure parameters have a large impact on the flow characteristics of the pintle injector than pressure drop.To specify,the structure parameters had a large impact.C_d decreases with the decrease of injection area.However,C_d increases when the blockage factor and sleeve expansion angle decrease.Secondly,by using high-speed photography,Malvern and NPLS technology,a series of experiments were conducted.The influence of blockage factor and sleeve expansion angle were investigated.The results show that the spray angle decreases to40°to the full extent when the blockage factor increases from 0.6 to 0.8,the SMD increases to 250?m and the spray gets more concentrated.The sleeve expansion angle has an indistinctive effect on the spray angle,but does influence the breakup of the spray.SMD plummeted to 30°when the sleeve expansion angle was reduced by more than 90°.Finally,in order to investigate the change of the spray characteristic essentially,the influence of the hole shape and the momentum ratio on the spray pattern was obtained by high-speed photography and NPLS technology.The results indicate that the half spray angle increases to 30°when the momentum ratio increases from 0.07 to 0.56.The flow field of the pintle injector with trapezoidal holes hole shocks sharply,mainly affected by LMR.Besides,the aspect ratio of the rectangular hole has a great influence on the spray pattern,the half spray angle decreases to 18.1°when the aspect ratio increases from 4.4 to 7.71.