Research On Key Techniques Of Platelet Injector In Rocket Engines

The platelet injector is a new type of liquid rocket injector that is widely used in low thrust attitude control engine because of unique features,including excellent response,simple structure,and potential high performance with reduced chamber length.However,understanding o n the atomization and combustion characteristics of platelet injector are still needed.In this work,a gaseous oxygen/methane splash platelet injector was designed on the basis of existing structures and current domestic and international experimental data.The numerical simulation method was used to model and analyze the injector.The structure of the injector was improved,and the combustion chamber wall was cooled through the film-cooling method.Finally,a test bench was constructed,and experimental methods were employed to study the atomization and combustion characteristics of single-and multi-element splash platelet injectors.The influences of different design parameters on the atomization and gas-gas combustion characteristics of the injector were also revealed.First,the combustion characteristics of single-and multi-element splash platelet injectors were simulated in accordance with the design parameters of different injectors.In addition,the relationship and differences between cold flow and combustion were analyzed.Results showed that different design parameters exert different effects on the gaseous methane/oxygen combustion characteristics of the injectors.For example,the analytical results for temperature distribution,composition distribution,and flow field structure revealed that expanding angle and length of trapezoidal orifice had considerable influences on the combustion characteristic of the single-element splash platelet injector.Comparing the analytica l results for the three types of injectors with different structures showed that cold flow was not an effective predictor of combustion characteristics.Cold flow and combustion characteristics varied when injector parameters were changed.Second,the numerical method was adopted to simulate film cooling performance in the proposed platelet injector.Gaseous methane was used as the coolant.Results showed that the film cooling method can effectively reduce the wall temperature of the combustion chamber.Decreasing the slot height improved cooling performance.Meanwhile,increasing the slot number and changing mixing ratios minimally affected cooling performance but greatly affected injector faceplate temperature.Changing the configuration of the cooling slots or the position of the injection slots did not improve cooling efficiency.Therefore,the influence of various factors should be comprehensively considered in future research to improve the cooling effect of the injector.Third,four kinds of single-element splash platelet injectors with different structures were designed.The flow and atomization characteristics of the injectors were studied through several test methods.The atomization characteristics of each injector under different pressures were identified.The atomization spray angle,impact angle,and impact point position of the injectors were obtained by combining the results of high-speed photography and test methods.Finally,the flow and combustion characteristic s of gaseous oxygen/methane were studied through experimental methods,and the feasibility of the ignition mode of the spark plug was verified.Results showed that enhancing the mixing ratio increased combustion efficiency and negligibly decreased the comb ustion efficiency of the combustion chamber.Combustion efficiency under the multi-element condition was slightly higher than that under the single-element condition.Heat load exerted considerable effects on the injector faceplate.The film cooling method can be used to reduce the faceplate temperature of the multi-element injector effectively.Under the single-element condition,the injector faceplate exhibited different degrees of deformation,and the SP1 injector faceplate was severely ablated.The defo rmation or failure area was located between the two injection holes.