Study On The Atomization Tests And Combustion Characteristics Simulation Of Air-Heater Pintle Injectors

Pintle injectors have the advantages of simple structure,wide range of flux adjustment,high combustion efficiency,and stable combustion so that they are widely used in variable thrust liquid rocket engines.Now pintle injector is combined with air heater for the development of a new air heater which can vary working conditions.In this dissertation,flow characteristics and atomization characteristics are studied by experiments,and combustion performance of air heater is studied by numerical simulation.The results obtained in this dissertation have some reference value for the optimal design of air heater which can vary working conditions.Firstly,flow characteristics are studied by experiments,the relationship between flow coefficient of each propellant and injection pressure drop is verified.It investigates whether one propellant's flow characteristic is affected by other propellants flow processes.the influences of structural parameters of ethanol pintle on flow characteristics are also studied.The results indicate that when outlet throttling area of ethanol is constant,if flow distance of ethanol becomes shorter,the number of ethanol injection holes becomes more,and the upward angle of ethanol injection holes becomes smaller,the pressure loss will reduce.Due to the compressibility of air,air has a certain blocking effect on the flow of liquid oxygen when air injection pressure drop is greater than liquid oxygen injection pressure drop.Secondly,atomization characteristics of tripropellant pintle injectors are studied by using high-speed photography and Malvern measuring instrument,the influences of each propellant injection pressure drop on atomization cone angles and SMD and drop distribution homogeneity factors were obtained,the influences of structural parameters of ethanol pintle on atomization characteristics were also studied.The results indicate that the greater injection pressure drop of air and liquid oxygen which are injected axially becomes,the smaller atomization cone angles can be got.When outlet throttling area of ethanol is constant,increase of the number of ethanol injection holes will make atomization cone angle distribution more evenly.In the axial direction,with the increase of the distance,SMD and drop distribution homogeneity factor are diminished,however,they maintain unchanged when the distance increases a certain value.The greater injection pressure drop of air and liquid oxygen becomes,the greater fragmentation of the ethanol droplets is obtained.Lastly,the influences of air heater's structure parameters on the air heater's combustion performance are studied by numerical simulation.The results indicate that two key parameters of air heater,characteristic length and combustion chamber diameter,have a great influence on combustion efficiency,however,the structure parameters of pintle injector have little influence on combustion efficiency,but they will affect the internal combustion flow field of the air heater.