Prformance Characteristic Analysis And Experimental Research Of Hot Water Rocket Motor

The development of rocket motor has shown a diversified trend nowdays. There areincreasing requirements in the areas of space exploration and ground propulsion. Chemicalrocket motor has been considered as priority selection of large thrust propulsion system,butthe propellant used in chemical rocket motor can cause certain pollution to the environ-ment.As the environment problem has been concerned by people,looking for new kinds ofpropellant becomes the urgent matter. The rocket motor which uses hot water as propellantcan be named as hot water rocket motor. Comparing with the rocket motor which uses purevapor as the propellant, hot water rocket motor has the advantage of large thrust due to thehigh spray density.Besides,it has the advantages of green and low cost,comparing with thetraditional chemical rocket motor.In order to understand the internal ballistic performance of the hot water rocket motor,the experimental system of hot water rocket motor was built.The experiments were carriedrespectively under different initial pressure, spray pipe diameter and water filling quantity.Itis experimentally found that in the process of motor working,the pressure curve experiencesa sharp decline first and then slowly drop process.It is also found that the specific impulseof the hot water rocket engine is greatly influenced by initial pressure.However,the spraypipe diameter and water filling quantity have no effect on specific impulse.In order to understand the working performance of the hot water rocket motor, anumerical model of the hot water rocket motor is established in this paper. And thenumerical model is validated via comparing the calculated results with experimental value.According to the study of the flow field in the nozzle,the flow process in the nozzlecan be divided into three processes, which are single-phase flow process, flash process dueto depressurization and expand-accelerating process.Results show that the pressure firstlydrops to the saturated pressure corresponding to the initial temperature in the convergentsection and then continuously decreases along the axial direction. Besides, the phasechange occurs at the nozzle throat, where the main flow would change into a two-phaseflow.Then, the two-phase flow transferred from a subsonic condition into supersonic flow after the throat because of the changing sound speed.In order to study the influential factors of nozzle performance of hot water rocketmotor,numerical simulations of the flow field in the nozzle were performed under differentparameter conditions.The effects of different initial conditions such as pressure,vaporvolume fraction,supercooling and different nozzle structures(nozzle expansion ratio,converging half-angle and expansion half-angle) on the thrust were systematicallyinvestigated.The calculating results showed that the greater the initial pressure, the greaterthe thrust.As the inlet vapor volume fraction increases, thrust would experience a process offirst increases and then decreases.Motor thrust is larger when the initial temperature iscloser to the saturation temperature.Thrust would experience a process of first increases andthen decreases with the increasing of nozzle expansion ratio.The impact of converginghalf-angle on the thrust is minor.The greater expansion half-angle, the smaller the thrust.By studying the influence of the blocking to the motor,it is found that the pressure atthe front part of the blocking is larger than the surrounding pressure.Meanwhile,the vaporvolume fraction is smaller than the surrounding value. And the speed increases firstly andthen decreases,and then increases.According to the study of the working process of the motor, the process can be dividedinto three stages,which are initial segment,middle segment,and a trailing segment.Totalimpulse of the motor is mainly concentrated in the middle segment.By studying the influence of non-condensable gas on the motor,it is found that thethrust is larger when the gas effect is ignored,while the working time of the motor is longer.Through studying the influence of the gravity on the motor,it is found that the gravityeffect can be ignored when the size of the motor is not big enough.As for the large sizemotor, the maximum thrust value is basically the same.While the working time becomeslonger and the total impact becomes larger when the gravity is considered.Put forward the formulas to calculate the maximum thrust, water added ratio andspecific impulse,and then the steps of the design of hot water rocket motor are summarized.