Experimental And Simulation Studies On The Spray Characteristics Of Impinging Nozzle

On the background of the liquid rocket engine,by using of HAN-Based liquid propellant simulated medium,the experiment.theory analysis and numerical simulation of the spray characteristics of the impinging nozzle are conducted both in atmosphere and in simulated combustion chamber.The main research contents and results are as follows:(1)The spray parameters in the spray field of the impinging nozzle are tested by using PDA system both in atmosphere and in simulated combustion chamber.The results show that,the higher the nozzle pressure is,the smaller the droplets’ Sauter mean diameter is at the same cross section.When improving the quality of atomization by increasing injection pressure,the injection pressure exists an optimum value.When the injection pressure is bigger than 2.2MPa,increasing the injection pressure has no effect on droplets’ D32.In the upstream of the spray field,the droplets’ number distribution fluctuates greatly in the radial direction,it becomes gentle downstream.The droplets’ diameter and axial velocity in simulated combustion chamber are bigger than that in atmospheric environment at the same injection pressure and the same cross section.(2)Based on maximum entropy principle,the droplet size distribution function was derived by using Lagrangian method under the given constraints that is mass con servation and that the sum of probability is constant.The distribution function of Nuki yama-Tanasawa is dN/dD = aD2 exp(-bD9).The results indicate that,an improved met hod of differential number distribution was revised by using least square method to op timize q,the function relationship between q and injection pressure p was fitted as g(p)=-3.44×10~3×p2+1.525×10-1×p+1.268.The results show that the changing tren d of the calculated droplet size differential number distribution agrees well with experi mental data of the impinging nozzle.(3)Multidimensional physical model and mathematical model(including continuous phase equations and discrete phase control equations)are established,the discrete phase model(DPM)is chosen to calculate the coupling of the discrete and continuous phases.The discrete phase is the droplets,the turbulence model SST κ-ω is used in the gas phase,the WAVE model is used in drop breakup.Both a two-dimensional model and a three-dimensional model are set up of the atmospheric environment and simulated combustion chamber,also,the grid independence of the model was carried out,all of these serves as a foundation for multidimensional numerical simulation of the impinging nozzle.(4)A two-dimensional unsteady simplified model above is established and numerical simulations are conducted with the help of Fluent,the spray presents a cone shape toped with the impinging point in atmospheric environment.The simulated results of droplets’ axial velocity and D32 agree well with the experimental results.The spray cone angle increases with the increasing of impinging angle,the time of the spray field being statistically stable takes longer time,the droplets’ D32 and axial velocity along the axial direction show a decreasing trend;The higher the viscosity of the simulated media,the more structured form of spray cone,with less discrete droplets at the edge of the spray field,the droplets’mean diameter increases and axial velocity decreases at the same cross section;When the diameter of the nozzle increases,spray penetration distance increases with less discrete droplets at the edge of the spray field.In simulated combustion chamber,when the impinging angle increases,both D32 and vz in the simulated chamber turn small;The viscosity of the simulated media becomes higher,the edge gathers more droplets compared with atmospheric environment,the droplets’Sauter mean diameter increases;The bigger diameter of the nozzle is,the bigger droplets’ D32 will be.(5)A three-dimensional unsteady spray model is established to calculate the spray parameters of the HAN-Based liquid propellant simulated medium in the spray field of the impinging nozzle with the help of Fluent in atmospheric environment and simulated combustion chamber,the results show the spray pattern can be obtained more clearly by the three-dimensional unsteady model.The droplets’ Sauter mean diameter and vz in atmospheric environment basically tally with the experimental results,the maximum deviation error is 5.38%;The droplet size of the atomized droplets is unevenly distributed along the circumferential direction,with the increasing of radial distance,the degree of fluctuation becomes larger;The maximum relative error of D32 and v2 between calculated results and the experimental results is 4.83%.The calculated droplets’ D32 along the circumferential direction agrees well with experimental results.Compared with calculated results and experimental results of the two-dimensional and three-dimensional spray results in both atmospheric environment and simulated combustion chamber,the deviation error differs little.So,the two-dimensional unsteady spray model can be used to satisfy engineering application.