Research On The Combustion Process And Combustion Technology Of Boron-based Solid Ducted Rockets

The investigation of combustion process and combustion organization technology in a solid ducted rocket chamber was conducted in this article.Theoretical analysis,numerical simulation and experiment were used in this study.The study focused on the combustion characteristic and performance evaluation of solid ducted rocket chamber,to increase the combustion efficiency.In this paper,theoretical modeling of boron and carbon combustion process was taken place firstly,then numerical approach and experiment methods were built,the combustion characteristic of solid ducted rocket chamber with a chin inlet was explored,finally,the combustion organization technology of solid ducted rocket chamber with different type was summarized.The detail combustion process of boron particles was analyzed,it contained four stages:the ignition stage,the combustion stage,the gas combustion stage,the boron oxide condensation stage.Theoretical modeling of each stage was taken place.The ignition and combustion model of boron was extended from the model formulated at Penn State University(PSU model).At the ignition stage,the balance of(BO)_n on the liquid oxide layer surface was considered.At the combustion stage,the evaporation and boiling processes of boron were considered.The validation showed that the extended model was suitable for a single boron particle,especially at the combustion stage.The results showed that combustion process was dominated by both chemical kinetics rate and diffusion rate.The control mechanism would change at different situation and different period at combustion stage.The oxygen mole fraction and pressure showed great influence on boron combustion.The Chemkin software was used to study the gas combustion process,the reaction time and reaction path was analyzed.The classical nucleation and continuous droplet growth model was used to deal with the condensation phenomenon of boron oxide.It was found that low temperature,high pressure,high concentration of boron oxide and nuclei particles could improve condensation of boron oxide.The carbon combustion model was built,parameter effect was conducted.Ground direct-connected experiment system was built,methods of the data measurement and data process of solid ducted rocket were established.Simulation model and approach were proposed,the feasibility of the approach was verified by experimental data.The experimental data of condensation of water vapor in a subsonic nozzle,the ethylene/air simulant fuel mixture experiment,the ground direct-connected experiments in this study were used to validation this numerical approach.Validation showed good agreement between the approach’s results and available experimental data.The predicted chamber pressure and thrust had an accuracy within 6%and 10%in comparison with the experimental data in this study.Numerical and experimental investigations on the characteristics of combustion chamber in a boron-based solid ducted rocket with a chin-type inlet were conducted.The combustion of fuel-rich gas from gas generator in this combustion chamber was difficult,the combustion efficiency was only 52.84%,because of the poor mixing and low ignition ability.A new configuration of solid ducted rocket with swirling flow was proposed,the results showed that the chamber with swirler I gained good performance of thermal protection and combustion efficiency of 88.14%.To increase the ignition ability,two holes were machined at the side wall of swirler,part of the ducted air could flow into the swirler and react with gas firstly,it produced high temperature and improved the ignition performance of boron particles.The combustion efficiency gained from 88.14%to 98.12%.Ground direct-connected experiments were conducted to verify the conclusion above.The performance of solid ducted rocket with swirler was revealed.The experimental results indicated that the conclusions above are right.They includes the effect of propellant,chamber length,swirling flow and air fuel ratio on the performance of solid ducted rocket chamber.The combustion efficiency of boron-based solid ducted rocket with swirling flow could reach 94.54%,6.5%more than the one without swirling flow.Finally,combustion characteristics of three chambers with different inlet type were conducted.the effects of air fuel ratio,pressure and chamber configuration on the flow field and combustion performance were analyzed.The results showed that the combustion performance differed,chamber with two inlets and inlet angle of 90°had the highest combustion performance.Recirculating flow and swirling flow was induced by the impinging jet,it would improve the ignition and combustion process.The combustion organization technology of solid ducted rocket chamber with different type was summarized.The decreasing of gas velocity,the increasing of gas port number could improve the combustion efficiency(90%or more).The design of characteristic length was established based on the combustion model of boron.