Internal Ballistics And Convection Base-heating Environment Of Solid Bundled Rocket

Solid bundled rocket with liquid core and four boosters not only hasthe advantages of simple structure, high reliability, long-term storage, italso has the advantage of easy control, high impulse. More and morecountries focus on the bundled rocket as their new high-thrust rocket. Withthe increasing demand of space exploration and space station construction,China has established a solid&LOX/kerosene rocket, which is the first tryof our country. Solid rocket would bring two main aspects:(1)booster jetsand liquid core jets will interact with each other, their collision can cause ahigh temperature region and cause backflow to heating the cryogenic tankequipment on the rocket bottom;(2)solid rocket motor plume containAl2O3solid particles, which will not only improve the plume radiationeffects, but also improve the backflow gas temperature. The two pointsabove can increase heat transfer to the bottom of the rocket body. If wecannot calculate the precious heat transfer value on the bottom based onin-depth study, we cannot make a reasonable thermal protective measures,it’s likely to result in cryogenic propellant tank explosion due tooverheating.Solid rockets ballistic and bundled rocket bottom thermal environmentare two key issues for the solid-liquid bundled rocket. Ignition, internalcombustion and grain motion transient processes are study by numericalsimulation method. The simulation can calculate the ignition delay time,burning energy, grain motion velocity and other key parameters of the trajectory. Numerical simulation model of HTPB propellant combustionwas established under the condition of six different lateral acceleration bycalculating the transient combustion rate based on the Greatrix algorithm.Non-uniform motion of annular combustion chamber was presented byFluent local re-mesh method. New combustion velocity formula has beenestablished as a function of acceleration and load-azimuth angle.Supersonic gas-particle two-phase method was used to simulate solidrocket flow field structure based on the booster trajectory parameters.Validation of bundled rocket numerical simulation method is ensuredthrough H-ⅡA rocket model. Finally, thermal environment of bundledrocket is calculated by using the new validated method, which present therelationship between flow structure and altitude.The results show that: the plume expansion angle of low altitude issmall, string-type tail shock is distribute below the nozzle outlet, shock sizeand energy will decrease with the increasing of distance from nozzle outlet.whirlpool will appeared near the jet flow epitaxy at moderate altitude. Withthe increasing of altitude, expansion angle increases. Flow continuity willbe destroyed due to the solid particle influence. Particles whose diameterlarge than10μm cannot move along the backflow. Maximum heat fluxappeared on the bottom of liquid core, heat flux at the upper rocket bodyside become negative when altitude large than10km. The heat flux showeda increasing trend at first,reaches the maximum at about30km altitude,andthen decreasing with the increasing of altitude. Environmental pressure,stream velocity, jet interference is the most critical factors of bundledrocket bottom thermal environment.