Formulation Design And Combustion Properties Of Composited Energetic Particle HTPB-based Fuel For Hybrid Propulsion

Hybrid rocket engine which present advantages over solid rocket motor and liquid rocket engine,with features such as high specific impulse,throttleability and high reliability is a fascinating propulsion system.However,the low regression rate of solid fuel is one key factor that restricts the development of hybrid propulsion.In consideration of the excellent mechanical property,solid fuel based on hydroxylterminated polybutadiene(HTPB)was selected.To improve the regression rate of solid fuel efficiently,the combustion characteristics of HTPB-based fuels doped with high energy particles were scientifically investigated by adding different metal particles with different diameters and mass fractions.The specific studies are as follows:The HTPB fuel comprises HTPB,dioctyladipate(DOA),isophorone di-isocynate(IPDI)and dibutyltin dilaurate(TIN).The formulations of HTPB-based fuels were prepared by addition of Mg particles and A1 particles with different diameters at a mass fraction from 5%to 15%.The density of HTPB fuel samples prepared by a home-made facility was measured to be 0.906 g/cm3,it is the theoretical charge density of 99.02%,which indicated the grain has good compactness.The SEM images revealed that the Mg particles were distributed evenly in grains,while Al particles grouped into agglomerates due to nano-diameter.The results of TG-DSC tests showed that the heat release of HTPB-based fuels would increase with the increasing the mass fractions of metal particles.The combustion characteristics of HTPB-based fuels were investigated by a testing system using high speed camera.Compared with undoped fuel,the combustion characteristics of the fuels of interest were improved remarkably owing to the evidently increased thermal feedback caused by high energy particles.When the oxidizer(Gox)mass flow is 370 kg/(m2·s),the regression rate of the formulations which were added with 20?m,50pm,100?m Mg particles at a mass fraction of 5%were increased by 75.61%?47.07%and 40.18%respectively,and at the same time the mass burning rate were increased by 80.13%?53.65%and 37.27%respectively,when compared with the pure HTPB fuel.When the mass fractions of 20?m Mg particles varied from 5%to 15%,the regression rate increased from 75.61%to 188.18%.The regression rate of fuels doped with A1 particles would increased as the content of Al went higher.The addition of nano-Al particles would weaken the combustion performance due to the existence of dense thin aluminum oxide layer produced by nano Al particles.The aluminum oxide layer would obstacle the burning of fuel.For the formulation of HTPB-based fuel added with 5%500nm Al,the growth in regression rate and mass burning rate reached maximum,and were 22.30%and 24.09%respectively.However,for the formulation of HTPB-based fuel added with 5%100nm Al,the values were 3.91%and-5.0%respectively.When the mass fractions of 500nm Al increased from 5%to 15%,the regression rate increased from 22.30%to 121.74%.In conclusion,the addition of high energy metal particles would improve the combustion performance of the HTPB-based fuels distinctly.