Study On The Combustion Mechanism Of GAP/CL-20 Solid Propellant

As the power source of rocket engine,solid propellant is the core technology of missile weapon equipment.Its combustion performance directly affects the ballistic performance of rocket engine,which affects the combat effectiveness of weapon system.With the rapid development of new missile weapons,the performance of existing solid propellant can not meet the technical requirements of future missile power.GAP/CL-20 solid propellant has the advantage of high energy,but its adjustable range of burning rate is narrow and pressure exponent is high.In this paper,the relationships between formulations and combustion performance of GAP/CL-20 solid propellant were investigated.the combustion mechanism of GAP/CL-20 solid propellant was revaeled,and the combustion performance was adjusted by it.Influence of binders,plasticizers,solid fillers and catalysts on the combustion performance of GAP/CL-20 solid propellant were studied by static burning rate test.It is revaeled that the particle size of CL-20 and AP are main controlling factors of burning rate,while the effect of binders,particle size of Al and catalysts is not significant.The solid contents and plasticizer ratioes have no impact on burning rate.The burning rate of GAP/CL-20 solid propellant drops from 16.94mm/s to 14.50mm/s with particle size of CL-20 decreased from 100μm to 20μm,descends from 27.32mm/s to 15.88mm/s with particle size of AP increased from 7μm to 140μm.TG-DSC was used to investigate the thermal decomposition properties of main components in GAP/CL-20 solid propellant and the interaction among them.The results show that the peak temperature and activation energy of decomposition of CL-20 are 246.9 ℃and 171.8k J/mol,lower than that of HMX.the decomposition heat of CL-20 is 1387J/g,larger than that of HMX.HMX was strongly enhanced by the existance of AP,the peak temperature and activation energy of decomposition can be reduced to 234.1 ℃and 176.6k J/mol.Wheares,the effect of AP on decomposition of CL-20 is not siginificant.The pyrolysis gas-phase products of HMX and CL-20 were studied by TG-FTIR and quantum chemical calculation.It is showed that NO2 and N2 O are the two main pyrolysis gas-phase products from HMX and CL-20,but the decomposition activation energy of NO2 and N2 O are different between HMX and CL-20,which resulted in the difference of the ratio of NO2 and N2 O.That is considered to be the primary cause of the difference of burning rate between CL-20-based propellant and HMX-based propellant.The flame structure and the morphology of quenched surface of GAP/CL-20 solid propellant were researched by CCD and SEM.As for GAP/CL-20 solid propellant,condensed-phase and gas-phase reactions are both existed,but gas-phase reactions are most important,and two kinds of reactions are all strongly affacted by the pressure.The combustion flames of GAP/CL-20 solid propellant contain the initial diffusion flame,CL-20 flame,premixed flame of binder system,AP flame and the final diffusion flame.A combustion physical model of GAP/CL-20 solid propellants was established,and the difference of burning rate between CL-20-based propellant and HMX-based propellant were explained by it.Based on the results of combustion performance and combustion mechanism of GAP/CL-20 solid propellants,the burning rates were adjusted by the increase of the particle sizes of AP,the reducation of the sizes of CL-20 powders and the usage of A2.The final burning rates of GAP/CL-20 solid propellants were reduced from 15.88 mm/s to 11.09mm/s.the pressure exponent was dropped from 0.75 to 0.59.