**Research on Testing Methods and Numerical Models of Pressure-coupled Response of AP/HTPB Composite Propellant**

Author:Yan Mi

Supervisor:wang ning fei li jun wei

Database:Doctor

Degree Year:2017

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Pages:179Size:8716K

Keyword:BDP combustion model，composite propellant，Numerical model，pressure-coupled response，pressure-triggered，pulse excitation，T-burner

In solid rocket motors,combustion response of composite propellant to pressure is one of the main reasons of combustion instability.In order to master the variation law of pressure-coupled response of composite propellant systematically,the pressure-coupled response of AP/HTPB composite propellant are studied experimentally,theoretically and numerically in this paper.The main research works and conclusions are as follows:A new triggered T-burner experiment platform is built,whose test frequency and test pressure are adjustable.T-burner can be pulsed spontaneously and reusable.The measuring method of pressure-coupled response is modified and improved,and subjected to test the pressure-coupled response function.When the test pressure is equal to 11.8MPa,and the test frequency are 138 Hz,142Hz and 140 Hz,the values of pressure-coupled response function are equal to 4.85,4.99 and 4.88,respectively.The three values are very close,which indicates that the experimental platform is reliability and reproducibility.The pulse excitation characteristics of black powder are studied experimentally and theoretically.The modified zero-dimension model and one-dimension model of pressure pulse are established.And a zero-dimensional prediction model of mean pressure is established.The effect of black powder performance on pulse excitation is studied.The results show that black powder performance can be expressed directly by burning time and weight.And both pressure pulse and mean pressure increment increase with increasing black powder weight,linearly.The pressure pulse is more sensitivity to the variations of burning time of black powder.Three-dimensional numerical simulation of pressure-triggered process in T-burner is carried out.The influences of pulse temperature,pulse mass flow rate and pulse waveform on pressure oscillation are studied.The results show that when the other performances of pulse are fixed,pulse temperature only can affect pulse amplitude.When pulse is weak,pulse amplitude has no effect on harmonic characteristic.As pulse intensity becomes larger to intensity of shock wave,increasing pulse amplitude will increase harmonic characteristic of pressure oscillation.Pulse waveform determines initial waveform of pressure oscillation,which decides harmonic characteristics.Attenuation characteristic of pressure oscillation is mainly determined by harmonic characteristic and pulse amplitude.And the influence of harmonic characteristic is much higher than that of pulse amplitude.Rules of pulse application for T-burner tests are summarized,which can be described as: mean pressure increment can not exceed 10% of test pressure;pressure pulse belongs to 1%~10% of test pressure;pressure pulse is at least twice of mean pressure increment;amplitude of two pulses should be close;and pulse waveform should be closed to sine wave.A BDP micro-scale combustion model of AP/HTPB composite propellant is established.Influences of AP particle size,AP mass fraction and pressure on AP/HTPB diffusion and combustion characteristics are analyzed.The results show that increasing of AP particle size and increasing of pressure will increase mixing distance of components,diffusion characteristic of flame,unevenness of gas temperature distribution,and height of flame.Changes of AP mass fraction only can affect the location of ultimate diffusion flame and exhaust temperature of gas.A numerical model of pressure-coupled response of AP/HTPB composite propellant is established.Pressure-coupled response function of the same AP/HTPB propellant is carried out under 10 MPa and 2MPa.The results show that pressure-coupled response function of composite propellant with the condition of medium/low-frequency is larger than that of high-frequency.The peak response frequency of 10 MPa is higher than that of 2MPa.Periodic oscillation characteristics of flame position,gas temperature distribution and combustion surface temperature distribution are analyzed.The results show that there are phase differences between the fluctuations of gas phase reaction and gas temperature distribution and the fluctuation of pressure fluctuation,which is caused by thermal lag of solid phase.And fluctuations of gas phase reaction and gas temperature distribution also are exacerbated by thermal lag of solid phase.The fluctuation of combustion surface temperature is very uneven,whose position and magnitude of the strongest response region changes with mean pressure and disturbance frequency.