The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning cal...The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning calorimetry(DSC). The naturally ageing AP/HTPB base bleed propellant samples have been stored in a sealed plastic bag at room temperature(5-25 ℃) for more than 20 years. The experimental DSC results were obtained by placing samples(each about 1.5 mg) in a sealed pan under non-isothermal condition under different heating rates, 5.0, 10.0, 15.0, 20.0 and 30.0 ℃·min^(-1). The activation energy and pre-exponential factor were estimated based on the relationship between the exothermic peak temperature and the heating rate by Ozawa and Kissinger methods, respectively. The decomposition kinetic parameters is lower the values under laboratorial aging condition.展开更多
A complex multiple flame structure is formed during the combustion of AP/HTPB base bleed propellant.The AP monopropellant flame is concentrated in a thin zone above the burning surface of AP crystal to maintain self-s...A complex multiple flame structure is formed during the combustion of AP/HTPB base bleed propellant.The AP monopropellant flame is concentrated in a thin zone above the burning surface of AP crystal to maintain self-sustained decomposition.Due to the low temperature near the burning surface,the diffusion between the decomposition products of AP and the pyrolysis products of HTPB occurs,and a partly pre-mixed diffusion flame structure-leading edge flame(LEF)is formed.The effects of pressure,chemical reaction rate and AP particle size on diffusion flame structure in the range from 20 atm to 100 atm are discussed.The Peclet number increases from 6.64 at 20 atm to 21.91 at 100 atm when AP particle size is 140 mm.The high temperature zone is blown away from the burning surface because the convective transport rate increases with the increase in Peclet number.The chemical reaction rate is enhanced and the diffusion mixing is inhibited as Damkohler number increases.The chemical heat release is more concentrated and the chemical reaction zone becomes narrow when Damkohler number changes from 330 at20 atm to 4700 at 100 atm.When AP particle diameter is decreased to 60 mm,the diffusion time scale is reduced due to the reduced diffusion length scale.So the diffusion mixing is enhanced and a more pre-mixed flame is formed.The burning rate increases because the more pre-mixed heat release increases the heat feedback to the HTPB binder.展开更多
In order to improve the benefits of base bleed in base flow field,the base flow with hot base bleed for two jet models is studied.Twodimensional axisymmetric Navier-Stokes equations are computed by using a finite volu...In order to improve the benefits of base bleed in base flow field,the base flow with hot base bleed for two jet models is studied.Twodimensional axisymmetric Navier-Stokes equations are computed by using a finite volume scheme.The base flow of a cylinder afterbody with base bleed is simulated.The simulation results are validated with the experimental data,and the experimental results are well reproduced.On this basis,the base flow fields with base bleed for a circular jet model and an annulus jet model are investigated by selecting the injection temperature from 830 K to 2200 K.The results show that the base pressure of the annular jet model is higher than that of the circular jet model with the changes of the injection parameter and the injection temperature.For the circular jet model,the hot gases are concentrated in the vicinity of the base.For the annular jet model,the bleed gases flow into the shear layer directly so that the hot gases are concentrated in the shear layer.The latter temperature distribution is better for the increase of base pressure.展开更多
为了研究底排点火具在弹丸出炮口时瞬态燃烧特性及工作性能,采用半密闭爆发器模拟炮口压力突降过程,借助高速录像系统,开展了高降压速率条件下底排点火具燃烧特性的实验研究。结果表明,在高速降压过程中,底排点火具燃烧受到强烈瞬态扰...为了研究底排点火具在弹丸出炮口时瞬态燃烧特性及工作性能,采用半密闭爆发器模拟炮口压力突降过程,借助高速录像系统,开展了高降压速率条件下底排点火具燃烧特性的实验研究。结果表明,在高速降压过程中,底排点火具燃烧受到强烈瞬态扰动。不同药剂的点火具抗干扰性能不同,其中以硝酸钡为药剂主成分的点火具和以镁粉+PTFE为药剂主成分的点火具燃烧性能稳定,以氢化锆、二氧化铅为药剂主成分的点火具工作稳定性较差,火焰持续时间标准差为523 m s,点火具喷孔堵塞严重。展开更多
文摘The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning calorimetry(DSC). The naturally ageing AP/HTPB base bleed propellant samples have been stored in a sealed plastic bag at room temperature(5-25 ℃) for more than 20 years. The experimental DSC results were obtained by placing samples(each about 1.5 mg) in a sealed pan under non-isothermal condition under different heating rates, 5.0, 10.0, 15.0, 20.0 and 30.0 ℃·min^(-1). The activation energy and pre-exponential factor were estimated based on the relationship between the exothermic peak temperature and the heating rate by Ozawa and Kissinger methods, respectively. The decomposition kinetic parameters is lower the values under laboratorial aging condition.
基金the financial support provided by the National Natural Science Foundation of China(No.51176076)
文摘A complex multiple flame structure is formed during the combustion of AP/HTPB base bleed propellant.The AP monopropellant flame is concentrated in a thin zone above the burning surface of AP crystal to maintain self-sustained decomposition.Due to the low temperature near the burning surface,the diffusion between the decomposition products of AP and the pyrolysis products of HTPB occurs,and a partly pre-mixed diffusion flame structure-leading edge flame(LEF)is formed.The effects of pressure,chemical reaction rate and AP particle size on diffusion flame structure in the range from 20 atm to 100 atm are discussed.The Peclet number increases from 6.64 at 20 atm to 21.91 at 100 atm when AP particle size is 140 mm.The high temperature zone is blown away from the burning surface because the convective transport rate increases with the increase in Peclet number.The chemical reaction rate is enhanced and the diffusion mixing is inhibited as Damkohler number increases.The chemical heat release is more concentrated and the chemical reaction zone becomes narrow when Damkohler number changes from 330 at20 atm to 4700 at 100 atm.When AP particle diameter is decreased to 60 mm,the diffusion time scale is reduced due to the reduced diffusion length scale.So the diffusion mixing is enhanced and a more pre-mixed flame is formed.The burning rate increases because the more pre-mixed heat release increases the heat feedback to the HTPB binder.
基金supported by National Nature Science Foundation of China(Grant No.51176076)
文摘In order to improve the benefits of base bleed in base flow field,the base flow with hot base bleed for two jet models is studied.Twodimensional axisymmetric Navier-Stokes equations are computed by using a finite volume scheme.The base flow of a cylinder afterbody with base bleed is simulated.The simulation results are validated with the experimental data,and the experimental results are well reproduced.On this basis,the base flow fields with base bleed for a circular jet model and an annulus jet model are investigated by selecting the injection temperature from 830 K to 2200 K.The results show that the base pressure of the annular jet model is higher than that of the circular jet model with the changes of the injection parameter and the injection temperature.For the circular jet model,the hot gases are concentrated in the vicinity of the base.For the annular jet model,the bleed gases flow into the shear layer directly so that the hot gases are concentrated in the shear layer.The latter temperature distribution is better for the increase of base pressure.
文摘为了研究底排点火具在弹丸出炮口时瞬态燃烧特性及工作性能,采用半密闭爆发器模拟炮口压力突降过程,借助高速录像系统,开展了高降压速率条件下底排点火具燃烧特性的实验研究。结果表明,在高速降压过程中,底排点火具燃烧受到强烈瞬态扰动。不同药剂的点火具抗干扰性能不同,其中以硝酸钡为药剂主成分的点火具和以镁粉+PTFE为药剂主成分的点火具燃烧性能稳定,以氢化锆、二氧化铅为药剂主成分的点火具工作稳定性较差,火焰持续时间标准差为523 m s,点火具喷孔堵塞严重。
