椭圆型喷嘴对凝胶推进剂雾化性能影响的理论研究

Theoretical Study on Effects of Elliptical Nozzle on Atomization Performance of Gel Propellant

关键词:  椭圆射流  喷嘴动力学  凝胶推进剂  线性稳定性理论  轴转换现象

Key words:  Elliptical jet  Injector dynamics  Gel propellant  Linear stability theory  Axis-switching phenomenon

摘要:

为了研究椭圆型喷嘴对凝胶推进剂雾化性能的影响规律，针对其初次雾化中的射流稳定性问题，利用线性稳定性理论，采用正则模方法，得到了凝胶推椭圆射流的色散关系，即空间增长率和扰动波数的理论关系，基于此，讨论了各个物理因素对于射流稳定性的影响规律，包括椭圆截面的离心率、表面张力系数、粘度、非牛顿流变特性中的弹性、时间常数比。同时，着重分析了弹性对于椭圆射流特有的轴转换现象的影响规律，结合稳定性分析，得到了各物理因素对于凝胶初次雾化的作用规律。本文发现随着表面离心率、表面张力的增加以及粘性的减弱，椭圆射流的增长率增加，有利于提高凝胶初次雾化效果；凝胶推进剂的非牛顿流变特性对其初次雾化过程影响显著，尤其是弹性的作用，随着弹性的增加或者时间常数比的减小，椭圆射流的稳定性减弱，导致射流更容易破裂，进而达到良好的雾化效果。并且，弹性会抑制射流轴转换。

Abstract:

In order to study the effects of elliptical nozzles on the atomization performance of the gel propellants， the dispersion relation that is the theoretical relationship between the spatial growth rate and the disturbance wave number of the gel propellant elliptical jet were obtained by using the linear stability theory. Because the jet stability plays the key role in the initial atomization， based on this， the effects of various physical factors on the jet stability were discussed， including the eccentricity of the elliptical section， the surface tension coefficient， viscosity， elasticity in non-Newtonian rheological properties， time constant ratio. At the same time， the influence law of elasticity on the special axis conversion phenomenon of elliptical jet was emphatically analysed. Combined with the stability analysis， the law of the effect of various physical factors on the initial atomization of the gel was obtained. It is found that with the increase of surface eccentricity， surface tension and the weakening of viscosity， the growth rate of elliptical jet increases， which is beneficial to improving the initial atomization effect of gel. The non-Newtonian rheological properties of gel propellant have a significant effect on the initial atomization process， especially the effect of elasticity. With the increase of elasticity or the decrease of the time constant ratio， the stability of the elliptical jet is weakened， which makes the jet more likely to break， thereby achieving a good atomization effect. Also， elasticity inhibits jet axis switching.