固体推进剂二维绝热微尺度燃烧模型的数值研究

Numerical Study on Two Dimensional Adiabatic Microscale Combustion Model for Solid Propellant

关键词:  二维绝热微尺度燃烧模型  简化化学动力学模型  分步凝相反应  数值研究  固体推进剂

Key words:  2D adiabatic microscale combustion model  Reduced chemical kinetic mechanism  Multi-step condensed phase reaction  Numerical study  Solid propellant

摘要:

为实现固体微推力器工作过程的一体化模拟，基于Fluent计算软件的二次开发功能(UDF)和简化化学动力学模型，实现了固体推进剂的二维气-凝相绝热微尺度燃烧模型的建立，该模型针对固体微推力器所用双基推进剂，包含两步凝相反应和五步气相反应，燃速、推进剂表面温度和组分质量分数基于燃面物理特性计算得到，并考虑了粘性作用对气相和凝相反应的影响。针对0.5MPa，1.0MPa，2.0MPa和5.1MPa四种工况进行了计算，结果表明，高压工作环境下出现发光火焰区，且随表面压力增大而逐渐靠近壁面，凝相反应区厚度和嘶嘶区、暗区主要反应物在燃面的质量分数随推进剂表面压力增大而减小。对称面处推进剂燃速，推进剂表面温度和气相火焰结构与实验结果基本一致。由于壁面附近较高的粘性作用，气相火焰在壁面位置更加靠近推进剂燃面，并导致壁面位置推进剂燃速高于对称面位置。该模型实现了二维环境下考虑分步凝相反应的推进剂绝热燃烧模型的一体化计算，较好地拓展了原模型的应用范围。

Abstract:

In order to realize integrated simulation on solid propellant microthruster’s working process，based on the computational software Fluent and reduced chemical kinetic mechanism，a 2D adiabatic microscale combustion model taking into consideration both gas reactions and condensed phase reactions was built，which contained two condensed phase reactions and five gas phase reactions of a double base solid propellant tested in a solid propellant microthruster. The burning rate，temperature of burning surface and species mass fraction were derived by calculating physics properties at and near propellant’s burning surface. The viscosity effect on gas phase reactions and condensed phase reactions was also taken into consideration. Calculation was performed for four different atmosphere pressure values: 0.5MPa，1.0MPa，2.0MPa and 5.1MPa，respectively. Results show that the flame zone emerges in high pressure atmosphere，moving nearer to burning surface of the solid propellant when pressure gets higher，and the thickness of condensed phase reaction zone diminishes with the rising of atmospheric pressure，together with mass fraction of major reactants of reactions in fizz zone and dark zone at the burning surface. The burning rate，burning surface temperature of the propellant and gas phase flame structure basically align with experimental results at the symmetry. Due to viscous effect at the wall，the flame moves nearer to burning surface at the wall than at the symmetry，which led to higher burning rate of solid propellant at the wall than at the symmetry. The model realized integrated simulation of a solid propellant’s 2D adiabatic combustion model taking the multi-step condensed phase reactions into consideration and it well extended the application field of the original combustion model.