固体燃料超燃冲压发动机燃烧室中PMMA自点火性能数值研究

Numerical Investigation on Self-Ignition of PMMA in Solid Fuel Scramjet

以PMMA为燃料对固体燃料超燃冲压发动机燃烧室的自点火性能进行了数值仿真研究。基于热解气体有限速率/涡耗散燃烧模型,通过求解装药壁面和内流场耦合的一维导热方程,得到稳态构型下的燃面退移率,数值结果和实验测量值吻合得较好。研究了进气流量、总温和燃烧室构型对自点火性能的影响,结果表明:成功自点火和未自点火的燃烧室内流场有明显差异。存在进气贫氧、进气富氧和进气总温自点火极限;提高进气总温有利于拓宽贫氧极限和富氧极限之间的范围。凹腔长度不足,即使增深凹腔也不能实现自点火;凹腔深度不足,即使加长凹腔也不能实现自点火;较长较深的凹腔能够实现自点火。平直段直径越大,越不利于自点火的实现。

The self-ignition performance of polymethylmethacrylate(PMMA) in solid fuel scramjet has been simulated numerically. Regression rate was obtained in steady state by means of solving one-dimensional heat conduction equation coupling the burning surface and the inner flow field,which was based on finite rate and eddy dissipation combustion model of pyrolysis gas. The simulation results were better consistent with the measured data. The effects of inflow air mass flux,total temperature and the configuration of chamber on self-ignition were studied. The results show that the internal flow field in the self-ignition chamber is significantly different with a chamber in which the ingition is not achieved. The PMMA has lean oxygen limit,rich oxygen limit and total temperature limit of self-ignition. Increasing the inflow total temperature contributes to broadening the scope of lean and rich oxygen limit. Self-ignition of PMMA in chamber can not be achieved with either rather short cavity or with a rather shallow cavity. A long and deep cavity is able to achieve self-ignition. The self-ignition is hard to be established with a large diameter of cylindrical section.