基于动网格技术的固体燃料冲压发动机燃面瞬态退移速率研究

Study of instantaneous regression rate in solid fuel ramjet based on dynamic mesh

为了研究固体燃料冲压发动机(SFRJ)燃面退移速率在工作过程中的变化特性,基于发动机工作特点及动网格技术,考虑到燃烧流动及燃料表面的对流、辐射换热与燃料热解退移等过程耦合的影响,建立了SFRJ燃面瞬态退移速率预示方法,并对某带补燃室、以聚乙烯(PE)为燃料的试验发动机的燃烧室-喷管统一内流场进行数值计算,得到在移动边界条件下的瞬态流场分布,并分析了内弹道参数云图及其随时间的变化规律。结果表明,燃烧主要发生在当量比函数φ在-2～2之间的区域;随着发动机工作,燃速逐渐降低,且再附点向下游移动,燃料通道出口处流速和温度有降低趋势;此外,在小型发动机工作初期,燃料通道尾部出现类似固体火箭发动机的侵蚀燃烧现象。研究表明,该方法能成功求解发动机复杂的非定常工作过程,较好揭示燃面退移过程。所得结论对发动机设计和试验具有一定指导意义。

In order to study the changes in regression rate of solid grain in solid fuel ramjet（ SFRJ）, a method to indicate the in stantaneous regression rate of solid grain in SFRJ was developed based on the operational feature, dynamic mesh, as well as coupled simulation of gas-phase combustion, heat transfer and regression of solid grain. Then whole inner flow of an experimental motor with additional chamber and polyethylene （PE） fuel was numerically simulated. The time dependent flow was obtained with dynamic boundaries, and the internal ballistic parameters were analyzed. The results show that combustion mainly occurs in the area where is between -2 and 2; as motor works,the regression rate decreases, the reattachment point moves downstream, and the velocity and temperature reduce at the outlet of solid grain; in addition, there is erosive burning in small SFRJ during initial operation stage. The study shows that this method can simulate the unsteady working process and fuel regression. The conclusions offer instruction for de- signing and experiment of solid fuel ramjet.