旋转爆震发动机燃烧室壁面烧蚀热防护研究

Ablation Thermal Protection of Combustor Wall in a Rotating Detonation Engine

关键词:  旋转爆震发动机  热环境  碳化烧蚀  动边界  热响应

Key words:  Rotating detonation engine  Thermal environment  Charred ablation  Moving boundary  Thermal response

摘要:

为了研究碳化烧蚀材料对旋转爆震燃烧室的被动热防护作用效果，建立了旋转爆震燃烧室热环境计算模型和多层复合壁一维烧蚀热响应分析模型。基于旋转爆震燃烧过程的数值模拟，确定了沿燃烧室轴向的壁面平均温度与热流的分布特征；针对典型的壁面热负荷输入条件，采用动边界隐式差分格式，对碳化型烧蚀材料的烧蚀过程和传热过程进行了耦合计算，分析了碳化层剥蚀、热解热、热解气体质量流率、材料厚度等因素对燃烧室壁面热防护效果的影响。研究结果表明，旋转爆震燃烧室温度和热流密度分布不均匀，斜激波扫掠区域热负荷更为剧烈；碳化层剥蚀后会使烧蚀材料的烧蚀率增加，壁面温度迅速上升；增大热解热及热解气体质量流率都有利于延长工作时间、降低壁面温度； 旋转爆震燃烧室不同区域的烧蚀有一定差异，增加烧蚀材料厚度无疑有利于壁面热防护，但是在实际应用中应综合考虑壁面重量和空间尺寸。

Abstract:

In order to demonstrate the role of charring ablative material on passive thermal protection of rotating detonation combustor， a computational model for determining the thermal environment of rotating detonation combustor and an analytical model for determining the one-dimensional ablative thermal response of multi-layer composite wall were established. From the numerical simulation of rotating detonation combustion， the averaged temperature and heat flux distributions on the combustor wall along the axial direction were obtained. Based on the typical thermal loads on the combustor wall， a computation was made by coupling the ablation process and the heat transfer process with the use of a moving boundary implicit-difference scheme for the charring ablative material. Some affecting factors on thermal protection were analyzed， including the charred layer erosion， pyrolysis heat， pyrolysis gas mass flow rate and ablative material thickness. The results show that the temperature and heat flux distribution on the combustor wall are not uniform. Corresponding to the local region suffering to the sweeping of oblique shock wave， the thermal load is significantly serious. The erosion of the charred layer results in the increase of ablation rate and wall temperature. Both the increase of pyrolysis heat and the mass flow rate of the pyrolysis gas are found to prolong the working time of ablation layer and reduce the wall temperature. The ablation behaved distinctly in different regions of the rotating detonation combustor. Increasing the ablation layer thickness is evidently beneficial to the thermal protection. However， the wall weight and space geometry should be taken into consideration during the real application.