【作者】 杨硕；

【导师】 周伟星；

【作者基本信息】 哈尔滨工业大学 ， 能源动力（专业学位）， 2023， 硕士

【摘要】 随着高超声速飞行器的飞行马赫数逐渐提高,以碳氢燃料为冷却剂的再生冷却系统面临着冷源不足、燃料裂解结焦等问题,飞行器面临的热防护需求日益严峻,新型热防护技术的研究迫在眉睫;同时由于燃烧组织以及通道结构的影响,使得通道之间的流量分配出现偏差,这种流量偏差会有受热偏差进一步放大,导致再生冷却系统的冷却性能下降,影响飞行器的安全运行。针对上述再生冷却系统面临的困境,本文以超燃冲压发动机燃烧室内壁面为研究对象,以超临界CO₂为冷却剂,进行了单通道内的流动换热、并联通道流量分配及均流化策略研究,为高超声速飞行器的高马赫数、长航时运行提供了保障。根据研究内容的需要,搭建了哈尔滨工业大学超高热流参数下的超临界CO₂流动换热实验台,通过直流电加热模拟超燃冲压发动机燃烧室内壁面的受热环境,进行了发动机壁面典型热流密度下的变工况加热试验。研究发现,随着热流密度的增大,传热恶化发生的位置逐渐前移且壁面温度的跃升值增大,增大出口压力有利于削弱传热恶化现象,整体上管内传热对压力变化并不敏感并建立了超高热流参数下的流动换热关联式;选用典型的判断准则对传热恶化现象进行分析,研究发现,在高热流参数条件下,引起传热恶化发生的原因主要是浮升力效应。接下来,针对超临界CO₂在并联通道内的流量分配问题展开了数值研究,分析了不同的并联形式对流量分配特性的影响,得到不同形式的通道流量分配规律;针对典型的U型并联通道,研究了运行参数以及结构参数对流量分配特性的影响,研究发现,运行参数中致流量分配不均的主要影响因素,结构参数中,增大通道长度、分流汇流结构长度以及减小通道个数均可以改善流量分配特性。最后,针对流量分配不均现象,进行了均流化研究,分析了通道间的流动参数差异,通过在通道中设置尺寸较小的压力平衡微孔,检验了微孔对于流量分配的均匀效果,研究了微孔布置位置、布置个数、倾斜角度对流量均匀的效果,微孔布置在压差最大位置、增大微孔数量、以及减小微孔与主流方向的夹角均可以增强流量均匀效果;设计了几何不均匀通道,通过调节通道内的沿程阻力损失调节通道间的流量分配关系,并通过数值计算进行了验证。更多还原

【Abstract】 With the increasing Mach number of hypersonic aircraft,the regenerative cooling system using hydrocarbon fuel as coolant is facing problems such as insufficient cold source and fuel cracking and coking.The thermal protection needs of aircraft are becoming increasingly severe,and research on new thermal protection technologies is urgent;At the same time,due to the influence of combustion organization and channel structure,there is a deviation in the flow distribution between channels.This flow deviation will be further amplified by the heating deviation,leading to a decrease in the cooling performance of the regenerative cooling system and affecting the safe operation of the aircraft.In response to the difficulties faced by the regenerative cooling system mentioned above,this article takes the combustion chamber wall of a scramjet engine as the research object,and uses supercritical CO2 as the coolant to study the flow and heat transfer in a single channel,flow distribution in parallel channels,and fluidization strategy.This provides a guarantee for the high Mach number and long endurance operation of hypersonic aircraft.According to the needs of the research content,a supercritical CO2 flow and heat transfer experimental platform was built at Harbin Institute of Technology under ultrahigh heat flux parameters.The heating environment of the combustion chamber wall of a scramjet engine was simulated through direct current electric heating,and variable condition heating tests were conducted under typical heat flux density of the engine wall.Research has found that as the heat flux density increases,the location where heat transfer deterioration occurs gradually moves forward and the jump in wall temperature increases.Increasing the outlet pressure is beneficial for weakening the phenomenon of heat transfer deterioration.Overall,heat transfer in the tube is not sensitive to pressure changes and a flow heat transfer correlation equation under ultra-high heat flux parameters has been established;Using typical judgment criteria to analyze the phenomenon of heat transfer deterioration,it was found that under high heat flow parameters,the main cause of heat transfer deterioration is the buoyancy effect.Next,numerical research was conducted on the flow distribution problem of supercritical CO2 in parallel channels,analyzing the impact of different parallel forms on flow distribution characteristics,and obtaining different forms of channel flow distribution laws;For typical U-shaped parallel channels,the effects of operating parameters and structural parameters on flow distribution characteristics were studied.The study found that the main factors causing uneven flow distribution in operating parameters were increasing the length of the channel,reducing the length of the diversion and confluence structure,and reducing the number of channels,all of which can improve the flow distribution characteristics.Finally,in response to the phenomenon of uneven flow distribution,a homogenization study was conducted to analyze the differences in flow parameters between channels.By setting smaller pressure balanced micropores in the channels,the uniform effect of micropores on flow distribution was tested.The effects of micropore arrangement position,number of micropores,and tilt angle on flow uniformity were studied.The micropores were arranged at the position with the maximum pressure difference,increasing the number of micropores Reducing the angle between micropores and the mainstream direction can enhance the uniformity of flow rate;A geometrically non-uniform channel was designed,and the flow distribution relationship between the channels was adjusted by adjusting the frictional resistance loss along the channel,which was verified through numerical calculations.更多还原