空气预冷器是预冷组合发动机的核心部件之一，它的换热能力将严重影响整台发动机的性能。因此，对其进行构型设计、数值计算、参数分析与实验研究具有重要意义。

本文在国内外学者对空气预冷器的研究基础上，结合目前的研究进展以及设计方案的优缺点，设计了面向3D打印加工的新型逆流管翅空气预冷器。翅片的使用增大了换热面积，增强了结构强度。文中通过物理几何关系、经验公式构建了预冷器设计管数与各个物理量之间的关系，利用经典的换热器设计方法ɛ-NTU法建立方程，利用MATLAB软件求解，得到初步设计结果。

为了对逆流管翅预冷器进行精确的数值校核，本文发展了一套快速计算方法来进行预冷器的设计校核，并编制了计算程序。程序中对空气的流动与传热、冷却剂的流动与传热、壁面及翅片的热导进行了解耦，以一维积分方程为基础，建立了考虑截面随位置变化、壁面摩擦、能量传递的计算方法，其中空气物性计算调用了物性拟合公式，冷却剂的物性计算调用了REFPROP或SUPERTRAPP物性计算子程序，壁面摩擦及传热运用了管流内的摩擦经验公式和湍流换热经验公式来计算，翅片采用了求解翅效率方法来等效计算。对于翅片上温度分布计算，运用了求解析解的方式。计算程序中考虑了使用碳氢燃料作为冷却剂的热裂解情况，加入了燃料裂解动力学模型和燃料裂解机理。最后通过利用商业计算平台对该模型进行了校核，两者误差在2%以内，但该方法使计算速度大大加快。

接下来使用本文发展的设计及校核方法，设计了甲烷为工质的空气预冷器，并对其进行了校核，最终校核修正结果与初步设计结果管数相差7%，从而验证了设计方案的准确性。

然后利用本文发展的计算方法，探究了预冷器管数、长度、来流空气马赫数及冷却剂种类对冷却性能的影响。研究表明预冷器内管数越多，换热效果越好，但管数的增加对换热性能提升越来越小。管数增加，空气压损增加，冷却剂压损减小；预冷器长度越长，换热效果越好，但预冷器长度的增加对换热能力提升越来越乏力，且预冷器功重比会减小；来流马赫数越大，预冷器的换热效率越高，但空气出口温度并不能都达到理想状态；不同的冷却工质在预冷器的流动中的流动状态不同，换热能力也不同，甲烷最具备作为冷却剂的初温优势。煤油的热裂解效应可以提高预冷器内冷却剂的吸热量，增强局部换热。氨的吸热能力最强，处于临界温度附近时对预冷器换热能力的提升最为明显，通过综合比较，氨最具备作为冷却剂的优势。

最后设计了与SABRE构型预冷器具有相同壁厚、相同体积的逆流管翅构型预冷器，进行了比较计算。发现流量大时逆流管翅空气预冷器更具换热优势，流量小时SABRE构型预冷器换热效果更好，逆流管翅构型的预冷器压降损失更小。

The air precooler is the core component of a precooled composite engine, and its heat exchange capacity will seriously affect the performance of the entire engine. Therefore, it is of great significance to conduct configuration design, numerical calculation, parameter analysis, and experimental research on it.

Based on the research of domestic and foreign scholars on air precoolers, combined with the current research progress and the advantages and disadvantages of the design scheme, this paper designed a new type of countercurrent tube fin air precooler for 3D printing processing. The use of fins increases the air side heat transfer area and enhances structural strength. In this paper, the relationship between the number of tubes designed for the precooler and various physical quantities is established through physical geometric relationships and empirical formulas. Establish equations using classical heat exchanger design methods, ɛ-NTU method, solve them using MATLAB software, and obtain preliminary design results.

In order to accurately verify the numerical value of a countercurrent tube fin precooler, a rapid calculation method has been developed for the design and verification of the precooler, and a calculation program has been compiled. In the program, the flow and heat transfer of air, the flow and heat transfer of coolant, and the thermal conductivity of walls and fins are understood and coupled. Based on one-dimensional integral equations, a calculation method is established that considers changes in cross-section, wall friction, and energy transfer. The physical property calculation of air uses a physical property fitting formula, and the physical property calculation of coolant uses a REFPROP or SUPERTAPP physical property calculation subroutine, The friction and heat transfer on the wall are calculated using empirical formulas for friction and turbulent heat transfer in the tube flow, and the fin efficiency method is used for equivalent calculation. For the calculation of temperature distribution on the fins, an analytical solution is used. The calculation program considers the thermal cracking situation using hydrocarbon fuel as a coolant, and adds a fuel cracking kinetic model and a fuel cracking mechanism. Finally, the model was checked using a commercial computing platform, and the error between the two was within 2%. However, this method greatly accelerated the calculation speed.

Next, using the design and verification methods developed in this article, an air precooler with methane as the working medium was designed and verified. The final verification and correction results differed by 7% from the preliminary design results in terms of the number of tubes, thereby verifying the accuracy of the design scheme.

Then, using the calculation method developed in this paper, the effects of the number and length of precooler tubes, the Mach number of incoming air, and the type of coolant on cooling performance were investigated. The research shows that the more the number of tubes in the precooler, the better the heat transfer effect, but the increase in the number of tubes has a smaller and smaller impact on the heat transfer performance. The more the number of tubes, the greater the air pressure loss, and the smaller the coolant pressure loss; The longer the length of the precooler, the better the heat exchange effect, but the increase in the length of the precooler is increasingly ineffective in improving the heat exchange capacity, and the power weight ratio of the precooler will decrease; The higher the incoming Mach number, the higher the heat transfer efficiency of the precooler, but the air outlet temperature cannot all reach an ideal state; Different cooling media have different flow states and different heat transfer capabilities in the flow of the precooler. Methane has the most advantage as the initial temperature of the coolant. The thermal cracking effect of kerosene can improve the heat absorption of the coolant in the precooler and enhance local heat transfer. Ammonia has the strongest heat absorption capacity, and the most significant improvement in the heat exchange capacity of the precooler is when it is near the critical temperature. Through comprehensive comparison, ammonia has the most advantage as a coolant.

Finally, a countercurrent tube fin precooler with the same wall thickness and volume as the SABRE precooler was designed and compared. It is found that the countercurrent tube fin air precooler has more advantages in heat transfer when the flow rate is large, and the SABRE precooler has better heat transfer effect when the flow rate is small, and the pressure drop loss of the countercurrent tube fin precooler is smaller.