逆流管翅式空气预冷器及其流动换热计算方法

A Counter-Flow Fin-Tube Air Precooler Design and Its Flow Heat Exchange Calculation Method

关键词:  空气预冷器  管翅  逆流式  碳氢燃料  裂解

Key words:  Air precooler  Fin-tubes  Counter-flow  Hydrocarbon fuel  Cracking

摘要:

空气预冷器用于在短时间内将高温来流空气高效冷却，是预冷吸气式空天发动机的核心部件。提出一种逆流管翅式的空气预冷器换热构型，经过与SABRE预冷器构型的比较，说明该新构型的预冷器可实现性更好。针对该构型，基于换热单元内部热通量平衡的基本假设，提出了一套流动及冷却效果的计算评估方法，考虑了冷却剂以及空气的流动摩擦损失。为解决以复杂碳氢燃料为冷却工质的空气预冷器设计难题，高温空气物性的计算使用NASA的物性拟合公式，碳氢燃料冷却工质及其裂解产物的物性计算，采用组分替代模型结合SUPERTRAPP物性计算子程序来实现；当燃料达到裂解温度后，采用燃料裂解机理计算更新燃料组分。此外为验证计算模型及程序的准确性，利用CFD软件与该程序进行同工况的比较计算，初步验证了该方法的可靠性，且采用本方法进行考虑碳氢燃料裂解的空气预冷器的典型工况计算，时间不超过30min。这一兼顾准确性和运算效率的新方法可用于逆流管翅式空气预冷器性能的快速评估。

Abstract:

The air precooler is used to efficiently cool the high-temperature incoming air in a short time， and it is the core component of the pre-cooled air-breathing aerospace engine. A heat exchange configuration of a counter-flow tube-fin air precooler is proposed， and the comparison with the configuration of the SABRE precooler shows that the precooler of this new configuration has better realizability. For this configuration， based on the basic assumption of heat flux balance in the heat exchange unit， a set of calculation and evaluation method for the flow and cooling effect is proposed， which takes into account the flow friction loss of the coolant and air. In order to solve the design problem of the air precooler with complex hydrocarbon fuel as the cooling medium， the physical properties of the high-temperature air are calculated using NASA’s physical property fitting formula， and the physical properties of hydrocarbon fuel cooling working medium and its cracking products are calculated using component substitution model combined with SUPERTRAP physical property calculation subroutine. When the fuel reaches the cracking temperature， the fuel composition is calculated and updated by the fuel cracking mechanism. In addition， in order to verify the accuracy of the calculation model and program， the CFD software is used to implement the calculation under the same working conditions with the program， and the reliability of the method was preliminarily verified. Moreover， this method is used to calculate the typical operating conditions of the air precooler considering hydrocarbon fuel cracking in no more than 30 minutes. This new method can be used to evaluate the performance of counter flow tube fin air precooler efficiently.