甲烷预冷器性能及与压气机参数匹配研究

Performance of Methane Pre-Cooler and Matching Characteristics with Compressor

关键词:  甲烷  预冷器  压气机  熵  发动机

Key words:  Methane  Pre-cooler  Compressor  Entropy  Engine

摘要:

以甲烷为冷却剂的预冷型涡轮基组合发动机以其较高的冷却性能和密度比冲等优点，成为未来宽速域飞行器动力装备问题的重要研究方向。针对该型发动机的核心部件——预冷器，建立理论计算模型对其综合性能进行了评估，并提出了一种熵函数分析法，对预冷器与压气机工作参数匹配特性开展理论分析。计算结果表明，所提出的预冷器方案换热有效度在0.5~0.72，功重比达到250kW/kg；甲烷预冷措施能将涡轮发动机工作速域扩展至Ma=3.1，此状态来流空气最高被冷却180K。对预冷器和压气机整体结构，“单位比热的比熵”与冷却剂当量比和压气机压比均成正相关。压气机能在根据材料耐高温极限设计的预冷器/压气机共同工作线上获得最高压比，但需消耗大量冷却剂，导致发动机比冲和热循环效率降低；冷却剂当量比始终控制在1.0左右的工作线能获得较高比冲、压比和热循环效率，同时消耗的功率和冷却剂均较低；保持较低熵增设计的工作线有较高热循环效率和较低功耗，但压比偏低，发动机难以提供较高输出功率。

Abstract:

The pre-cooled turbine-based combined engine with methane as coolant has become an important research field of power equipment for future wide speed range aircraft due to its high cooling performance and density specific impulse. A theoretical calculation model was established to evaluate the comprehensive performance of the pre-cooler， which is the core component of the engine， and an entropy function was proposed to theoretically analyze the matching characteristics of operation parameters between the pre-cooler and compressor. The calculation results show that the heat transfer efficiency of the pre-cooler is 0.5~0.72， and the power to weight ratio reaches 250kW/kg. The working velocity range of the turbine engine can be extended to Mach 3.1 using methane pre-cooler， and the incoming air was cooled by 180K at most. For the combined structure of the pre-cooler and compressor， the specific entropy per unit capacity is positively correlated with coolant equivalence ration and compressor pressure ratio. The maximum pressure ratio can be obtained from the co-work line of the pre-cooler and compressor designed according to the temperature limit of the compressor， but a large amount of coolant has to be consumed， which results in lower specific impulse and thermal cycle efficiency. The operation line with the coolant equivalence ratio invariably controlled at about 1.0 can obtain high specific impulse， pressure ratio and thermal efficiency， and the power consumption and coolant consumption are low as well. Although the operation line designed with low entropy generation brings low power consumption and high thermal efficiency， the compressor pressure ratio is relatively low， which makes the engine output power very low.