基于推阻平衡的喷管型面截短方法研究及试验验证

Experimental and Numerical Study of Truncation Method for Thrust Nozzle Profile Based on Balance of Thrust and Friction

关键词:  推力喷管  壁面剪切力  截短  推阻平衡  推力系数 

Key words:  Thrust nozzle  Shearing stress  Truncation  Thrust friction balance  Thrust coefficient

摘要:

出于减小喷管壁面摩擦损失的考虑以及发动机的整体布局的受制,传统推力喷管设计方法得到的理想喷管通常需要进行适当截短。合理的截短方法有助于保持喷管性能,因此,通过壁面单元受力分析并考虑单元体内的推力与阻力关系,提出了一种推阻平衡的喷管截短设计方法。使用上述方法对一个三次曲线型面的三维原始完全膨胀喷管进行截短,使喷管长度减小25%,重量减小34%。通过风洞试验与数值模拟结果对比发现,截短后的喷管推力系数提高1.5%,升力也得到有效提高,验证了此种截短方法的正确性。截短后喷管处于欠膨胀状态,与理论分析得到的最大静推力状态结果相符。 

Abstract:

Considering the adverse effects of wall friction and restricted by the overall layout of scramjet, thrust nozzles designed by traditional methods sometimes are too long and need to be truncated. A new truncation method based on the balance of thrust and friction was brought forward. To verify the method, an ideal expansion nozzle with a cubic curve as the expansion profile was designed, and then truncated by the new method. As a result, the length and the weight of the nozzle are reduced by 25% and 34%, respectively. Cold-flow experiment and numerical simulation were conducted on the truncated nozzle, and they fit well. The simulation results show that the thrust coefficient increases by 1.5% and the lift performance increases as well. The truncated nozzle works at under-expanded condition,and the truncation method is fully verified. 