对转叶轮机技术挑战分析

Analysis for technique challenges on counter-rotating turbomachinery

关键词:  涡轮机  风扇  压气机  涡轮

Key words:  Turbine engine  Fan  Compressor  Turbine

摘要:

为获得关于对转叶轮机共性问题的认识,在回顾对转叶轮机发展之后,采用速度三角形方法分析了“对转”造成的气流预旋范围和变工况运行方面的技术挑战。分析表明:除带来更严峻的噪音、振动及高周疲劳问题外,对转叶轮机还将面临气流预旋范围受限、变工况运行更加复杂两个挑战。使用对转叶轮机方案前提条件是对转导致的气流预旋范围能满足总体循环提出的要求;对转叶轮机设计时尽量选取低转速比、低流量系数;对大转速比、高流量系数对转叶轮机,应尽量使前排出口相对气流角β1<40°~50°,否则,对于对转风扇/压气机就只有改变下游叶片安装角;有时需要采用可调叶片以应对对转风扇/压气机变转速变工况问题。研究结果将直接用于判断对转叶轮机适用性及确定对转叶轮机基本设计参数选取原则和范围。

Abstract:

Review on counter-rotating turbomachinery(CRT) is first presented.Then,two technique challenges on aspects of flow preswirl and off-design operation are analyzed by using velocity triangle method.It is shown that the range of preswirl angle will be more narrow and the off-design operation will be more complex in CRT except for more severe noise,vibration and perhaps high cycle fatigue problems.Some suggestions have been obtained.First,the precondition of adopting counter-rotation scheme is that the narrowed range of preswirl would still satisfy the engine cycle requirements.Secondly,CRT is more suitable for ones with low speed ratio and low flow coefficients.As to CRT with high speed ratio and high flow coefficients,the exit flow angle of preceding rotor should satisfy β1<40°～50°.Otherwise,the downstream rotor will have to change its stagger angle for counter-rotating fan or compressor.In some circumstances,the rotor also needs to change its stagger angle to resolve problems encountered in off-design operation with different speed.The present results can be directly used to judge the applicability of CRT and determine basic rules and ranges in selecting design parameters of CRT.