涡轮增压离心压气机非对称有叶扩压器扩稳机理研究

发布时间：2018-02-08 16:10

本文关键词： 涡轮增压离心压气机有叶扩压器稳定性畸变　出处：《清华大学》2014年硕士论文　论文类型：学位论文

【摘要】：内燃机节能减排的需求及日益严格的排放法规要求涡轮增压离心压气机具有宽广的稳定工作范围。涡轮增压离心压气机的流动稳定性成为发展涡轮增压技术的主要瓶颈之一。涡轮增压离心压气机具有周向非对称的蜗壳结构，导致离心压气机的周向流场结构在非设计工况下不均匀；传统流动控制措施认为离心压气机为轴对称结构，忽略了此流场结构非对称性。清华大学基于涡轮增压离心压气机固有的非对称流场特征，提出了“非对称流动控制”思想。扩压器对涡轮增压离心压气机稳定性具有重要影响，本论文基于“非对称流动控制”思想，探索非对称有叶扩压器扩稳新方法，，以期实现离心压气机稳定工作范围的大幅度拓宽。为方便改变出口畸变的参数，定量分析扩压器出口压力畸变对离心压气机性能影响，本文用周向非均匀压力分布作为出口边界条件代替蜗壳建立了畸变模型，并证明了畸变模型可以用来分析蜗壳产生的畸变对离心压气机性能的影响。基于畸变模型，通过给定出口压力畸变不同的幅值研究了压力畸变在离心压气机中的传播规律及压力畸变幅值对离心压气机压比、效率和稳定工作范围的影响。结果表明出口压力畸变会降低离心压气机的压比、效率和稳定工作范围，随着畸变幅值的增加，离心压气机性能降低增加。扩压器出口压力畸变能够传播到上游的扩压器和叶轮，导致部分流道率先发生失速，进而引发整个离心压气机喘振，随着出口压力畸变振幅的增加，率先发生失速时的流量也会增加，导致离心压气机稳定工作范围降低，从而揭示了局部失速诱发系统提前喘振的物理机理。基于蜗壳导致的压力畸变对离心压气机性能影响机理，突破目前国际上离心压气机的有叶扩压器均为对称分布的传统，首次提出并发展了“非对称有叶扩压器”流动控制新方法：通过分析蜗壳引起的扩压器出口的压力畸变，判断率先发生失速的区域，通过有叶扩压器叶片安装角或稠度非对称布置，抑制此区域的流动分离，从而提高有叶扩压器离心压气机的稳定工作范围。根据此方法设计了非对称有叶扩压器改型方案，并进行了仿真和试验验证。仿真结果表明：非对称有叶扩压器叶片安装角或稠度分布能够抑制蜗壳畸变导致的有叶扩压器局部失速，从而拓宽有叶扩压器离心压气机的稳定工作范围。试验结果表明：转速为90%时，离心压气机的稳定工作范围由25.4%提高到33.1%。
[Abstract]:The demand for energy saving and emission reduction of internal combustion engines and the increasingly stringent emission regulations require a wide range of stable operation for turbocharged centrifugal compressors. The flow stability of turbocharged centrifugal compressors has become one of the main bottlenecks in the development of turbocharging technology. The circumferential asymmetric volute structure of the turbocharged centrifugal compressor leads to the non-uniformity of the circumferential flow field of the centrifugal compressor under non-design conditions, and the conventional flow control measures consider the centrifugal compressor to be an axisymmetric structure. The asymmetry of the flow field structure is ignored. Based on the inherent asymmetric flow field characteristics of the turbocharged centrifugal compressor, Tsinghua University puts forward the idea of "asymmetric flow control". The diffuser has an important effect on the stability of the turbocharged centrifugal compressor. Based on the idea of "asymmetric flow control", this paper explores a new method for stabilizing the asymmetric blade diffuser in order to widen the working range of centrifugal compressor by a large margin. In order to change the parameters of outlet distortion and quantitatively analyze the influence of diffuser outlet pressure distortion on the performance of centrifugal compressor, a distortion model is established in this paper, in which the circumferential non-uniform pressure distribution is used as the outlet boundary condition instead of the volute case. It is proved that the distortion model can be used to analyze the effect of the distortion produced by the volute on the performance of centrifugal compressor. The propagation law of pressure distortion in centrifugal compressor and the pressure ratio of pressure distortion to centrifugal compressor are studied by giving different amplitudes of outlet pressure distortion. The results show that the pressure ratio of centrifugal compressor, the efficiency and the working range of centrifugal compressor will be decreased with the increase of distortion amplitude. The pressure distortion at the outlet of the diffuser can propagate to the diffuser and impeller upstream, which leads to the first stall in some of the flow channels, which leads to the surge of the whole centrifugal compressor, and with the increase of the amplitude of the pressure distortion at the outlet, The flow rate will also increase when the first stall occurs, which leads to the decrease of the stable working range of the centrifugal compressor, thus revealing the physical mechanism of the local stall induced system surge ahead of time. Based on the influence mechanism of pressure distortion caused by volute on the performance of centrifugal compressor, this paper breaks through the tradition that the vaned diffuser of centrifugal compressor in the world is symmetrical distributed at present. For the first time, a new flow control method for "asymmetric vaned diffuser" is proposed and developed. By analyzing the pressure distortion at the outlet of the diffuser caused by the volute, the region where the stall occurs first is judged. The flow separation in this area is restrained by asymmetric arrangement of the blade mounting angle or consistency of the blade diffuser, thus increasing the stable working range of the centrifugal compressor of the blade diffuser. According to this method, the modification scheme of the asymmetric blade diffuser is designed. The simulation results show that the distribution of blade mounting angle or consistency of asymmetric blade diffuser can restrain the local stall of blade diffuser caused by volute distortion. The experimental results show that the stable working range of centrifugal compressor increases from 25.4% to 33.1 when the rotating speed is 90.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TH452

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