摘要
近年来,级环境下的流动成为叶轮机械气体动力学研究的焦点。与轴流式叶轮机械比较,离心式叶轮机械内部的流动更加复杂,亟待解决的问题也更多;本文以某离心压缩机为研究对象,通过对三维雷诺平均N-S方程组进行有限差分离散,结合Baldwin-Lomax代数湍流模型对离心式压缩机整级进行了三维流场数值模拟,得到了速度、压力和温度等微观流动参数以及级效率、压比等宏观性能参数,在以下几方面进行了较详细的分析:
利用NUMECA软件包建立离心压缩机整级周期性气体流动计算几何模型,在定常、可压条件下数值模拟了马赫数分别为0.8、0.75、0.65、0.55时具有无叶扩压器的整级流动性能,并与实验测量结果进行了比较。对比分析了每个马赫数下性能曲线的相同与不同之处,并通过对叶轮、扩压器、回流器内流动的详细分析,找出了非设计点外性能下降的原因。
对全高、盘侧半高、盖侧半高三种直板型扩压器模型下,压缩机整级在0.8马赫数的流动进行了数值模拟,对相同工况下的效率和总压比进行了比较,并通过叶轮、扩压器、回流器等元部件内的流动分析,阐述了每个模型性能优劣的原因,得出盖侧半高直板型叶片扩压器对压缩机的级性能改善最明显。
本文计算结果对流场流动参数的分布情况分析为减少级内损失提供数值依据,有助于进一步的理论研究;另一方面对整级和级内元、部件宏观性能参数的比较可以指导压缩机基本级的开发,指导工程实际应用。
In recent years, study of multistage internal flow has become one of the major research areas in turbomachinery aerodynamics. In comparison with the axial turbomachinery, internal flow in centrifugal compressors is more complex, and the achievement in centrifugal compressors is left behind of their axial counterpart. Furthermore, many questions concerning the 3D flow structure in centrifugal compressors are yet to be solved. This dissertation develops research work on a sort of centrifugal compressor stages, Numerical simulation on three-dimensional viscous flow fields of centrifugal compressor stages are carried out using Baldwin-Lomax algebraic turbulent model. The velocity and pressure distributions are obtained by employing Reynolds-Averaged N-S equation. This thesis tries to carry out a deeper investigation in the following aspects:
Periodic gas about geometrical model of centrifugal compressor is set up from NUMECA software package, which is used in flow calculating. under several Mach numbers numerical simulation using NUMECA software package is carried out for a centrifugal compressor with vane-less diffuser, such as 0.8, 0.75, 0.65, 0.55,etc. the simulation be developed in a steady condition which can be also compressed. analyze the homologies and the differences of the characteristic curve of the same operating mode from comparing with experimental results under every mach numbers. Through analyzing the flow field detailedly inside impeller, vaneless diffuser and return channel, it is found out the reason why performance drops in some other operating modes.
Numerical simulation about three sorts of centrifugal compressors with different straight plate diffusers are developed under 0.8 mach. Launch a comparison about their efficiency and absolute pressure ratio, and analyze the flow inside impeller, vaneless diffuser and return channel, show the reason about every model is good or bad, find out that compressor with half of height vane near shroud in diffuser is the best one.
The results are meaningful to both theoretical research and industrial application, and they provide useful data for analysis of loss in the stage and further development of a new basic stage.
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