【作者】 孙宇涛；

【导师】 任玉新；

【作者基本信息】 清华大学 ， 力学， 2009， 博士

【摘要】 压气机性能的进一步的提高很大程度上依赖于我们对其内部非定常流动机理及相应损失机制的认识。数值模拟的方法在这方面发挥着日益重要的作用,但是还面临很多问题。本文将在计算压气机内部复杂非定常流动的数值方法和合理衡量压气机的损失等方面开展工作,并基于这些工作,对跨声速压气机级Rotor35/Stator37内的损失进行分析。在数值方法方面,构造了以下三个不同程度上反应多维效应的数值格式,(1)将精度和稳健性都已得到广泛认可的二维旋转迎风格式推广为三维。(2)通过在计算数值通量时近似求解完整的流体力学方程来体现多维效应的影响,本文构造了多维输运格式。对于粘性流动,该格式无粘通量的计算能够考虑粘性通量的影响。(3)基于线化多维欧拉方程的次特征线理论构造了考虑无限多方向影响的局部演化迦辽金格式。这三种方法的共同特点是相对于已有的考虑多维效应的格式更加简单、高效,且可以直接推广到非结构网格的计算。本文将三维旋转迎风格式格式应用到自行开发的多级叶轮机械模拟程序中。数值验证表明多维格式在模拟跨声速压气机内复杂流动方面有一定优势。在衡量压气机内损失方面,本文基于热力学定律,在有用功分析的框架提出了一种相比现有损失评估方法更适于非定常流场局部损失分析的损失评估参数-损失功,其强度量-损失功强度便于用来将流场结构与损失联系起来。这两个参数物理意义明确,能够被用来方便的、定量的研究局部区域内由于不可逆过程导致的熵产引起的损失。相比于先前同类方法,这两个参数能够考虑具体流动结构对于局部熵增的影响,从而能够更准确的衡量局部自身熵产的大小。这两个参数为压气机的设计、优化和改型提供了一个有效工具。更多还原

【Abstract】 To further improve the performance of the compressor in the aero-engine and other gas-turbines, it is of great importance that the mechanism of the unsteady flow in the compressor is well understood. In this thesis, efforts are devoted to developing advanced numerical methods to simulate the complex unsteady flow field in the compressor and constructing reasonal parameters to measure the loss in the compressor. Based on the achievements in these two aspects, the unsteady loss in a one-stage transonic compressor is analyzed.In the aspect of numerical method, three numerical schemes which can take multi-dimensional effects into account are developed. 1) Extension of a two-dimensional rotated Riemann solver, which has already proven its excellent robustness, to three-dimensional system. 2) A multi-dimensional upwind scheme was developed by computing the numerical fluxes at cell interfaces through solving full governing equations. This scheme can include the viscous contribution during the evaluation of the inviscid fluxes of the Navier-Stokes equations. 3)A finite volume local evolution Galerkin (FVLEG) method which is based on the bicharacteristics for linear (or linearized) hyperbolic systems were derived. The common advantages of the three schemes are simple, efficient and can be extended to unstructured grid directly. The 3D rotated Riemann solver has been already integrated into our in-house code for the compressor simulation. The numerical simulations show that the multi-dimensional scheme has better abilities to capture the discontinuities in the transonic compressor flow field.The previously developed loss audit parameters coming from the steady compressor design system do not fit the measurements of the loss generation in some local regions. The values of these parameters usually reflect the accumulating loss of a fluid element or a system. Because flows in compressor are essentially unsteady and because it is meaningful to know the influence of some design modifications on the local loss, it is therefore necessary to develop new methods to measure the loss generation in particular region of the flow field. Based on the first and second laws of thermodynamics, an expression of irreversibility for arbitrary control volume has been derived under exergy analysis framework. The intensity of the irreversibility thus computed reveals relationship between the loss generation and flow structures. Irreversibility and its intensity can provide relevant information in compressor design and optimization.更多还原