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首页> 外文会议>ASME(American Society of Mechanical Engineers) Power Conference; 20070717-19; San Antonio,TX(US) >A COMBINED NUMERICAL MODEL AND OPTIMIZATION FOR LOW PRESSURE EXHAUST SYSTEM IN STEAM TURBINE
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A COMBINED NUMERICAL MODEL AND OPTIMIZATION FOR LOW PRESSURE EXHAUST SYSTEM IN STEAM TURBINE

机译：汽轮机低压排气系统的组合数值模型与优化。

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摘要

Computational fluid dynamics is widely used in the aerodynamic performance analysis of the low pressure exhaust system (LPES) which consists of the exhaust hood and condenser neck. However, most of the former studies analyzed the exhaust system separately without considering the effect on flow field from the last stage. In order to get the detailed information of flow field in LPES of steam turbines and reduce energy loss, a numerical model includes condenser neck, exhaust hood and last stage was constructed. This model can describe the effect of unsymmetrical inlet flow on the aerodynamic performance of LPES, so the effect of the inhomogeneous flow from the last stage was taken into account. The Reynolds averaged N-S equations with RNG k-ε turbulence model were adopted to analyze the flow field in the exhaust system considering the interaction between the exhaust system and the last stage, the mixing plane approach was used. The combined model can provide more reasonable numerical results of LPES, it shows that the inhomogeneous flow from the last stage is one of the main reasons leading to flow separation in diffuser. The influence of inner low pressure heater and the diffuse function of the condenser neck structure are the main reasons for the nonuniform velocity distribution of the flow field at the LPES outlet. Furthermore, based on the numerical results, an optimal LPES which has better aerodynamic performance and more reasonable flow is obtained. The optimal structure has low steam resistance and low exhaust pressure, so it can increase the efficiency of turbine.
机译：计算流体动力学被广泛用于由排气罩和冷凝器颈部组成的低压排气系统（LPES）的空气动力学性能分析中。但是，大多数以前的研究都单独分析了排气系统，而没有考虑最后阶段对流场的影响。为了获得汽轮机LPES中流场的详细信息并减少能量损失，建立了包括冷凝器颈，排气罩和末级的数值模型。该模型可以描述不对称进气流对LPES空气动力学性能的影响，因此考虑了最后阶段的不均匀流的影响。考虑到排气系统与末级之间的相互作用，采用带有RNGk-ε湍流模型的Reynolds平均N-S方程分析排气系统中的流场，并采用混合平面法。组合模型可以提供更合理的LPES数值结果，表明最后一级的不均匀流动是导致扩压器内流分离的主要原因之一。内部低压加热器的影响和冷凝器颈部结构的扩散功能是LPES出口处流场速度分布不均匀的主要原因。此外，基于数值结果，获得了具有更好的空气动力学性能和更合理的流动的最佳LPES。最佳结构具有较低的耐蒸汽性和较低的排气压力，因此可以提高涡轮机的效率。

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