大功率汽轮机低压排汽缸与末级联合计算及优化改型-动力机械及工程专业论文.docx

摘 要 汽轮机低压排汽缸是连接末级叶栅和凝汽器的通流部件。它的主要功能是 把末级排出的蒸汽很好地组织输送到凝汽器中去，同时回收排汽的余速动能， 转化成压力能。排汽缸气动特性的好坏直接关系到末级出口背压的大小、排汽 余速动能的回收率以及凝汽器入口的气流状况。因此，从改善排汽缸气动特性 着手，透彻认识缸内流场结构，分析气动损失来源，研究优化改型方法，对提 高汽轮机组的效率有着非常重要的意义。 本文首先以干蒸汽为工质进行了不同进口旋流角下排汽缸流场的单独模 拟，分析排汽缸内的流动结构和参数分布。分析表明，排汽缸内存在复杂的涡 系结构，这些涡系结构是排汽缸流动的主要特征，同时也是造成缸内气动损失 的主要因素。对比不同进口旋流角下排汽缸气动特性可以发现，一定的进口旋 流可以改善排汽缸的静压恢复性能和气动效率，但会导致出口气流不均匀性增 加。 为了获得更加接近真实的排汽缸入口条件，本文在排汽缸单独计算的基 础，又开展了排汽缸和末级叶栅的联合模拟，计算工质选用与实际机组运行相 符的湿蒸汽，末级叶栅采用全周通道。研究表明，排汽缸和末级叶栅间存在强 烈的相互作用，这种相互作用对排汽缸和末级全周通道内的流动都会产生影响。 在对排汽缸流场进行分析时，发现扩压器内环附近发生比较大的流动分离，导 致排汽缸静压恢复性能恶化，气动损失增加。为了改善排汽缸的气动性能，本 文进行了优化改型，通过控制扩压器的扩散比和前壁面倾角有效抑制了内环附 近的分离，使排汽缸的静压恢复性能和气动效率都得到提高。 关键词：汽轮机；低压排汽缸；湿蒸汽；联合模拟；优化改型 Abstract The low-pressure exhaust hood in steam turbine connecting the last stage and condenser is userd to recover leaving kinetic energy of the last stage and convert it to pressure, while guiding the steam flow from the last stage to conderser. The aerodynamic characteristics of exhaust hood have a dirct bearing on the pressure of turbine outlet, the recovery of leaving kinetic energy of the last stage and the steam condition of conderser inlet. Therefore, the analysis of flow field structure and sources of aerodynamic loss in exhaust hood as well as the study of its modified method of optimizaition ,which aim to improve its aerodynamic performance, have great important significance to increasing the efficiency of steam turbine unit. This paper firstly simulated and analyzed the complex flow field inside an exhaust hood model with dry steam model under different inlet swirl conditions. Result indicates that there are many complex vortices which seem to be the major sources of kinetic consumption and presssuse loss in exhaust hood. It is shown clearly by comparing different conditions that a certain inlet swirl angle has a favorable effect on the pressure recovery and aerodynamic efficiency of exhast hood, while also has an unfavorable effect on the uniform of outflow. In order to obtain more accurate inle