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《动力工程学报》2020,(6)
蒸汽自发凝结过程具有明显的非平衡特性,对凝结过程的预测存在困难。基于非平衡凝结模型,采用表面张力修正系数来修正液滴表面张力,并对Laval喷管及平面叶栅内蒸汽自发凝结流动进行多工况数值模拟。分析了表面张力修正系数对蒸汽凝结流动模拟精度的影响,着重讨论表面张力修正系数的最佳取值与蒸汽膨胀速率、进口参数的相关性,并研究其随进口参数的变化规律。结果表明:相同工况下,表面张力修正系数最佳取值对蒸汽膨胀速率变化不敏感,与进口总温相关性不显著,而与进口总压呈显著正相关;基于数值计算结果,通过拟合出的表面张力修正系数最佳取值与进口总压的三次关系曲线,可在进口总压为1.5×10~4~9.8×10~4 Pa范围内确定表面张力修正系数最佳取值范围,为汽轮机低压级湿蒸汽流动数值模拟提供依据。 相似文献
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汽轮机级内湿蒸汽凝结流产生的水滴会降低汽轮机做功功率,同时对汽轮机叶片带来潜在威胁。为研究不同负荷下汽轮机湿蒸汽内的非平衡凝结流动特性,采用非平衡凝结流动模型对汽轮机末两级叶片进行数值模拟计算。结果表明:不同负荷下,过冷度最大值均在次末级静叶,最大值为20K,然后逐级降低至0K;同一负荷下,汽轮机湿蒸汽级内的湿度大小逐渐增加,且末级动叶20%叶高处的湿度最大,最大值为9.5%;同一负荷下,湿蒸汽的成核率在次末级的静叶处达到最大值,且3种不同负荷下成核率最大值分别是50/(m3·s)、45/(m3·s)、13/(m3·s);凝结水滴的直径较小,在0~1μm之间。这对汽轮机通流部分设计和改造提供了理论参考。 相似文献
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采用真实气体平衡态计算模式和非平衡态自发凝结两相流动计算模式两种不同的计算方法对某大功率汽轮机低压末两级内三维湿蒸汽两相凝结流动进行了模拟和分析。计算表明非平衡效应引起湿蒸汽级组内流量、焓降在各级之间的分配、叶栅出口气流角、各级反动度都有发生变化。 相似文献
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The aim of presented work was the prediction of the losses in the wet steam flow through the last stage of 200MW steam turbine LP part.To this end,three numerical tools were used.The first method was the streamline curvature method (SCM) used on the meridional plane with losses correlations.The next two methods,TASCflow commercial CFD code and an in-house CFD code,based on the solution of the Reynolds- averaged Navier-Stokes equations (RANS).Ap- plication of three independent numerical tools al- lowed to make the more reliable losses analysis and made possible to compare applied numerical methods with each other. For the flow modeling in the last stage of LP steam turbine the various two-phase flow models were used and compared.The equilibrium model and non-equi- librium models with homogeneous and/or heterogeneous condensation were considered.The boundary conditions at the inlet and outlet from the stage were selected in such way to get the beginning of the homogeneous condensation process in the sta- tot.It corresponded to the part load of the turbine, i.e.140MW power and pressure in condenser 2.7kPa. 相似文献