汽轮机排汽通道喷水减温对末级流场的影响

Effect of Water Spray in Exhaust Passage of Steam Turbineon Flow Field of the Last Stage

汽轮机超低负荷运行时,末级的鼓风工况导致汽轮机排汽超温,因此需要对排汽通道进行喷水减温。采用欧拉-拉格朗日质子追踪法对排汽通道内喷水减温的传热传质特性进行了数值研究,分析了喷水减温对末级流场的影响。结果表明:排汽通道内的流场具有蒸汽与减温水温差小、蒸汽流动速度快的特点,导致减温水的蒸发量极小。喷水对动静间隙涡和分离涡的影响不明显,但增加了回流涡的高度和流速。同时,喷水使末级压力增加,动叶压比增大,导致动叶消耗的轴功降低。

Under the ultra-low load condition ofsteam turbine,the windage condition of the last stage leads to the overtemperature of exhaust steam.Waterspray is an effective way to lower the temperature in exhaust passage.The Euler-Lagrange particle tracking method is used to study the heat and mass transfer of the water spray in exhaust passage.The effect of water spray on the last stage flow field is analyzed.The results show that there is a small temperature difference between steam and liquidin the exhaust passage and a minimum evaporation of droplets for high steam velocity.The water spray has little effect on the rotor-stator clearance vortex and the separation vortex,but the height and velocity of the back flow vortex are increased.Meanwhile,the pressure of the last stage and the pressure ratio of the rotor blade increase,which result in the dissipating shaft powerofthe rotor blade reduces.