Wet Steam Flow Characteristics And Dehumidification Technology In Turbine

Steam turbines at the last stage of condensing steam turbines and PWR nuclear steam turbines at most stages are still wet steam at most rated loads.Severe water erosion of the blades will not only cause blade damage,but also cause blad e rupture,resulting in serious property damage and personal injury accident.Well-designed dehumidification program to remove most of the large damage to the blade of water droplets,can slow and eliminate wet steam on the blade of water erosion,reduce moisture loss and improve efficiency.In this paper,through the establishment of the steam turbine last stage cascade model and the coupling of DPM and EWF model,the flow,deposition,form the film of wet steam in the last stage of the turbine stator vane passage are established on the pressure side and the suction side of the vane channel suctions of the liquid film were numerically investigated.The results show that most of the water droplets with small particle size in wet steam have good followability,large impulse,and very good on the blade a large probability of rebound,and therefore basically no deposition on the leaves;wet steam in a larger diameter of the droplets and all the secondary water droplets is the main source of water film formation on the leaves.The area where the liquid film is formed mainly concentrates in the region of 0.5 or more of the pressure surface rel ative to the leaf height and 0 to 0.2 of the relative blade width of the suction surface,and is more obvious when the relative blade height is 0.4 or more.Under the condition of more than 70% load,the moisture change of the former stage wet steam is not very big.The different load has no obvious influence on the deposition area of the water droplet.The load mainly affects the speed of the water droplet particles forming the liquid film on the blade.Large,the faster the liquid film is formed,and vi ce versa,the slower.On the suction side and the pressure side of the blade,four dehumidification channels each having a width of 1.5 mm and a direction of 30 ° to 90 ° along the mainstream of the steam are provided.When simulating the flow of wet steam inside the prototype cascade channel,all the channel inlets need to be set to WALL,then the channel calculations can be closed to close.When the channel inlet is set to INTERIOR,the channel inlet face and its corresponding SHADOW automatically merged surface,the channel can be calculated open.Two different dehumidification schemes are designed according to the deposition and film formation of water droplets on the prototype blade and the movement tendency of the liquid film in the wet steam: option 1 choose one of the multiple channels on the pressure and suction surfaces of the blade;option 2 in the blade pressure surface and the suction surface of each of the plurality of channels to select two suitable channels.The results show that the scheme 2 is more effective than scheme 1 in inhibiting the formation of water film on the blade by the wet steam under the two slotted schemes.Thick and to the trailing edge of the trend of movement,with good dehumidification effect.At loads greater than 70%,the difference in load has less effect on both pumping schemes.