Energy losses caused by steam humidity are one of the main components of losses in the steps of nuclear power plants’ wet-steam turbines. The presence of moisture droplets in the flow part of the turbines also poses a serious danger due to erosion wear of their blades. Various separation systems remove part of the erosion-hazardous moisture. However, along with moisture, a certain amount of steam is removed from the flow part of the turbine, which will not take part in performing beneficial work in subsequent stages of this turbine. Other losses are steam leaks through seals, the largest of which occur in seals located above the turbine blades. On the basis of the rectangular-mesh seals developed and studied earlier, the design of a special peripheral seal for NPP turbines was developed at NRU MPEI. The new seal is capable of simultaneously performing two functions: to reduce over-leakage leaks and to ensure the separation of moisture from the flowing part. The results of the studies showed that the presence of special channels in the seal for removing drip moisture hardly worsen the flow characteristics of the new seal. This paper presents the results of experimental studies into the separation ability of new peripheral seals. As a two-phase medium, specially prepared moist air was used. To do this, a plant for the preparation of water and the generation of the droplet phase was designed and manufactured. During the experiments, the ability of the seal structure to remove moisture was investigated. The use of humidified air made it possible to accurately determine the amount of droplet moisture supplied to the seal and separated through it and the separation coefficient of the seal. Studies have shown that the amount of moisture separated through the seal depends on the pressure drop across it, the rotor speed, and the initial degree of humidity of the compressed air supplied to the seal. It is shown that the use of a new seal in the studied range of initial degrees of humidity allows the separation of up to 45% of the moisture passing through the peripheral gap above the working blades. In general, the results of the experiments showed that the use of a rectangular-cell seal from NRU MPEI as a peripheral seal in turbines of nuclear power plants is advisable to remove moisture from the gap above the working blade and to reduce peripheral steam leaks. |
