The Retrofit Scheme Research And Result Analysis Of Extraction Condensing Turbine Soft Tooth Seal

In the recent 20 years, the flow passage of thermal power steam turbine has made many improvements by the promotion of computational fluid dynamics. To some extent, the performance has improved. But with the steam parameters increase, steam leakage loss become the main limiting factor for higher steam turbine efficiency. The steam turbine unit thermal efficiency could be reduced by 1.0%～1.5% as a result of steam leakage when steam flow across the turbine diaphragm gland, gland over shroud and shaft gland. And this part of the energy loss is mainly affected by the size of the sealing clearance. Common rack-type labyrinth sealing is rigid, the too small clearance may lead to friction, vibration, even deformation between the gland comb and shaft. However, spring-back sealing is elastic, which make it restore to installed state by the function of elasticity and steam flow after lodging due to the gland comb friction. As a result, clearance of this spring-back sealing can be designed under the rack-type labyrinth steam sealing standard clearance. The size of gland clearance has a large effect on the sealing leakage quantity. Usually for every 0.10 mm sealing clearance reduction compared to designed value, the overall steam leakage quantity decrease by more than 30%.Therefore, reduction of steam turbine vapor leakage is of great practical significance for higher turbine efficiency, energy saving and lower consumption. Based on technology analysis to many kinds of glands, the implementation of spring-back sealing as an alternative to rack-type labyrinth sealing in turbine is outlined in this article, reforming scheme for Huaneng Linyi power generation co., LTD#6 unit is determined.Huaneng Linyi power generation co., LTD.,#6 unit is a 140 mw homemade coal-fired turbo-driven set, turbine produced in Shanghai Steam Turbine co.,LTD is 140 mw ultra high pressure, reheat type, double-cylinder double-exhaust, uniaxial and extraction condensing steam turbine. In the reforming scheme, HP and IP balance piston gland, HP (IP,LP) cylinder shaft gland and LP diaphragm gland are all replaced by spring-back sealing, which helps reduce the average clearance by 0.10mm～0.35mm compared to design value. After gland reforming, steam leakage in sealings is reduced by more than 30%, with which high/medium-pressure cylinder efficiency respectively increased by more than 2.5%/1.5%.Research for spring-back sealing in extraction condensing turbine in this article will be referable for gland reforming which aims to reduce steam leakage.