Journal of Mechanical Engineering (Mar 2020)

The Efficiency Increase of the Steam Turbine Low Pressure Cylinder Last Stage by the Blades Spatial Profiling

  • Andrii V. Rusanov,
  • Viktor L. Shvetsov,
  • Svitlana V. Alyokhina,
  • Natalia V. Pashchenko,
  • Roman A. Rusanov,
  • Mykhailo H. Ishchenko,
  • Liubov O. Slaston,
  • Riza B. Sherfedinov

DOI
https://doi.org/10.15407/pmach2020.01.006
Journal volume & issue
Vol. 23, no. 1
pp. 6 – 14

Abstract

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The paper presents an option of the steam condensing turbine K-325-23.5 (K-300 series) low pressure cylinder flow part improvement due to the last stage modernization. The K-325-23.5 turbine is designed to replace the outdated K-300 series turbines, which together with the K-200 series turbines form the basis of Ukraine's thermal energy. In the modernized flow part, new last stage guide apparatus blades with a complex circular lean near the hub are used. The purpose of the modernization was to increase the low-pressure cylinder efficiency in the "bad" condenser vacuum to ensure that it did not "decrease" its efficiency at rated operating modes. The modernized low-pressure cylinder flow part is developed with the usage of modern methods of the viscous three-dimensional flow calculation based on the numerical integration of the Reynolds-averaged Navier-Stoks equations. For the turbulent effects, a two-parameter differential SST Menter turbulence model is applied, and for the hydraulic fluid real properties, the IAPWS-95 state equation is used. To construct the axial blades three-dimensional geometry, the original method, the initial data for which was the limited number of parameterized quantities, was used. The applied methods of gas-dynamic calculations and design of flow turbomachines are implemented in the IPMFlow software package, which is the development of the FlowER and FlowER-U software packages. The researched low-pressure cylinder flow part is limited by the last two stages (4th and 5th). A difference grid with a total element volume of more than 3 million is used to construct the calculation area. The research examined more than 20 options of the last stage stator blades. In the modernized flow part of the low-pressure cylinder last stage at rated operating mode, the gain of the efficiency coefficient (efficiency) is 0.9% and power – 0.61 MW. In the mode of "bad" condenser vacuum (with high pressure) a significant increase is achieved: efficiency – by 11.5%, power increased by almost 2 MW.

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