Session: 21-01: Last Stage Blades and Low Pressure Sections

Paper Number: 127659

127659 - Experimental and Numerical Investigations of Flow Patterns at Low Volume Flow Rate Conditions in Low Pressure Steam Turbine 

    This study focuses on the flow patterns at the last stage outlet under low volume flow conditions in a low-pressure steam turbine.

    With regard to environmental issues such as CO2 emissions and stable power supply, the demand for high-efficiency and flexible operation steam turbines is increasing. Steam turbines can be used in power plants that use non-fossil fuels as heat sources, such as geothermal and nuclear power plants. As a result, steam turbines are becoming increasingly important in providing stable power generation now and in the future, when power generation from renewable energy sources will flourish.

    As a result, steam turbines are often used under a variety of conditions. In particular, steam turbines often operate at low volume flow conditions as the electrical power generated by renewable energy increases. The large separation occurs around the last stage outlet under low volume flow conditions. This large separation affects blade vibration and turbine performance. From the point of view of turbine performance and strength assessment, flow pattern prediction and investigation are important, both numerically and experimentally.

    In this study, the flow pattern at the last stage exit is evaluated both numerically and experimentally under the low volume flow conditions. In the experimental framework, 5-stage 1/3 scaled steam turbine tests were conducted and the flow pattern at the last stage exit was measured by a 5-hole pitot tube. The wall pressure was also measured to evaluate the reverse flow at the last stage exit.

    The numerical results in this study were in good agreement with the experimental data. First, the characteristic power curve of the experimental data and the CFD results with the moisture loss model were almost the same. The numerical predictions of the flow pattern were in good agreement with the test data even in the low volume flow conditions. As for the swirl angle at the last stage outlet, the non-equilibrium condensation effect should be considered under the design condition, but it is not necessary to consider the non-equilibrium effect under the low volume flow conditions due to the reverse flow at the last stage outlet.

Presenting Author: Soichiro Tabata Mitsubishi Heavy Industries, Ltd.

Presenting Author Biography: Dr. Soichiro Tabata (born in Japan, in Dec. 1983) received B.S. and M.S. degrees in mechanical engineering from Kyushu University, Japan, in 2007 and 2008, respectively. Then, he received a Ph. D. in mechanical engineering from Kyushu university in 2011. Since 2011, he has been an engineer at Mitsubishi Heavy Industries, Ltd. Then, he has been an engineer at Mitsubishi Hitachi Power Systems, Ltd. which is formed as a joint venture between Mitsubishi Heavy Industries, Ltd. and Hitachi, Ltd. He is in charge of development of last stage blade in steam turbine in Mitsubishi Power, Ltd. Mitsubishi Power has been merged into Mitsubishi Heavy Industries, Ltd. As of July 2022. So, He is now an engineering manager of steam turbine blade development of MHI.

Authors:

Soichiro Tabata Mitsubishi Heavy Industries, Ltd.
Kiyoshi Segawa Mitsubishi Heavy Industries, Ltd.
Tadashi Takahashi Mitsubishi Heavy Industries, Ltd.
Jin Aoyagi Mitsubishi Heavy Industries, Ltd.