Research on unsteady aerodynamic performance of last stage for low pressure cylinder of steam turbine

Abstract

Abstract. The last stage of the turbine low pressure cylinder has a complex flows, especially under the high mass flow and low mass flow conditions, where there is an obvious unsteady flow phenomena and obvious rotor-stator interaction. In order to further research on the flow of the last stage for the low pressure cylinder, the last stage blade of low pressure cylinder of 150 MW steam turbine is taken as the research object. Unsteady numerical simulation on the aerodynamic characteristics of the last stage blade for the steam turbine is conducted under a series of mass flow conditions (high mass flow condition, design condition and low mass flow condition) using the commercial CFD software ANSYS-CFX. As a result, rotor-stator interaction is most obvious in the root of the blade, followed by the midspan region, it is weaker in tip of the blade. Comparing internal flow details of the last stage blade in the three conditions, stator flow export and rotor blade passage have a larger energy loss under the low mass flow condition, and the flow is relatively smooth under the high mass flow and design conditions. Finally, energy conversion efficiency of the last stage blade is the highest under the design condition, followed by the high mass flow, and energy conversion efficiency of the last stage blade is the lowest under the low mass flow condition.

Theoretical foundations in research in Engineering

“…It is noted that when modeling the flow path of LPC at the low-flow rate modes, it is necessary to consider the hydrodynamic processes occurring in the turbine stages. Non-stationary aerodynamic characteristics in a low-pressure steam turbine were numerically studied under off-design operating conditions using commercial software ANSYS-CFX [77]. This paper discusses the issues of changing the torque on the steam turbine blade, the distribution of Mach number, the determination of the flow line and the distribution of static pressure over the surface of the blade at different heights.…”

Analysis on strength performance of the last stage blade in steam turbine under low mass flow conditions

“…When the load is reduced to a certain level, the windage condition will occur, resulting in overheating of blade. 2,3,4 Then, the blade faces the danger of increasing stress and over-temperature deformation. 5,6 Therefore, it is necessary to study the blade strength performance of coal-fired power generating units under low mass flow conditions in depth.…”