Abstract
Flow separation and different kinds of stall flows occur under low load conditions for steam turbine last stage blades. In order to delay the flow separation and increase turbine power production, we applied suction side tubercles on steam turbine low-pressure last stage blades in the present study. The amplitude, wavelength, position, and thickness were considered as our design variables. We used the orthogonal test method (OTM) to generate modified blades with different tubercle variables that were then numerically simulated by a three-dimensional computational fluid dynamics (CFD) analysis. The blade axial torque of the nine modified tests was compared with the original blade. The results showed that the application of bionic tubercles on the suction side of the steam turbine blade is a promising solution to improve the blade axial torque for all modified tests with a maximum increase of 33.32% due to the turbulent vortices generated by bionic tubercles.
Highlights
With the energy structure reform in many countries of the world, the development of renewable energy generation, such as wind and solar power, is happening at an increasing rate [1]
The results in terms of the blade axial torque of the nine modified tests were compared with the baseline value, and a physical explanation of the mechanism was given by looking at the flow characteristics around the bionic tubercles
In order to better visualize the evolution in the blade axial torque given by bionic tubercles under different mass flow rate conditions, the non-dimensional blade axial torque was generated as follows:
Summary
With the energy structure reform in many countries of the world, the development of renewable energy generation, such as wind and solar power, is happening at an increasing rate [1]. The requirement for operational flexibility of power plants has increased. As an important part of power production devices, steam turbines face relevant problems, such as operating under partial load conditions to adjust the electrical frequency. Under low load conditions, due to the increase of the impact angle of the steam flow, flow separation and different kinds of stall flows will occur in steam passage. This makes the flow characteristics inside the turbine more complicated than the design condition and causes various losses, which reduce the steam turbine power production [2]. In terms of delaying the flow separation, the application of bionic tubercles on turbine blades can be used as a research hotspot, as this can facilitate the momentum exchange between the boundary layer and the mainstream
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