Passive control optimization of condensation flow in steam turbine blades

Due to the decrease in steam temperature in the low-pressure steam turbine, nucleation occurs, and liquid droplets form, reducing thermodynamic efficiency and damaging the blades. A new flow control method and optimization of two-phase flow among stator blades are discussed in this paper. During this flow control, steam is taken from upstream flow and injected into downstream flow through two holes in the turbine's blade. For the current simulation, an in-house code has been developed. This code is density-based, two-dimensional, compressible, and viscous, with a three-equation turbulence model. The main aim of the present study is to increase the thermodynamic performance by reducing the droplet radius and wetness fraction; these features are affected by changing the hole characteristics. Response Surface Optimization Method (RSM) is applied to find the best width and location of the inlets and outlets of the holes (eight independent variables). The optimization method is applied to a two-phase steam turbine flow for the first time. Also, a parametric study of this flow control on the thermodynamic and aerodynamic characteristics has not been done before. Turbine blade changes may result in a loss of aerodynamic performance, such as a reduction in velocity; thus, throughout the optimi-zation process, it's better to consider the impact of holes on this efficiency. The results for the optimum case demonstrated that the average velocity and entropy at the blade output are almost identical to the baseline. However, the droplet radius and wetness fraction are decreased by 5.91 and 16.37 percent, respectively, and these decreases could significantly enhance the thermodynamic efficiency.

Automated summary

This paper discusses a new flow control method and optimization of two-phase flow, aiming to improve thermodynamic efficiency by reducing droplet radius and wetness fraction.