Enhancing low-pressure stage steam turbine using the TDLD criterion and the TOPSIS analysis

The liquid phase in the wet steam flow causes thermodynamics losses and affects steam turbine blade durability. The main objective of the present research is the design of the rotor stagger angle and different operating conditions in the low-pressure stage of the steam turbine. A two-phase Eulerian-Eulerian model and the SST k - omega model are used to simulate the viscous wet steam flow inside the steam turbine stage. Frozen rotor methodology is employed for modeling the stator-rotor interaction. The effects of different rotor stagger angles and different outlet pressure levels on the wet steam flow parameters are studied to introduce an improved case. The turbine stage efficiency, droplet average radius, liquid mass fraction, and degree of reaction (TDLD) are considered as design criteria. The search for the improved value of pressure ratio and rotor stagger angle is performed using the TDLD criterion by TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution). The improved case is selected with a rotor stagger angle of 64 degrees and outlet pressure of 6.5 kPa, at which the turbine stage efficiency (TSE) is increased by 21.3% compared to (TSE) over bar. Also, the liquid mass fraction (LMF) and the degree of reaction (DOR) reduced by 39.53 and 26% relative to (LMF) over bar, and (DOR) over bar, respectively. In addition, droplet average radius (DAR) increases by 26.14% compared to (DAR) over bar.

Automated summary

The design of the rotor stagger angle and operating conditions in the low-pressure stage of the steam turbine can reduce the effects of liquid phase in the wet steam flow, improving turbine efficiency. Simulations and experiments were conducted to determine the optimal rotor stagger angle and outlet pressure, resulting in a significant increase in turbine stage efficiency.