Numerical analysis of saturated steam injection effects on steam turbine performance considering condensation losses and turbine stage efficiency

Abstract

Steam turbines play a crucial role in electricity production, and any enhancement in their performance can significantly reduce energy losses. During operation, steam expands in the low-pressure sections of the turbine where supercooling, can lead to non-equilibrium condensation (NQC), transforming the flow into a two-phase state. This NQC, an irreversible phase change, results in the formation of liquid droplets, which reduce efficiency, cause blade wear, and lead to mechanical damage. This study proposes the use of a saturated steam injection technique to mitigate the detrimental effects of the liquid phase on steam turbine blades. Given the high energy content of hot steam, saturated steam is selected for injection. Initially the effects of this technique on parameters such as pressure, temperature, and Mach number are examined. Subsequently, its impact on nucleation, droplet radius, liquid mass fraction (LMF), turbine stage efficiency (TSE), and condensation losses is analyzed. The results show that the saturated steam injection technique effectively reduces the liquid phase in the flow. However, it also reduces the TSE due to flow disturbance. Optimization of saturated steam injection parameters reveals that injecting steam at specific conditions (location 3, saturation pressure 140 kPa, injection slot width 0.09, inlet length and angle 90 degrees) results in a reduction in, LMF, condensing losses and vane inlet flow by (22.82 %, 23.69 % and 1.5 %, respectively).