Reduction of water droplets effects in steam turbine blade using Multi-objective optimization of hot steam injection

Abstract

As one of the most important equipment for energy conversion, steam turbine plays an irreplaceable role in industry. Due to the high velocity, the non-equilibrium condensation will take place in the steam turbine, emerging lots of tiny droplets. The tiny drops will not only deteriorate the efficiency but also endanger the safety of the steam turbine. The control of droplets size and liquid mass fraction is essential issue in steam turbine blade. One of the techniques that reduce the effects of the liquid phase on steam turbine blades is to inject hot steam. This study investigates hot steam injection in steam turbine blades for dehumidification by considering friction and thermal entropy generation. First, the injection parameters (injection location, slot width, pressure and temperature) are examined parametrically, and their impacts on the generated friction and thermal entropies, condensation loss, erosion rate, hot steam injection rate, and blade inlet flow rate are investigated. The optimization is carried out by the genetic algorithm. The results show the generated friction and thermal entropies increase through the hot steam injection, which, in an optimum state, can reduce the condensation loss, erosion rate, and blade inlet flow rate by 21%, 89%, and 4.9%, and raise the generated entropy by 22%. Moreover, the rate of the hot steam injection equals 4.3% in this condition.