Abstract
Flow injection is being used in steam turbines for some combined or geothermal plants in order to increase its total thermal efficiency. It can be easily imagined, however, that such a flow injection is accompanied by additional aerodynamic loss due to the flow mixing or the change in local flow angle. Preliminary three-dimensional steady numerical simulations are conducted for the flow field inside the chamber from which the secondary flow is injected. The results showed a small variation of the flow velocity at the injection slot and provided useful information concerning the magnitude of the pitchwise variation of the injection angle. Further numerical simulations in a turbine stage were then performed by prescribing different injection angle distribution at the injection slot. The turbine stage computations revealed the existence of a high loss region generated from the interaction of the injected flow and the passage vortex near the tip of the nozzle vanes. It was found that injection angles orientated to the suction side of the stator provided lower loss values, while cases where flow was injected to the pressure side minimized the flow angle deviation.
