Experimental Study of Intrachannel Separation in a Flat Nozzle Turbine Blade Assembly With Wet Stream Flow1

Abstract

This is an experimental study of wet steam flows in a nozzle turbine array with an intrachannel separation system that makes it possible to reduce the amount of erosion-hazardous droplets in a turbine stage. Separation is found to affect the parameters of the liquid phase beyond the array. Experiments were done on a test stand at the Moscow Power Engineering Institute with an initial steam humidity of 6.5% and a theoretical Mach number of M _1t = 0.6 beyond the array. Two separation slots at an angle of 90° to the generatrix of the profile surface were made on the concave surface of each blade in the test channel. The effect of the pressure drops in the slots on the wet steam flow downstream of the nozzle blade array was studied and the flow rates of the separated steam and liquid were measured separately. The efflux of the steam-water mixture into the slot was modelled in the ANSYS Fluent CFD computer code. This yielded a more complete picture of the flow structure in the slot and made it possible to explain the behaviors of the experimentally observed separated steam and liquid flows. The velocity distributions of the liquid phase beyond the nozzle were obtained by particle image velocimetry (PIV). The experimental data can be used to modify the parameters of intrachannel separation systems for steam turbine stages and to increase the reliability and operating efficiency of turbine blades.