Turbine-Blading Development Using a Transonic Variable-Density Cascade Wind Tunnel

Abstract

The thermal development of the modern steam and gas turbine over the past two decades has been greatly assisted by a much better understanding of the fluid behaviour as it passes through the machine. This has been brought about by the increasing amount of aerodynamic research and development being carried out on the many components of these turbines. This paper concentrates on the fixed and moving-blade elements of the large steam turbine, and describes the design and operation of a transonic variable-density wind tunnel for static cascade testing of turbine blading. The importance of Reynolds number and Mach number is emphasized, and the manner in which these parameters influence the blading losses. The origin of the trailing edge shock waves on blades discharging obliquely, and their effect on performance, is discussed in some detail, drawing on both experimental and theoretical techniques. A large proportion of the flow section of long last 1.p. stages is operating in the supersonic region, and possible future blades may have relative discharge tip Mach numbers approaching 20.