The Design, Performance and Analysis of a High Work Capacity Transonic Turbine This paper describes the design and testing of a high work capacity single-stage transonic turbine of aerodynamic duty tailored to the requirements of driving the high-pressure core of a low cost turbofan engine. Aerodynamic loading was high for this duty (AH/U 2 =2.1) and a major objective in the design was the control of the resulting transonic flow to achieve good turbine performance. Practical and coolable blading was a design requirement. At the design point (pressure ratio = 4.48), a turbine total to total efficiency of 87.0 percent was measured -this being based on measured shaft power and a tip clearance of 1.4 percent of blade height. In addition, the turbine was comprehensively instrumented to allow measurement of aerofoil surface static pressures on both stator and rotor-the latter being expedited via a rotating scanivalve system. Downstream area traverses were also conducted. Analysis of these measurements indicates that the turbine operates at overall reaction levels lower than design but the rotor blade performs efficiently.
The heat transfer and aerodynamic characteristics of a turbine nozzle guide vane with a supersonic exit velocity have been measured in a transient cascade facility. The vane possesses a convergent-divergent passage, and this, together with a low trailing edge wedge angle, is seen to control the supersonic flow efficiently at design conditions. Heat transfer measurements have been taken on both suction and pressure surfaces. On the suction surface, transition is marked by a rapid increase in heat transfer, whereas on the pressure surface a slow increase in heat transfer indicates the gradual onset of turbulence. The measurements also indicate possible relaminarisation of the suction surface boundary layer at the impingement of the trailing edge shock. Predictions are presented of aerodynamic flow, using an inviscid time-marching calculation, and heat transfer, using a differential method applied to the vane surface.
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