Overview
The Peregrine turbine facility has two controls: the motor and the eddy-current brake. The variable speed motor drives the centrifugal fan at the rear of the facility, which draws in ambient air through the working section. This effectively sets the mass flowrate through the facility. The eddy-current brake absorbs the power generated by the turbine in order to control the rotational speed of the turbine. Thus, the non-dimensional flow-coefficient and Reynolds number of the facility can be controlled.
The facility has a sophisticated control code which uses PID controllers to hold the required operating point (flow coefficient and Reynolds number) taking account of real time ambient variations in temperature, pressure and humidity. As such, the required flow coefficient and Reynolds number are held fixed with less than 0.01% variation. There is also a fault tolerant emergency stop shutdown system.
The configuration in the working section is representative of a two-stage LPT with high aspect ratio blading and fully-featured endwall geometry, with stator under-hub and rotor over-tip cavities. Upstream of the working section there is a turbulence grid to generate a representative level of inlet turbulence that corresponds to an embedded stage in the low pressure turbine of an engine.
The working section of the two-stage turbine consists of five casing rings, one over each blade row plus an additional upstream ring. Each ring can be independently circumferentially indexed over three stator pitches to within 0.1% of a stator pitch. This allows area traverses to be undertaken and the potential benefits of ‘clocking’ to be investigated.
The facility has seven measurement planes, where area traverse measurements can be taken using pneumatic instrumentation. The axial locations of the measurement planes allow for traverse measurements to be taken within the end-wall cavities, as well as the main-flow regions. Hence, the cavity fluid mechanics can also be interrogated.