Isentropic Compression Tube Annular Cascade Facility CT-3
The CT-3 turbine facility is able to reproduce the operating conditions encountered in the high-pressure stages of modern aero-engines and/or stationary gas turbines. The Reynolds and Mach numbers can be adjusted independently. Heat transfer between the hot gas and the cold blades is also reproduced.
The test section can model up to 1 1/2 HP turbine stages. It is supplied by a 1.6 m diameter 8 m long cylindrical reservoir. A free-moving, light-weight piston is used to achieve a quasi-isentropic compression of the reservoir gas. When the stage inlet conditions are reached, a fast opening shutter valve is actuated and the hot pressurized gas is released through the turbine test section. The downstream throat is adjusted to keep the mass flow constant for test durations between 0.2 - 0.4 s. During blow-down, the acceleration of the rotating parts is limited by an inertia wheel.
The inlet to the test section reproduces the exhaust of a combustion chamber. Typical test section dimensions are 800 mm for the outer diameter and 50 mm for the blade height. Cooling of the vanes and the rotor blades, and/or the ejection of cold gas at the hub between the vane and rotor platforms can also be accomodated with representative temperature ratios.
Pitot and thermocouple rakes quantify the stage inlet profiles. The inlet turbulence can be varied using bars or meshes. The static pressure downstream of the vane can be measured with both pneumatic and fast response pressure transducers at hub and tip. Fast response instrumentation is also used to resolve the fluctuating aero-thermal flow at vane/blade passing frequencies downstream of the stator, on the rotor blades and down-stream of the stage. The tunnel is currently equipped with a 16 channel infrared opto-electronic transmission system that transfers the measurements performed on the rotor blades to a fixed high-speed data acquisition system.