Engine aerodynamics test facilities

Large-Scale Subsonic Linear Cascade

This subsonic test facility consists of an open-circuit wind tunnel with a variable-incidence linear cascade test rig.

The test rig is used to investigate the steady and unsteady aerodynamics of turbine and compressor airfoils, at design and off-design conditions. The air flow is supplied by a radial blower at a maximum flow rate of about 5 kg/s at a total pressure rise of about 1.8 kPa. High-quality flow uniformity is achieved by several fine screens in the wide-angle diffuser and the settling chamber. After the settling chamber, the nearly stagnant flow is smoothly accelerated through a 14:1 contraction before entering the cascade test rig. The flow is essentially incompressible and the wind tunnel is capable of maintaining stable velocities from 3 m/s to 30 m/s at the inlet of the cascade. Turbulence grids can augment the 0.3% background turbulence intensity to 5% upstream of the cascade. The rig is also equipped with precision traverse mechanisms for detailed measurements upstream and downstream of the cascade.

The test section has a span of 20 cm and the airfoil chord is typically 7.5 cm for a cascade with 9 blades.

Large-Scale Transonic Linear Cascade

The cascade test rig is used to study aerodynamics and heat transfer of transonic turbine vanes. The vane span is 11.3 cm, and the vane chord is typically 17.5 cm for a cascade with 6 blades. In this continuous flow facility, air is drawn into the cascade at a maximum flow rate of 5 kg/s. The isentropic exit Mach number can be varied between 0.3 and 1.4. Data obtained include surface static pressure, quasi-wall shear stress, flow-field pressure (time-resolved and time-averaged), angle, and total temperature distributions.

Low-Subsonic Probe Calibration Rig

Pressure and hot-wire probes are calibrated in this blow-down rig prior to testing at subsonic speeds. The rig consists of an open-circuit wind tunnel with a 16:1 axisymmetric large core jet. Excellent jet flow uniformity is guaranteed between 1 m/s and 60 m/s at a low free stream turbulence intensity of 0.3%. The probe stem is secured on the arm of a precision three-degree-of-freedom traverse mechanism, which provides variation in the roll, pitch and yaw angles without changing the absolute position of the probe tip.

The traverse mechanism provides ± 70° probe rotations in pitch and yaw with an estimated accuracy of ± 0.01°.

High-Subsonic Probe Calibration Rig

This cold flow, suction-type rig has a large test section (175 cm2) and is capable of delivering uniform flow between free stream Mach numbers of 0.15 and 1.2. The ambient air is drawn into the test section through a contraction.

Schlieren imaging

The inner sidewalls of the test section are porous, which enables operation at subsonic and transonic conditions with high blockage tolerances. Pressure and temperature probes are calibrated for recovery and time response at about 9 cm downstream of the throat, where the static pressure is fairly uniform. Probes are mounted on a two degrees-of-freedom traverse mechanism on one side of the tunnel. The air flows through a diffuser downstream of the test section, before entering the pipes leading to the compressor.

Other measurement capabilities

Available experimental techniques includes temperature and multi-hole pressure probe measurements multi-wire, hot-wire and surface-mounted hot-film measurements; schlieren flow visualization; and particle image velocimetry.

Data acquisition and control systems are developed mainly by internal staff.