Gas turbines operate at extreme temperatures and pressures, constraining the use of both optical measurement techniques and probes. A strategy to overcome this challenge consists of instrumenting the external part of the engine with sensors located in a gentler environment using numerical inverse methodologies to retrieve the relevant quantities in the flowpath. An inverse heat transfer approach is a procedure used to retrieve the temperature, pressure, or mass flow through the engine based on the external casing temperature data. An improved Digital Filter Inverse Heat Transfer Method that consists of a linearization of the heat conduction equation using sensitivity coefficients was validated in the BRASTA module, with flow temperatures up to 500K.

Particle Image Velocimetry (PIV) is a well-established technique for determining the flow direction and velocity magnitude of complex flows and successfully tested in BRASTA to study a scaled-up turbine vane geometry within an annular cascade at engine-relevant conditions. Custom optical tools such as laser delivery probes and imaging inserts were manufactured to mitigate the difficult optical access of the test section and perform planar PIV. With the use of a burst-mode Nd: YAG laser and Photron FASTCAM camera, the frame straddling technique is implemented to enable short time intervals for the collection of image pairs and velocity fields at 10 kHz. Different Mach and Reynolds number operating conditions were achieved by modifying the temperature and mass flow. With careful spatial calibration, the resultant velocity vector fields are compared with Reynolds Averaged Navier Stokes (RANS) simulations of the vane passage with the same geometry and flow conditions. Uncertainty analysis of the experimental results is also presented and discussed, along with prospects for further improvements.

A single flow conditioning gauze equipped with numerous radial and circumferential blades replicates the total pressure and whirl angle radial profiles experienced by a turbine blade in its relative frame. This setup bridges the gap between linear cascades and rotating turbine facilities while maintaining high-resolution measurement techniques and optical access. To ensure homogeneous inlet profiles, the positioning of the gauze relative to the turbine is informed by results from 3D steady Reynolds Averaged Navier Stokes simulations. The final design was machined as a single piece of stainless steel. The inlet flow quality was assessed using total pressure probes and static pressure taps around the annulus; the total pressure, whirl angle, and Mach number profiles downstream of the gauze were examined using Kiel and Five Hole probe traverses, showing good agreement with the required design conditions, thus confirming the viability of this configuration to a turbomachinery experiment. Future test campaigns can integrate rainbow annular cascades to test multiple geometries simultaneously, while performance studies can extend beyond five-minute blow-down test durations, allowing for high-resolution complete circumferential traverses. The turbine exit Reynolds number can range from as low as 30,000 under vacuum conditions to 1,000,000 when exhausting to atmosphere, with the ability to independently adjust the pressure ratio for testing across a range from low subsonic to sonic speeds.

The development of efficient small core turbines is critical as the aviation industry pushes to higher OPR engines, hybrid propulsion concepts, and multi-stream engines. In response to the small core advancement, the Small Turbine Aerothermal Rotating Rig was designed to address small core turbine challenges. Its two-stage turbine module is designed for continuous and transient operation, enabling precise efficiency and heat flux measurements. The test section is designed to test both uncooled and cooled geometries with 15 different cooling configurations. The modularity of the rig allows for experiments to be performed in any stator-rotor configuration. The rig is equipped with two traverse rings, where different types of probes can be installed to measure temperature, pressure, flow direction, and Mach number. In addition, specially designed blade track inserts allow for a wide range of instrumentation and optical measurement techniques at the rotor tip of both stages. This includes PIV, PSP, low/high frequency pressure sensors, and tip clearance capacitance probes. These measurements will facilitate the detailed study of aero-thermal tip flows at various operating conditions.

The facility is complemented with a auxiliary cooling system, which can provide multiple gases including N2, CO2, or dry air, providing coolant and control fluids with a large variability of density and blowing ratios. The energy extracted from the turbine is absorbed by a direct drive (no gearbox) high speed AC electric motor, enabling engine representative transient operation. The STARR test section, built in collaboration with Rolls-Royce, together with its auxiliary systems is the state-of-the-art facility to evaluate efficiency in small core turbines at a TRL of 5-6.