Heat transfer and cooling

Current research activities are focused on the development of novel combustor effusion cooling designs which exploit new manufacturing techniques such as direct laser deposition (DLD). Typical tests involve creating large scale segments of the combustor liner using materials with appropriate thermal properties. This enables accurate scaling of both thermal and aerodynamic conditions (Re, Nu, Biot, etc.) in a low temperature laboratory environment allowing high fidelity measurements to be made. Overall cooling effectiveness is assessed using time averaged IR surface measurements to establish a thermal ranking of different designs. The most promising schemes are then investigated further on a high turbulence film cooling test facility, which enables an in-depth analysis of coolant film development using a combination of IR thermography, thermally sensitive liquid crystal coatings and temperature traverse data.

High pressure/temperature tests are also performed with multiple HP air supply lines at 14 bar. The UTC's high pressure test facility is highly reconfigurable; a small gas turbine combustor can be used to heat air to 1000K and a chiller system can be installed to cool air, these operations can be run simultaneously on differing streams, providing a wide range of application possibilities. The facility can be used for aerodynamic assessment of propulsion exhaust nozzles and associated cooling studies. Data acquisition techniques include pneumatic probes, LDA, thermal cameras, constant current and constant temperature anemometry. These provide details of flow field velocity, turbulence measurements, heat transfer surface film effectiveness and heat transfer coefficients. The excellent uniformity of the delivered air is also exploited to perform high accuracy calibration of engine gas-path instrumentation.