Energy Saving Through An Innovative Aircraft Turbine Thermal Control

One of the most important challenges for the next generation of aircraft propulsion systems is an engine more efficient, with less pollutants emission and so definitely more sustainable. To reach this goal a lot of new technical solutions must be exhibit in order to optimize the main engine parts, but the attention should also be focused on how the different engine components work, due to the thermal loads they undergo during the different phases of the flight. Typical examples of the effects that the thermal loads produce are the gaps among the different components, producing unavoidable leakages, due to their differential thermal expansion. Actually in the Low Pressure Turbines (LPT) one of the countermeasures applied to control and to minimize these gaps consists in blowing into the stator cavities some relatively cold air bled from one of the compressor stages. This technique, even if effective for the turbine thermal control, results in supplementary fuel consumption. In this research a first attempt to reduce the required cooling air, by introducing insulating materials in the proper LPT cavities, is shown. The preliminary numerical analyses performed to point out and compare suitable configurations are here presented. The configuration, identified as the most performing, has been used to forecast the insulation technology effectiveness. The obtained numerical results evaluated both in terms of temperature decreasing of the Casing plate and of Cooling air reduction, are reported. The technological solution, numerically pointed out, has been experimentally validated by means of the available testing facility, whose Test Article reproduces, properly scaled, one stage of a modern LPT. After the experimental campaign, the experimental data and the ones obtained by running the numerical model have been compared in order to evaluate the final model accuracy. Finally, a thermal insulating selection has been performed to overcome the limits that the tested technology has exhibited. The studied alternative solutions and the obtained results are here reported and compared with the ones obtained with the technology previously implemented.