High pressure turbine rotor blades heating duration experimental estimates prior to the bypass turbofan engine start for reducing thermal stresses

Reducing the durability cost of an aircraft product is an issue either addressed at the design stage or causing significant design modifications. Turbine preheating of a gas turbine engine (GTE) allows for the thermal stress of the rotor blades (RB) to be reduced at the engine start without making design changes, but only by implementing the engine heating technology into the operational process. Values of thermal stresses on rotor blades of a high-pressure turbine of a bypass turbofan engine (TFE) with and without heating allow us to determine the change in the total HPT RB damage rate. In the concept of preheating a GTE prior to the start in order to comply with the preheating technology, it is necessary to know the duration within which the RB will heat up to the required temperature. Thus, the research objective, presented in the paper, is to empirically determine the HPT RB heating time, using thermocouples and pyrometers on a full-scale body depending on the methods of air supply for heating and rotor spinning. A distinctive feature of this work is the application of the empirical approach to determine HPT RB heating time to evaluate the feasibility of the GTE preheating technology application prior to the start and the selection of the most efficient heating method according to the duration criterion. Several methods of engine heating prior to the start, using different sets of equipment and the method of supplying hot air to the turbine, were considered. The results of RB heating time measurements made it possible to establish the method of heating with minimal time expenditure prior to the engine start.

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