A New Experimental Facility for the Study of Blade Tip Rubs at Engine Relevant Temperatures

As aircraft engines become more and more efficient, minimizing blade tip clearance in all rotating components of the turbomachinery is critical. This has reduced the distance between the rotating blade tips and the stationary casing to the point that small deviations in manufacturing, uneven thermal expansion, or centrifugal growth can cause the blade to contact the engine’s abradable casing lining. This abradable lining is added to the casing with the foresight that blades are likely to rub against it. In some cases, the clearances are designed so that the blades will cut into this abradable on the first run of the engine. Understanding the interactions between this abradable casing lining and the blades at engine relevant conditions is imperative to the safe and efficient operation of engines. The Ohio State Gas Turbine Laboratory and Pratt & Whitney have developed an in-ground experimental facility for studying the material interactions occurring during blade tip rub events. This facility is designed to allow for variable abradable incursion rates, abradable incursion depths, and blade rotational speed. Additional capabilities of the facility include: the use of an optical temperature sensitive paint system for non-contact sub ambient blade temperature measurements, high speed infrared measurement of blade temperatures, temperature control capabilities for the blades and abradable liner, and blade force measurements on the abradable liner. In this work, a temperature control system for sub and hyper ambient temperatures is presented along with the philosophy and design process for the creation of this system. To aid in designing the temperature control system, a transient heat transfer model was developed and validated in non-rotating experiments. The results of these experiments are discussed and the applicability of these results to the rotating case are examined.