Method of mitigating thermal rotor bow in a turbine engine
Publication Date: 2016-May-24
The IP.com Prior Art Database
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Method of mitigating thermal rotor bow in a turbine engine Background:
Turbine engines, such as turbofan engines, experience several different phases of operation including, but not limited to, startup to idle speed, warmup, acceleration to higher power and speed for takeoff, climb, cruise, steady-state, deceleration to lower speed and power for descent, landing and taxi, shutdown, and cool-down. Turbine engines may cycle through the different phases of operation several times a day depending on the use of the aircraft in which the turbine engines are attached. For example, a commercial passenger aircraft typically shuts down its engines in between flights as passengers disembark from the aircraft. As such, residual heat remains in the aircraft's engines, which can cause a phenomenon known as thermal rotor bow. Thermal rotor bow is generally defined by deformation in the rotating and stationary components of the turbine engine. Deformation in the components of the turbine engine can result in contact- related damage between the rotating and stationary components of the turbine engine during engine startup, thereby reducing the service life, performance, and operability of the turbine engine. Thermal rotor bow is especially prominent at times after engine shutdown, and before the engine is allowed to fully cool. Moreover, many known turbine engines are unable to naturally mitigate thermal rotor bow during startup as the design of modern commercial turbofans shifts towards having higher bypass ratios and greater length-to-diameter ratios, as well as tighter clearances between rotors and stators of the engine.
The systems and methods described herein are for mitigating the formation of thermal rotor bow in a turbine engine. More specifically, the systems and methods described herein facilitate exhausting residual heat from within the turbine engine after engine shutdown to reduce a thermal imbalance therein, thereby inhibiting the formation of thermal rotor bow. The residual heat is exhausted from within the turbine engine by orienting a centerline axis of the turbine engine with the vector of gravity after engine shutdown. For example, when mounted to an airframe, such as to a wing of an aircraft, the centerline axis of the turbine engine is aligned substantially parallel with the surface of the ground such that the residual heat is trapped within the engine nacelle housing. Orienting the centerline axis of the turbine engine at least partially
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towards the vector of gravity enables hot air formed from the residual heat to be naturally exhausted from the turbine engine as the hot air becomes comparatively less dense than the ambient air. As such, convective heating occurs along the centerline axis rather than radially, thereby reducing thermal gradients within the turbine engine.
Referring to FIG. 1, a side view schematic illustration of an exemplary aircraft is shown. The turbine engine is mounted to an un...