Generator Survivability in the Hot Environment Associated with Low Pressure Turbine Installation 2004-01-3155
Aircraft generators are usually installed on an engine-mounted gearbox pad. In this type of installation, the speed range can be adjusted to match available generator speeds, and the installation environment is not as harsh as the engine operating environment. On the other hand, mounting the generator directly to the engine main shaft provides significant advantages, such as eliminating the generator gearbox pad, yielding major weight and cost savings. Furthermore, the low-pressure turbine spool might have excess power that could be used to power the generator, thus enhancing the overall engine performance.
Innovative Power Solutions, LLC (IPS) has developed a generator that is directly mounted to the low-pressure spool of the engine inside the tail cone. The obvious disadvantage is the hot environment inside the tail cone, which can reach 500°F. In this installation, heat transfers to the generator by convection from the surrounding air, conduction through the mounting plate, and radiation from the 1200°F tail cone.
The stator housing includes a sleeve in which cooling oil is continuously flowing, effectively separating the environment inside the generator from the outside, and isolating the electromagnetic components inside the generator from the ambient heat. In addition, using a technique patented by IPS, the rotor is oil cooled in a way that assures that each turn of every winding is cooled along its full length.
An insulating plate could be mounted between the generator and the mounting plate to prevent heat conduction into the generator from the engine rear bearing housing.
A thermal shield is installed on the generator to protect it from the additional heat load induced by radiation. The thermal shield is fabricated from .003″ thick corrugated stainless steel with a MIN-K thermal insulation blanket.
The generator was tested successfully on an engine for approximately 100 hours.