Abstract: A hydrocarbon presence sensor used to detect for the presence of a fuel in a buffer cavity of an inter-propellant seal. A sensor is formed on a rotor shaft in the buffer cavity and an optical imaging device is used to view a change in appearance of the sensor when a hydrocarbon forms on the surface. In one embodiment, the sensor is a coating of porous silicon. In other embodiments, the sensor can be a mirrored or frosted surface on the shaft. A white light source or a laser is reflected off of the sensor and an optical imaging device reads the reflected light to detect for a change in color or intensity of the light to indicate if a hydrocarbon is present on the sensor surface.

Abstract: A squeeze film damper assembly having a variable stiffness and damping control. The squeeze film damper includes a damper chamber formed by two flexible bellows chambers of the sides. A first pressure source is applied to the damper chamber to regulate the damping. A second pressure source is applied to the flexible bellows chambers to vary the stiffness of the damper. The flexible bellows chambers are secured between an outer member and an inner member of the damper assembly and form the sealed damper chamber. A pressure ratio between the bellows chambers and the damper chamber can vary to control the stiffness of the squeeze film damper.

Abstract: A squeeze film damper assembly having a variable stiffness and damping control. The squeeze film damper includes a damper chamber formed by two flexible bellows chambers of the sides. A first pressure source is applied to the damper chamber to regulate the damping. A second pressure source is applied to the flexible bellows chambers to vary the stiffness of the damper. The flexible bellows chambers are secured between an outer member and an inner member of the damper assembly and form the sealed damper chamber. A pressure ratio between the bellows chambers and the damper chamber can vary to control the stiffness of the squeeze film damper.