Systems and methods for monitoring and controlling a gas turbine engine

A system for controlling a gas turbine engine in response to a thickness of a lubricant film in a journal bearing of an epicyclic gear system of the gas turbine engine, the system comprising:

• the epicyclic gear system, wherein the epicyclic gear system comprises a sun gear driven by a first shaft of the operating gas turbine engine, a ring gear connected to a fan shaft of the operating gas turbine engine, and a set of star gears radially intermediate and meshing with the sun gear and the ring gear, wherein a journal pin is disposed inside a first star gear of the set of star gears and is connected to a gear carrier, wherein the first star gear rotates relative to the journal pin to define a bearing interface between the journal pin and the first star gear, and wherein the ring gear rotates relative to the first star gear to define a gear mesh between the first star gear and the ring gear;
• a first electrical lead having a first end in communication with a first conductive element on a static side of the journal bearing and a second end connected to a signal processor, wherein the first conductive element comprises the journal pin or the gear carrier;
• a second electrical lead having a first lead end connected to a second conductive element on a rotating side of the journal bearing and a second lead end connected to the signal processor to complete an electrical circuit, wherein the second conductive element comprises the ring gear or the fan shaft, wherein the signal processor is electrically connected to the first electrical lead and the second electrical lead, the signal processor configured to:
• measure an electrical property of the electrical circuit to obtain an electrical property measurement, wherein the electrical property measurement is taken across both the bearing interface and the gear mesh, wherein the electrical property measurement taken across the bearing interface is taken between an interface surface of the journal pin and an inner surface of the first star gear, wherein the inner surface of the first star gear extends parallel to the bearing interface of the journal bearing;
• compare the electrical property measurement with a reference measurement for the electrical property and detect contact of bearing surfaces if the electrical property measurement comprising a bearing resistance is zero;
• convert the electrical property measurement into a calculated lubricant film thickness measurement;
• compare the calculated lubricant film thickness measurement with a predetermined minimum lubricant film thickness;
• and
• restrict a subsequent engine restart of the gas turbine engine if at least one of the calculated lubricant film thickness measurement is less than the predetermined minimum lubricant film thickness and bearing surface contact is detected,
• wherein restricting the subsequent engine restart of the gas turbine engine comprises at least one of preventing the subsequent engine restart, limiting a subsequent operating state of the gas turbine engine to an operating speed of the gas turbine engine after the subsequent restart, and preventing the gas turbine engine from operating above idle after the subsequent engine restart.

A method for controlling a gas turbine engine in response to a thickness of a lubricant film in a journal bearing of an epicyclic gear system of the gas turbine engine, the method comprising:

• receiving, from an electrical circuit by a signal processor from a sensor, an electrical property measurement across the lubricant film, wherein the electrical property measurement is taken across a bearing interface of the journal bearing wherein the measurement further comprises bearing resistance;
• detecting, by the signal processor, contact of the bearing surfaces if the electrical property measurement is zero;
• converting, by the signal processor, the electrical property measurement into a calculated lubricant film thickness measurement;
• determining, by the signal processor, whether the calculated lubricant film thickness measurement is at or near zero or below a predetermined minimum lubricant film thickness;
• and
• in response to at least one of the calculated lubricant film thickness measurement being below the predetermined minimum lubricant film thickness and detecting contact of the bearing surfaces, restricting, by the signal processor, a subsequent engine restart of the gas turbine engine,
• wherein restricting comprises at least one of limiting a subsequent operating state of the gas turbine engine to an operating speed of the gas turbine engine after the subsequent restart and preventing the gas turbine engine from operating above idle after the subsequent engine restart.