Method and apparatus for assessing thrust loads on engine bearings

In an operating gas turbine engine having a rotor located by an axial bearing having first and second races, said rotor being displaceable relative to said bearing in accordance with applied loads along a longitudinal axis from said first race to said second race with a null position of zero load therebetween, and further having a selectively pressurized axial trim cavity capable of generating said bearing axial loads in accordance with the magnitude of pressure therein, a method for use in selecting rotor load, said method comprising the steps of:

• varying the pressure in said axial trim cavity between low and high values;
• measuring the axial position of said rotor within the bearing for each of said trim cavity pressure values;
• determining from said measured rotor position values those values indicative of a shift in rotor position from said first race to said second race corresponding to said null position value of zero load;
• determining from said null position value a corresponding value of trim cavity pressure;
• comparing said null position trim cavity pressure value with a predetermined null position trim cavity pressure value to determine a deviation value therefrom;
• adjusting rotor load values pre-correlated with values of trim cavity pressure in accordance with said deviation value;
• and
• selecting a value of axial trim cavity pressure to generate a preferred value of rotor load.

In an operating gas turbine engine having a rotor located by an axial bearing having first and second races, said rotor being displaceable relative to said bearing in accordance with applied loads along a longitudinal axis from said first race to said second race with a null position of zero load therebetween, and further having a selectively pressurized axial trim cavity capable of generating said axial loads in accordance with the magnitude of pressure therein, a method for use in determining a value of null position deviation from a predetermined value thereof, said method comprising the steps of:

• varying the pressure in said axial trim cavity between low and high values;
• measuring the axial position of said rotor within the bearing for each of said trim cavity pressure values;
• determining from said measured rotor position values those values indicative of a shift in rotor position from said first race to said second race corresponding to said null position value of zero load;
• determining from said null position value a corresponding value of trim cavity pressure;
• and
• comparing said null position trim cavity pressure value with a predetermined null position trim cavity pressure value to determine said deviation value.