Predicted and experimental performance of jet-lubricated 120-millimeter-bore ball bearings operating to 2.5 million DN

SUMMARY Bearing performance characteristics, such as inner- and outer-race temperaturesand friction power loss, can be predicted using recently developed computer programs.Two such programs were used, and the calculated values obtained were compared withthe corresponding experimental data obtained previously for 120-millimeter-bore bear-ings. The bearings were operated at thrust loads of 6672, 13 350, and 22 240 newtons(1500, 3000, and 5000 Ib) and shaft speeds of 12 000, 16 700, and 20 800 rpm with lubri-cant flow rates of 3. 8xlO~ 3 and 8. 3xlO~ 3 cubic meter per minute (1.0 and 2.2 gal/min).The oil inlet temperature was maintained constant at 394 K (250° F).The first computer program, one previously used in the design of the test bearings,predicted reasonable temperatures with proper consideration of required input data ofhousing and shaft end temperatures. However, this program severely underestimatedthe bearing power losses. The second program, called SHABERTH, also predictedreasonable race temperatures, but it did not require the input of housing and shaft endtemperatures. Furthermore, SHABERTH provided a good estimate of bearing powerloss. The bearing power loss predictions by both computer programs were a strongfunction of the value assumed for volume percent of the bearing cavity occupied by thelubricant.INTRODUCTIONBearings in current commercial aircraft turbine engines operate at speeds to 2. 3million DN (the speed parameter DN is the bearing bore in mm multiplied by the shaftspeed in rpm). However, for some time, trends in gas turbine design have indicatedthat future engines may require bearings that can operate reliably at DN values of 3million or higher (ref. 1). Therefore, there has been a great amount of work performed