An Analytical Method to Predict Efficiency of Aircraft Gearboxes

Abstract

A spur gear efficiency prediction method previously developed by the authors was extended to include power loss of planetary gearsets. A friction coefficient model was developed for MIL-L-7808 oil based on disc machine data. This combined with the recent capability of predicting losses in spur gears of nonstandard proportions allows the calculation of power loss for complete aircraft gearboxes that utilize spur gears. The method was applied to the T56/501 turboprop gearbox and compared with measured test data.Bearing losses were calculated with large scale computer programs.Breakdowns of the gearbox losses point out areas for possible improvement.

Tooth friction losses in internal gears: Analytical formulation and applications to planetary gears

“…For example, presents the load-dependent power losses measured forthe following operating conditions: a sungear torque of 500 Nm and a rotational speed varying from 1000 to 4000 r/min. Assuming that tooth friction losses are the major source of load-dependent energy dissipation, the efficiency formulae (9) and (14) have been used with two values of friction coefficients (0.04 and 0.07 which correspond to realistic bounds in gearing) (cf. Figure 7).…”

Analysis of no-load dependent power losses in a planetary gear train by using thermal network method

“…Numerous experiments have demonstrated that no-load power losses become prominent at high speeds, thus justifying in-depth investigations. Regarding multi-mesh planetary gears, the literature mainly focuses on global losses but the power loss distribution, associated with the above-mentioned sources, has rarely been analysed (2)(3)(4)(5)(6).…”

Experimental investigations on churning power losses generated in a planetary gear set

“…As far as experimental studies are concerned, the power losses in planetary gears have generally been measured on backto-back test rigs which make it possible to separate no-load losses from those under load. As an example, by using the back-to-back test rig at NASA Research Center, Anderson et al (1984), Krantz (1990) or Rohn and Handschuh (1988) developed several empirical formulae in order to estimate planetary gear losses in aircraft and helicopter applications. All these studies clearly show the friction loss predominance as soon as planetary gears are significantly loaded.…”