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

Abstract

This study aims to experimentally investigate churning power losses generated by a planetary gear set which is splash lubricated. To this end, a specific test rig has been used to operate a planetary gear train under unloaded conditions in various configurations within a range of the planet-carrier rotational speed. Churning loss is isolated from the measured drag torque and the effects of several parameters (rotational speed, temperature, oil sump level, planet number…) on this source of dissipation are quantified. Beyond the influence of speed or oil level, it is concluded that the number of planets is of primary importance on churning power losses. Moreover, a first assumption is made concerning the oil sump behavior regarding the experiments: an oil ring is created explaining the evolution of the churning losses measured. In addition, this study compares the churning phenomenon occurring in cylindrical gear trains with the one observed during the experiments. It is shown that the approach used for conventional gear trains cannot be used for epicyclic ones: in planetary gear sets the centrifugal effects are predominant whereas the gravity forces have a larger influence on the free surface flows which occur in cylindrical gear sets.

Numerical and Experimental Analysis of the Oil Flow in a Planetary Gearbox

“…A slight decrease in the oil sump level could be observed on the right side of the planet carrier (blue dashed dot rectangle). At the highest velocity (SIM-id2v3, Figure 11), similarly to SIMI-id1-v3, the centrifugal forces create an evident oil ring around the planet carrier (red dashed arc), in accordance with the observations by Boni et al [8]. The oil is splashed all around the gearbox (blue dashed dot rectangle), resulting in a completely different behavior with respect to the other investigated velocities, in which the oil is also present in the front region.…”

“…De Gevigney et al [7] performed an experimental campaign on a planetary gearbox aimed at studying the impact of injection volume rate, lubricant temperature, and rotational speed on efficiency. Recent experiments by Boni et al [8,9] focused on the detailed analysis of the oil distribution in a dip-lubricated planetary gearbox and its efficiency. They used a front housing made from acryl glass that allowed observation of the oil level and its flow during operation.…”

“…Following Liu et al [2], planet carrier speeds ranging from 81 rpm to 324 rpm were considered in the experimental and numerical investigations so that the results could be compared with each other. Two oil filling levels were considered: a low one corresponding to 3 times the normal module with respect to the ring gears, as investigated by Liu et al [2], and a high one corresponding to the centerline level (as a typical operating condition of planetary gearboxes, which was previously investigated numerically by Cho et al [20] and experimentally by Boni et al [8]). In Table 3, the analyzed operating conditions are summarized.…”

Characteristics of internal flow field and convection heat transfer in planetary gear reducer of shield machine

“…Planetary gear transmission system is widely used in many fields due to compact structure and strong bearing capacity. Boni et al [1] obtained the relationship between sun gear rotational speed and oil distribution through splash lubrication experiment of single stage planetary gear system. Based on CFD method, Concli et al [2] proposed a meshing method for the splash lubrication single stage planetary gear system to realize the efficient solution of the system.…”

Flow Characteristics of Oil-Guiding Splash Lubrication: Simulation and Experiment Studies

“…Laruelle et al [16] presented a theoretical analysis about churning power losses of a spiral bevel gear, and the experimental values obtained by the test bench shows a good agreement with the theoretical results. Similar experiments for a planetary gear set were done by Boni et al [17], a specific test facility was developed to explore the churning losses of the gear set. The housing structure and shape of the gearbox also significantly influenced the splash lubrication performance.…”