Ensuring optimal gearbox lubrication
As critical transmission element, gearbox must be designed to ensure optimal lubrication of the engaged gears. To design innovative solutions, for which neither empirical expertise nor experimental testing can provide worthwhile results, numerical simulation is greatly needed.
The particle-based Lagrangian SPH-flow solver offers key features and characteristics that address the challenge of simulating gearbox splash lubrication. Beyond its ability to account for viscosity, its ability to inherently track free surfaces makes all the difference. It can properly describe the essential scattering of the fluid into multiple droplets, pulled off from the lubricant pool by spinning gears. The possible coalescence of those droplets into jets and their behavior during splash-landing is also well captured.
We have gained long-term experience in the simulation of gearbox lubrication. For years, half a dozen gearbox designs have been studied. Starting from elemental geometry of simplified splash lubrification, the key physical phenomena have been addressed using advanced SPH-flow numerical models.
For example, the influence of the air flow on the oil has been investigated, mono-fluid and bi-fluid simulations were compared and analyzed on an elementary 2-dimensional single-gear circular configuration (only the oil phase was computed for the mono-fluid case, while both the oil and air phases were accounted for in the bi-fluid simulation). The corresponding algorithms have been improved, and their suitability was validated
Based on such solid foundations, we have tackled more realistic designs, including industrial 6-speed manual transmission. A numerical probe, measuring the mass flow rate, was used to assess the relevancy of the simulation result. The versatility of SPH-flow allowed a fast 2-hour setup. Moreover, this easy configuration also allowed for flexible methodologies: for instance, the flow rate registered by the probe was re-used, as an input parameter, to set an equivalent inlet for a new computation. The downstream part of the flow was thus specifically studied without the need for full domain computation.
Beside splash lubrication, spray lubrication was also addressed. Although not applied to a gearbox but to an electric engine, the lubrication issue is similar in many aspects. The wettability of the solid can be monitored, time after time, as can other near-wall quantities like pressure, temperature or shear-stress.
We have addressed many other gearbox lubrication issues, including sensitivity to leakage, thermal influence, lubrication in planetary gear trains, etc.