Gearbox Simulation by SPHinXsys

Dong Wu

Introduction

The lubrication system of a gearbox is critical to its performance and reliability. Lubricating oil reduces gear wear and heat generation during operation, impacting the system’s overall efficiency. Optimizing the quantity and management of lubricating oil is essential for enhancing equipment performance. However, excessive lubrication increases churning resistance and reduces efficiency, while insufficient lubrication may lead to excessive gear wear and a temperature rise. Therefore, balancing between minimizing wear, controlling temperature, and improving efficiency becomes a key design objective.

Gearbox simulations using SPHinXsys provide specific data support by analyzing gear meshing, lubrication distribution, and temperature management, offering practical design and optimization solutions.

Lubricating Oil Flow Characteristic

In-depth studies of lubricating oil flow behavior enable a better understanding of its distribution and support during gearbox operation. Figure 1 illustrates the flow characteristics of lubricating oil in a double-gearbox setup, while Figures 2 and 3 further describe the lubrication distribution in complex gear systems, including planetary gearboxes and helical gear reducers. These simulation results reveal lubrication behaviors during gear operation and provide explicit references for optimizing lubrication pathways and improving gearbox efficiency.

Fig. 1. Flow characteristics of lubricating oil in a double-gearbox.

Fig. 2. Flow characteristics of lubricating oil in a planetary gearbox.

Fig. 3. Flow characteristics of lubricating oil in a helical gear reducer.

Churning Loss Assessment

The churning loss of lubricating oil is a key indicator of gearbox energy consumption. Experimental results and analytical data indicate that high-load operating conditions result in significant churning losses, which can be effectively reduced through optimized design. Figure 4 compares a double-gearbox simulation’s average churning loss results using SPHinXsys with experimental data. Furthermore, Figure 5 illustrates the variation of churning loss over time in a helical gear reducer.

Fig. 4. Comparison of churning loss between SPHinXsys simulation and experimental data.

Fig. 5. Comparison of churning loss between SPHinXsys simulation and experimental data.

Oil Film Thickness Analysis

Oil film thickness in contact regions is key to lubrication effectiveness and performance during gear operation. It varies with lubrication contact, pressure, and friction. Figures 6 and 7 show the oil film thickness factor, where higher values indicate better lubrication and reduced friction.

SPHinXsys enables precise evaluation of lubrication states, supporting real-time analysis, optimized design, and efficient lubrication management under high-load conditions.

Fig. 6. Oil film thickness factor of a helical gear reducer.

Fig. 7. Oil film thickness factor for multi-resolution gears.

Mesh-in and Mesh-out Flow Statistics

The mesh-in and mesh-out flow ratio during gear meshing is essential for evaluating lubrication uniformity and effectiveness. Figure 8 presents the temporal variation of mesh-in and mesh-out flow for two gears meshing in Figure 6. The findings provide data support for gearbox design optimization and suggest directions for improving lubrication uniformity.

Fig. 8. Mesh-in and mesh-out flow statistics of a helical gear reducer.

Thermal Management Analysis

Frictional heat generation and temperature distribution are critical factors in gearbox design. High temperatures not only degrade lubricant performance but also accelerate gear wear. Figures 9 and 10 depict the temperature distribution of lubricating oil and gear surfaces, respectively. Simulations capture the dynamic evolution of temperature distribution during gearbox operation, offering practical guidance for optimizing gearbox thermal management design.

Fig. 9. Lubricating oil temperature distribution (°C) in a helical gear reducer.

Fig. 10. Gear surface temperature distribution (°C) in a helical gear reducer.

Conclusion

This blog analyzes key performance indicators during gearbox operation, including lubricating oil distribution, churning losses, oil film thickness evaluations, mesh-in and mesh-out flow statistics, and temperature distribution. It demonstrates the feasibility, verifiability, extendibility, and applicability of SPHinXsys in complex fluid-solid-thermal coupling problems. The established model can be extended to simulations such as the gradual deceleration of gear speed due to oil injection in a hydraulic retarder. Combining these simulations with gearbox theories lays a crucial foundation for optimizing lubrication, thermal management, and overall gearbox design while providing promising solutions for future engineering applications.