The multi-power face gear split flow system is a new type of transmission system, which has the advantages of stable and reliable transmission and strong carrying capacity. And it has great potential in the application of helicopter transmission systems. In this paper, the multi-power face gear split flow system was taken as the research object. Based on the lumped parameter method and Newton’s second law, the translational-torsional dynamic model of the system was established considering the translational vibration and the torsional vibration of the gears, and the meshing force curves and load-sharing coefficient curves were drawn. At the same time, the factors affecting the load-sharing characteristics of the transmission system were studied. The impacts of manufacturing errors, assembly errors, manufacturing error phases, assembly error phases, meshing damping, support stiffness, and the input power on the load-sharing coefficients were analyzed. The research shows that the errors and error phases of spur gears have small impacts on the load-sharing coefficients, while the support stiffness of spur gears has a great impact on the load-sharing coefficients. The errors and error phases of face gears have small impacts on the load-sharing coefficients, while the support stiffness of spur gears has a great impact on the load-sharing coefficients. The load-sharing coefficients increase constantly with the increase in the meshing damping between face gears and spur gears, whereas the load-sharing coefficients decrease constantly with the increase in the input power.

In order to study the influence of fuel injection nozzle arrangement on the lubrication effect of arc tooth cylindrical gear, a model of fuel injection lubrication was established, and computational fluid dynamics (CFD) software was used for simulation calculation. The focus on the influence of gear parameters, oil jet conditions and nozzle layout on gear lubrication performance is studied. The results show that reducing the oil jet distance not only improves the lubrication performance of the gear but also reduces the offset of the oil jet streamline. The reasonable of nozzle layout is the premise of ensuring better lubrication conditions, and the best nozzle layout scheme is obtained through data comparison analysis. The lubrication effect decreases when the nozzle angle is offset. The lubrication effect does not change when the nozzle is horizontally offset by a distance of 0.5 module in the direction of the pinion, and the lubrication performance is degraded when the distance exceeds 0.5 module. Finally, the influence of nozzle diameter on lubrication is analyzed, the lubrication effect is directly proportional to the nozzle diameter.

Aiming at the asymmetric helical gear injection lubrication, simulation models for coast flank and drive flank injections were established by computational fluid dynamics (CFD). Firstly, the two oil injection methods of the asymmetric helical gear were explained. Then, a mathematical calculation model suitable for gear injection lubrication analysis was established. Finally, the model is simulated by CFD software. The oil volume fraction and pressure at the meshing point during the gear meshing process of the two injection models are obtained. The effects of gear speeds and spray velocities on the oil volume fraction and pressure are analysed. By comparing the two oil injection methods, when the spray velocity is more than 2.7 times the pitch line velocity, better lubrication is obtained by the drive flank injection method. When the spray velocity is less than 2.7 times the pitch line velocity, the coast flank injection method can achieve better lubrication.

This article studies the lubrication state of the arc tooth cylindrical gears during injection lubrication. The mathematical model of arc tooth cylindrical gears are established based on meshing principle. The lubrication characteristics of arc tooth cylindrical gears under different injection methods and conditions are analysed by using computational fluid dynamics (CFD) model. The variation law of oil volume fraction in the gear-meshing zone is obtained.Comparing the two oil jet methods in into mesh lubrication, when the ratio of the pitch line velocity to the injection velocity is less than 1.5 times, the best lubrication is gained through the concave surface injection method, when the ratio of the pitch line velocity to the injection velocity is more than 1.5 times, the best lubrication is gained through the convex surface injection method. It shows that the tooth shape has significant influence on lubrication when the lubricating oil is injected.