Abstract
To provide a basic guidance for the selection of nozzle layout, a mathematical model of the impingement depth for helical gears under oil jet lubrication is established. Furthermore, computational fluid dynamics (CFD) methods are adopted to validate the effectiveness and accuracy of the derived impingement model. Firstly, the distribution characteristics of the oil volume fraction and oil-gas pressure in meshing area were obtained in flow field simulation. Meanwhile, the influence of spray angle, jet velocity, and gear ratio on lubrication effect was obtained. Then, the transient temperature field of the tooth surface was simulated by the method of thermal-fluid coupling analysis, and the lowest temperature distribution and the corresponding oil jet velocity were determined. Finally, experiments on the temperature characteristics measured by an infrared thermal imager of helical gears with different nozzle parameters were carried out in a gear test rig. The simulation results of transient temperature field are in good agreement with those obtained by experiments, and it indicates that the thermal-fluid coupling analysis method is correct and feasible to predict the temperature field of the helical gear pair under oil injection jet lubrication.
Highlights
In the rotating process of a helical gear pair under jet lubrication condition, the initial time is set as t0, and the position parameters of the driving and driven gears at this moment are expressed by the geometrical relationship of the helical gear pair end face
E offset distance S is defined as the straight-line distance between the jetting point and the common tangent of the indexing circle of the pinion and gear; the oil injection angle β describes the included angle between the oil jet flow and the common tangent of the indexing circle of the pinion and gear; the deviation distance L is the straight-line distance between the nozzle and the common tangent of the indexing circle between the pinion and gear. e oil jet height H denotes the linear distance between the nozzle and the center line of the pinion and gear. e parameters above are positive to the pinion and negative to the gear
(1) e mathematical model of impingement depth for the helical gear under oil jet lubrication is established, which provides useful guidance for the layout of the nozzle. e flow field simulations are used to analyze the influence of different injection angles, oil jet velocities, and gear ratios on lubrication performance. e results show that the lubrication effect achieves the best when the nozzle is biased toward the driving gear by 5°, and increasing the oil jet velocity within certain range is beneficial to the lubrication oil entering the gear meshing area, thereby increasing the oil pressure in the meshing area and improving the lubrication performance of helical gears. e lubrication effect of helical gears is the best when the oil jet velocity is 30 m/s
Summary
In the rotating process of a helical gear pair under jet lubrication condition, the initial time is set as t0, and the position parameters of the driving and driven gears (the pinion and gear) at this moment are expressed by the geometrical relationship of the helical gear pair end face. E oil jet height H denotes the linear distance between the nozzle and the center line of the pinion and gear. Where inv φ and inv φt are, respectively, the function of the pressure angle of the pinion and gear, indicating the angle of expansion at the intersection of the reference circle and the involute of the pinion and gear, and invφ tan φ − φ, (14).
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