| Oil-air lubrication, as a typical way of precise lubrication, is more and more widely used along with the development of the machinery industry. The lubricated points are lubricated by oil-air lubrication in the form of annular flow driven forward by high-speed air. Therefore, the changes of characteristics of the annular flow during the conveyance, from one part of the system to another or one side of the pipe to another, are crucial to lubrication application.Nozzle is the last component that the annular flow passed through before working on the lubricated points which is installed at the end of the oil-air lubrication system. The working performance of the nozzle has directly influence on the lubrication application. Therefore, the research on the working performance of the nozzle in oil-air lubrication system is very significant.The processes of the two-phase annular flow in the oil-air lubrication system through different sudden contractions have been simulated by Fluent, a kind of application software based on Computational Fluid Dynamics (CFD), in order to analysis the flow characteristics of the annular flow in this thesis. An oil-air lubrication experimental rig designed by our research group and a friction experimental bench named MRH-3are employed to research the working performance of the nozzle. The main research work and conclusions are as follows,(1) The characteristics of the oil-air annular flow through the sudden contraction fluid area, which is constrained by different parameter structures, have been simulated by Fluent. The distribution of the oil film, the change of pressure drop and the distribution of velocity by changing the inlet diameter, the outlet diameter and the contraction angle are curved and analyzed. Then the characteristics of the annular flow with difference system parameters, the distribution of the oil film, the pressure drop and the distribution of velocity, by changing the air velocity are also analyzed. The results show that the lower air velocity is more conducive to convery the oil-air annular flow smoothly.(2) According to the characteristics of the bearing and the oil-air lubrication system, the temperature of metal block, the temperature of the cavity and the friction coefficient are chosen as the evaluations for the working performance of nozzle. The nozzles are designed and manufactured with different structural parameters. And the friction experiments are also designed.(3) The influence of the system parameters on the working performance of the nozzle are researched with different oil mass and air velocity. The temperature of metal block, the temperature of the cavity and the friction coefficient are curved and analyzed. The friction coefficient, the temperature rising of the metal block and temperature rising of the cavity are minimum when the oil mass is the optimum one, while the evaluations are decreased with the increasing of the air velocity.(4) The influence of the structural parameters, including outlet diameter, contraction angle and working angle, on the working performance of the nozzle are researched by the orthogonal experiment of three factors at three different levels. The curves of the temperature of metal block, the temperature of the cavity and the friction coefficient are obtained and analyzed. The results show that the temperature of metal block varies linearly with time, and the temperature of cavity present to rise logarithmically with time. And the outlet diameter is the most significant factor to affect the working performance of the nozzle, while the working angle is the more significant factor and the contraction angle has the least influence on the working performance of the nozzle. The optimum structural parameters are ascertained for the working performance of the nozzle in oil-air lubrication system. |
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