Caculation Of Transient Flow Field Of Journal Bearing Based On CFD

As rotary machinery with large scale, high speed and large capacity is developed, the vibration fault in rotor-bearing system appears more and more. As the main support part of large rotary machinery, the performance of journal bearing affects the working precision, life-span, reliability and other technical indexs, so it is the focus problem of keeping good dynamic quality in rotary machinery. Based on a lot of study about it before, there are two aspects to study continuously:one aim is to looking for the more accurate boundary condition of oil film to improve the calculating precision; another aim is to reseach one new method of calculating transient flow field of journal bearing with nonlinear oil film force. With dynamic theory, fluid lubrication theory, computational fluid dynamics, the main work is as follows:Firstly, the mathematical model of journal bearing flow field is built, and the calculating conditions of journal bearing flow field are determined. By calculating and comparing, some parameters of model are also determined rationally. The result shows that it is coincidence between the result of cavitation model and factual situation.Secondly, the model of rotor-bearing system is built, and one new dynamic mesh method which will be input FLUENT software is put forward to calculate the transient flow field of journal bearing, and the corresponding initial condition and influence factor are determined. The influence of unbalance quantity and rotary speed on the whirl orbit are also studied. In addition, the stability of bearing with different aspect ratio, different shape of bearing pads, different clearance ratio are researched by calculating whirl orbit and static equilibrium.Thirdly, the comparison between using CFD to calculate flow and traditional solving Reynolds eqution is realized, and the results show that the influence of some items which are ignored in traditional solving on oil film performance, so the precision of calculating with CFD is higher. Besides, the complicated structure of bearing can be solved with CFD which can not be solved with traditional method, and it is easy to treat the unknown free boundary condition or interface of different mediums in solving area.At last, the tendency of results between new method of solving oil film force in this study and steady bearing oil film force model is almost unanimous by comparison, and there is a little difference because of different boundary condition. In addition, the oil film force which is obtained with new method in the study is nonlinear, so it provides the basis to study the rotor-bearing system more accurately.