The transient simulation of the journal bearing temperature in the internal gear pumps is hard due to the complicated shaft motion caused by the complicated loads. In this paper, a thermohydrodynamic analysis method, based on dynamic mesh techniques, is presented with the application of the general computational fluid dynamics (CFD) code fluent. This method can simulate the complex whirling orbit induced temperature variation in internal gear pumps and has taken into account the conduction in the rotating and orbiting rotor of a hydrodynamic bearing. A test rig has been built according to the structure of an internal gear pump to carry out the validation. The results show that the model is reliable. The relationship between bearing temperature, leakage, and axial clearance in the internal gear pump has been studied. It is found that the bearing temperature will decrease slightly, while the leakage increases heavily with larger axial clearance. A thermohydrodynamic analysis of the self-lubricating bearing in the internal gear pump has been done based on this method. The results show that the pressure profile changes regularly with the whirling motion of the journal, while the whirling motion has little effect on the distribution of the temperature. Besides, the increase of the whirling radius will result in the decrease of the pressure profile and the increase of the temperature profile.

For middle-pressure and high pressure gear pumps, the temperature failure problem of bearings is now of considerable concern due to their heavy loads. A self-circulating oil bearing system has been developed for gear pumps in this paper to solve this problem. A test rig has been designed and built to carry out a series of tests for variable loading directions and rotational speeds. An experimental investigation and numerical model development to predict the behaviour of the self-circulating bearing subjected to different loading directions is described. The experimental and numerical results agree well. It was found that the variation of loading directions has a strong effect on the oil flow rates of the system. The maximum oil flow rate can be achieved when the loading direction is along the hole axis direction and a considerable part of the friction heat can be carried away by the oil. The lubrication of the bearing will also be improved.

Purpose For moderate pressure and high pressure gear pumps, the temperature failure problem of bearings is now of considerable concern because of their heavy loads. However, the compact structure and the efficiency consideration make it extremely difficult to improve the bearing cooling. A self-circulating oil bearing system is developed for gear pumps with self-lubricating bearings to solve this problem. The oil is aspirated in from the low pressure chamber of the gear pump and discharged to the same chamber by using the pressure difference in the journal bearing, thus achieving the self-circulation. Design/methodology/approach An experiment test rig has been built for the feasibility study. The oil flow rate under different speeds has been recorded. Furthermore, the temperatures of the bearings with or without the oil circulation have been compared. Additionally, the oil flow in the test rig has been simulated using computational fluid dynamics codes. Findings The experimental and numerical results agree well. The experimental results indicate that the oil flow rate increases approximately linearly with the speed and the bearing temperature can be lowered successfully. The calculation results indicate that the bearing load capacity is nearly the same. Both the experimental and numerical studies establish that the self-circulating oil bearing system works successfully. Originality value As far as the authors know, it is the first time to find that the self-circulation can be built using the pressure difference in the bearing oil film, and this principle can be applied in the cooling and lubrication of the gear pumps to solve the temperature failure problem.

Hydrodynamic journal bearings are key components for supporting the rotating shafts in high-speed machinery. The shaft misalignment due to the heavy load, the thermal effects, and the manufacturing errors may introduce problems during running such as rub-impact. So the journal bearing with a pre-tilted angle has been introduced in this paper to solve the problem. The pre-tilted journal bearing is allowed to be adjusted to the proper attitude angle according to the tilt of the shaft under working condition. Thus ensuring the symmetric pressure distribution of the bearing and avoiding the rub-impact. A test rig has been designed and built to validate the working effect of the pre-tilted journal bearing. A design method for the pre-tilted journal bearing has also been introduced in this paper. In this method, a transient coupling model is adopted to precisely calculate the attitude angle of the bearing and a special dynamic mesh method is used to guarantee the mesh quality with arbitrary motion of the journal.

Labyrinth seals are widely used in turbomachines. In this paper, a transit simulation method is introduced to model the relationship between the journal offset in Labyrinth seals and the system stability based on Fluent UDF. A special dynamic mesh method has been adopted to ensure fine mesh quality during the arbitrary motion of the journal. In each time step, the transient fluid seal force on the journal surface is obtained by the solving Navier-Stokes equations. Then the displacement of the journal in the next step can be numerically solved by the FEM model of the rotor system. For every transient time step, the computed fluid seal force and the rotor motion displacement were coupled by data exchange. The experiment is carried out in a steam turbine with a position adjustable labyrinth seal. The experimental results show that the amplitude of the vibration decreases after the change of the relative position between the journal and the labyrinth seals and the numerical results show that the locus of the journal under different labyrinth seal offsets has some half-frequency components. Both the simulation and the experiment validates that the relative position between the journal and the labyrinth seals can greatly affect the stability in the coupled rotor-seal system.