Computational fluid dynamics (CFD) analysis, which solves the full three-dimensional (3D) Navier–Stokes equations, has been recognized as having promise in providing a more detailed and accurate analysis for oil-film journal bearings than the traditional Reynolds analysis, although there are still challenging issues requiring further investigation, such as the modeling of cavitation and the modeling of conjugate heat transfer effects in the CFD analysis of bearings. In this paper, a 3D CFD method for the analysis of journal bearings considering the above two effects has been developed; it employs three different cavitation models, including the Half-Sommerfeld model, a vaporous cavitation model, and a gaseous cavitation model. The method has been used to analyze a two-groove journal bearing and the results are validated with experimental measurements and the traditional Reynolds solutions. It is found that the CFD method which considers the conjugate heat transfer and employs the gaseous cavitation model gives better predictions of both bearing load and temperature than either the traditional Reynolds solution or CFD with other cavitation models. The CFD results also show strong recirculation of the fresh oil in the grooves, which has been neglected in the traditional Reynolds solution. The above results show conclusively that the present 3D CFD method considering the conjugate heat transfer and employing the gaseous cavitation model provides an efficient tool for more detailed and accurate analysis for bearing performance.

In thrust bearings, cavitation may occur at high rotational speeds or low lubricant supply pressures, and it will influence the bearing performances. In this paper, a hydrodynamic tapered land thrust bearing has been studied both experimentally and numerically, with concentration on the cavitation phenomenon and its effects on the bearing performances. Evident cavitation regions have been observed in the experiments at higher rotational speeds. Traditional Reynolds equation and 3D Navier–Stokes equation (3D NSE) with a cavitation model have been used for numerical simulation, and the predicted results are examined against the experimental results. Compared with Reynolds equation, 3D NSE with Rayleigh–Plesset model provides better predictions of both oil–film pressure profile and cavitation area. Furthermore, the effects of the cavitation phenomenon on the thrust bearing performances are studied by parametric studies involving various rotational speeds and oil feeding pressures, using 3D NSE. It is found that the load capacity decreases at higher speeds because of enlargement of the cavitation area. And the negative effects of cavitation can be reduced at smaller film thickness and higher oil supply pressure. Conclusively, the above results show that the cavitation phenomenon has significant influences on the bearing performances at higher speeds, and 3D NSE provides an effective tool for analyzing the cavitation effects in thrust bearings.

Though the importance of curvature continuity on compressor blade performances has been realized, there are two major questions that need to be solved, i.e., the respective effects of curvature continuity at the leading-edge blend point and the main surface, and the contradiction between the traditional theory and experimental observations in the effect of those novel leading-edge shapes with smaller curvature discontinuity and sharper nose. In this paper, an optimization method to design continuous-curvature blade profiles which deviate little from datum blades is proposed, and numerical and theoretical analysis is carried out to investigate the continuous-curvature effect on blade performances. The results show that the curvature continuity at the leading-edge blend point helps to eliminate the separation bubble, thus improving the blade performance. The main-surface curvature continuity is also beneficial, although its effects are much smaller than those of the blend-point curvature continuity. Furthermore, it is observed that there exist two factors controlling the leading-edge spike, i.e., the curvature discontinuity at the blend point which dominates at small incidences, and the nose curvature which dominates at large incidences. To the authors’ knowledge, such mechanisms have not been reported before, and they can help to solve the sharp-leading-edge paradox.

The prediction of cavitation in lubricants is of significance to the design and analysis of hydrodynamic bearings. In this paper, a numerical model for the gaseous cavitation in hydrodynamic lubrication problems is derived based on the cavitation mechanism and origination, which is different from the conventional cavitation conditions. The proposed gaseous cavitation model is then used to calculate the performance of several types of bearings, including a two-axially grooved plain journal bearing, a misaligned journal bearing and parallel thrust bearings with surface textures. The results are validated with experimental data and numerical results calculated by the Half-Sommerfeld, Reynolds, and JFO conditions. The advantage of this new model lies in its accuracy and its independence from the cavitation pressure, which is usually difficult to be accurately defined. Thus this gaseous cavitation model can be useful in the accurate prediction of the cavitation phenomenon and performance of hydrodynamic bearings under steady state.

Conjugate heat transfer is a key feature of modern gas turbine, as cooling technology is widely applied to improve the turbine inlet temperature for high efficiency. Impact of conjugate heat transfer on heat loads and thermodynamic efficiency is a key issue in gas turbine design. This paper proposes a through-flow method for the design of cooled turbines, taking into account the influence of the complicated interaction between the flow field and heat transfer in cooled turbines. The energy and continuity equations are rederived theoretically by considering the historical influence of cooling with the method that deals with viscous losses. A cooling model is introduced to the through-flow method to predict the coolant requirement. This paper applies the method in the design of a high-pressure turbine with convective cooling. With the prescribed blade temperature limitation and the knowledge of the flow variables of the mainstream at the turbine inlet, such as the total pressure, total temperature, and mass flow rate, the convergence of the calculation is then obtained and the properties of the flow field, velocity triangles, and coolant requirement are well predicted. Three-dimensional conjugate heat transfer analysis is performed for the validation of the through-flow method. By comparing these two calculations, it is shown that the through-flow method is a useful tool for flow analysis and coolant requirement prediction in the design of cooled turbines.