Austenitic stainless steel was cladded with Cobalt-based alloy by means of Tungsten inert gas (TIG) welding to improve the performance of the working parts such as the thrust bearing plates under dynamic loads and corrosive liquid. Specimens were prepared with different welding parameters, namely the cladding current, preheating temperature, inter-layer temperature and post heat treatment temperature, so as to investigate their influence on micro-hardness, as well as tensile and bending strength. It is revealed that the lower welding current coincides with higher micro-hardness as well as tensile and bending strength. The higher inter-layer temperature will result inhigher overlay micro-hardness. The post weld heat treatment temperature influences the bending strength of the overlay weld specimens. In addition, the accumulation of Cr and Ni compounds on weldment surface is found to coincide with higher corrosion resistance in over-layers by means of XRD.

The highly turbulent flow and heat-transfer in a semi-closed rotating disk cavity is numerically simulated based on a hybrid RANS/LES turbulence model. The superimposed radial outflow, which enters into the cavity from the inlet and exits the cavity from the discharge holes, results in the three flow region formed in the disk cavity. The effects of rotating Reynolds’ number and cavity aspect ratio on the pumping mass flow, local momentum coefficient as well as radial heat-transfer coefficient are fully examined. And the corresponding correlations are established with respect to rotating Reynolds’ number and aspect ratio. It is revealed that the radial heat-transfer from the periphery of the cavity to discharge hole is highly correlated to the secondary flow pumped by the rotating disk. Based on those prediction models, an equivalent thermal network for the radial heat-transfer is proposed, which can efficiently predict the radial temperature distribution in the semi-closed disk cavity, and estimate the effects of viscous-heating as well as temperature-viscosity correction.

The flow in annular gap with a restrictor mounted on outer cylinder is numerically simulated based on the hybrid Reynolds Averaged Navier-Stokes (RANS)/Large eddy simulation (LES) model. In stationary inner cylinder case, the pressure drop, mean axial velocity profiles and characteristic length scale of the recirculation zones are analyzed. Then the effects of rotating inner cylinder on the axial pressure distributions and the size of recirculation regions are examined. With the increase of rotating Reynolds number, the pressure loss of flow past the forward-backward step pair is greatly increased. Meanwhile, the transient pressure difference between the upstream inlet and downstream outlet gradually becomes fluctuating periodically due to the vortex shielding at the edge of backward step regularly. And the amplitude of the fluctuating pressure difference is comparable to its mean value. Moreover, the size of recirculation regions is reduced with the rising azimuthal Reynolds number, resulting from the interacting with enhanced Taylor vortices.

A special structure named auxiliary impeller is designed in the large capacity canned-motor pump to improve the performance of inner loop cooling system. The structure is set on the rotor shaft using the center hole as the inlet conduit and four holes perpendicular to the center hole as the blade channels. The auxiliary impeller is driven by the rotor shaft of the motor and functions as a centrifugal pump. The inner coolant circulates in the clearance of the pump under the effect of centrifugal force generated by the impeller. In this paper, the output pressure of the auxiliary impeller at different rotational speeds is investigated by numerical simulation. Three geometric parameters including the diameter of the inlet channel, the diameter of the blade flow channel, and the rotating radius are considered in the research. The pressure drop curves of the auxiliary impeller at different rotational speeds are drawn and a mathematical model is given to interpret it. The results show that both the three geometric parameters have influence on the output performance of the auxiliary impeller, and the diameter of the blade channel and the length of the rotating radius are the primary factors.

The present work numerically considered the turbulent flow in a semi-closed rotor-stator cavity with a superimposed throughflow based on Reynolds Stress Model (RSM). The mean flow structure and turbulent field in the semi-closed cavity (SC) were identified by comparison with the flow in open cavity (OC) and closed cavity (CC). Then the effects of rotation Reynolds number, ranging from 1 × 10 6 to 4 × 10 6 , on the flow in SC were investigated. The superimposed flow noticeably decreases the tangential velocity, resulting that the pressure difference between central hub and periphery in SC is greater than the OC but less than the CC. The flow in SC belongs to Stewartson type in the region between inlet and outlet, but to Bachelor type between outlet and periphery. Around the outlets, the flow is greatly affected, especially for turbulent field, where the turbulence intensities maintain at higher levels outside the two boundary layers. With the increase of Reynolds number, the tangential velocity goes up, resulted the attenuation of jet impinging effects, the shrinking of affected zones by outlets and the enlargement of pressure difference. Moreover, with the Bödewadt layer moving toward the central hub, the turbulence intensities increase inside two boundary layers but decrease outside them. Consequently, the flow is transited to Stewartson and then Batchelor type.

As significant fluid machinery, canned motor pumps are widely applied in industrial field. The typical characteristic of canned motor pump is that the fluid comes into the narrow gap and affects the performance of canned motor. The coolant flow in the narrow annular gap between rotor and stator cans belongs to Taylor-Couette-Poiseuille flow which has been investigated for a long time while the thermal design is a key function of internal narrow gap annular flow of canned motor. However, the temperature distribution prediction of canned motor deviates from the experiments, especially in the high-capacity canned motor due to the large shear rate of fluid and eddy-current loss of motor’s can. According to the researcher’s work, the significant work lies in the heat transfer coefficient that different researchers give various numerical prediction and experimental measurement. It brings big challenge in thermal design of high-capacity canned motor pump. In this paper, the author focuses on the reason why the heat transfer coefficient is remarkably lower than that other’s forecast. In this paper, the heat transfer behavior of the boundary layer near surfaces in the annular flow is investigated by using the commercial fluid dynamic (CFD) method. Firstly, the Naiver-Stocks (N-S) equations and energy conservation equation are employed for modeling the flow and heat transfer behavior, and the k-ω turbulent model is used for solving the flow control equations. Secondly, the fluid domain is described by a simplified geometrical model: two concentric cylinders with finite gap length. Thirdly, numerical approach is used to analyze the subject with tools of Solidworks, ICEM CFD and Ansys Fluent. Two parameters are analyzed in the research, namely the rotating speed and the wall heat flux, without considering the fluid viscous dissipation and thermal contact resistance. Numerical simulation results indicate that Taylor vortex exists in the flow regime, and the temperature distribution is affected by both the rotating speed and the wall heat flux, named thermal barrier effect under large heat flux condition. The thermal barrier effect lies in that the temperature gradient of interface decreases compared to the peak value of temperature gradient near the surface, so that the heat transfer coefficient is reduced remarkably. This effect leads to the temperature prediction deviates from the experiment measurement.

Hundreds of mirror segments are needed to realize the laser fusion system and the next generation ground based extra-large telescopes. In order to manufacture the mirror segments, the ultra-precise optics grinding machine is essential equipment. As the most widely used motion transfer device in these machines, the ball screw mechanism need predetermine its positional accuracy. And the positional accuracy is based on load distribution of ball screw. This will be discussed in the article. Based on existing analytical models, an improved model is developed to accurately predict load distribution of ball screw. In this model, variation of contact angle is considered. And a simple approach considering of the influence of the geometry errors on the load distribution is developed. The results of this model demonstrate the load distribution of ball screw is not average and load of every ball falls from the position near the load to further. Downward trend is more marked when introducing the variation of contact angle into the model. Besides, the effect of geometry errors on the load distribution is not as remarkable as existing models. Based on the model, the larger ratio of helical pitch to screw diameter is, the worse the nonuniformity of load distribution is. This will impair the stiffness of ball screw and its positional accuracy. The calculated results are significant to ball screw design.