Advanced Materials Research Vols. 354-355

Abstract: The six kinds of different models were simulated by FLUENT software under certain circumstances. As a result, their pressure distributions and liquid film opening force with different thickness were obtained. The relationship between liquid film thickness and opening force was obtained by least square fitting. And then the relationship between stiffness and liquid film thickness was calculated and analyzed. The result shows that: seal opening force and liquid film stiffness decrease as the liquid film thickness increase, this simulation results is identical with the theoretical data. In larger film thickness range, the opening force is larger, and so was the liquid film stiffness, which provide the basis for seal optimization design and the stable operation.

Abstract: The results of the experimental investigations and numerical simulations of droplet impact on a stationary horizontal surface are presented. The impact process of a droplet with high impact energy on a horizontal surface was photographed by a high-speed CCD. In addition, two-dimensional numerical simulation of the impact process was also performed using the VOF model. Comparison between the experimental and numerical results shows that the chosen computational model is suitable to simulate such impact processes. Furthermore, the effect of the droplet impact velocity and diameter on the impact process was studied in detailed. The numerical results show that the variation in droplet impact velocity has a significant effect on the maximum spread factor and spread speed, whereas, the variation in droplet diameter considerably influences the maximum spread factor and the oscillation of the drop in the receding phase.

Abstract: Hydraulic drive mixers are widely employed to process the cohesive mixture, especially the dusty and energetic mixture. In this study, the modeling method of the AC frequency control speed regulating system of a planetary mixer was presented. The speed regulating system consists of links of frequency converter(FC), asynchronous motor(AM), and hydraulic circuit(HC). The stability analysis was conducted by applying specification parameters of the FC, AM and HC. Result shows that the speed regulating system is stable by Routh criterion with amplitude margin 21.4db and phase margin 17.9degree.

Abstract: Side-entering agitators are the main mixing system in the process of petroleum blending. Based on the three-dimensional gasoline components mixing model, the incompressible Reynolds equation is selected as the momentum equation and the algorithm of SIMPLE is employed to simulate the flow field of three side-entering agitators. In the unsteady multiphase flow, moving mesh and the standard k-ε turbulent model has been employed to get the mixing time. The results show that the model of side-entering agitators exists low-velocity zones, which are like structures of vortex in the central regions of blending tank, and the mixing time is 33.7s.

Abstract: The flow pattern in a two-dimensional wall-driven semi-circular cavity is analyzed using the lattice Boltzmann method (LBM). The treatment of curved boundary with second-order accuracy is used. The streamline contours as well as dimensionless velocity component along the central line of a semi-circular cavity are obtained for different Reynolds numbers. The numerical results show that the LBM can capture the formation of primary, secondary and tertiary vortices exactly as the Reynolds number increases and has a great agreement with those of current literatures.

Abstract: Based on the good function for 3D modeling of Pro/E software, 3D geometry modeling for the entire flow passage of HLA351 which is the Francis turbine with long and short blades was realized by means of a series of methods of drawing from inside to outside, drawing from top to bottom, drawing lines from points, drawing surfaces from lines, and finally getting body from surfaces, so as to provide a reliable foundation for the future CFD calculation and performance prediction.

Abstract: The 3D flow field generated by two-stage impellers in the agitation of xanthan gum, a pseudoplastic fluid with yield stress, was simulated using the commerical CFD package. The effect of impeller speed and impeller spacing on power number, cavern size and viscosity distribution was investigated in this work. The results showed that the power number was slightly influenced by impeller spacing. Higher impeller speed and larger impeller spacing contributed to creation of a bigger cavern. The range of high viscosity zone between the impellers increased with an increase in impeller spacing. Impeller speed and impeller spacing could be used as important parameters to improve the mixing performance of multi-stage impellers in the mixing of pseudoplastic fluids with yield stress.

Abstract: Experimental studies of a water drop impinging on a rotating disk using a high-speed video camera have been performed. The photos of the impact were analyzed in detail. Three kinds of the deposition patterns were observed with the variation in Rossby number. It is found that Rossby number plays an important role in the deposition process of the drop impacting on the rotating disk, leading to some new stages not observed for drop impact on a stationary plate.

Abstract: In order to research the effect of the blade wrap angle and outlet angle on the hydraulic performance of the low-specific speed sewage pump, the Reynolds time-averaged Navier-Stokes equations was discretized based on the finite volume method, and the modified k-ε turbulence model were chosen in FLUENT. Numerical simulation of the internal flow within the centrifugal pump with the specific speed of 60 at different blade wrap angle and outlet angle is carried out. The analysis of the velocity and the turbulent kinetic energy distribution in different cases, and predicts the external characteristics of the several cases based on the loss analysis method. The study results show that the efficiency of pumps increase with decreasing the outlet angle and increasing the wrapping angle at the design of sewage pumps. According to the analysis, changing the blade outlet Angle has much more influence on the performance of the pump than changing the wrap angle.

Abstract: Practically, the distribution and variation of the bottom-hole hydraulic energy has significant influence on drilling rate, and it’s helpful to induce bottom-hole hydraulic pulse to improve the rock breaking and drilling efficiency. The analysis of bottom-hole rock stress condition and cuttings start-up mechanism indicates that, bottom-hole hydraulic pulsation can decrease the bottom hole pressure, reduce the fracture strength of rock, and strengthen bottom-hole purification, thus improve the efficiency of rock breaking and drilling. The higher the pulsation value is, the more effective of the acceleration of the drilling rate, while well depth increases, the acceleration effect diminishes gradually. Simulation of jet flow field drilled by 3-nozzle 3-cone bit, combined with field application, verify the mechanism that bottom-hole hydraulic pulsation could improve ROP. The result of the study provides a basis for the development of practical technology.