Jian Ping Yuan

Optimal Design of a Non-Overload Centrifugal Pump

Three experiment factors including outlet blade angle β2, b2 and impeller wrapping angle θ are selected for optimal design of a non-overload pump. Numerical simulation with CFD is employed to reduce the cost and shorten the design period. The time-averaged Navier-Stokes equations of 3D steady flow in the pump are calculated by CFD based on the SST k-ω turbulence model and standard wall function. The structured grids of different qualities are used in one scheme for comparison to confirm that the results are not influenced by the quality of mesh. The optimal scheme is obtained when β2, b2, θ are 20 degrees, 7mm, 170 degrees, respectively. Its pressure head is 89.75m achieving the pump efficiency of 57% at maximum. The performances of NCPs at other working conditions satisfy the requirement of heads and efficiencies from China National Standard. The shaft power reaches to 15kW at 1.5QR (35.5m3/h), showing that the non-overload performance is also significantly improved. The impeller is considered as the optimal scheme and produced for experiments. Experiment data prove that it is effective and reliable to improve a non-overload pump’s performance by maximum flow design method and non-overload pump design method. The results provide a reference for increasing the efficiencies and pressure heads of non-overload pumps at multiple operating conditions.

Effect of Diesel Nozzle Geometry on Internal Cavitating Flow

The presence of cavitation and turbulence in a diesel injector nozzle has significant effect on the subsequent spray characteristics. However, the mechanism of the cavitating flow and its effect on the subsequent spray is unclear. The initiation, development and collapse of the cavity are strongly influenced not only by the injection pressure and back pressure but also by the nozzle geometry. The numerical simulation of cavitating flow in nozzle holes of a vertical multi-hole injector with mixture multi-phase cavitating flow model was carried out. The effects of sac geometry, hole entrance curvature radius and hole inclination angle on the cavitating flow in nozzle holes were investigated. It is finally concluded that the performance of IMPROVED nozzle is better than that of STD nozzle and VCO nozzle and small inlet turning angle of the orifice can enhance the atomization of the spray.

Numerical Simulation Research on Vortex Characteristics of Centrifugal Pump Inlet Recirculation

The 3-D steady turbulent flow in a centrifugal pump under different conditions was simulated by ANSYS CFX software. The intensity, location and the morphology of the inlet recirculation vortex were analyzed using standard k-ε turbulent model through steady simulation. Based on the results, the turbulent flow in the impeller inlet was simulated by Large Eddy Simulation. The dynamic characters and the whole changing process of the recirculation vortex during the rotation of the impeller were analyzed. The results indicate that the critical flow rate of the recirculation onset is 0.7Qd. As the flow rate decreases, the size and the intensity of the recirculation vortex increase and the vortex partially block the flow passage. The vortex first appears in the passage which passes by the outlet section of the volute. During one rotating, the vortex undergoes a whole process of onset, developing, decreasing and disappearing. As the relative speed and the pressure gradient change under different conditions, the vortices present different morphologies.

Effects of Twisted and Cylindrical Blades on the Flow Characteristics inside Blade Inlet and Outlet for a Centrifugal Pump

In this paper, the performance between cylindrical and twisted blades are analyzed for the same centrifugal pump. The three-dimensional steady and unsteady flow fields under 0.7Qd, Qd and 1.3Qd are simulated. The blade inlet and outlet flow and pressure pulsation inside the centrifugal pumps are discussed by using mathematical statistics and frequency domain analysis methods. The research is verified by experiments. The results show that the twisted blade controls blade outlet better than cylindrical blade at small flow and design flow, cylindrical blade controls blade outlet better than twisted blade at large flow. In the blade inlet and outlet, as the flow changes, the instability of cylindrical blade loading is higher than that of twisted blade. The cylindrical blade inlet pressure is affected by the shaft frequency more than that of the twisted blade. At shaft frequency and blade frequency, pressure pulsation coefficient of cylindrical blade outlet is higher than that of twisted blade outlet. The cylindrical and twisted blades effect on the blade inlet and middle gradually accumulates, resulting twisted blade outlet has larger pressure pulsation. The result can guide the optimum design of centrifugal pump to consider the performance balance between twisted and cylindrical blades.

Fluid Mechanics Analysis and Effect of Splitter Blades on the Characteristics of High-Speed Centrifugal Pump

Due to its single-stage high head, compact structure, convenient maintenance, low cost and high reliability, the high-speed centrifugal pump has been widely used in refining, petrochemical, chemical industry, and aerospace engineering fields. However, as the speed increases, the increasingly high demand for stability is showing and cavitation characteristics of the high-speed centrifugal pump is emerging. Reducing the mechanical vibration, hydraulic losses and improving the pressure distribution of the high-speed pump have become one of the main research fields for high-speed pumps. Three types of splitter blades were designed in this paper. Numerical simulations of the 3D steady flow in the high-speed pump have been carried out by using the software ANSYS CFX 12.0 and the comparative analysis of the velocity, pressure distributions and fluid mechanics in the high-speed pump under three different flow conditions were also carried out，Respectively. The effects of splitter blades on the high-speed pump performance were studied by analyzing both its inner flow field and hydraulic performance. The calculated H-Q curve of the high-speed pump was compared with the test results, and they agreed well with each other. The relative error of head at design conditions was lower than that at the non-design conditions.

A Study of Flow-Induced Noise in the Volute of Centrifugal Pump Based on Sysnoise

The internal flow-induced noise of the centrifugal pump is essentially caused by its complex internal flow, hence the research on the pump internal flow pattern is a crucial part of studying the flow-induced noise for centrifugal pumps. The DES unsteady simulation based on S-A model was applied to analyze the noise in the flow domains which are consist of the volute and the impeller passage in the paper. The frequency domains of pressure fluctuation at monitoring points under different operating conditions for different zones were analyzed by using SYSNOISE sound processing platform. The results show that the distribution of the acoustic source which was directly associated to the pressure fluctuation of the volute face generally aggregate at cutwater with the same frequency characteristic. Field sound pressure and dipole source do not have simple linear relationship and the strongest acoustic radiation intensity appears at blade passing frequency. Pipeline method applied in flow-induced noise measurement is effective and the flow rate is one of the major factors in acoustic radiation.

Study on the Influence of Volute to Flow-Induced Noise in Centrifugal Pump

More and more attention has been attached on flow-induced noise of centrifugal pump in recent years because of strict environmental noise restrictions and demands of clients.. In this paper, the role of volute impacted on flow-induced noise generation and propagation in centrifugal pump were summarized. The process of internal wave propagation was analyzed, and the transmission coefficient and loss of volute were calculated; In order to compare the effect of volute vibration on the sound field in a centrifugal pump, a hybrid algorithm based on CFD + BEM was adopted. The results reveals that: full reflection of sound wave occurs on the fluid-steel volute wall when the incidence angle is more than or equal to 13.8 °; otherwise a sound transmission appears; For onshore pumps, For onshore pumps the A-weighted sound transmission loss is more than 55dB under the condition that thickness volute is not less than 8mm; For submersible pumps, all-bottom sound below 3000Hz almost transmits to the outside field entirely; structure acoustic coupling between volute and the internal sound field influence little on directivity of sound field and the change of law, but structure vibration would average the sound pressure level in frequency.

Visual Computation of Thermohydrodynamic Lubrication of Dynamically Loaded Journal Bearings

The Reynolds equation and energy equation with the thermal balance equation in combination were applied to build the thermohydrodynamic (THD) computational model of the dynamically loaded journal bearings. The most popular development platform——Visual C ++ in the field of computer science and the drawing platform of AutoCAD were combined with the medium of ObjectARX and the object oriented programming technology was used, on the basis of which, the visual computational software of the THD lubrication of the dynamically loaded journal bearings for main shaft and connecting rod bearings of automobile engines was developed. The analysis results of an example indicate that the bearing behaviors are closely tied to the radial clearances and inlet lubricant temperature of the bearing.