Effect of Tip Clearance on Suction Performance at Different Flow Rates in a Mixed Flow Pump

This paper presents a numerical investigation of the effect of tip clearance on the suction performance and flow characteristics at different flow rates in a vertical mixed-flow pump. Numerical analyses were carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations. Steady computations were performed for three different tip clearances under noncavitating and cavitating conditions at design and off-design conditions. The pump performance test was performed for the mixed-flow pump and numerical results were validated by comparing the experimental data for a system characterized by the original tip clearance. It was shown that for large tip clearance, the head breakdown occurred earlier at the design and high flow rates. However, the head breakdown was quite delayed at low flow rate. This resulted from the cavitation structure caused by the tip leakage flow at different flow rates.

Development of High Efficiency and Low Noise Cross-Flow Fans for Room Air Conditioner Indoor Unit

Cross flow fans are used for fan systems in a household room air conditioner indoor unit. In recently, in the view of environmental problem and cost saving, energy saving performance is important specification for users. Reducing fan motor electric power consumption is effective for this purpose. And also low noise fans are needed for comfortable circumferences. To meet these user needs, we developed a high efficiency and silent cross flow fan using CFD (Computational Fluid Dynamics) and experiments. In CFD, numerical model is calculated by commercial software using steady state, Reynolds-averaged Navier-Stokes (RANS) and k-ε turbulent flow model. The developed cross flow fan is geometrically characterized by the solidity (the ratio of the blade pitch and blade cord length) distribution, and the blade edge shape. The solidity average of developed fan was larger than the conventional fan and the solidity distribution was smooth. And the developed fan has the sinusoidal shape of the outer diameter edge. This sinusoidal shape edge makes pressure distribution on the tongue to be more dispersed compare to that of conventional straight edge so that tonal noise was restrained.

Numerical Research of the Effect of the Outlet Diameter of Diffuser on the Performance and the Radial Force in a Single-Stage Centrifugal Pump

In this paper, a single-stage pump with diffuser vanes of different outlet diameters has been investigated both numerically and experimentally. The influence of the diffuser vane outlet diameter on pump hydraulic performance and on the radial force of the impeller is explored. Pumps equipped with three different diffusers but with impellers and volutes of the same parameters were simulated by 3D Navier-Stokes solver ANSYS-FLUENT in order to study the effect of the outlet diameter of vaned diffuser on performance of the centrifugal pump. Structured grids of high quality were applied on the whole computational domain. Experimental results were acquired by prototype experiments and were then compared with the numerical results. Both experimental and numerical results show that the performance of a pump with a diffuser of smaller outlet diameter is better than of bigger outlet diameter under all operating conditions. The radial force imposed on the impeller obtained by unsteady numerical simulation was analyzed. The results also indicated that an appropriate decrease in the outlet diameter of the diffuser vane could increase the radial force.

Numerical Investigation of Positive Displacement Rotary Lobe Pump With Twisted Rotors

The three-dimensional flow field characteristics are obtained by performing numerical simulation of flow in a lobe pump with twisted rotors. The relationship between the dynamic flow structure and the flow fluctuation is explored. Actually, the viscous incompressible Navier-Stokes equations are solved within an unsteady flow model. The dynamic mesh technique is applied to obtain the dynamic flow structure. By comparing the simulated results of straight rotor with those of twisted rotor, the effect of rotor shape on the flow fluctuation was revealed. Finally, the impact of the lobes number of rotors on flow pulsations is discussed. The results show that there is an intrinsic relationship between the flow fluctuation and the vortex in the lobe pump. The use of twisted rotors can effectively improve the internal flow characteristics of lobe pump and reduce flow fluctuation. With the increase of the number of lobes, the lobe pump output is more stable and capacity has been improved.

Initial Findings on the Feasibility of Real-Time Feedback Control of a Hazardous Contaminant Released Into Channel Flow by Means of a Laboratory-Scale Physical Prototype

The threat of accidental or deliberate toxic chemicals released into public spaces is a significant concern to public safety. The real-time detection and mitigation of such hazardous contaminants has the potential to minimize harm and save lives. We develop a computational fluid dynamics (CFD) flow control model with the capability of detecting and mitigating such contaminants. Furthermore, we develop a physical prototype to then test the computer model. The physical prototype is in its final stages of construction. Its current state, along with preliminary examples of the flow control model are presented throughout this paper.

Numerical Investigation of the Effect of Balancing-Hole on the Axial Force of a Partial Emission Pump

In this paper numerical simulations were conducted to analyze the effects of design parameters and distribution of balancing-hole on the axial-force of a partial emission pump. The studied pump is a single stage pump with a Barske style impeller. Based on the original impeller, we designed 7 pumps with different balancing-hole diameters and the partial emission pump equipped with different impellers were simulated employing the commercial computational fluid dynamics (CFD) software Fluent 12.1 to solve the Navier-Stokes equations for three-dimensional steady flow. A sensitivity analysis of the numerical model was performed with the purpose of balancing the contradiction of numerical accuracy and the cost of calculation. The results showed that, with increasing of the capacity, the axial force varies little. The diameter of the inner balancing-hole plays a dominant role of reducing axial-force of partial emission pump, the axial-force decreases with increasing of inner balancing-hole diameter on the whole range of operation, the axial-force of impeller without inner balancing-hole is approximately 3 times larger than that of impeller with inner balancing-hole. While the diameter of outer balancing-hole has a reverse effects compared with that of inner balancing-hole. With increasing of outer balancing-hole, the axial force increases accordingly.

Predictive Erosion Modeling in an ESP Pump

Electrical Submersible Pumps (ESPs) are widely used in upstream oil production. The presence of a low concentration solid phase, particle-laden flow, in the production fluid may cause severe damage in the internal sections of the pump which reduces its operating lifetime. To better understand the ESP pump’s endurance, an ESP-WJE1000, manufactured by Baker Hughes Company was studied numerically to determine the pump’s flow behavior at its best efficiency point. Computational Fluid Dynamics (CFD) analysis was conducted on two stages of the pump’s primary flow path employing Eulerian-Granular scheme in ANSYS-Fluent. The key parameters affecting the erosion phenomena within the pump such as turbulence kinetic energy, local sand concentration and near wall relative sand velocity were identified. The predictive erosion model applicable to pumps was developed by correlating the erosion key parameters with available experimental results.

Fluidic Deformation Under Hypervelocity Impacts

The increased frequency of exploration into space has caused a dramatic rise in the density of debris in orbit. Orbital debris, both natural and man-made, poses an extreme impact risk to satellites and spacecraft. The relative velocities between orbital components and debris can exceed thousands of meters per second, giving rise to immense kinetic energies even for small objects. In such a hypervelocity impact event, the shock pressures exceed the strength of common aerospace materials, and brief shock-induced temperature rises cause melting and vaporization of most structural bodies. Under these extreme conditions, the failure and deformation of solids can resemble fluid flow. By using meshless Lagrangian models in an explicit computational framework, this work identifies analogous fluidic interactions and further quantifies the role of shear and inertial forces in hypervelocity impacts (HVI).

Domain Partitioned Transformation of Pump-Turbine Characteristic Curves in 3-D Space

Pump-turbine characteristic curves are the most important boundary condition in the hydraulic transient simulation of a pumped-storage hydropower station. Conventional representation of them, however, has serious defects, For instance, the “S” and “hump” shapes, composed of multiple values and steep twists, lead to the difficulty in interpolation between known guide-vane opening curves, which is necessary in hydraulic transient simulations. Here, a new transformation method was figured out to settle this problem thoroughly and to improve the accuracy of interpolation between the constant opening curves. Prior to the transformation, the characteristic curves are partitioned into eight domains. Curves of each domain were transformed through different formulae that fit the curves well. Eight characteristic surfaces in the 3-D space can be obtained by adding the guide vane opening as the coordinate axis. The theoretical method has been validated by the excellent agreements achieved by comparing the curves interpolated on the characteristic surfaces with the measured data.

Heat Transfer Enhancement of Channel Flow via Vortex-Induced Vibration of Flexible Cylinder

Thermal diffusion in a developed thermal boundary layer is considered as an obstacle for improving the forced convective heat transfer rate of a channel flow. In this work, a novel, self-agitating method that takes advantage of vortex-induced vibration (VIV) is introduced to disrupt the thermal boundary layer and thereby enhance the thermal performance. A flexible cylinder is placed at the centerline of a rectangular channel. The vortex shedding due to the cylinder gives rise to a periodic vibration of the cylinder. Consequently, the flow-structure-interaction (FSI) strengthens the disruption of the thermal boundary layer by vortex interaction with the walls, and improves the mixing process. This new concept for enhancing the convective heat transfer rate is demonstrated by a three-dimensional modeling study at different Reynolds numbers (84∼168). The fluid dynamics and thermal performance are analyzed in terms of vortex dynamics, temperature fields, local and average Nusselt numbers, and pressure loss. The channel with the self-agitated cylinder is verified to significantly increase the convective heat transfer coefficient. When the Reynolds number is 168, the channel with the VIV improves the average Nu by 234.8% and 51.4% as opposed to the clean channel and the channel with a stationary cylinder, respectively.