Impeller Surface Research Articles

Improving the Efficiency of Submersible Multistage Pumps Based on the Hydrophobization of the Flow Part Surfaces

The paper presents an experimental study of an assembly of five stages of an electric centrifugal pump (ECP) installation, the flow part of which is modified according to the principles of biomimetics, namely using the “lotus leaf effect”. The object of the study was a 5A-35 ECP. The surfaces of the blade systems of impellers and guide devices of stages 5 A-35 were hydrophobized using the method of applying surfactant layers. The degree of impellers hydrophobicity was estimated by the wetting angle average value measured by three drops at three different points on the impeller surface. The impellers surface roughness under study was determined by the arithmetic mean profile deviation Ra and the profile height irregularities Rz. The issues related to the surfactant coating modification effect salt deposition and corrosion were studied. For this purpose, the surfaces of the original and modified impellers were subjected to intensive forced salt deposition as a result of prolonged exposure to saline solution. The conclusion about the samples corrosion resistance degree was made by changing their mass, which was due to the salt deposits formation during 15 hours of stay in solution, as well as using the drop method. Both methods have shown that the surfactant coating can serve as a salt deposition inhibitor, and the pump impeller modified by it has increased corrosion resistance. Thus, during comparative tests, a smaller mass of salt was deposited on the modified impeller sample during 15 hours of exposure in saturated saline solution than on the original sample. This indicates that the surfactant layer prevents the salt deposits fixation on the working surfaces of the pump stage. On the modified sample examined by the drop method, the indicator color changed in 20 minutes, and on the original one – in 2 minutes. Experimental studies have been carried out, during which the operation energy parameters of a five stages 5A-35 pumping package with initial and modified surfactant-coated impellers have been determined. The studies have shown a 2 % increase in efficiency in the pum-ping package of stages with modified impellers. The results of the study can be useful in the oil production, chemical industry, as well as in the housing and communal services sector.

Study on Microstructure and Wear Resistance of WC-based Cermet Coatings Prepared by HVAF

Abstract To mitigate the risk of vapor corrosion damage to the overflow mechanical parts, WC-based metal-ceramic coatings were applied to the surface of a 45-gauge steel substrate by supersonic air-assisted flame spraying (HVAF). The mechanical and wear-resistant qualities of the coating were identified by Vickers micro-hardness, ball-disc friction, and wear test, as well as optics, scanning electron, X-ray diffractometer, and white light interferometer systems. The findings demonstrate the layered structure of the WC-based coating, which is made up of the bonded phase and its distribution of hard phase particles that are diffusely dispersed. The coating is free of cracks, inclusions, and other defects, and its structure and organization are dense with a porosity of 0.86 ± 0.05%. The phenomenon of oxidative decarburization did not occur in the process of preparing the WC hard phase for WC-based metal-ceramic coatings. As a result, the coating’s micro-hardness of 11.83 ± 0.55 GPa is eight times that of the substrate. The results of comparing the three-dimensional abrasion patterns of the coating and the substrate reveal that the coating has superior abrasion resistance because its width and depth of abrasion are smaller than that of the substrate and a lot of furrows have formed on the substrate material’s surface. In contrast, the sprayed layer only had faint traces of abrasion. After three years of actual service, the impeller surface coating is essentially unaltered, which effectively addresses the issue of vapor corrosion damage to the slurry pump’s impeller and extends the pump’s service life to guarantee the overflow mechanical components operate safely and steadily.

Design and numerical simulation analysis of a miniature Mixed-flow compressor

This paper completed the pneumatic design of a mixed-flow compressor, adopted RANS turbulence model, and chose Spalart-Allmaras model to complete the numerical simulation of the flow field of the S1 flow surface, meridian flow surface, and impeller surface, and then analyzed the working performance at 90%, 100%, and 110% design speed to explore whether the mixed-flow compressor technology suitable for micro turbojet engines as well as the internal flow field flow state and loss mechanism. The results indicate that the shock wave at the front edge of the main blade and the low energy gas gathered at the tail edge of the main blade and the shunt blade, which causes serious flow blockage, are the main causes of the instability of the mixed-flow compressor at the design point. At 100% design speed, the compressor has higher reliability, stronger adaptability, and the best working performance for its working margin, isentropic efficiency, and pressure ratio with lower loss. The results may provide some references for the further optimization design of the current compressor.

Numerical Analysis of Unsteady Internal Flow Characteristics in a Bidirectional Axial Flow Pump

A bidirectional axial flow pump that utilizes an S-shaped hydrofoil design exhibits low efficiency and hydraulic instability when operated in reverse. In order to understand the unsteady flow characteristics of this bidirectional axial pump under different operating conditions, the SST k–ω turbulence model was applied to carry out a three-dimensional unsteady numerical simulation of the full flow channel of the pump. The reliability of the numerical calculation model was verified by comparing it with the experimental head and efficiency. The pressure pulsation characteristics on the impeller surface and the pump device under different operating conditions and the transient forces on the impeller were analyzed. The results show that the head and efficiency in reverse operation were lower than in forward operation and the flow streamline of the impeller outlet area was more turbulent in the reverse operation condition. The monitoring points at the inlet and the top of the impeller surface showed the largest pressure pulsation amplitude. The radial and axial forces on the impeller in the reverse operation were greater than those in the forward operation. Under a reverse 1.0 Qdes condition, the average pressure pulsation amplitudes at the inlet of the impeller were 19.2 times and 5.7 times of that at the inlet of the guide vane and the outlet of the impeller, respectively. This study provides a reference for the hydraulic design and optimization of bidirectional axial flow pumps.

Effects of sediment properties on abrasive erosion of a centrifugal pump

The presence of sediment particles in flows of centrifugal pumps significantly enhances the erosion rate which leads to reduced efficiency and shortened operational life of the pump. To investigate the performance and wear characteristics of a centrifugal slurry pump, the Eulerian-Lagrangian approach has been adopted in this study under various slurry flow conditions. The pump performance decreased whereas the average erosion rate of impeller blades and volute casing increased linearly with an increase in sediment concentration, according to the results of numerical simulations. The particle size distribution, from mono-sized distribution to a very broad distribution, reduced the average erosion rate by 20% on the impeller surface. In contrast, the erosion rate of the volute surface increases by 30% from mono-sized distribution to very broad distribution. Angular particles yield a higher rate of erosion for both blades and volutes as compared with spherical particles.

Tool path generation for 5-axis flank milling of ruled surfaces with optimal cutter locations considering multiple geometric constraints

Ruled surfaces found in engineering parts are often blended with a constraint surface, like the blade surface and hub surface of a centrifugal impeller. It is significant to accurately machine these ruled surfaces in flank milling with interference-free and fairing tool path, while current models in fulfilling these goals are complex and rare. In this paper, a tool path planning method with optimal cutter locations (CLs) is proposed for 5-axis flank milling of ruled surfaces under multiple geometric constraints. To be specific, a concise three-point contact tool positioning model is firstly developed for a cylindrical cutter. Different tool orientations arise when varying the three contact positions and a tool orientation pool with acceptable cutter-surface deviation is constructed using a meta-heuristic algorithm. Fairing angular curves are derived from candidates in this pool, and then curve registration for cutter tip point on each determined tool axis is performed in respect of interference avoidance and geometric smoothness. On this basis, an adaptive interval determination model is developed for deviation control of interpolated cutter locations. This model is designed to be independent of the CL optimization process so that multiple CLs can be planned simultaneously with parallel computing technique. Finally, tests are performed on representative surfaces and the results show the method has advantages over previous meta-heuristic tool path planning approaches in both machining accuracy and computation time, and receives the best comprehensive performance compared to other multi-constrained methods when machining an impeller.

Experimental Investigation on Improving Lifetime of Peripheral Pump Impeller under Cavitation Using Different Techniques

The industry is becoming more interested in peripheral pumps because they are inexpensive, have low specific speeds, and are small. One of the more serious problems that may occur with any pump is cavitation. That has a significant impact on pump components, particularly the impeller. This work presents a detailed experimental study on prolonging impeller lifespan under cavitation conditions by studying the effect of impeller surface finishing and coatings on its lifetime. For this purpose, seven impellers, in addition to the original one of the peripheral pump, had prepared and treated. Three impellers with three different levels of arithmetic surface roughness (Ra) were produced using a low-cost and customizable hand grinding procedure. And four impellers have been coated thermally with four different erosion-resistant composite materials. All of the impellers were cavitated for 300 minutes at normal and one at high water temperatures. The result showed that the mass loss percentages with the smallest (Ra) of 0.35µm, and coated with yellow epoxy were 84.86% and 48.50% lower than the original impeller, respectively. Thus, improving the quality of impeller surface finishing, and thermal coatings are excellent method for increasing the impeller's cavitation erosion resistance and thereby extending its lifetime.

Computational Fluid Dynamics Model of Continuous-Flow Total Artificial Heart: Right Pump Impeller Design Changes to Improve Biocompatibility.

Cleveland Clinic is developing a continuous-flow total artificial heart (CFTAH). This novel design operates without valves and is suspended both axially and radially through the balancing of the magnetic and hydrodynamic forces. A series of long-term animal studies with no anticoagulation demonstrated good biocompatibility, without any thromboemboli or infarctions in the organs. However, we observed varying degrees of thrombus attached to the right impeller blades following device explant. No thrombus was found attached to the left impeller blades. The goals for this study were: (1) to use computational fluid dynamics (CFD) to gain insight into the differences in the flow fields surrounding both impellers, and (2) to leverage that knowledge in identifying an improved next-generation right impeller design that could reduce the potential for thrombus formation. Transient CFD simulations of the CFTAH at a blood flow rate and impeller rotational speed mimicking in vivo conditions revealed significant blade tip-induced flow separation and clustered regions of low wall shear stress near the right impeller that were not present for the left impeller. Numerous right impeller design variations were modeled, including changes to the impeller cone angle, number of blades, blade pattern, blade shape, and inlet housing design. The preferred, next-generation right impeller design incorporated a steeper cone angle, a primary/splitter blade design similar to the left impeller, and an increased blade curvature to better align the incoming flow with the impeller blade tips. The next-generation impeller design reduced both the extent of low shear regions near the right impeller surface and flow separation from the blade leading edges, while maintaining the desired hydraulic performance of the original CFTAH design.

Interfacial Characteristics and Mechanical Properties of CuSn15/HT250 Prepared via Additive Manufacturing Combined with an Inconel 718 Interlayer

Tremendous discrepancies in the positive enthalpy of mixing and the coefficient of thermal expansion emerge between the copper alloy and the gray cast iron, accounting for numerous pores and cracks in the interfacial region during the metallurgical bonding process. To enhance the interfacial bonding properties of these two refractory materials, laser-directed energy deposition was applied to fabricate the CuSn15 alloy on the HT250 substrate; meanwhile, Inconel 718 alloy, acting as the interlayer, was added to their bonding region. Firstly, the effect of the deposition process on deposition layer quality was investigated, and then the effects of Inconel 718 addition on the interfacial morphology, element distribution, phase composition, bonding strength, microhardness were studied. The results showed that a substrate (HT250) without cracks and a deposition layer (CuSn15) free from pores could be obtained via parameter optimization combined with preheating and slow cooling processes. Adding the Inconel 718 interlayer eliminated the interfacial pores and cracks, facilitated interfacial element (Cu, Fe, Ni) diffusion, and enhanced interfacial bonding strength. The interface between HT250 and CuSn15 mainly contained the FeSn2 phase, while the interfaces of the CuSn15-Inconel 718 and the Inconel 718-HT250 were mainly composed of the Ni3Sn4, Cr5Si3, FeSi2, Cr7C3. The microhardness and fracture morphology of the interfacial region in the samples with and without the interlayer were also studied. Finally, CuSn15 was also successfully deposited on the surface of the HT250 impeller with large size and complex structure, which was applied in the root blower.

Cavitation control using passive flow control techniques

Passive flow control techniques, and particularly vortex generators have been used successfully in a broad range of aero- and hydrodynamics applications to alter the characteristics of boundary layer separation. This study aims to review how such techniques can mitigate the extent and impact of cavitation in incompressible flows. This review focuses first on vortex generators to characterize key physical principles. It then considers the complete range of passive flow control technologies, including surface conditioning and roughness, geometry modification, grooves, discharge, injection, obstacles, vortex generators, and bubble generators. The passive flow control techniques reviewed typically delay and suppress boundary layer separation by decreasing the pressure gradient at the separation point. The literature also identifies streamwise vortices that result in the transfer of momentum from the free stream to near-wall low energy flow regions. The area of interest concerns hydraulic machinery, whose performance and life span are particularly susceptible to cavitation. The impact on performance includes a reduction in efficiency and fluctuations in discharge pressure and flow, while cavitation can greatly increase wear of bearings, wearing rings, seals, and impeller surfaces due to excessive vibration and surface erosion. In that context, few studies have also shown the positive effects that passive controls can have on the hydraulic performance of centrifugal pumps, such as total head and efficiency. It is conceivable that a new generation of design in hydraulic systems may be possible if simple design features can be conceived to maximize power transfer and minimize losses and cavitation. There are still, however, significant research gaps in understanding a range of impact factors such as manufacturing processes, lifetime, and durability, and essentially how a static design can be optimized to deliver improved performance over a realistic range of operating conditions.

Redesign of Centrifugal Pump with Capacity 286.8 M3/hrs and Head 32 Metre at Karawang International Industrial City

Mechanical equipment has an important role to support the needs of a process. There is mechanical equipment, namely a pump that functions to move liquid fluid from one place to another through the piping medium. Based on report from customer, Centrifugal pump ETA-N 150 x 125 - 315 which functions as supply distribution of clean water from Water Treatment Plant (WTP) to the Karawang area International Industrial City (KIIC) experienced a decrease in capacity and Head and happened unbalance on the pump drive motor rotor. After an investigation by the team engineering PT. TG Engineering, found problems such as heavy corrosion and corrosion erosion on surface impeller, spoons impeller and volute chamber, deep scratch and light corrosion on shaft / shaft, as well as malfunction bearing on bearing pump and bearing pump drive motor unbalance. Referring to the results of the investigation, the authors design and select centrifugal pump components based on the results of the investigation. So that after calculating the dimensions of impeller, shaft, key and component selection such as type bearing, lubrication bearing, as well as coupling.

Analysis of Centroid Trajectory Characteristics of Axial-Flow Pump Impeller Under Hydraulic Excitation

The hydraulic excitation characteristics of axial flow pump unit are studied through theoretical analysis, numerical simulation and field test in this paper. The correlation between impeller hydraulic and radial vibration displacement of impeller centroid is obtained through theoretical analysis. Through the 1-way fluid-solid-interaction (FSI) numerical simulation, the distributions of water pressure and displacement on the impeller surface are obtained, and the time-domain and frequency-domain characteristics of transient hydraulic and radial displacement are revealed. Through the field test, the external characteristics of axial flow pump unit and the time-frequency characteristics of the pressure pulsation at the measuring points beside the inlet of the impeller are obtained. The comparisons between simulation results and experimental results show that the former is accurate and reliable.

On the Correlation Between Spanwise Inducer Incidence and Impeller Diffusion for Ruled Surface and Barreled Sweep-Bow Impeller Design at Inlet Guide Vane-Off-Design

AbstractIn the present paper, three centrifugal stages of high volume flow coefficient are compared to each-other regarding their aerodynamic performance in design point and off-design point conditions at different speed and inlet guide vane (IGV)-setting angle: two stages with full-blade design (no splitter blades) have been numerically designed with different design geometry methodology. One geometry is based on a classical ruling surface design with a linear leading edge, the second geometry based on a fully-three-dimensional surface including a blade bow at the trailing edge and a barreled sweep at the leading edge. According to impeller test rig measurements and computational fluid dynamics (CFD) calculation, the classical ruling surface designed impeller outperforms the more sophisticated centrifugal stage with fully 3D-blade at fully axially guided IGV-flow. In the contrary, at closing IGV-off-design setting angles, toward surge operation, the fully 3D-blade impeller performs with higher efficiency and steeper negative pressure slope. On the search of the geometrical causes for the different aerodynamic performance (especially at IGV-off-design conditions), focus is set on the analysis of IGV-flow-interaction with the inducer flow and impeller diffusion. The one-dimensional analysis of the spanwise flow at the impeller leading edge reveals that, compared with the ruling surface impeller, the fully 3D-blade performs with lower flow incidence losses in favor to IGV-off-design operation than at IGV-neutral position. The streamwise flow analysis confirms the improved flow incidence characteristics of the 3D-blade impeller due to reduction of aerodynamic blockage and entropy production in the vicinity of the impeller leading edge. Based on CFD calculations, a new correlation of secondary flow and flow incidence is proposed, to be used for one-dimensional modeling.

Numerical Research of Pump-as-Turbine Performance with Synergy Analysis

The wide use of pumps and turbines has significant value in energy conservation and utilization. In this work, a three-dimensional Computational Fluid Dynamics (CFD) model and a one-dimensional theoretical model of a Pump as Turbine (PAT) were established. On this basis, the correlation between pressure and velocity was quantitatively investigated by a proposed sensitivity index (SPV). A synergy field analysis was then applied to evaluate the flow characteristics of a pump and PAT, providing a perspective from the mechanism of the energy transfer enhancement for hydraulic devices. Moreover, the hydraulic and synergy performances of PAT were studied under various operating conditions. The results show that the minimum SPV is obtained in the impeller. With increasing flow rate, the SPV of the PAT generally increases, and the synergy angle of the impeller surface increases as well. A strong disordered synergy field is observed in regions of the blade leading edge, trailing edge, and volute tongue. The variations in efficiency and head with flow rate showed similar trends, respectively, with the synergy angle of the outlet and the mid-plane. This study provides an analytical method for quantitative evaluation of flow synergy characteristics, and it supplies a basis for further design improvement of the pump and PAT.

Biologisation of the Left Ventricular Assist Device

Purpose Left ventricular assist devices (LVADs) are established implantable devices in patients with end-stage heart failure. Due to their artificial materials, anticoagulative therapy is needed, though leading to partly lethal complications and limited clinical applications. Improved LVAD hemocompatibility of all blood contacting surfaces can be achieved by their endothelialisation. Additionally, the endothelial monolayer need to resist clinically relevant flow-conditions, for which we established a new approach using magnetic forces and intracellular superparamagnetic nanoparticles (NP). Methods Endothelial cells (EC) were incubated with nanoparticles of different concentrations and coatings (sodium citrate, polyvinylpyrrolidone) for various time periods. Nanoparticulate absorption behaviour was visualized by Prussian blue staining. Batches with high intracellular nanoparticle quantities were analysed for cell viability by immunofluorescence staining and proliferation assay, possible cytotoxicity by flow cytometry. Following, cellular alignment induced by different magnetic forces was examined and transferred to LVAD impeller endothelialisation. Results Concentration-, coating- and time-dependent changes in cell viability, proliferation and cytotoxicity could be shown, indicating best results for low concentrated sodium citrate nanoparticles, which were used for subsequent cell migration experiments. Magnetic field sufficiently affected endothelialisation as significantly more NP loaded ECs adhered to the impeller surface compared to the unloaded control group. Conclusion These results are promising steps towards the effective biologisation of the LVAD, as the LVAD itself may provide the needed magnetic field for sufficient and flow-resistant endothelialisation. This hypothesis needs to be analysed within the following experiments.

An in-depth quantitative analysis of wind turbine blade tip wake flow based on the lattice Boltzmann method.

With the continuous increase in the total quantity and quality of wind energy used by society, the aerodynamic complexity of wind turbine impellers has also gradually increased. This requires a more accurate analysis and understanding of the aerodynamic performance of important parts of the wind turbine impeller. The blade tip vortex is undoubtedly one of the most important issues. This article used the state-of-the-art lattice Boltzmann method (LBM), combining large eddy simulation (LES) and wall-adapting local-eddy (WALE) model, to investigate the unsteady flow characteristics of the blade tip region due to impeller wake for a wind turbine. The trend of this calculation result is consistent with the experimental data, both for the axial force and the torque on the impeller. Therefore, it indicates the calculation model of LBM is reasonable and effective. The relevant in-depth results clearly showed the dynamic stability of a spiral structure will increase as operating conditions continue to advance and it is also synchronously affected by the tower wake flow structures. The fluctuation amplitude of the static pressure value on both sides of the impeller gradually decreases with time. The distribution of static pressure near the leading edge of the tip is very different for each blade due to the influences of turbulence intensity and the tower shadow effect. The random minor fluctuations of the axial force and torque both exhibit similar characteristics, and the overall torque is more sensitive to random changes in the tip vortex on the impeller surface.

Pump Thrombosis, Scratching the Surface

Pump thrombosis (PT) remains a serious complication in patients supported with a ventricular assist device (VAD). In our institution, HeartWare HVAD patients with PT are thrombolysed with systemic Alteplase infusion until restoration of normal power consumption or maximum infusion duration of 20 hours. Although most PT events resolve with single thrombolysis, PT can re-occur requiring further thrombolysis and/or pump exchange. In this prospective exploratory observational study, we opened and inspected all explanted pumps that required thrombolysis for PT. VADs were retrieved post-heart transplantation and opened for inspection. All impeller (rotor) surfaces, and internal upper and lower pump housing surfaces were inspected and photographed. From August 2017 through September 2019, 7 patients (mean age 54±7.6 years, 57% male) were thrombolysed for PT with a median duration of support to first thrombolysis of 307 days (range, 99 to 852 days). Five patients were thrombolysed once, 1 twice and 1 three times. Clinical parameters and pump power consumption returned to normal for each thrombolysis event for all patients. Inspection of the pump at explant was normal in all cases, except for the patient thrombolysed multiple times. In that patient (thrombolysed on days 99, 154, 204), the lower surface of the impeller was worn on one edge, suggesting impeller imbalance with corresponding marking on the ceramic housing surface. (Image) CONCLUSION: Patients with recurrent PT episodes requiring thrombolysis may have changes in pump surface not previously reported. Pump replacement may be warranted in these cases. Whether this is due to impeller instability or other factors is unknown. Routine inspection of explanted pumps may provide insights into thrombosis mechanisms.

Experiment on the straw particle flow in a centrifugal pump

Centrifugal pump is extensively used in wastewater, pulp, and biomass industries for transporting of particle flows. The motion and distribution of flexible particles are critical for continuous and stable pumping. In this work, a test rig is set up for straw particle flow pumping. A stroboscopic flash is employed to capture the distribution of the straw particle. The pump performance is measured and compared to that of clear water. By increasing the particle concentration, the process from stable pumping to eventually clogging is observed. Firstly, in a wide operation range with 0.1% concentration, the particle is uniformly distributed in the flow passage and the pump is running in a hydrodynamic stable mode where the power increases gradually and is slightly over the pure water circumstance. However, the high efficiency region is shifted to lower flow rate and it becomes narrower as compared to the pure water case. Secondly, at 0.2% and 0.4% concentration, the performance resembles the 0.1% case. But with increasing concentration, the inception of small flocs is observed. In addition, small air bubble is formed near the rotating axis. This subtle change continues until clogging happens. By gradually increasing the concentration of particle, more and more particles are attached to the growing flocs. Finally, the pump runs into mechanical wear between particles and flow passage, and then it is fully clogged. In this condition, the power consumption increases rapidly and the variable frequency drive is used to bring down the shaft speed. The long-term running shows relatively light erosive wear on the surface of impeller and volute by the particles, but no damage is observed.

DESIGNING THE UNPLOITING BLADES OF THE DRIVE WHEEL OF THE HYDROTURBINE ON SCANING

The article discusses the possibility of designing the surfaces of the impeller surfaces by directly calculating the sweep. It uses the properties of flat sections of the end surfaces.

The effect of surface roughness of the impeller to the performance of pump as turbine pico power plant

Pump as Turbine (PAT) is one of a hydropower plant that applies a pump with a reversed flow, working as a turbine to generate electrical power. It has the advantages of low-cost, widely available in the market and user-friendly. However, like other hydropower plants, PAT technology has low performance in term of power output. The impeller surface roughness is one of critical aspect, which influences PAT performance because poor surface roughness causes losses and cavitation. The objective of the research is to increase the PAT performance by improving the quality of the surface roughness and validate by the experimental tests. A low-cost and customize hand grinding process was applied to produce five impellers with three different levels of surface roughness (average surface roughness of 0.16 mm, 0.24 mm, and 0.40 mm), an edge rounded impeller, and a varnish lacquer coated impeller. All of the impellers undergo performance testing. The performance of the original impeller (without modification) used as a comparison. The experiment result shows that an impeller with a lower surface roughness (lower Ra number) has a higher performance. An impeller with an average surface roughness of 0.16 mm improved 10.9% of its initial performance. Additional edge rounding for a 0.16 mm surface roughness impeller would improve its performance by 13.1%. The optimum turbine efficiency of 15.45% was achieve-able by implementing an impeller with the lowest surface roughness.