Balance Holes Research Articles

Influence of the Balance Hole Circumferential Position on the Cavitation Performance of the Semiopen Impeller Centrifugal Pump

In order to study the influence of the circumferential position of the balance hole on the cavitation performance of the semiopen impeller centrifugal pump, a low specific speed semiopen impeller centrifugal pump is taken as the object, and 4 kinds of circumferential positions of balance holes are designed. The SST k-ω turbulence model and the Rayleigh–Plesset cavitation bubble dynamics equation are used to calculate the full flow field of the centrifugal pump. Research shows that, under cavitation conditions, as the circumferential position of the balance hole is farther away from the blade working surface, the cavitation performance of the pump is reduced, and the larger θ (the angle of the balance hole and the leading edge of the blade in the direction of rotation) is, the easier the jet cavitation occurs near the balance hole. On the other hand, with the development of cavitation, the axial force of the impeller has also changed greatly. In contrast, the farther the balance hole is arranged in the circumferential direction (i.e., the greater θ), the more limited is the ability of the balance hole to balance the axial force.

Research on the Influence of Balance Hole on the Performance of Ocean energy gas-liquid multiphase pump

In this paper, the Euler-Euler heterogeneous flow model is used to simulate the models of centrifugal deep-sea multiphase pump before and after the balance hole is opened under different inlet air ratios. The effect of the balance hole on the external characteristics of the pump is illustrated by comparing the static pressure distribution on the blade surface before and after the opening and the hydraulic loss in the impeller. The research results show that when the inlet air content is less than 5%, the external characteristics of the multipahse pump are reduced, and when the inlet air content is greater than 5%, the balance hole has an improved effect on the external characteristics of the mixed pump. At this time, the static pressure on the blade surface is increased compared with the original model, and the flow loss on the impeller is significantly reduced.

Influence of Balance Hole Diameter on Leakage Flow of the Balance Chamber in a Centrifugal Pump

The balancing holes in centrifugal pumps with seals mounted in both suction and discharge sides are one of the approaches used by pump manufacturers to reduce the axial thrust. The balance hole diameter directly affects the axial force of the centrifugal pump. The flow characteristics in the balance chamber are closely related to the balance hole diameter. However, research is not very clear on the internal flow of the balanced chamber, due to the small axial and radial sizes and the complicated flow conditions in the chamber. In this paper, we analyzed the influence of the balance hole diameter on the liquid leakage rate, flow velocity, and vortex motion in the balance chamber. The results indicated that when the balance hole diameter was lower than the design value, the volume flow rate of leakage flow was proportional to the diameter. The liquid flow rate and vortex distribution rules in the balance chamber were mainly associated with the coeffect of radial leakage flow in the rear sealing ring interval and the axial balance hole leakage flow. The research has revealed the mechanisms of leakage flow of the balance chamber in the centrifugal pump and that this is of great significance for accurate calculation and balancing of the axial force.

Axial forces in multistage back-to-back pumps

Since the pressure of the pumps for the oil and gas industry and feed water pumps for the thermal and nuclear power plants are increasing and at the same time the production costs need to be reduced, the demands for development of the modern multistage centrifugal pumps are increased. An enlargement of stage numbers results in an increase in the distance between the bearings and as a result the shaft deflection increases. Also, a large number of stages leads to occurrence of a significant axial force acting on the pump rotor. These issues are solved by applying a back-to-back design with a throttling bush between the groups of stages. An arrangement with such throttling bush results in an additional axial force due to the different directions of leakage in the channels (side wall gaps) between the main disks of the last impellers of both stage groups and stator elements. Therefore, the design of a throttling bush with special balancing holes was proposed. This paper examines the processes occurring in the throttling bush and compares the operating parameters for two design options-with special balancing holes, and without them.

CFD Analysis on the Balancing Hole Design for Magnetic Drive Centrifugal Pumps

Balancing holes in single-suction centrifugal pumps are generally applied to attenuate the axial thrust caused by a pressure difference between the front side of a shroud and the rear side of a hub of an impeller. The magnetic drive pump, the subject of this study, has a leak-free airtight structure and an integrated structure of the impeller and inner magnet. To prevent the performance degradation of the magnetic drive caused by heat during operation, complex cooling flow paths connected to balancing holes have been designed so that a sufficient amount of coolant would flow around the magnetic drive. Due to this spatial characteristic, when balancing holes are applied to a magnetic drive pump, the balancing hole flow path becomes very long compared to that of balancing holes applied to conventional pumps. When the balancing hole flow path is long, the flow path loss increases, which in turn increases the adverse effect of balancing holes on the pump performance. Therefore, the design of highly efficient balancing holes to which a sufficient amount of coolant can be supplied is critical in a magnetic drive pump. To this end, two types of balancing holes were investigated in this study. First, balancing holes are drilled in the impeller that rotates during operation. Second, balancing holes are drilled in the inner shaft installed to maintain the centre of rotation of the impeller during pump operation. The results confirmed the flow characteristics of the two types of balancing holes and verified the effect of each balancing hole on the pump performance. Finally, this study found that drilling balancing holes in the shaft were appropriate for the magnetic drive pump, and this type can maintain relatively high efficiency and supply a sufficient amount of coolant to maintain the efficiency of the magnetic drive.

Study on the influence of the specific area of balance hole on cavitation performance of high- speed centrifugal pump

In this paper, the influence of the specific area of balancing hole on the cavitation performance of high-speed centrifugal pump is studied by numerical method. The results show that in the initial cavitation stage, with the increase of the specific area, the head and efficiency of the pump decreases, and the shaft power increases in a small range. The specific area of the balance hole can change the magnitude and direction of the rotor axial force. With the increase of the specific area, the anti-cavitation performance of the pump is weakened, especially when the specific area reaches a certain value, the vortex flow appears in the balance hole, which causes serious distortion of the flow condition at the inlet of the centrifugal impeller. Meanwhile, cavitation also occurs in the balance chamber and is mainly concentrated near the hub of the centrifugal impeller.

A Pressure Model for Open Rotor–Stator Cavities: An Application to an Adjustable-Speed Centrifugal Pump With Experimental Validation

Abstract For a centrifugal pump, the interaction between the leakage and the pressure profile in the side chambers is crucial to the performance and reliability of the pump. However, existing theoretical models for directly predicting the flow in the pump side chambers suffer from nonself closure, low accuracy, and slow convergence, and hardly any research presents such predictions for the adjustable-speed centrifugal pump. A pressure model for the simplified geometric configuration of the side chambers in turbomachinery, specifically the open rotor–stator cavity, is established by introducing Poncet's K formula. With the application of this theoretical model, as well as the consideration of the static pressure rises in the impeller and the pressure drops through seals and balance holes, a new one-dimensional (1D) pressure model is built and developed as a design tool for solving the flow in the pump side chambers. Compared with the pressure measurements on the casing wall of an adjustable-speed centrifugal pump, the predictions made by the new 1D pressure model indicate good accuracy and are better than the predictions made by the pressure model using the conventional constant K. It is found that the thrust acting on the shrouds varies almost linearly with the squared rotating speed, whereas the rotating speed hardly influences the volumetric efficiency. Since only the flow rate, rotating speed, and geometric parameters are required, the new 1D pressure model can be readily applied to other pumps, and it is preferred for good and fast prediction in the preliminary design stage.

Do stellar-mass and super-massive black holes have similar dining habits?

Over the years, numerous attempts have been made to connect the phenomenology and physics of mass accretion onto stellar-mass and super-massive black holes in a scale-invariant fashion. In this paper, we explore this connection at the radiatively efficient (and non-jetted) end of accretion modes by comparing the relationship between the luminosity of the accretion disc and corona in the two source classes. Motivated by the apparently tight relationship between these two quantities in active galactic nuclei (AGNs), we analyse 458 RXTE-PCA archival observations of the X-ray binary (XRB) GX 339–4, using this object as an exemplar for the properties of XRBs in general. We focus on the soft and soft-intermediate states, which have been suggested to be analogous to radiatively efficient AGNs. The observed scatter in the logLdisc − logLcoronarelationship of GX 339–4 is high (∼0.43 dex) and significantly larger than in a representative sample of radiatively efficient, non- or weakly jetted AGNs (∼0.30 dex). At first glance, this would appear contrary to the hypothesis that the systems simply scale with mass. On the other hand, we also find that GX 339–4 and our AGN sample show different accretion rate and power-law index distributions, with the latter in particular being broader in GX 339–4 (dispersion of ∼0.16 cf. ∼0.08 for AGN). GX 339–4 also shows an overall softer slope, with a mean value of ∼2.20 as opposed to ∼2.07 for the AGN sample. Remarkably, once similarly broad Γ andṁdistributions are selected, the AGN sample overlaps nicely with GX 339–4 observations in the mass-normalised logLdisc − logLcoronaplane, with a scatter of ∼0.30 − 0.33 dex in both cases. This indicates that a mass-scaling of properties might hold after all, with our results being consistent with the disc-corona systems in AGNs and XRBs exhibiting the same physical processes, albeit under different conditions for instance in terms of temperature, optical depth and/or electron energy distribution in the corona, heating-cooling balance, coronal geometry and/or black hole spin.

Optimization design for reducing the axial force of a vaned mixed-flow pump

Vaned mixed-flow pump is widely used for liquid transportation in industry and agriculture. The structural-asymmetricity induces large axial force which causes axial vibration and shaft system damage. In this study, impeller forces are analyzed and optimized based on numerical simulation and experiment. Balance holes and a balance plate are used in cooperation. Orthogonal experiment is conducted to analyze the effects of balance hole diameter, sealing clearance width on the hub, and balance plate clearance width on axial force at design condition. Then, BP-artificial neural network is established with Global Dynamic Criterion algorithm. Efficiency and axial force at design condition are chosen as optimization objectives. The results prove that optimized pump has lower axial force and higher efficiency at design condition. The head coefficient meets design requirement. Accordingly, a cooperative method named the ‘Combining Hole-Plate Pressure Balancing Method’, made by adding balance holes and installing a balance plate in the hub clearance chamber, is proposed. The method can effectively reduce axial force and improve the adverse effect of axial force on the pump without obvious influence on hydraulic performance. This study is significant as a means to reduce axial force, lessen damage to a shaft system, and improve operation stability.

Numerical investigation of rotor–stator interaction for canned motor pump under partial load condition

Numerical simulations of a canned motor pump at partial load condition have been conducted for studying the strong rotor–stator interaction. SST [Formula: see text] turbulence model with wall function was adopted for solving three-dimensional (3D) unsteady Reynolds-averaged Naiver–Stokes (URANS) equations. The inner flow field for four typical rotor positions, where the head changes significantly, was explored. It has been shown that when blade approached tongue region, the radial velocity decreased where the pressure at suction side was bigger than pressure side. As a result, a negative work was exerted on the fluid which led to minimum work done by the impeller. At this condition, maximum work was resulted in due to the upstream blade. The fluid from balance hole affected the main flow near hub region which caused a vortex near channel pressure side. Due to impeller channel rotation through tongue, the vortex was enlarged which contributed separation flow at impeller inlet region. The separated flow caused pressure reduction in the channel. Static pressure at impeller outlet near shroud side was always greater than at near hub side which resulted in negative radial velocity at impeller outlet near shroud side. Due to the blade accession to the tongue, the static pressure at impeller channel increased meanwhile the area characterized by negative radial velocity enlarged.

Investigation of the Integrated Model of Side Chamber, Wear-Rings Clearance, and Balancing Holes for Centrifugal Pumps

The characteristics of radial pressure distribution inside side chamber and leakage flow through balancing holes of centrifugal pumps are very important for accurately predicting the axial thrust produced by a balancing system. Therefore, a rapid and sufficiently accurate calculation method is required. An integrated model describing the characteristics of radial pressure distribution inside side chamber and leakage flow rate through balancing holes was established. In this model, the correction coefficient of liquid pressure at side chamber entrance and the discharge coefficient of balancing holes were obtained by experiment. The IS 80-50-315 type single-suction, single-stage, and cantilevered centrifugal pump with the structure of double wear-rings and balancing holes was employed as a model to investigate the characteristics of internal liquid flow of the balancing system. Under different pump flow rates, pump performance curves, radial pressure distribution inside side chamber, and leakage flow rate through balancing holes were examined with different balancing hole diameters. Afterward, the experimental data were compared with the predicted results. The comparisons showed a reasonable consistency. Consequently, according to detailed pump dimensions and operating conditions, the integrated model in current form is recommended for centrifugal pumps, which have low specific speed and are with balancing systems of double wear-rings and balancing holes. This can be used for the prediction of radial pressure distribution inside side chamber and leakage flow rate through balancing holes and can be used both at the design stage and nondesign stage.

Influences of the diameter of the balance hole on the flow characteristics in the hub cavity of the centrifugal pump

The diameter of the impeller balance hole in a centrifugal pump is closely related to axial force. Thus, to select the appropriate diameter of a balance hole is crucial for balancing the axial force of the centrifugal pump. After the validation of the CFD method and the grids independence study, the characteristics of flow in the hub cavity have been analyzed in 4 cases with different diameters of balance holes. The leakage rate of the liquid in the hub cavity of the centrifugal pump is calculated and compared with the test result. According to the research, when no balance hole exists, the distribution of liquid velocity in the core area of the hub cavity exhibits axial symmetry, and the circumferential velocity component is approximately 0.4 times of the impeller’s rotational speed. When the balance hole exists, the distribution of liquid velocity in the hub cavity does not exhibit axial symmetry, and the circumferential velocity component is larger than 0.4 times of the impeller’s rotational speed. The radial leakage velocity on the turbulent boundary layer of the pump cover will increase with the increasing diameter of the balance hole.

The effect of balancing holes on performance of a centrifugal pump: numerical and experimental investigations

In the present work, the effect of balancing hole’s diameter on the performance of a centrifugal pump is experimentally and numerically investigated. Normally, in centrifugal pumps, design of impeller and volute is carried out in such a way that pressure distribution on both sides of the impeller becomes similar, thus minimizing the axial force exerted on the pump impeller and bearings. However, in reality this goal is not totally fulfilled and due to design and manufacturing circumstances and limitations, significant axial forces are generated. As a result excessive load on bearings, noise, vibration and damage to pump performance are experienced. In order to reduce the axial force, several methods are proposed. The simplest method is drilling balancing holes on the impeller eye. In this study, numerical and experimental investigations have been conducted to study the effect of balancing holes on a centrifugal pump performance and axial force reduction. A test rig is designed and equipped with measuring instruments. Experimental data for pump performance including flow, head, power and efficiency were obtained. Next, numerical results were validated against experimental data and a good agreement was observed. It was found that increasing balancing holes diameter up to 5 mm can lead to 5.6% reduction in head at design point. Furthermore, it was found that the diameter of balancing hole affects the pump efficiency and can reduce it by 2.6%. Numerical investigation showed that the diameter of balancing hole can play a prominent role on the axial force reducing it significantly. Extreme care must be taken in selecting the diameter of balancing holes since increasing holes diameter beyond a specific value does not reduce the axial force significantly, but, still aggravates the pump performance undesirably. Therefore, an optimum diameter of 3.5 mm was selected whereby the axial force is reduced up 56% at design point while reduction in performance characteristics are acceptable.

Bifunctional electron transporting layer/perovskite interface linker for highly efficient perovskite solar cells

The electron transporting layer/perovskite interface is crucial to the power conversion efficiency of perovskite solar cell. In this work, we study the effect of bifunctional 4-picolinic acid self-assembled monolayer as electron transporting layer/perovskite interface linker on perovskite crystallinity and electron transporting layer/perovskite interface transfer property for high performance perovskite solar cell. Our result shows that the 4-picolinic acid self-assembled monolayer modified device exhibits the highest efficiency of 18.90% and negligible hysteresis index of 0.03 under illumination of AM 1.5G (100 mW cm−2), compared to that (14.65%) of the unmodified device. It can be concluded that the bifunctional self-assembled monolayer can be grappled with the TiO2, increase grain sizes of MAPbI3, effectively passivate TiO2/perovskite interface, and preferably balance electrons and holes transfer, which significantly improves device performance with negligible hysteresis. Our results also indicate bifunctional self-assembled monolayer is a preferable pathway for fabricating high performance and low hysteresis perovskite solar cells.

Numerical Investigation of the Fluid Flow Characteristics in the Hub Plate Crown of a Centrifugal Pump

Due to the lack of understanding in the flow mechanism of the hub plate crown, the current calculation of the disc friction loss and the axial thrust in the centrifugal pump often uses empirical formulas. Research on the flow characteristics of the hub plate crown is of practical significance. The shroud and hub cavities are respectively studied with regard to tangential and radial velocities at the four different angular positions (0°, 90°, 180°, and 270°) at the four different operational points (0.6Qsp, 0.8Qsp, 1.0Qsp, and 1.2Qsp). Results indicate that at the same operational point, the smaller the volute chamber sectional area is, the higher the tangential velocity of the fluid core zone of the shroud cavity is. Radial leakage flow from the volute to the seal ring at the same operational point appears in 0° and 90° direction; when the flow is large, the tangential and radial velocities of the shroud and hub cavities with the same radius tend to be equal with axial symmetry. The axial leakage flow through the balance holes significantly affects the radial distribution of both tangential and radial velocities of fluid flow in the hub cavity. The numerical calculation results of fluid leakage through the clearance of back sealing ring are in good agreement with the test results. Accordingly, the magnitude of leakage is closely related to the fluid pressure and velocity distribution in the hub plate crown of the centrifugal pump. The analysis of the flow characteristics in the hub plate crown of the centrifugal pump could reveal the cause of the disc friction loss from the mechanism, providing a significant guidance for improving the accuracy of calculation and balancing the axial thrust in the centrifugal pump.

Research on Axial Forces Balance of Stamping-welding Canned Motor Pump

In order to balance axial forces on stamping-welding canned motor pump for safe and reliable operation, the type PBCY80-65-160 pump was selected as the computational model. Combined with various reasons why axial forces of the pump were generated, the theoretical calculation and methods of numerical simulation were chosen to analyze the size, directions and rules of axial force. At the same time, the distribution and trend of the axial force components of the impeller under different working conditions are studied whether there is the balance hole or not. The results show that, in the theoretical calculation and numerical simulation calculation, the gap and internal impact loss of the internal flow field of axial forces were neglected when the internal flow of the motor was seen as an ideal flow through the resistant elements. Hence, it could not fully represent the internal pressure distribution of the pump, which caused the calculated data a little larger than simulated data. Also, the method of combining the balance hole and impeller rear seal ring could effectively balance the axial force and extend the service life of stamping-welding canned motor pump.

Deep Blue Phosphorescent Organic Light-Emitting Diodes with CIEy Value of 0.11 and External Quantum Efficiency up to 22.5.

Organic light-emitting diodes (OLEDs) based on red and green phosphorescent iridium complexes are successfully commercialized in displays and solid-state lighting. However, blue ones still remain a challenge on account of their relatively dissatisfactory Commission International de L'Eclairage (CIE) coordinates and low efficiency. After analyzing the reported blue iridium complexes in the literature, a new deep-blue-emitting iridium complex with improved photoluminescence quantum yield is designed and synthesized. By rational screening host materials showing high triplet energy level in neat film as well as the OLED architecture to balance electron and hole recombination, highly efficient deep-blue-emission OLEDs with a CIE at (0.15, 0.11) and maximum external quantum efficiency (EQE) up to 22.5% are demonstrated. Based on the transition dipole moment vector measurement with a variable-angle spectroscopic ellipsometry method, the ultrahigh EQE is assigned to a preferred horizontal dipole orientation of the iridium complex in doped film, which is beneficial for light extraction from the OLEDs.

Numerical investigations on effect of wear-ring clearance on performance of a submersible well pump

A typical submersible well pump was investigated in this article. The whole flow field of submersible well pump was numerically simulated by computational fluid dynamics software. The influence of clearance of wear-rings on the external characteristic and internal flow field was analyzed through comparing the calculation results with experimental results. The result of the numerical simulation shows that changing clearance of front wear-ring has a greater impact on pump performances than changing clearance of back wear-ring, and the head and efficiency of pump decrease with the increase in the size of clearance. Especially when the size of clearance is larger than 0.5 mm, decreasing becomes more obvious. When the front and back wear-ring size of the clearance comes to 1.0 mm, the efficiency decreases from the highest point of 75.31% to 65.44% at rated flow, and the head of pump decreases about 3.5 m. When the size of clearance is 0.2 mm, reverse-flow will appear in the front shroud cavity of the impeller, and leakage from back wear-ring through the balance hole into the impeller, which has a little influence on the flow field of the impeller inlet.

Experimental and CFD investigation of a multistage centrifugal pump including leakages and balance holes

Experimental and CFD investigation of a multistage centrifugal pump including leakages and balance holes

The Effect of Viscosity on Performance of a Low Specific Speed Centrifugal Pump

Centrifugal pump delivery head and flow rate drop effectively during the pumping of viscous fluids. Several methods and correlations have been developed to predict reduction rate in centrifugal pump performance when handling viscous fluids, but their results are not in very good agreement with each other. In this study, a common industrial low specific speed pump, which is extensively used in different applications, is studied. The entire pump, including impeller, volute, pipes, front and rear sidewall gaps, and balance holes, is simulated in Computational Fluid Dynamics and 3D full Navier Stokes equations are solved. CFD results are compared with experimental data such as pump performance curves, static pressure in casing, and disk friction loss. Dimensionless angular velocity and leakage rate are investigated in sidewall gap and efficiency variation due to viscosity is studied. The results demonstrate that the behavior of the fluid in sidewall gap is strictly sensitive to viscosity. Increasing viscosity improves the volumetric efficiency by reducing internal leakage through wear rings and balance holes, causing, however, a significant fall in the disk and overall efficiency. Results lead to some recommendations for designing centrifugal pumps which may be used in transferring viscous fluids.