Mixed Pump Research Articles

STORE TIME OF PERMETHRIN IN THE TRUCK-MOUNTED ULV SPRAY TANKS CAUSED DEGRADATION IN THE CONCENTRATIONS

Permethrin is one of the few active ingredients found in commercial adulticides available for adult mosquito control. The permethrin concentrations in the adulticide Aqualuer 20-20 formulation stored in the 21 ultra-lowvolume (ULV) truck-mounted spray tanks after 4, 6, and 8 months were sampled and analyzed by gas chromatography mass spectroscopy (GC-MS). Additionally, the permethrin stored in a mixing pump and a stock container were sampled and analyzed by GC-MS. The results showed that 46%, 42%, and 82%, permethrin in Aqualuer 20-20 were decomposed in the ULV spray tanks at 4--, 6--, and 8 months-storage, respectively. For the mixing pump, 17% of the permethrin in the Aqualuer 20-20 were decomposed. The storage time of permethrin in ULV spray tanks resulted in the degradation in the concentrations of permethrin after more 4 months, compared with the concentration in stock control. The degradation of permethrin in ULV spray tanks may directly impact the control efficacy for adult mosquitoes and result in an economic loss.

Enhancing biological removal of nitrogen from wastewater in activated sludge process

ABSTRACT The removal of total nitrogen from wastewater has become a worldwide emerging concern because the compounds of nitrogen, ammonium, nitrite, also nitrate are toxic to aquatic species and causes eutrophication in natural water environments; although activated sludge technology is old, but until now it is effective in the removal of nitrogen compounds. To enhance the removal of nitrogen compounds, a modified process including the usage of internal mixed liquor recycling pump (IMLR), with variable rates starting gradually from one to fifth of influent flow. A Pilot plant consists of three tanks, the first and the second tanks are rectangular, and the third is circular with a conical bottom which acts as a final sedimentation tank. The experiments divided into four phases; phase (1) consists of (A.T), anoxic T. and finally, sedimentation tank with using (IMLLR) rates from (1-4) influent flow, phase (2) as phase (1) but without using (IMLR), phase (3) consists of anoxic tank, (A.T) and final sedimentation tank with using (IMLLR) rates from (1-5) influent flow, finally phase (4) as phase (3) but without using (IMLLR), the average DO in (A.T) about 2.5mg/l, the temperature ranged from (18 – 21), PH ranged from (6.5 – 8). Total nitrogen removal was 61.5% in phase one, 27% in phase two, 64.5% in phase three, and 27% in phase four. The most effective removal of nitrogen in phase (3), with rateQIMLR = 2QINFachieve 64.5% of total nitrogen removal, then in phase (1) with rate QIMLR=3QINF. Achieve 62.39% of total nitrogen removal.

Research and application of solid-liquid dual material sand control technology

A new type of solid-liquid dual material artificial shaft wall sand control technology was developed for some special Wells (such as sidewall drilling, causing damage repair well, etc.) with low construction pressure and unsuitable mechanical sand control technology in dagang oilfield. The process is use solid and liquid mixing resin solution pump into the formation to form a complete artificial borehole wall, solid material filling the cavity of formation, act as proppant. Liquid as resin bonding agent, used for cementing solid material and formation of particles sand. In addition to evaluate the solid liquid double material of various performance indicators. Field test shows that this technology can be consolidated at well temperature, and the compressive strength can reach 8Mp and permeability can reach 1 μ m2 after consolidation. This technology has been successfully applied to sand control in 5 Wells in dagang oilfield and achieved good sand control effect.

Development and Validation of Reverse Phase High Performance Liquid Chromatography Method for the Estimation of Canagliflozin in Bulk and its Pharmaceutical Formulation

Objectives: Study was initiated to develop simple, specific, precise, selective and accurate reverse phase high performance liquid chromatographic method for the estimation of canagliflozin in bulk and pharmaceutical formulation. Sodium glucose co-transporter 2 inhibitors for glycemic control activity are categorized under type 2 classification under antidiabetic drugs. Methods: Development of method was initiated by determining solubility in acetonitrile and detection at 290nm for the drug canagliflozin. The chromatographic separation was achieved on Shimadzu LC-20AT (Shimadzu Corporation, Japan). The system for chromatographic analysis was equipped with binary low-pressure mixing pump (LC-20AT) and an UV-detector (Shimadzu SPD-20A), a Princeton C18 column (250 x 4.6mm; 5μm), 20 μl sample loop volume. Results: Concurrent results were obtained in the developed and optimized method. Linearity was found to be 0.998 over the range of 0.098μg/ml– 50μg/ml. Sensitivity of the developed method was 98ng/ml. The mobile phase optimized for method was composed of acetonitrile: water (50:50, %v/v) at a flow rate of 1.0 ml/min. Canagliflozin was detected at 290 nm with retention time of 7.3±0.2 min in concurrent manner. Quantitative assay of the marketed formulation had been carried out and the percentage of drug was determined in the limits of specification. Percentage recovery was found between 98.9 to 99.8%, Accuracy and precision studies performed had achieved metrics under the specified limits. The validation was successfully performed according to ICH guideline Q2R1. Conclusion: The developed method can be employed for the estimation of canagliflozin in pharmaceutical formulation and also for a bioequivalence study to evaluate its applicability further. Key words: Canagliflozin, Method development, RP-HPLC, SGLT-2 Inhibitor, Validation.

Remote Sensing and Argo Float Observations Reveal Physical Processes Initiating a Winter-Spring Phytoplankton Bloom South of the Kuroshio Current Near Shikoku

BIO-Argo float (chlorophyll a (Chl-a), temperature, and salinity profiles) and remote sensing data (Chl-a, photosynthetic available radiation (PAR), and wind) located south of the Kuroshio current near Shikoku from September 2018 to May 2019 were used to study phytoplankton bloom and their mechanisms of development in open oceans. Results show that higher (lower) Chl-a concentrations are correlated with a deeper (shallower) mixed layer (RPearson = 0.77, Rcrit = 0.12 (alpha = 0.05, n = 263)) compared to the average of Chl-a and mixed layer depth (0.13 mg/m3 and 105 m). The average net accumulation rates (r) of phytoplankton were close to 0.08 d−1. An increasing r corresponds to a gradually increasing surface Chl-a (S (Chl-a): 0–20 m average Chl-a) and integrated Chl-a inventory (I (Chl-a): integrated Chl-a from surface to euphotic depth). These phenomena indicate that the mechanism of winter-spring phytoplankton blooms is consistent with the dilution-recoupling hypotheses (DRH). During the bloom formation, winter deep mixing and eddy-wind Ekman pumping are enhanced by a strong winter monsoon. The enhancement may disturb predator–prey interactions and dilute zooplankton in deep mixed layers. Moreover, winter deep mixing and eddy-wind Ekman pumping can cause the nutrients to be transported into the euphotic layer, which can promote the growth of phytoplankton and increase grazing. During the bloom extinction, the stratification strengthens and the intensity of light increases; this increases grazing and nutrient consumption, and decreases the phytoplankton bloom significantly (S (Chl-a) and I (Chl-a) increase by 0.3 mg/m3 and 27 mg/m2, respectively). The output from a biogeochemistry model shows that nutrients are consistent with the temporal distribution of S (Chl-a) and I (Chl-a). Our results suggest that physical processes (deep winter mixing and eddy-wind Ekman pumping) under the DHR framework are critical factors for winter-spring blooms in open oceans with an anticyclone eddy.

Time delay in the mixed pump two-stage cascade erbium-doped fiber

This thesis mainly focuses on the study of slow light under the mixed pump two-stage cascade erbium-doped fiber. Compared with previous studies, we adopt different pump optical fiber connections in structure and this structure can produce larger time delay. We specifically explore the relationship between modulation frequency, group velocity and time delay under different pump ratios. We find that the time delay gradually increases and the group velocity gradually decreases as the pump ratio M (M = P1480:P980) decreases. We also study length ratio and time delay at different frequencies. With the increase of length ratio N (N = L1:L2, L1 and L2 represent the length of the first and second cascaded optical fibers, respectively), the time delay all increases at different frequencies, and the time delay changes significantly at low frequencies.

Effects of Tropical Cyclones on Sea Surface Salinity in the Bay of Bengal Based on SMAP and Argo Data

This paper uses the Argo sea surface salinity (SSSArgo) before and after the passage of 25 tropical cyclones (TCs) in the Bay of Bengal from 2015 to 2019 to evaluate the sea surface salinity (SSS) of the Soil Moisture Active Passive (SMAP) remote sensing satellite (SSSSMAP). First, SSSArgo data were used to evaluate the accuracy of the 8-day SMAP SSS data, and the correlations and biases between SSSSMAP and SSSArgo were calculated. The results show good correlations between SSSSMAP and SSSArgo before and after TCs (before: SSSSMAP = 1.09SSSArgo−3.08 (R2 = 0.69); after: SSSSMAP = 1.11SSSArgo−3.61 (R2 = 0.65)). A stronger negative bias (−0.23) and larger root-mean-square error (RMSE, 0.95) between the SSSSMAP and SSSArgo were observed before the passage of 25 TCs, which were compared to the bias (−0.13) and RMSE (0.75) after the passage of 25 TCs. Then, two specific TCs were selected from 25 TCs to analyze the impact of TCs on the SSS. The results show the significant SSS increase up to the maximum 5.92 psu after TC Kyant (2016), which was mainly owing to vertical mixing and strong Ekman pumping caused by TC and high-salinity waters in the deep layer that were transported to the sea surface. The SSSSMAP agreed well with SSSArgo in both coastal and offshore waters before and after TC Roanu (2016) and TC Kyant (2016) in the Bay of Bengal.

Acoustic characteristics of water-jet propulsion with screw mixed-flow pump under quasi-submerged state

As a key point of the stealth performance, acoustic characteristics of a screw mixed water-jet pump were investigated under the quasi-submerged state. The relationships between thrust and rotation speed of screw-mixed pump, drag, and submerged velocity of water-jet propulsion were obtained from the flume tests and numerical simulation. Based on the results of the unsteady flow field calculation with the detached eddy simulation (DES), the sound radiation fields of the screw mixed water-jet propulsion at different rotation speeds were investigated by the finite element method (FEM) coupled with the vibro-acoustic method. The flow-induced dipole source noise of every flow passage component increases with the increasing of rotation speed. The mathematical relations of the flow-induced noise at impeller between different rotation speeds were established. The maximum sound pressure level (SPL) of every flow passage component appears at the impeller blade-passing frequency (BPF). In the medium-high frequency domain, dipole source induced noise from the impeller is the main external noise field during the propulsion process. At the first-order BPF, the ratio of SPL of the impeller is equal to the 0.5 power of the rotation speed in the phase of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]. At the sixth-order BPF, the ratio of SPL of the impeller is directly proportional to the reciprocal power of rotation speed ratio in the phase of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text].

Designing nano-aluminum laden fuel pump for aviation applications

In view of the fact that traditional liquid propellants cannot meet the design requirements of large-thrust flight vehicle, it has become a new trend to add nano-metal powder to liquid propellants to greatly increase density and specific impulse. In order to achieve the variable flow-rate and variable-proportion transportation of aviation fuel with nano-aluminum, a new type of solid-liquid mixing pumping system is designed, including powder conveying device, stirring device, pump and corresponding drive and transmission system. For the purpose of avoiding the frictional contact between the rotors, which will bring potential hazard to nano-aluminum powder, a non-contact twin-screw pump with synchronous gears is designed. Among them, based on the considerations of flow pulsation, volumetric efficiency and manufacturing difficulty, cycloid profile is adopted for screw rotors. After completing the functional design, geometric parameter design, structural design, 3D modeling, prototype manufacturing and preliminary performance estimation of the mixing pumping system, the performance of the screw feeder, agitator, screw pump was tested through experiments to meet the expected design requirements. The designed agitator can achieve sufficient mixing at 500 rpm in less than 10 s. Even though 50-micron clearances are designed with a relatively small rotor diameter, the volumetric efficiency of screw pump can reach above 50% when the discharge pressure is below 450 kPa and the flow rate is set as 10 L/min, the power of the screw pump is less than 700 W. This design facilitates the rapid real-time preparation of metallized propellants and provides a reference for further improving the design and control methods of nanoparticle two-phase flow pumping.

Experimental Investigation on a Slurry Pump at Different Operating Parameters

Study on slurry pump performance has attracted much interest in many engineering fields. When pumps are required to handle slurries. The pump head and efficiency are mainly affected by the solid size, solid concentration and solid density. Centrifugal slurry pumps are benign used extensively for pipeline transportation systems and phosphate extraction industry because of their capabilities to economically convey large size abrasive solids in bulk. There is a lack of information about the effect of slurry on the performance characteristics of conventional centrifugal pumps when working without and with cavitation. A test rig with a testing centrifugal pump was constructed. The suction pipe between the mixing tank and pump inlet was designed to avoid solid deposition in suction pipe and to keep the pressure loss between the sump and the pump as low as possible. The rig was designed so that the flow rates, suction pressure, rotational speed, and solid concentration could be varied independently. The results showed that the head generating capability and pump efficiency decrease, also the power consumption increases with increasing solid concentration, consequently the head and efficiency of the pump with NPSH decreases with increasing the solids concentration and particle size, and cavitation inception accelerates with increase the solid concentration.

Transient Characteristics of Water-Jet Propulsion with a Screw Mixed Pump during the Startup Process

In order to investigate the transient hydrodynamic characteristics of water-jet propulsion with a screw mixed pump during the startup period and to overcome the difficulties in measuring the transient process parameters over a very short period of time, a method based on a flume experiment combined with computational fluid dynamics (CFD) is proposed. The thrust and torque of the pump-jet propulsion according to mooring status at different rotational speeds were measured by the test, which provided a group of data for the boundary and initial conditions of the numerical calculation of the user-defined function (UDF). Consecutive changes in the parameters of the water-jet propulsion dynamics can be captured from the numerical simulation of the startup process with the UDF. Thus, the transient hydrodynamic characteristics of water-jet propulsion according to time or rotation speed were obtained. The results show that the relationship between the thrust or torque of the water-jet propeller and pump rotational speed is close to the quadratic functions. The energy characteristic parameters of screw mixed water-jet pump, such as the flow rate, head, shaft power, and efficiency, rapidly increase and decrease and then remain relatively stable.

Numerical simulation and performance analysis of mixed flow blood pump

The high rotational speed of the axial flow blood pump and flow separation of the centrifugal blood pump are the main causes for blood damage in blood pump. The mixed flow blood pump can effectively alleviate the high rotational speed and the flow separation. Based on this, the purpose of this study is to explore the performance of the mixed blood pump with a closed impeller. A mixed flow blood pump with closed impeller was studied by numerical simulation in this paper. The flow field characteristics and the pressure distribution of this type of blood pump were analyzed. The hydraulic performance of the blood pump and the possible damages to red blood cells were also discussed. At last, pump performance was compared with the mixed flow blood pump with semi-open impeller. The results show that the mixed flow blood pump with close impeller studied in this paper can operate safely and efficiently with a good performance. The pump can reach the pressure head of 100 mmHg at 5 L/min mass flow rate. Flow in the blood pump is uniform and no obvious separation or vortex occurs. Pressure distribution in and on the impeller is uniform and reasonable, which can effectively avoid the thrombosis of blood. The average mean value of hemolysis index is 4.99 × 10 -4. The pump has a good biocompatibility. Compared with the mixed flow blood pump with semi-open impeller, the mixed flow blood pump with closed impeller has higher head and efficiency, a smaller mean value of hemolysis index prediction, a better hydraulic performance and the ability to avoid blood damage. The results of this study may provide a basis for the performance evaluation of the closed impeller mixed flow blood pump.

Analysis of reliable and safe heat supply of residential buildings using waste water after DHW heat exchangers

A modified scheme of heat supply of residential buildings with dependent connection to external heating networks, providing reliability of heat supply and the necessary comfort in the premises due to mixing of waste water after domestic hot water (DHW) heaters at an outdoor temperature exceeding the temperature graph break point, is considered. A review of possible ways to improve the reliability and safety of heat supply, improve the efficiency of heat sources, as well as regulate heat supply and prevent overheating near the beginning and end of the heating period is carried out. Calculations are carried out to determine the actual amplitude of temperature fluctuations in residential buildings with a daily variation in water flow rate after hot water heaters in the conditions of application of the considered scheme of connecting buildings to the heating network. Analysis of obtained results is given, and conclusions are drawn concerning the expediency of application of the above scheme. It is established that, given the thermal stability of enclosing structures, the daily flow rate fluctuations have no significant effect on the stability of the temperature regime of residential buildings and the comfort of their indoor microclimate at high outdoor air temperatures. It is shown that, in terms of reliability of heat supply of the main group of residential buildings and ensuring the life safety, the offered scheme is not inferior to the standard two-stage scheme of connection of DHW heat exchangers, with restriction of the total consumption of network water and with dependent control of heat supply to DHW, heating and ventilation. It is noted that in the scheme under consideration, the daily average consumption of network water to domestic hot water heaters over most of the heating period is higher or equal to the estimated consumption for heating and ventilation systems, which minimizes the time of using the mixing pump and provides for the regulation of heat supply only at the expense of the wastewater circuit.

Effect of Diversion Cavity Geometry on the Performance of Gas-Liquid Two-Phase Mixed Transport Pump

For the purpose of improving the transport capability of the mixed transport pump, a new self-made three-stage deep-sea multiphase pump was taken as the research object. Based on the Euler-Euler heterogeneous flow model, liquid (water) and gas (air) are used as the mixed media to study the external characteristics and internal flow identities of the mixed pump under different gas volume fraction (GVF) conditions. According to the simulation results, a local optimal design scheme of the diversion cavity in the dynamic and static connection section is proposed. The numerical results before and after the optimization are compared and analyzed to explore the effect of the diversion cavity optimization on the performance, blade load and internal flow identities of the pump. The results show that the head and efficiency are obviously improved when the inner wall of the diversion cavity is reduced by 4 mm along the radial direction. After optimization, under the condition of 10% gas content, the head and efficiency is increased by 3.73% and 2.91% respectively. Meanwhile, the hydraulic losses of the diversion cavity and diffuser are reduced by 9.11% and 4.32% respectively. The gas distribution in the impeller is improved obviously and the phenomenon of a large amount of gas phase accumulation is eliminated in the channel. In addition, the abnormal pressure load on the blade surface is eliminated and the turbulent flow energy intensity is reduced. The average turbulent kinetic energy ( T K ) at i = 0.51 of the first stage impeller passage is reduced by 35%. Finally, the reliability of the numerical method is verified by the experimental results. To sum up, the performance and internal flow identities of the optimized mixed transport pump are improved, which verifies the availability and applicability of the optimization results. This provides a reference for the research and design of a multiphase mixed transport pump in the future.

Computational Investigation of Flow Over Nose Cap of Closed Impeller of Mixed Flow Centrifugal Pump

Abstract Flow turbulence near the suction region and over the eye of a closed impeller may be troublesome during the operation of a centrifugal pump. This article aims to bring out a methodology for minimization of flow turbulence and for providing guidance to suction flow by modifying the surface design of the lock nut into a nose cap of optimized profile. The effects of this modification on the performance parameters of closed impeller of a low head, mixed flow centrifugal pump are presented here. Based on geometric constraints and impeller eye diameter, nose caps of 65 mm diameter and various nose tip angles (15–90 deg) and lengths (50–80 mm) are evaluated. Parametric studies are carried out via computational fluid dynamics (CFD) analyses using ansysfluent 17.0 as well as experimental investigations to investigate the effects on head, energy consumption, and overall efficiency for flowrates in the range of 0.25–1.5 times the flowrate at best efficiency point (BEP). The estimates of head developed obtained using CFD and experimental studies match within 4.23%. Results confirm improvement in performance parameters like head and overall efficiency due to the reduction of losses and better flow guidance in the suction region. The performance improvement is greatest for the nose cap of 900 tip angle and 50 mm length at all flowrates.

Proposal of Ring Structure to Reduce Expansion Diameter for Peristaltic Mixing Pump

Proposal of Ring Structure to Reduce Expansion Diameter for Peristaltic Mixing Pump

Technologies for mathematical and computer modeling to automate the process of operational states development for heat supply systems

This article proposes the new technology for development of operational states for HSS of arbitrary structure and dimension. Technology is based on multilevel modeling and a new method for adjustment calculation of thermal hydraulic states. It is implemented in the information and computer complex «ANGARA-HN». Technology includes checking the permissibility of states, calculating the throttling devices on the network and inputs of consumers’ buildings. It allows calculating large systems with intermediate stages of regulation, developing adjustment measures to improve the quality of heat supply and consumer provision, reducing circulation flow rates and pressure in networks. The development of modeling methods is carried out in the following directions: taking into account the new composition of equipment, including mixing pumping stations; development of nontraditional methods of calculation, such as object-oriented modeling; development of tasks of hierarchical optimization and identification of state parameters, as task of rising for model adequacy; development of task for finding of sectioning variants for multi-circuit heat network with several sources. The application of methodological and software developments makes it possible to obtain both an economic and a social effect by identifying and realizing of the energy saving potential, improving the quality and reliability.

DESIGN AND EVALUATION OF A HELICAL-TUBULAR PHOTOBIOREACTOR FOR MICROALGAE PRODUCTION

Photosynthetic microalgae are important bioresource for producing desired and environmentally safe products including biodiesel production as third generation biofuels. Photobioreactor play important role in this process. Designing and manufacture the bioreactor for photocatalysis is still challenging at present time due to the important factors that must be closely considered with regard to light requirements. The aim of the present study was to design and evaluate a helical-tubular photobioreactor for algae production. The design considerations included light intensity controller circuit, surface-to-volume ratio, power required of both air pump and mixing pump to reach up the optimum operating parameters. Experiments were conducted to optimize light intensity and light/dark duration cycle. The photobioreactor performance was evaluated in terms of biomass productivity, lipid productivity, carbon capture efficiency and energy balance of algae production system. The experimental results reveal that the helical-tubular photobioreactor is recommended to be used under light intensity of 8 kLux and light/dark duration cycle of 18:6 h to obtain the highest biomass productivity of 1.80 kg.day-1 and lipid productivity 432 g.day-1 with carbon capture efficiency 87%. The manufactured photobioreactor is capable of produce 4.74 kWday which is equivalent to 4.39 kWday of net energy output.

Numerical simulation of buckling and asymmetric behavior of flexible filament using temporal second-order immersed boundary method

PurposeThe purpose of this paper is to perform two-dimensional numerical simulation involving fluid-structure interaction of flexible filament. The filament is tethered to the bottom of a rectangular channel with oscillating fluid flow inlet conditions at low Reynolds number. The simulations are performed using a temporal second-order finite volume-based immersed boundary method (IBM). Further, to understand the relation between different aspect ratios i.e. ratio of filament length to channel height (Len/H) and fixed channel geometry ratio, i.e. ratio of channel height to channel length (H/Lc) on mixing and pumping capabilities.Design/methodology/approachThe discretization of governing continuity and Navier–Stokes equation is done by finite-volume method on a staggered Cartesian grid. SIMPLE algorithm is used to solve fluid velocity and pressure terms. Two cases of oscillatory flow conditions are used with the flexible filament tethered at the center of bottom channel wall. The first case is sinusoidal oscillatory flow with phase shift (SOFPS) and second case is sinusoidal oscillatory flow without phase shift (SOF). The simulation results are validated with filament dynamics studies of previous researchers. Further, parametric analysis is carried to study the effect of filament length (aspect ratio), filament bending rigidity and Reynolds number on the complex deformation and behavior of flexible filament interacting with nearby oscillating fluid motion.FindingsIt is found that selection of right filament length and bending rigidity is crucial for fluid mixing scenarios. The phase shift in fluid motion is also found to critically effect filament displacement dynamics, especially for rigid filaments. Aspect ratio, suitable for mixing applications is dependent on channel geometry ratio. Symmetric deformation is observed for filaments subjected to SOFPS condition irrespective of bending rigidity, whereas medium and low rigidity filaments placed in SOF condition show severe asymmetric behavior. Two key findings of this study are: symmetric filament conformity without appreciable bending produces sweeping motion in fluid flow, which is highly suited for mixing application; and asymmetric behavior shown by the filament depicts antiplectic metachronism commonly found in beating cilia. As a result, it is possible to pin point the type of fluid motion governing fluid mixing and fluid pumping. The developed computational model can, thus, successfully demonstrate filament-fluid interaction for a wide variety of similar problems.Originality/valueThe present study uses a temporal second-order finite volume-based IBM to examine flexible filament dynamics for various applications such as fluid mixing. Also, it highlights the relationship between channel geometry ratio and filament aspect ratio and its effect on filament sweep patterns. The study further reports the effect of filament displacement dynamics with or without phase shift for inlet oscillating fluid flow condition.

Effect of Reflux Hole on the Transient Flow Characteristics of the Self-Priming Sewage Centrifugal Pump

The reflux hole has a large effect on the performance of self-priming centrifugal pumps. In order to study the effects of the reflux hole on the performance and transient flow characteristics of the self-priming centrifugal pump, four different areas of the reflux hole inside an external mixed self-priming pump were proposed. The 3D transient flow was numerically simulated under different operating conditions for the investigated pump. The differential pressure, reflux quantity and transient flow characteristics near the reflux hole were analysed, and then the effects of the reflux hole area on the pressure fluctuation characteristics and performance of the pump were further researched. The results show that the differential pressure and reflux quantity is zero around the best-efficiency point. The vorticity magnitude near the exit of the reflux hole is significant, and the unsymmetrical flow structures represent periodic motion over time in the cross-section. The pressure fluctuation intensities of monitoring points P2-P5 upstream of the reflux hole were generally larger than others and decreased with a decrease in reflux hole area. With a decrease of the reflux hole area, the performance of the pump improved to some extent.