Pump Impeller Research Articles

Numerical Investigation of Flow Characteristics in a Centrifugal Pump Impeller with Sinusoidal Flow Rates of Different Oscillation Amplitudes

This study describes the large eddy simulations of a centrifugal pump impeller considering a sinusoidal flow rate and a constant rotation speed. Five different oscillation amplitudes of flow rate (A = 0.1Qd, 0.15Qd, 0.2Qd, 0.25Qd, and 0.3Qd, Qd indicates the design flow rate) are selected to determine the influence of oscillation amplitude on the internal flow characteristics. The simulation results show that, with increasing oscillation amplitude, the alternating stall phenomenon weakens or even disappears during the dropping stage, whereas the opposite trend is observed during the rising stage. The total mean normal vorticity is insensitive to changes in the oscillation amplitude. Moreover, the difference in pressure fluctuations between adjacent passages decreases with increasing oscillation amplitude. The first and second dominant frequencies of the pressure fluctuations are mainly affected by the oscillation amplitude in the non-stall passage. The internal flow exhibits a clear hysteresis effect, and the lag time of the head increases with the oscillation amplitude. Additionally, the average head is approximately 2.38 m, regardless of the oscillation amplitude.

Lagrangian wavelet analysis of turbulence modulation in particle–liquid mixing flows

A new experimental–theoretical framework has been developed to investigate turbulence and turbulence modulation in a two-phase multicomponent particle–liquid flow in a mechanically agitated vessel. A discrete wavelet transform is used to decompose long-term three-dimensional Lagrangian trajectories of flow phases, acquired by a technique of positron emission particle tracking, into their deterministic and stochastic sub-trajectories. The sub-trajectories are then used to construct the different-scale local velocity and turbulent kinetic energy (TKE) fields of the two-phase flow. The effects of the particle size and size distribution mode (mono, binary, and polydisperse), particle concentration, impeller agitation speed, and pumping mode on turbulence intensity are investigated. Amongst these factors, the particle size, impeller pumping mode, and particle size distribution mode have a significant impact on liquid turbulence. The presence of large particles enhances liquid turbulence and broadens the region in the vessel characterized by high local TKE values. Results also show that a down-pumping pitched-blade turbine generates significantly greater local maxima in the TKE field, which tend to be more localized in the impeller discharge stream. In addition, binary or polydisperse suspensions containing higher fractions of larger particles produce higher turbulence intensities in the carrier phase. The detailed information obtained on the turbulence intensity is crucial for better understanding of the dynamics of particle–liquid flows inside mixing vessels to aid the rational design of these units.

Wear Evaluation Results from a Practical Trial of Laser-Coated Pump Parts in the Mineral Processing Industry

Slurry pumps in the mineral processing industry are parts that erode very quickly. Erosion is predominantly caused by abrasion from fine particles of the ores. Because of this, the erosion process takes place on impeller blades and cover plates that directly contact the slurry. This paper evaluates the wear of laser-coated pump parts in the mineral processing industry. Building upon previous research conducted by the authors, we aimed to determine the best laser coating powder system to extend the useful life of specific laser-coated pump parts. Four blades of a slurry pump impeller were each treated with a different laser powder coating, then assessed for wear after 19 days of operation. During this real-life trial, each powder system performed differently. The laser coatings were worn away in two general directions. The first direction was along with the blade pattern, and the second wear direction was from the center of the impeller to the direct blade surface. Partial surface cladding led the material to wear away faster than complete surface cladding due to perpendicular force. Based on these results, in order to use material hardness and wear resistance to higher efficiency, we need to cover all surfaces with different thicknesses depending on the wear rate of the part. This study also showed that Powder System 2 was the most suitable coating material for this type of slurry pump.

A Systematic Investigation on the Damage Characteristics of Fish in Axial Flow Pumps

An axial flow pump is a kind of high-specific revolution vane pump that has the characteristics of large flow, low head, and high efficiency. Due to its unique properties, it is widely used in large water diversion projects, such as the South-to-North Water Diversion Project. However, during the operation of the pump, some fish enter the axial flow pump together with the water flow through the screen before the entrance of the pump station. Consequently, some fish are inevitably damaged or even die in the process of traversing through the pump. Meanwhile, the decay of dead fish directly affects the quality of water, hence, posing serious ecological pollution and destabilizing the ecological balance. Therefore, understanding the dynamics of axial flow pumps in relation to fish species in water bodies for biodiversity and ecosystem services remain vital for nature conservation. In this paper, the impact of damage of the model pump on fish is exhaustively investigated according to the theory of blade impact model, impact probability, impact mortality, and mortality distribution under different working conditions. Through the simulation of the flow state inside the impeller, the areas that are lower than the pressure threshold, higher than the shear strain rate threshold, and higher than the pressure gradient threshold in the impeller at different flow rates are analyzed. Based on the unsteady results, the volume fluctuation characteristics of the three damage mechanisms in the impeller are analyzed. Furthermore, Powell vortex acoustic equation is used to locate the high noise source region of the axial flow pump. After extensive comparison of the dipole sound source intensity, it is revealed that the dipole noise source in the impeller and guide vane is dominant. In conclusion, this study provides a holistic perspective for evaluating fish damage caused by the flow in the impeller of the axial flow pump. Furthermore, it will proffer significant references to the construction of ecological water conservancy projects.

Development and assessment of a particle tracking velocimetry (PTV) measurement technique for the experimental investigation of oil drops behaviour in dispersed oil–water two-phase flow within a centrifugal pump impeller

The objective of the current work is to present the development of a Particle Tracking Velocimetry (PTV) algorithm for the analysis of oil drops behaviour in two-phase oil–water dispersions within a centrifugal pump impeller. The drop tracking was realized through high-speed camera images in a transparent pump prototype, which enabled the visualization of oil drops dispersed in water in all the impeller channels. The PTV algorithm is based on deep-learning techniques for image processing. The drops are detected by a combined U-Net and Convolutional Neural Network (CNN) method, with the former generating a binary image and the latter detecting valid oil drop contours. After detection, the Labelled Object Velocimetry (LOV) is adopted to calculate the instantaneous oil drop velocity. A synthetic image generator based on a Generative Adversarial Network (GAN) is then developed to assess the results from the U-Net, CNN, and LOV models. Additional validation studies are performed using the results from Perissinotto et al. (2019a). The results reveal that the presented deep-learning PTV algorithm is robust and provides consistent and reliable data for the dispersed oil phase in two-phase oil–water flows.

Understanding of energy conversion and losses in a centrifugal pump impeller

As energy consumption saving becomes an urgent need in the contemporary world, the demand for improving pump energy efficiency is attracting increasing attention. This paper presents an extensive numerical investigation of energy transfer and dissipation in a centrifugal pump impeller, with the aim of elucidating the underlying mechanisms of loss and revealing the energy conversion processes in the impeller. The turbulent flows of the impeller are studied using very large eddy simulation under nominal flow rate and two part-load conditions. A new loss assessment model, which quantifies total loss by mean-flow viscous loss and turbulent loss, is proposed based on a detailed analysis of the budgets of the mean-flow kinetic energy and turbulent kinetic energy (TKE). Results show that the turbulent loss supplied by TKE production is the main part of the total loss in all investigated cases. The mean-flow viscous dissipation related loss decreases significantly under part-load conditions. Energy conversion processes and their relevance to the flow structures have been revealed by investigating the spatial distributions of TKE production, mean-flow viscous dissipation and turbulent dissipation. Finally, the contributions of each subcomponent of the TKE production term to TKE production have been explored.

Experimental study on unbalanced response characteristics of the impeller of mixed transport pump in deep-sea mining

The mixed transport pump is the core equipment of hydraulic lifting deep-sea mining system. The conveying medium is a solid-liquid two-phase flow. The impeller is prone to mass eccentricity due to the wear of ore particles. Therefore, it is great significance to study the unbalanced response characteristics of the impeller of the mixed transport pump. The unbalanced test of the impeller of the pump was carried out in a closed-cycle test bench. The unbalanced response characteristics were proved by data analysis method. The results indicated the hydraulic performance of the pump with the rotor system balance quality grade in G2.5 (scheme 2) was better than that of the balance quality grade in G6.3 (scheme 1). The pump efficiency was increased by 3.12%. When the medium was a solid-liquid two-phase flow, the amplitude of the vibration acceleration level ( La) of the pump outlet flange in scheme 2 was generally lower in the low frequency range than that in scheme 1. The periodic variation law of the pump outlet pressure coefficient ( Cp) was obvious. With the increase in the volume fraction of ore particle, the amplitude of the main frequency of the La in scheme 1 gradually was increased, which were 91.16, 97.11, and 102.57 dB, respectively. The main frequency amplitude of scheme 2 was basically unchanged. The main frequency amplitude change rates of the two schemes were −1.72%, −7.58%, and −12.78%, respectively. With the increase in the running time, the periodic change trend of the time-domain signal of the pump outlet flange vibration acceleration in scheme 1 was more obvious than that in scheme 2. The axial passing frequency amplitude was gradually increased. The pump efficiency was gradually decreased. Finally, the sliding bearing B2 was severely worn and the service life was greatly reduced.

Design Studies Using Corrosive and Non-Corrosive Materials to Improve on Reliability and Efficiency of an Impeller of a Centrifugal Pump

Design Studies using Corrosive and Non-corrosive Materials to Improve on Reliability and Efficiency of an Impeller of a Centrifugal Pump N. Idris*1, 3and I. U. Umaru2 1Department of Chemical EngineeringUniversity of MaiduguriBorno State, NigeriaEmail: idrismn@unimaid.edu.ng ABSTRACT The quest to improve on the reliability, operability, sustainability of centrifugal pumps in all facets of process operations, oil and gas industries across the globe have a pivoted role to play in the development of world energy technology and sustainability in numerous ways. This is because several operability challenges and malfunctioning of centrifugal pumps can usually results to unexpected shutdown of process operations and mostly in cases with faulty standbys.Centrifugal pump is a type of a turbo machine in which mechanical energy is converted into pressure energy by means of centrifugal force acting on the fluid. The impeller is the revolving component of the centrifugal pump that transmits energy from the electric motor that drives the pump to the fluid being pumped by acceleration of the fluid outwards from the centre of rotation.Several researches have been conducted using experiment and numerical simulations to design the centrifugal pump impellers. As a result of recent research, the performance of contemporary centrifugal pump impellers yielded positive results. However, for sustainability there is a need to design the impellers using corrosive and non-corrosive materials to improve on its reliability and efficiency of the pump.The aim and objective of the studies are: to analyze the pressure, head and efficiency of the designed centrifugal pump impeller, to improve on the efficiency and reliability of a centrifugal pump impeller by changing the blade angle and the use of corrosive and non-corrosive fluids, experimental measurements to analyze the pressure fluctuation performance of a centrifugal pump impeller using CFD. Keywords: Oil and gas, centrifugal pump, reliability, sustainability Correspondence about this article: Please for all correspondence on this article, kindly contact the principal author as stated above. Thank you.

Numerical study on a coupled viscous and potential flow design method of axial-flow pump impeller

Axial-flow pump is widely used in water-jet propulsion, and its hydrodynamic and cavitation performance have an important effect on the performance of the vessel. Therefore, the study of pump design is very important. In this work, a coupled viscous and potential flow three-dimensional design method for impeller of axial-flow pump with pre-swirl stator is developed. The body-force model (BFM) is used to solve the effective inflow field for impeller design by using a viscous Reynolds-averaged Navier-Stokes equations (RANS) commercial software, and the lifting-surface vortex lattice method (VLM) is used to design the impeller. The feasibility of the design scheme is verified by quasi-steady numerical simulation, and the uncertainty analysis of the numerical simulation is carried out according to the uncertainty analysis method recommended by International Towing Tank Conference (ITTC). The design and verification of axial flow pump are carried out in this paper, and the results show that the design method developed in this work is feasible. In addition, the cavitation performance can be improved by adjusting the load distribution reasonably.

Flow mechanism and axial force distribution characteristics of multistage pump cavity.

The gap leakage between the impeller ring leads to the change of the pump cavity flow characteristics, resulting in the uneven pressure distribution of shroud, which causes the axial force of the cavity to change. In this paper, the flow in the front and the rear cavity of the multistage centrifugal pump was taken as the research object. Through the numerical method, the radial flow velocity, the leakage flow size and its direction, the core zone rotation factor of the front and the rear cavity of the multistage pump impeller at all stages and the axial force of pump cavity were studied. The results show that the leakage in the front cavity of multistage pump impeller at all stages flows inward along radial direction (i.e. it flows from the inlet of pump cavity to the front ring clearance). The rotation factor in core zone is higher than 0.5, and with the increase of rotation factor, the axial force of the front pump cavity increased. The leakage in the rear pump cavity flows outward along radial direction (i.e. it flows from the rear ring to the inlet of pump cavity). The rotation factor in core zone is less than 0.5, and with the increase of rotation factor, the axial force decreased gradually. Besides, the radial velocity and rotation factor in the front and the rear multistage pump of impellers were obviously along the axial direction at three regions, the regions are pump case boundary layer, core zone and impeller boundary layer. The flow in the core zone is dominated by circumferential circular motion, and the radial velocity in the core zone is 0. It is shown that the direction of the leakage in the pump cavity and the rotation effect of the flow micelle in the mainstream core zone are the main factors affecting the axial force of the pump cavity, and the research results can provide theoretical guidance for the calculation and suppression of axial force of multistage pumps.

Analysis of the axial force distribution characteristics of multistage pumps and its correlation with hydraulic property

As the centrifugal pump is running, the fluid usually flows into the impeller along pump shaft, and the fluid flows out radially by the force of the impeller. The force is mutual, so the impeller is also subjected to the reaction force of the fluid, but the distribution of this force on the blades is uneven. In addition, the front and rear shrouds of the impeller are asymmetric, which are the main causes of axial force. This paper adopts numerical calculation method studying the mechanism of axial force of impeller at all stages of multistage pump at various working conditions, and exploring the formation mechanism of shroud pressure differential force and blade twisting axial force and its variation laws of similarities and differences, analyzing the steady state and transient characteristics between axial force and hydraulic property of double-casing multistage pump. The results show that the rotational angular velocity of the fluid in the front and rear pump chamber at each stage impeller is distributed along the axial direction in three regions, the regions are pump body boundary layer, core region, and impeller boundary layer. The working surface and back surface of the blade twist have the high and low axial force area, and its distribution is staggered, at the same number of stages, the greater the flow rate, the smaller the blade twisting axial force. The shroud pressure differential force with the increase of impeller stages presents a linear increasing trend, conforms to the principle of linear superposition of cover pressure differential force. The total axial force pulsation of multi-stage pump is related to the number of secondary impeller blades, its primary frequency coincides with the secondary impeller blade frequency, increasing the flow rate can reduce the multi-stage pump axial force pulsation amplitude. The pulsation period of single-stage impeller head and efficiency are related to the number of impeller blades, the smaller the number of impeller stages, the stronger the pressure dynamic, and static interference effect of the impeller inlet and outlet. Rotation of the secondary impeller causes dynamic and static interference, which is the main reason for the pulsation of the axial force coefficient in double-casing multistage pumps, the pulsation intensity is related to the periodic generation and shedding of the blade vortex. The results of the study can be used as a reference for optimizing the axial force of double-casing multistage pumps.

Energy-saving oriented optimization design of the impeller and volute of a multi-stage double-suction centrifugal pump using artificial neural network

To broaden the efficient operating zone and increase the energy efficiency of a multi-stage double-suction centrifugal pump, a multi-component and multi-condition optimization design method involving high-precision performance predictions, a flow loss visualization technique based on entropy production theory, and machine learning is proposed. First, the accuracy of the baseline pump numerical methodology is verified via a grid convergence analysis and experiments. Thereafter, nine design parameters of the impeller and double volute are selected as design variables. Subsequently, 150 designs are created according to the Latin hypercube sampling method (LHS) and numerically simulated using an automatic simulation program. A backpropagation neural network (BPNN) and a multi-objective genetic algorithm (MOGA) are adopted to maximize the efficiency at 0.6Q d, 1.0Q d, and 1.2Q d. Finally, the optimal results are verified via numerical calculations and analyzed. The results indicate that the efficiency of the optimized pump is increased by 2.05%, 3.56%, and 5.36% at 0.6Q d, 1.0Q d, and 1.2Q d, respectively. The comparative analysis of the energy characteristics reveals that the improved performance of the optimized pump can be attributed to the improved matching between the rotor and stator. This research further demonstrates the accuracy and reliability of the optimization method using an artificial neural network (ANN).

Comparative design and performance of surface water irrigation pumps for smallholder farmers in South and Southeast Asia

An experimental study on the performance of various Thai irrigation pump impellers and a newly design conical hollow-shaped impeller was investigated. They were tested experimentally. The design pump based on a similar theory was developed. The objectives of this experiment were to provide data for comparison of Thai irrigation pump impellers, to evaluate, and to improve the current design of Thai irrigation pumps in a cost-effective and energy-efficient manner. The efficiency and design variables of Thai irrigation pump impellers were presented as a function of dimensionless specific speed in the range, 2.1 < Ns < 4.1. The geometric and design variables as functions of the specific speed and the specific diameter or Cordier diagram presented in this paper could be used as a practical design guide for Thai irrigation pump impellers. This is a preliminary design phase of Thai irrigation pump impellers and the result from this study is intended to make a modest contribution. However, they are facing new challenges that require pump performance improvement and innovative design.

Fast‐flowing LBE corrosion of the SiC pump impeller: Numerical and experimental investigations

AbstractIn order to determine the stress state and the specific dynamic corrosion behaviors of the cooling pump impeller in the liquid lead‐bismuth eutectic alloy (LBE), the numerical and the experimental investigations on the fast‐flowing LBE corrosion behaviors of the SiC impeller were conducted. The distributions of stress and displacement of the SiC impeller were simulated, and then the microstructure and mechanical properties of the corroded impeller were characterized. The results indicated that the SiC impeller met the strength requirement of 1000 rpm in LBE, and the dynamic LBE corrosion had little effect upon structure safety of the SiC impeller. The maximum stresses of the SiC impeller without and with LBE loading were .452 and 9.736 MPa, respectively. The maximum displacements of the SiC impeller without and with LBE loading were 76.385 and 4.096 μm, respectively. The LBE loading reduced the axial displacement of the impeller and acted as an impeller stabilizer to some extent. Blade elongating and flapping were the main vibration mode of the SiC impeller. The mechanical properties of the SiC impellers before and after corrosion were basically the same.

Hydraulic optimization design of centrifugal pumps aiming at low vibration noise

In order to reduce the vibration noise generated by the centrifugal pump in the working process and improve the working efficiency of the centrifugal pump, the sound field numerical calculation of IS80-65-160 single-stage single-suction centrifugal pump was carried out. Under the condition that the parameters of the pump body and the impeller remain unchanged, the number of blades of the prototype pump impeller was designed as 4, 5, 6, and 7, respectively. The flow-induced vibration and noise characteristics of centrifugal pumps were studied from two aspects of numerical simulation and test, and the renormalization group k-ε model was used to simulate the steady and unsteady state of centrifugal pumps with different blade numbers. The external characteristics, pressure pulsation characteristics, vibration, and noise of the centrifugal pump were obtained, and the flow-induced vibration and noise test platform of the centrifugal pump was built for experimental verification. The research showed that the flow induction in the model pump was the main factor affecting the vibration of the prototype pump, and the shaft frequency and blade frequency were the main reasons causing the noise of the prototype pump. The vibration of each blade was the most concentrated at onefold blade frequency, and the peak of the sound field acoustic pressure level of the pump body was higher than other frequencies at threefold blade frequency, which was most obvious in the tongue region of the volute. With the increase of blades, the noise in volute decreased. The vibration intensity of the 4-blade prototype pump was lower, but the efficiency and head were also lower. The vibration intensity of the 5-blade prototype pump was the highest, the comprehensive performance of the 6-blade prototype pump was better, and the vibration of the 7-blade prototype pump was unstable. The test results showed that six blades could effectively reduce the flow-induced vibration noise of centrifugal pumps and improve the working environment, which provided certain application value and guiding significance for the hydraulic design of the subsequent low-noise centrifugal pumps.

Lattice Boltzmann simulation of the ERCOFTAC pump impeller

The analysis of unsteady flows is becoming more and more important in the field of hydraulic turbomachinery applications, both for stable and especially for unstable operating conditions and other transient phenomena. Unsteady Reynolds-averaged Navier-Stokes (RANS) methods for incompressible flows, implemented via finite volume or finite element approaches, reach their limit in both accuracy and acceptable computational time. The accuracy mainly suffers due to the strong dependence of the solution on turbulence model variants. Furthermore, incompressibility of the flow and the linked implicit pressure equation makes large eddy simulations (LES) of Navier-Stokes-based methods for such flows prohibitively expensive. An alternative to Navier-Stokes fluid solvers are methods based on the solution of the discrete Boltzmann equation, so-called Lattice Boltzmann Methods (LBM). The purpose of this work is to present first results of an ongoing project involving the simulation of unsteady hydraulic turbomachines at high Reynolds numbers. For this purpose, the ERCOFTAC pump impeller was selected as a test case. Results obtained with the current implementation of the in-house code suggest, that the present methodology could provide a viable alternative for the analysis of unsteady flow phenomena in hydromachines.

Energy Characteristics and Internal Flow Field Analysis of Centrifugal Prefabricated Pumping Station with Two Pumps in Operation

In order to study the hydraulic performance and internal flow field of dual pumps in centrifugal prefabricated pumping station under operation conditions, this paper carried out a numerical calculation based on CFD software for dual pumps in a centrifugal prefabricated pumping station under different flow conditions and verified the internal flow field through test. The results show that the efficiency of centrifugal prefabricated pumping station under design conditions (Qd = 33.93 m3/h) is 63.96%, the head is 8.66 m, the head at the starting point of the saddle area is 10.50 m, which is 1.21 times of the designed head. The efficiency of the high-efficiency zone of the prefabricated pump station is 58.0~63.0%, and the corresponding flow range is 0.62Qd~1.41Qd (21.0~48.0 m3/h). The uniformity of the inlet flow rate of impeller of pump 1 is 74.70%, and that of pump 2 is 75.57%. The flow fields of water pumps on both sides are inconsistent. The results of the flow field indicate that there are severe back flow phenomena at the prefabricated bucket intake, more back flow in the bucket, and many eddies on the side wall. With the increase in flow rate, the eddy structure at the intake expands continuously and moves towards the center area, which has a negative impact on the flow field in the center area. The research results of this paper can provide a theoretical reference for the research and operation of the same type of prefabricated pumping stations.

Development of Ultra-Low Specific Speed Centrifugal Pumps Design Method for Small Liquid Rocket Engines

With the growth of the satellite industry, the demand for a propulsion system for small launch vehicles and spacecraft has increased. Small liquid rocket engines may require Ultra-Low specific speed centrifugal pumps due to the low required thrust and volumetric flow rate and high combustion chamber pressure. Therefore, in this study, a design method of Ultra-Low specific speed centrifugal pumps for several hundred Newton class small liquid rocket engines was developed by combining various empirical formulas. In addition, centrifugal pump impellers were designed using the Stepanoff method, which is typically used in pump design, and the circular arc method. The most appropriate method for designing Ultra-Low specific speed centrifugal pumps was determined through a comparative analysis with other methods and validated through CFD. As a result, the pump designed using the proposed method exhibited a performance of pumping and suction superior to the Stepanoff method. Although the number of arcs did not considerably influence the pump performance, the single arc method was confirmed to be the most appropriate design approach in terms of the design productivity and simplicity.

Numerical study on the performance of centrifugal blood pump with superhydrophobic surface.

In order to reduce the blood damage of an artificial heart pump and optimize its hydraulic performance, a centrifugal blood pump with superhydrophobic characteristics is proposed in this study. To study the influence of superhydrophobic surface characteristics on the performance of centrifugal blood pumps, the Navier slip model is used to simulate the slip characteristics of superhydrophobic surfaces, which is realized by the user defined function of ANSYS fluent. The user defined functions with different values of slip length are verified by two benchmark solutions of laminar flow and turbulence in the pipeline. The blood pump model adopts the designed centrifugal blood pump, and its head, hydraulic efficiency and hemolysis index are calculated. The Navier slip boundary condition (a constant slip-length of 50 μm) is applied to the walls of the blood pump impeller and a volute at different positions, and the influence of the superhydrophobic surface on the performance of the blood pump at the design point Q = 6 L/min was compared and analyzed. The results show that the centrifugal blood pump model used in this paper has good blood compatibility and meets the design requirements; the superhydrophobic surface can significantly reduce the scalar shear stress in the blood pump. At the design point, when the slip length is 50 μm, the mass-average scalar shear stress in the impeller area and the volute area reduction rate is about 5.9%, the hydraulic efficiency growth rate is about 3.8%, the hemolysis index reduction rate is about 18.4%, and the pressure head changes little with a growth rate of 0.3%. Centrifugal blood pumps with superhydrophobic surfaces can improve the efficiency of blood pumps and reduce hemolysis. Based on these encouraging results, vitro investigations for actual blood damage would be practicable.

КАВИТАЦИОННЫЕ РАЗРУШЕНИЯ В ЖИДКОСТНОКОЛЬЦЕВЫХ ВАКУУМНАСОСАХ

The relevance of studying the parameters of operation of liquid ring vacuum pumps and the development of new designs is due to their demand in the agro-industrial complex. The paper provides a description of the cavitation phenomena that occur during the operation of a liquid ring vacuum pump. Cavitation degrades pump performance and can often cause failure. It can occur due to: low barometric pressure; large vacuum suction height; high temperature of the pumped liquid; additional pressure loss in the pump impeller. To identify the possibility of cavitation in a liquid ring vacuum pump, a cavitation characteristic is compiled. It is based on testing the pump at a constant flow rate of the working fluid and the speed of the impeller, performed on a special installation, the scheme of which is presented in the article. Cavitation phenomena in a liquid ring vacuum pump with water occur at a vacuum above 90%. For a single-stage liquid ring vacuum pump, this value corresponds to a vacuum range of 20-10 kPa, for a two-stage one - 10-1 kPa. A photo of the impeller blades of a liquid ring vacuum pump exposed to cavitation is presented. The formula for calculating the cavitation coefficient, which characterizes the cavitation reserve, is given. Its value depends on the design of the considered pump and the operating conditions of its operation and can be determined empirically. Practical recommendations are offered to prevent the occurrence of cavitation phenomena: decrease in water temperature; improving the accuracy of model selection; equipping the pump with an air ejector; use as a working fluid with a low content of saturated steam; production of the impeller from materials with increased anti-cavitation properties