Pump Performance Research Articles

Influence of axial distance between impeller and diffuser on the hydraulic performance and flow loss characteristics of bulb tubular pump

Abstract Bulb tubular pumps used in regional water transfer projects consume substantial power. Optimizing the geometric parameters of tubular pumps is crucial for enhancing efficiency and minimizing hydraulic losses. ANSYS CFX is used to investigate the axial distance between the impeller and the diffuser on the hydraulic performance and flow loss characteristics of the rear-bulb tubular pump, and the numerical simulation results are compared with the experimental data. Then, the entropy production theory is introduced to analyze flow losses. As the axial distance increases, the diffuser’s rectification effect on the flow at the impeller outlet deteriorates, leading to increased flow losses and decreased head and efficiency of the device. Flow losses in the bulb tubular pump are ranked from largest to smallest as follows: impeller, outflow channel, diffuser, inlet channel. The impeller exhibits the highest entropy production ratio, reaching 61.05% at an axial distance of 25 mm. By elucidating the energy loss distribution of each component under varying axial distances, this paper offers insights for the hydraulic optimization design of bulb tubular pumps.

Effect of Gasket Wear Rate on Hydraulic Performance and Internal Flow of Multistage Centrifugal Pump with Floating Impellers

Abstract The sealing gaskets of multistage centrifugal pumps are prone to wear during operation. This study investigates the influence of gasket wear rate on hydraulic performance and internal flow field through numerical simulations. As the wear rate of the gasket increases, both the efficiency and head coefficient of the pump gradually decrease. When the gasket is completely worn out, the efficiency decreases by 5.6% and the head coefficient decreases by 9.5% compared to the unworn gasket condition. Analysis of the internal flow field reveals that the front side chamber is most significantly affected by gasket wear. As the gasket wears, the flow velocity within the front side chamber increases gradually, and the high-entropy production zone expands, thereby affecting the hydraulic performance of the pump. The findings of this study provide practical engineering insights for enhancing the operational performance of multistage centrifugal pumps.

Experimental study on hydraulic performance and cavitation characteristics of a R134a refrigerant self-lubricating centrifugal pump

As the primary power equipment in pump flooding cooling systems, the efficiency and performance of mechanical pumps play a crucial role in two-phase cooling systems. A high-speed centrifugal pump with self-lubricating working fluid was designed with a speed of 7500 rpm and a flow coefficient of 0.0506. The hydraulic and cavitation performance of the pump were tested with R134a as the working fluid. The results show that the working fluid pump is capable of efficiently pumping R134a with an efficiency of 40.3% and a head coefficient of 0.988 under the design condition. Within the tested range of inlet temperature from 5°C to 15°C, the flow coefficient from 0.01 to 0.105, and the height of the refrigerant tank from 1.4 m to 5 m, lower net positive suction heads available at the same flow rate will reduce the pump head, increase power consumption, and decrease efficiency. Increasing the pump speed from 3000 rpm to 7500 rpm can improve the pump's performance. At 6000 rpm, the critical cavitation number of the working fluid pump increases with the increase in flow coefficient. At 7500 rpm, the critical cavitation number has a minimum value when the flow coefficient φ = 0.0434. At the design speed and flow rate, both the critical cavitation coefficient and fracture cavitation number increase as the inlet temperature decreases. The inducer can significantly reduce the critical cavitation number of the pump. Finally, an empirical correlation considering the thermodynamic effects is proposed to predict the increase in the critical cavitation number.

Effect of baffles on internal flow characteristics of double-inhalation centrifugal pumps under low flow conditions

In order to investigate the impact of baffles in the inhalation chamber on the external characteristics and operational stability of a double inhalation centrifugal pump under low flow conditions, the flow field simulation software ANSYS CFX and the shear stress transport formulation were employed to numerically simulate the internal flow field of a double inhalation centrifugal pump with and without baffles. Two models were subjected to performance curve simulation and prediction, with the internal flow field, pressure pulsation, and impeller force of the two models being compared and analyzed under three small flow conditions of 0.6Qd (rated flow), 0.5Qd, and 0.4Qd. The velocity and vortex distribution inside the semi-spiral inhalation chamber, as well as their impact on the flow state in front of and inside the impeller, were analyzed. Research has demonstrated that the addition of baffles can enhance the pump head and efficiency in flow conditions of 0.5Qd–0.8Qd. However, there is a tendency for obstruction of flow in conditions below 0.5Qd. Baffles can reduce the amplitude of pressure pulsation within the impeller and the radial force exerted by the impeller as a whole. Consequently, the incorporation of baffles within the inhalation chamber during flow conditions of 0.5Qd–0.8Qd can enhance the operational efficacy of the pump. Nevertheless, within the flow range of <0.5Qd, the pump's performance will decline. This study serves as a foundation for the design of double inhalation centrifugal pumps with semi-spiral inhalation chambers.

Multiscale Fiber Remodeling in the Infarcted Left Ventricle using a Stress-Based Reorientation Law

The organization of myofibers and extra cellular matrix within the myocardium plays a significant role in defining cardiac function. When pathological events occur, such as myocardial infarction (MI), this organization can become disrupted, leading to degraded pumping performance. The current study proposes a multiscale finite element (FE) framework to determine realistic fiber distributions in the left ventricle (LV). This is achieved by implementing a stress-based fiber reorientation law, which seeks to align the fibers with local traction vectors, such that contractile force and load bearing capabilities are maximized. By utilizing the total stress (passive and active), both myofibers and collagen fibers are reoriented. Simulations are conducted to predict the baseline fiber configuration in a normal LV as well as the adverse fiber reorientation that occurs due to different size MIs. The baseline model successfully captures the transmural variation of helical fiber angles within the LV wall, as well as the transverse fiber angle variation from base to apex. In the models of MI, the patterns of fiber reorientation in the infarct, border zone, and remote regions closely align with previous experimental findings, with a significant increase in fibers oriented in a left-handed helical configuration and increased dispersion in the infarct region. Furthermore, the severity of fiber reorientation and impairment of pumping performance both showed a correlation with the size of the infarct. The proposed multiscale modeling framework allows for the effective prediction of adverse remodeling and offers the potential for assessing the effectiveness of therapeutic interventions in the future. Statement of SignificanceThe organization of muscle and collagen fibers within the heart plays a significant role in defining cardiac function. This organization can become disrupted after a heart attack, leading to degraded pumping performance. In the current study, we implemented a stress-based fiber reorientation law into a computer model of the heart, which seeks to realign the fibers such that contractile force and load bearing capabilities are maximized. The primary goal was to evaluate the effects of different sized heart attacks. We observed substantial fiber remodeling in the heart, which matched experimental observations. The proposed computational framework allows for the effective prediction of adverse remodeling and offers the potential for assessing the effectiveness of therapeutic interventions in the future.

Experimental investigation of a novel gas-liquid homogenizer methodology for ESP in high GVF flow applications

This paper presents a new homogenizer for Electric Submersible Pumps (ESP). Experiments were carried out using a two-stage radial-type pump with perforated vanes running at 3400 RPM. A test rig was designed to measure pressure and observe flow patterns. Results showed excellent performance for intake GVF ranging from 25 % to 89 %. Using the proposed homogenizer in the multistage ESP improves pump performance for gas-liquid mixtures. The study explored parameters to improve pump performance in high GVF conditions. The proposed homogenizer is more cost-effective and efficient by integrating into the existing pump stage and allowing customizable perforations. This design flexibility improves performance while avoiding the need for extra space or components. Moreover, numerical simulations with a helico-axial rotating multiphase pump and ANSYS-CFX software were conducted to prove the concept numerically. The focus was on gas-liquid two-phase flow and the effects of inlet GVFs. Modifications to the impeller blades, such as grooves, slits, or holes, were designed to enhance performance. The study found that CFD simulations accurately predict pump performance and that modified impellers improve performance in specific GVF ranges.

Study on the impact of turbulent spatiotemporal propagation in the outlet passage on the performance of vertical axial flow pumps.

Abstract Pumping station engineering is crucial for our country’s national economy as a part of water conservancy infrastructure. The vertical axial flow pump commonly used in pumping station construction features a high flow rate and low discharge pressure. Understanding the impact of turbulence on the flow of water entering and leaving the pump unit is crucial for the efficient and reliable operation of a pumping station. This paper examines the internal flow and hydraulic characteristics of the device for vertical axial flow pump at a pumping station through numerical simulation technology and experimental validation. It is inferred that turbulent flow develops in the outlet flow passage while the pump device is currently functioning, impacting the impeller’s outlet bend and guide vane. This leads to the formation of vortices, backflow, and folding flow at the guide vane and outlet bend. As water flows out through the outlet passage, bias and backflow develop, causing erosion on both sides of the outlet pool and impacting the pump unit’s overall head and efficiency.

Influence of guide groove structure on in-flow drag reduction in spiral axial gas-liquid mixing pumps

Abstract With the onset of the fossil energy crisis, demand for oil has skyrocketed, and the spiral axial flow gas-liquid mixing pump has emerged as the primary piece of equipment for deep-sea oil extraction. However, at high gas content, the problems of separation of mixed media from hydraulic components, gas-liquid separation and gas phase aggregation are faced. The difficulties of gas-phase aggregation and bubble trajectory in the impeller channel have received much attention, while the problem of increased medium flow resistance induced by flow separation has received less attention. The spiral axial gas-liquid mixing pump is numerically calculated using the Eulerian multiphase flow model and the SST k- turbulence model in this work. The pump is designed with the design flow rate Q = 100 m3/h, rotational speed n = 4500 rmin, and head H = 30m by arranging guide slots with different relative depths and different number of slots to reduce the dissipative vortices, thus reducing the flow resistance in the 1/5 region behind the suction surface. The findings reveal that when the relative depth of the slots is 1/7 and the number of guide slots arranged is 5, the highest drag reduction rate in this location is 69.6% under the design flow condition. When the relative depth of the guide channel is1/7 and the number of guide channels is 3, the performance of the mixing pump is improved most, with an efficiency increment of 1.9% and a head increment of 4.2%, which can provide technical support for the flow resistance reduction of gas-liquid mixing pumps.

Experiments on the performance of low temperature air source heat pump based on parallel connection of evaporators

An air source heat pump experimental bench with evaporators connected in parallel at low ambient temperatures is established to investigate the key parameters and operating performance after this retrofit. Experimental tests are conducted on the novel heat pump unit to study the optimal refrigerant charge, heat production capacity and COP at different ambient temperatures, to observe the frost condition in the operation of the unit, and to optimise the control logic. Results show that the optimum refrigerant charge amount after retrofit is 26 kg. Further experiments show that under the condition of −12 °C, heat production capacity of the retrofitted unit is increased by 5.39%, the COP is increased by 4.13%, and the evaporating temperature is increased by 1.50 °C; under the condition of 2 °C, the heat production capacity of the retrofitted unit is increased by 5.72%, the heating COP is increased by 2.51%, and the evaporating temperature is increased by 2.93 °C. At the same operating time, the modified unit has less frost on the evaporator surface. The optimum suction superheat after the modification is 1 °C, and it is at this point that the unit has the highest heating COP, which is 7% higher than at 0 °C suction superheat. The heat production and COP are less affected by the supplement gas superheat. Through the modification of the parallel evaporator, the overall heating performance and frost prevention ability of the unit are greatly improved.

Hemolysis analysis of centrifugal blood pump based on numerical simulation

Abstract The operation of blood pump will cause mechanical damage to red blood cells and lead to hemolysis. Based on this, CFD technology is used to simulate the three-dimensional flow field of centrifugal blood pump. According to the analysis of velocity field, pressure field and stress field; Based on the hemolysis power function model, the hemolysis performance of blood pump is predicted by Lagrange particle tracking method, and the impeller structure is adjusted to improve its flow performance and reduce the hemolysis index. The research results can provide a basis for the structural improvement and performance improvement of centrifugal heart pump.

Numerical analysis of performance and internal flow characteristics of a gas-liquid multiphase rotodynamic pump

Abstract Inlet Gas Void Fraction (IGVF) and rotating speed are key parameters influencing the flow characteristics of gas-liquid multiphase pumps. To explore the influence of these two factors on the flow characteristics of gas-liquid multiphase rotodynamic pumps, CFD simulations were carried out based on the Euler two-fluid model to analyze the flow characteristics in an axial-flow pump at three different rotating speeds (1450 r/min, 2200 r/min, 2950 r/min) with different IGVFs. The numerical results indicate that the pump efficiency and head are first increased and then decreased with the increase of IGVF. When the IGVF is 5%, the head and efficiency reach their maximum values. This is attributed to the minimum vorticity and turbulence kinetic energy in the impeller passage at IGVF= 5%, and the small vortex range at the hub of the guide vane, thus resulting in the stable two-phase flow state in the impeller and guide vane. At the same IGVF, with the increase of the rotating speed, the head and efficiency of the multiphase pump increase accordingly. This is closely related to the smallest vortex range formed by gas-liquid flow separation at n=2950 r/min, indicating a better flow state.

Performance characteristics of a contra-rotating pump-turbine in turbine and pump modes under cavitating flow conditions

Recent studies have indicated the potential of a contra-rotating pump-turbine (CRPT) as a low-head design that enables pumped hydro storage in regions with flat topography. However, the effects of cavitation have scarcely been investigated for the CRPT. The current paper utilises computational fluid dynamics simulations to study a model scale CRPT subjected to cavitating flow conditions to determine how cavitation affects the machine’s operating performance in both pump and turbine modes. In total, eight operating conditions have been evaluated for each mode. The inlet flow rate is considered fixed at 0.27 m3/s, while the outlet pressure is gradually changed to induce cavitating conditions. The study demonstrates that the pump mode operation of the CRPT is more sensitive to cavitation compared to the turbine mode. The pump mode operation shows a steady decline in efficiency with decreasing inlet pressure, whereas in turbine mode the efficiency settles at a lower level. The 3% head drop occurs at la Thoma number of 1.0 in pump mode and at 0.6 in turbine mode. At the 3% head drop, a large cavitating region is already present at the runner blades’ suction side of the runner closest to the lower reservoir in both modes. The large cavitating region causes the flow to separate from the runner blade surfaces, which explains the reduced operating performance. To ensure an almost cavitating-free operating condition and unaffected performance, the Thoma number needs to be above 1.0 in turbine mode and at least 1.5 in pump mode. A frequency analysis reveals that the presence of cavitation affects the dominant pressure pulsations in the system. A dynamic mode decomposition analysis is carried out, demonstrating that the non-trivial pressure pulsations are connected to the support struts.

Design and performance study of a novel variable cross-sectional rotor for twin-screw vacuum pumps

The variable cross-sectional rotor is considered as a potential technology to further improve the performance of twin-screw vacuum pumps, due to its remarkable advantages of large internal volume ratio. In this study, a mathematical model of variable cross-sectional rotors was established to obtain its generation method. A novel type of variable cross-sectional rotor was constructed by using the proposed method, and this rotor exhibits superior sealing performance. The variable cross-sectional rotor was geometrically compared with the traditional equal cross-sectional rotor. Then the accuracy of the proposed generation method as well as the advance of the generated variable cross-sectional rotor were verified by experimental test results. Results show that this design method achieves the construction of high accuracy variable cross-sectional rotors by generating 3-D helical surfaces. Compared with the traditional equal cross-sectional rotor, the geometric pumping speed and internal volume ratio of the variable cross-sectional rotor are increased by 7.57 % and 10.45 %, respectively. The volumetric efficiency of the variable cross-sectional rotor is increased by 6.52 % and the time to reach the ultimate pressure is reduced by 9.42 %, demonstrating superior pumping and sealing performance.

Fast-airflow tumble clothes dryer with small thermoelectric heat pump: Experimental evaluation

Residential clothes drying accounts for about 5 % of the total residential-sector energy consumption in the United States. Most dryers use electric resistance heaters to dry clothes and have low efficiencies. Higher-efficiency dryers that use vapor compression heat pumps are expensive and complex and have not gained a large market share in the United States. A novel tumble clothes dryer using a small thermoelectric heat pump with faster airflow than typical dryers is presented in this work. The benchtop performance of the thermoelectric heat pump and high-speed blower are presented, and the development of the prototype dryer is described. The dryer was tested for efficiency and dry time for a range of airflow rates and applied currents to the thermoelectric heat pump. The combined efficiency factor was 5.09–6.29 lbBDW/kWh (specific moisture extraction rate of 1.23–1.53 kgw/kWh) with 100–138 min dry times for these tests. The measured efficiency was 36 %–68 % greater than the minimum efficiency standard in the United States, and compared with vapor compression heat pump–based clothes dryers, the prototype dryer had less expensive, less complex components and did not use refrigerants. The performance of this small thermoelectric heat pump clothes dryer is also compared with previous iterations of the thermoelectric tumble clothes dryer described in the literature.

Analysis of the influence of different support types on the operation performance of bidirectional shaft tubular pump

Abstract Because of the particularity of the pump’s bidirectional operation, and the difference of the flow channels on both sides of the pump. The device has a mature impeller and guide vane combination when it is running forward. And when the device runs in reverse, the support on the shaft side acts as the rear guide vane of the impeller, which has great influence on the performance of the device. However, due to the few operating conditions in reverse operation, the importance of support is often ignored. In this paper, the influence of different support types on the bidirectional flow pattern and performance of the device is analyzed by numerical simulation. The results indicate that by optimizing the variation trend of the edge arc radius of the supporting baffle section, it is possible to effectively control the section with poor flow distribution, thereby reducing hydraulic losses. The support adopts three partitions arranged at an interval of 120°, which has little difference in performance during forward operation compared with other schemes. But during reverse operation, it reduces the impact and friction losses of water flow. And it fully utilizes the direct guide vane function of recovering vorticity, resulting in a significant increase in efficiency. At the same time, the accuracy of numerical simulation results is verified by model tests. The stability of positive and negative operating pressure pulsation supporting the inlet and outlet under the optimal scheme is analyzed.

Experimental study on energy and hydraulic performance of the axial flow pumping device with bell-shaped inlet channel

Abstract Due to the unique inlet design of the axial flow pump device with a bell shaped inlet channel, there is currently insufficient quantitative research on its hydraulic characteristics. This study investigates the hydraulic behavior of a vertical axial flow pumping device equipped with a bell-shaped inlet channel, analyzing various blade angles. Energy, cavitation, runaway, and pressure pulsation characteristics were assessed through meticulous testing on a high-precision test bench. Experimental findings indicate that altering the blade angle of the vertical axial flow pumping device with a bell-shaped inlet channel can influence its overall efficiency to some extent. Moreover, as the pump’s blade angle increases incrementally, the device’s cavitation performance gradually diminishes. Pressure pulsation tests reveal a relatively minor amplitude of pressure pulsation at the impeller outlet, contrasting with a more pronounced amplitude observed at the guide vane outlet compared to the pump outlet. These research results provide valuable insights for the design and optimization of actual pumping stations.

Effects of distribution valve spring stiffness and opening pressure on the volumetric efficiency of micro high-pressure plunger pump

With the rapid development of material science and manufacturing capabilities, hydraulic technology is increasingly high-pressure, lightweight and miniaturizing. Micro plunger pump is widely used in the field of deep-sea hydraulic equipment and advanced intelligent hydraulic equipment, owing to its high-power density, high output pressure and many other advantages. Its broad application aims to examine the inlet and outlet distribution valve spring parameters change on the micro high-pressure plunger pump volumetric efficiency, by changing the inlet and outlet distribution valve. This paper is based on the simulation of AMESim engineering software to derive multiple sets of data. It compared and analysed the specific effect of different spring stiffness and opening pressure on the volumetric efficiency of the micro high-pressure plunger pump which was then verified through experiment. Results of this study have certain reference significance for the design of the spring of the inlet and outlet distribution valve of the micro high-pressure plunger pump, which facilitates the optimization and improvement of the dynamic performance of the micro high-pressure plunger pump.

Experimental investigation on the low temperature performance of a novel three-pressure air source heat pump

As people’s demand for living comfort grows, the problems of conventional air source heat pumps (ASHPs) become more prominent in low-temperature and high-humidity environments: heating performance attenuation, low defrosting efficiency, and significant impact on indoor thermal comfort during defrosting. Existing literature usually focuses on only one or two of these issues, and few comprehensively cover them. Based on current literature, this paper proposes a novel multi-functional three-pressure ASHP that can cover the above three aspects with a series–parallel combination structure featuring dual compressors and dual cycles. This design enables switching multiple heating and defrosting modes through valve combination and improves performance through two-stage throttling and subcooling. An experimental platform is constructed to evaluate its operational performance. The experimental results show that: (1) In heating modes, the average heating capacity of the three-pressure cycle heating mode is 2897.15 W, and the average COP is 2.47, while these two data of the conventional cycle heating mode are 2393.65 W and 2.4, and the improvement rates of 20.4 % and 2.9 %, respectively. It also extends the high-efficiency heating period of the system, enables rapid heating at start-up, increases compressor suction and discharge pressure, and improvs system stability. (2) In defrosting modes, compared with the conventional defrosting cycle, the three-pressure defrosting cycle raises the condensation temperature faster, reduces the defrosting time from 448 s to 265 s (40.8 % shorter). The auxiliary defrosting cycle has little effect on indoor thermal comfort and less defrosting power consumption, with the power saving rate as high as 44.6 %. Overall, the novel three-pressure ASHP has a unique and innovative structure, significantly optimizing performance under low-temperature and frosting conditions and improving energy efficiency and comfort. The results of this study provide a new solution concept for the future development of ASHPs, offering significant reference value for further development and application.

Coupled Effects of Hub Diameter Ratio and Blade Angle on the Performance of Spiral Axial Flow Gas Liquid Multiphase Pump

Coupled Effects of Hub Diameter Ratio and Blade Angle on the Performance of Spiral Axial Flow Gas Liquid Multiphase Pump

Influence of the channel inclination on the exchange flow and vorticity transport characteristics in a regenerative flow pump

To enhance the overall performance of regenerative flow pump (RFP) to achieve efficient and stable operation over a broad range, this paper employs numerical simulation to study the internal flow conditions of RFP models with three different inclination coefficients (Ic = −0.25, Ic = 0, Ic = 0.25). The analysis focuses on the pressure distribution, energy exchange, velocity variation, and vorticity distribution characteristics within the impeller and channel. The comparison indicates that at Ic = −0.25 with an outward channel, the flow within the pump is stabilized, and the rate of pressure growth and exchange intensity are increased. When Ic = 0 with a semi-circular channel and Ic = 0.25 with an inward channel, there are narrower flow space at the channel's outer diameter, impeding effective fluid motion along the channel and inducing chaotic flow. This condition escalates flow losses and adversely affects the hydraulic performance of the RFP. Additionally, the analysis based on the vorticity transport equation reveals that the Coriolis force term significantly contributes to the generation and transport of vortex in the impeller, while the vortex stretching term dominates the transport of vortex in the channel.