Search Results (36)

This study investigates the influence of modifications in the geometry of the blades—specifically, the introduction of a gap blade into the impeller blades—on the hydraulic performance of a low specific speed centrifugal pump. The research addresses the problem of efficiency losses in such pumps and explores whether implementing a blade gap can improve energy characteristics without altering the primary flow path. A set of impellers with different gap configurations was designed and manufactured using 3D printing. Experimental tests were carried out on a laboratory test rig equipped with standard pressure, flow, and power measurement instruments. Next, numerical simulations were performed using CFD methods in Ansys CFX, using the k-ω SST turbulence model. The results show that impellers with gap blades achieved higher efficiency—up to 4 percentage points compared to the reference design—and an increase in the maximum pump capacity. CFD analysis confirmed more uniform velocity distributions and reduced separation zones in the interscapular channels, along with a smoother pressure gradient across the blade surfaces. The results demonstrate that modifying impeller geometry using gap blades can improve hydraulic efficiency and expand the range of stable operation. These conclusions support further research on performance optimisation in low-specific-speed centrifugal pumps. Full article

In firefighting operations, the efficiency of centrifugal fire pumps is crucial for effective fire suppression. Designs aiming for lower shaft power enhance not only the pump’s energy efficiency and reliability but also lead to a reduction in size and weight. This research targets a single-stage centrifugal fire pump with a specific speed of 44.5, employing numerical simulations alongside orthogonal experiments to primarily focus on reducing shaft power. Based on a prototype, an L₁₆(4⁴) orthogonal experiment was conducted on four critical parameters: blade outlet angle, wrap angle, outlet width, and blade count. The study analyzed the impact of these parameters on pump performance, clarifying their influence on the hydraulic performance and proposing an optimal power-efficiency scheme. The optimized design successfully reduced the motor power from 18.5 kW to 15 kW, improved the impeller’s internal flow, minimized flow losses, and effectively managed the hump phenomenon. Operating at 1.5 Q_n, the optimized pump’s power decreased by 2.67 kW, meeting head requirements while boosting efficiency, reducing resonance frequency, and lowering the pressure amplitude at the tongue. The optimized pump’s blade frequency distribution was more regular than the original, with the first-order mode’s average deformation decreasing from 3.6 mm to 3.3 mm, and average entropy production at rated flow dropping from 424.118 [W·m⁻³·K⁻¹] to 384.957 [W·m⁻³·K⁻¹]. These outcomes offer theoretical insights and practical guidance for designing low-shaft-power single-stage centrifugal fire pumps, significantly impacting energy efficiency and operational costs. Full article

The low specific speed centrifugal pump plays a crucial role in industrial applications, and ensuring its efficient and stable operation is extremely important for the safety of the whole system. The pump must operate with an extremely high head, an extremely low flow rate, and a very fast speed. The internal flow structure is complex and there is a strong interaction between dynamic and static components; consequently, the hydraulic excitation force produced becomes a significant factor that triggers abnormal vibrations in the pump. Therefore, this study focuses on a low specific speed centrifugal pump and uses a single-stage model pump to conduct PIV and pressure pulsation tests. The findings reveal that the PIV tests successfully captured the typical jet-wake structure at the outlet of the impeller, as well as the flow separation structure at the leading edge of the guide vanes and the suction surface. On the left side of the discharge pipe, large-scale flow separation and reverse flow happen as a result of the flow-through effect, producing a strong vortex zone. The flow field on the left side of the pressure chamber is relatively uniform, and the low-speed region on the suction surface of the guide vanes is reduced due to the reverse flow. The results of the pressure pulsation test showed that the energy of pressure pulsation in the flow passage of the guide vane occurs at the f_BPF and its harmonics, and the interaction between the rotor and stator is significant. Under the same operating condition, the RMS value distribution and amplitude at f_BPF of each measurement point are asymmetric in the circumferential direction. The amplitude of f_BPF near the discharge pipe is lower, while the RMS value is higher. A complex flow structure is shown by the larger amplitude and RMS value of the f_BPF on the left side of the pressure chamber. With the flow rate increasing, the energy at f_BPF of each measurement point increases first and then decreases, while the RMS value decreases, indicating a more uniform flow field inside the pump. Full article

Centrifugal pumps are one of the most commonly used devices in all branches of industry. Their application area is very broad and practically related to all sectors of the economy. Such pumps are widely applied in the chemicals industry, liquid gas technology, and machine lubrication systems, among others. On the basis of available data, it can be assumed that pumps consume approximately 27% of the world’s electricity. For this reason, their efficiency has a significant impact on the energy consumption of many technological processes. This article presents a summary of the research concerning the cooperation between a multi-piped impeller and a concentric casing. A multi-piped impeller is a completely new concept of a centrifugal impeller, which is characterized by the fact that the energy of the liquid is transferred as a result of the flow of media through the internal flow channels, and also the flow of media around it. The type and design of the casing, with regard to the flow in it and around the impeller’s pipes, plays an extremely important role. Numerical analysis was used as the main research method, which was based on a rotatable experimental plan. The CFD simulation results were validated on a test stand. Finally, the mathematical model and the rules for selecting the geometric features of such a stator were proposed in order to achieve the highest possible efficiency when cooperating with the multi-piped impeller, which constitutes a scientific novelty. Full article

This paper investigates the influence of the volute geometry on the hydraulic performance of a low-specific-speed centrifugal pump using numerical simulations. The performance characteristics for the pump with the volute geometry designed using the constant velocity method show a significant discrepancy between the design point and the best efficiency point (BEP). This design methodology also results in a relatively flat head–capacity curve. These are both undesirable characteristics which can be mitigated by a reduction in the volute throat area. This design methodology also leads to a reduction in the power consumption and an increase in efficiency, especially at underload and design flow conditions. These impacts of the volute throat area on performance characteristics are investigated in terms of the change in internal flow characteristics due to the reduction in the volute throat area. Another aspect of the study is the impact of the width of the volute gap on performance characteristics. A reduction in the gap width results in a nearly vertical shift of the head–capacity curve, so that head delivered is higher across all the flow rates as the gap width is reduced. This is also accompanied by a slight improvement in efficiency under design flow and overload conditions. Numerical simulations are used to relate the change in performance characteristics with internal flow characteristics. Full article

The characteristics of pressure pulsations in centrifugal pumps have attracted considerable attention. In this study, principal component analysis is used to discuss the pressure pulsations in a centrifugal pump with a low specific speed, and the primary causes for these pressure pulsations are analyzed in conjunction with experimental results. The results indicate that principal component analysis effectively separates the primary modes that influence the flow field characteristics. An excessive wrap angle results in the formation of a backflow vortex on the working face of the blade. Obvious stratification of the zero-order modal pressure indicates that the geometric structure of the impeller is rational and that the transient flow field is stable. The second- and third-order modes are conjugates, and their dominant frequency coincides with the dominant rotating frequency of the impeller, indicating that the pulsations of a single channel are the primary component of the pressure pulsations. The primary frequency (148.54 Hz) of the pressure pulsations at monitoring points distributed across the volute is three times the rotational frequency (49.51 Hz) of the impeller. The different positions and sub-frequencies of the monitoring points mean that the principal component analysis can effectively identify the impeller-induced sub-frequency difference. Full article

Centrifugal pumps are one of the most widely used machines in all branches of industry. For this reason, their efficiency has a significant impact on energy consumption in global industry (about 20%). It is extremely difficult to design low-specific-speed centrifugal pumps at acceptable efficiency levels due to increasing losses in the impeller (hydraulic, volumetric, and mechanical). This article presents the influence of the geometric features of grooves (width, depth), and the number of them, on the operating parameters of the impeller in a centrifugal pump with microgrooves. The principle of operation of this solution involves the passive control of the flow in the boundary layer using rectangular grooves. The grooves are made inside the flow channels of the impeller and are intended to reduce hydraulic losses occurring during flow. This is mainly due to a reduction in losses in the boundary layer. In order to determine the influence of the grooves’ parameters on the energy characteristics of the impeller, numerical calculations and experimental measurements were performed on 15 sets of impellers, which were obtained using experimental planning methods. The CFD calculations were conducted in order to understand the flow phenomena that occur in the impeller with the microgeometry and their effect on a reduction in internal flow losses. Based on the research results, useful guidelines for designing impellers with low-speed characteristics were formulated. Full article

The acoustic properties of a single-stage centrifugal pump with low specific speed are investigated by means of compressible 3D CFD simulations (URANS) and experiments. In order to determine the pump’s acoustic transmission and excitation characteristics, a four-pole approach in the frequency domain is used. The transmission parameters determined by simulation are compared to experiments in water and air as functions of the Helmholtz number. The results indicate that the acoustic transmission characteristics within the experiments are significantly influenced by the structural compliance of the volute casing in terms of a fluid–structure interaction (FSI). A modelling approach for a one-dimensional representation of the centrifugal pump’s acoustic transmission characteristics in the time and frequency domains is applied to the current pump. As one model parameter, the effective speed of sound in the 1D model needs to be reduced to 607 $\mathrm{m}{\mathrm{s}}^{-1}$ to account for the FSI. The agreement of the simulation results and the experiments underlines the above statement about the influence of the FSI. In a last step, the acoustic excitation parameter, depicted as monopole and dipole amplitudes, at two different blade-passing frequencies ($f_{BP}\approx [111;169]$ Hz) are determined for several operating points. Especially for dipole amplitudes, a good agreement between experiments and simulations can be seen. The monopole amplitudes are also of similar orders of magnitude, but show stronger deviations. The cause of discrepancies between the 3D CFD simulations and experiments is believed to be the neglected influence of the FSI and surface roughness as well as the inaccurate reproduction of flow separation at the volute’s tongue due to the use of wall functions. A final important observation made during the numerical investigations is that the excitation mechanisms at the blade-passing frequency are probably independent of the piping system’s acoustic impedance. Full article

This research conducts a comprehensive comparative analysis of simulation methodologies for spindle pumps, with a specific focus on steady-state CFD, transient-CFD, and lumped-parameter approaches. Spindle pumps, renowned for their reliability, efficiency, and low noise emission, play a pivotal role in Thermal Management for Battery Electric Vehicles, aligning with the automotive industry’s commitment to reducing pollutants and CO₂ emissions. The study is motivated by the critical need to curtail energy consumption during on-the-road operations, particularly as the automotive industry strives for enhanced efficiency. While centrifugal pumps are commonly employed for such applications, their efficiency is highly contingent on rotational speed, leading to energy wastage in real-world scenarios despite high efficiency at the design point. Consequently, the adoption of precisely designed spindle pumps for thermal management systems emerges as a viable solution to meet evolving industry needs. Recognizing the profound impact of simulation tools on the design and optimization phases for pump manufacturers, this research emphasizes the significance of fast and accurate simulation tools. Transient-CFD emerges as a powerful Tool, enabling real-time monitoring of various performance indicators, while steady-CFD, with minimal simplifications, adeptly captures pressure distribution and machine leakages. Lumped-parameter approaches, though requiring effort in simulation setup and simplifying input geometry, offer rapid computational times and comprehensive predictions, including leakages, Torque, cavitation, and pressure ripple. Breaking new ground, this paper presents, for the first time in the literature, accurate simulation models for the same reference machine using the aforementioned methodologies. The results were rigorously validated against experiments spanning a wide range of pump speeds and pressure drops. The discussion encompasses predicted flow, Torque, cavitation, and pressure ripple, offering valuable insights into the strengths and limitations of each methodology. Full article

In this study, an analysis of a low-specific-speed pump is carried out based on the methods of one-way and two-way fluid–structure interactions (FSIs). This study analyzes the influence of FSIs on the internal flow field and external characteristics of the pump. Utilizing a two-way FSI, the signal coherence analysis method is employed to analyze the coherence of signals between the flow field and the structural field. Addressing the issue of a lack of a connection between the two signals, this study bridges a gap in the existing research. The results indicate that different interaction methods have certain influences on impeller stress and deformation. However, in both coupling modes, the maximum deformation and the maximum equivalent stress have the same distribution position. The head error obtained using the two-way coupling method is lower than that of the uncoupled results, which indicates that the two-way FSI calculation results are closer to the experimental results. The pressure pulsation signals at the interface of the impeller and volute exhibit strong coherence with the structural field signals. For low-specific-speed centrifugal pumps, establishing a clear connection between the flow field signals and structural field signals will help guide further optimization of their performance through design. Full article

In order to meet different operational requirements, existing low specific speed centrifugal pumps may have to be run at high speeds. Therefore, it is crucial to understand the transient performance of such centrifugal pumps during high speed starting and stopping. However, there are currently no experiments on the starting and stopping of low specific speed centrifugal pumps. In this paper, transient hydraulic performance experiments during starting and stopping had been carried out on an atypical open impeller centrifugal pump with a rated flow rate of 6 m³/h using an updated test rig. The correlation of speed, flow, head and shaft power with time was obtained for four flow ratios of 0.353, 1.022, 1.654 and 2.343 operating conditions. It was found that the fluctuation of the shaft power curve was the strongest during the starting process, and there was a significant impact phenomenon. The corresponding impact shaft power from small to large flow rates were 0.167 kW, 0.409 kW, 0.234 kW and 0.215 kW, and the shaft power impact phenomenon was the most obvious under rated operating conditions. During the stopping process, the speed, flow rate and head all remain stable for a small period of time, and the time required to decrease to 0 is longer than the time required to reach a stable state during starting. During stopping, the shaft power will instantly decrease, accompanied by varying degrees of fluctuations. Full article

Centrifugal pumps are the most common machines responsible for the increase in hydraulic energy in a piping system. Their proper design, operation, and maintenance have a strong influence on the performance of technological processes carried out in many industrial units. For the ultra-low specific speed (n_q < 10) application, there is no economical reason for these pumps to be used. This is caused by an increase in internal losses in the pump. The article concerns the problem of the hydraulic operation of a new type of labyrinth pump—the radial labyrinth pump (RLP), which is a developed axial unit. The main research method involves the experimental research of hydraulic sets consisting of passive and active discs. The analyses were preceded by dimensional analysis and experimental planning. The study investigates the influence of a chosen structural parameter of both discs on the process of energy conversion obtained in the pump. The influence of parameters such as number, depth and width of the grooves, as well as inlet angle and diameter on the properties of the pump was studied and discussed in detail. The essential novelty of the article is the recognition of the hydraulic performance of the RLP with grooved discs. To extend the scope of the conducted research for the chosen hydraulic sets, a comparison of the mutual cooperation of an active disc with a smooth and grooved passive one was conducted. It was identified that not every geometric relationship of the parameters of the active and passive discs results in an increase in head with respect to cooperation with a smooth passive disc (motionless). The highest head and high efficiencies were obtained for sets with short channels with large inlet diameters—zk12 and zk13—ratios for zk12 d_1ap/d_2ap = 0.78, and for zk13 zk12 d_1ap/d_2ap = 0.81. Based on the obtained results, preliminary recommendations for the construction were made. Full article

Low specific speed centrifugal pumps typically suffer from low efficiency and severe backflow; adding optimally structured splitter blades can play a role. In this paper, the distribution of pressure and velocity in the flow channel is analyzed using CFD simulation for a low specific speed centrifugal pump. The geometric parameters of the splitter blade are optimized using an orthogonal test and an artificial fish swarm algorithm; then the optimal splitter blade structure is obtained. Results showed that the splitter blade not only effectively solves the backflow of the flow channel and compresses the range of the trailing vortex, but it also alleviates the cavitation at the inlet of the main blade. When considering the best head, the order of influence of each factor is: Splitter blade thickness > Splitter blade inlet diameter > Splitter blade inlet width. At this time, the thickness of the splitter blade is 4.5 mm, splitter blade inlet diameter is 155 mm (0.775) and Splitter blade inlet width is 23 $\mathrm{m}\mathrm{m}$. Through the closed pump experimental system, it is confirmed that hydraulic performance has been improved. Full article

Low specific speed centrifugal pumps are widely used in urban water supply, agricultural irrigation, petrochemical and other fields due to their small flow rate and high head. Therefore, the study of unsteady flow characteristics plays a vital role in its safe and stable operation. In this paper, numerical simulation and experimental methods are used to explore the unsteady performance of the pump. The results show that the fluctuations of the external characteristic such as head, shaft power and energy loss are due to the periodic disturbance of the flow field of pump. But the transient performance of shaft power and head shows different changing trends due to different influencing factors. In this paper, the transient process of hydraulic performance is divided into three stages according to the causes and characteristics of hydraulic fluctuations. Most of the hydraulic losses occur inside the impeller, so the impeller flow field determines the level of time average hydraulic performance. Although the hydraulic loss of the spiral case is small, it is greatly affected by the rotor-stator interaction, which affects the strength of the hydraulic fluctuation. This study is of great significance to the mechanism of rotor-stator interaction and the stable operation of low specific speed centrifugal pumps. Full article

In this paper, the effects of blade trailing edge (TE) profile modification of the suction side on the internal flow and hydraulic performance in a low-specific speed centrifugal pump are investigated through particle image velocimetry (PIV) analysis. Three impellers with different blade trailing edge profiles named original trailing edge (OTE), arc trailing edge 1 (ATE1), and arc trailing edge 2 (ATE2) are designed for PIV experiments. Results show that blade trailing edge modification of the suction side can significantly change the flow pattern, affecting the hydraulic performance of the model pumps. There is a definite counterclockwise backflow vortex near the suction side of OTE at deep-low flow rate, resulting in a decrease in the uniformity of the flow field at the outlet and the hydraulic performance. ATE1 with a reasonable larger blade outlet angle has the best flow field, and the head and efficiency are increased by about 1.2% and 8%, respectively under the same working condition. The hydraulic performance of ATE2 with the blade outlet angle of 59° is better than that of OTE under low flow rate, but it is less than that of OTE under high flow rate due to the streamline deviation generated on the pressure side. Meanwhile, the energy conversion abilities of the modified model pumps are evaluated by slip factor and the deviation degree of the nominalized local Euler head distribution (NLEHD). Since there is no definite counterclockwise backflow vortex at the outlet after modification, the slip factor of ATEs increases and the energy conversion ability is enhanced. Moreover, the jet-wake phenomenon of ATEs is weakened, and the local Euler head (LEH) increases near the outlet, decreasing the deviation degree of the NLEHD to obtain better energy conversion ability. Full article