Original Impeller Research Articles

Research on optimization methods for large-flow coefficient centrifugal compressors

The present paper focuses on the optimization of large-flow coefficient centrifugal compressors, utilizing a mature centrifugal compressor impeller with a flow coefficient of 0.16 under design point condition in engineering as the research subject. Due to the more complex flow mechanism and more design parameters in the impeller with large flow coefficient, the traditional artificial optimization method is insufficient. In present paper, the impeller with a large flow coefficient is optimized using the concept of combining physical principles and artificial intelligence tools. Firstly, the impeller underwent a redesign based on the theory of maximum flow capacity, with the aim of reducing the Mach number at the impeller inlet to enhance the compressor’s performance. And the efficiency of the impeller at the design point has been increased from 88.6% to 89.9%. In order to further improve the performance of the impeller, an optimization algorithm grounded in gradient variation was employed to facilitate the automatic compressor optimization, and the flow losses at the impeller’s top under low-flow conditions has been mitigated. The results of three-dimensional numerical simulation showed that the operating range of the new impeller is 7% wider than that of the original impeller.

Enhancing Pump as Turbine (PAT) performances: A numerical investigation into the impact of impeller leading edge rounding

Pump As Turbine (PAT) utility represents a major advance in the field of hydraulic engineering. This work aims to improve the PAT performance characteristics. The sharp impeller leading edge (original impeller) was revealed by flow analysis as exhibiting negative effects on the PAT performances due to flow separation and flow misalignment. The performances of rounded and original impeller leading edge were studied by Computational Fluid Dynamic (CFD) method carried out on ANSYS CFX. Although impeller leading edge rounding has notably improved the performances in off design conditions, the difference of efficiency between the both impeller types was decreasing when increasing the discharge. The hydraulic head generated by the rounded impeller leading edge was also slightly higher at part load conditions, but when increasing the discharge, the difference between the both heads became negligible. It appeared from numerical simulations that the impeller leading edge rounding allows to decrease the hydraulic losses of the individual sub-domains except the outlet pipe. For the seek of a comprehensive analysis, the significant losses were computed for the two impeller geometries. It was observed that the shock losses and swirling losses of the rounded impeller leading edge were lower at part load conditions, but when increasing the discharge, the both losses were lower for the original impeller geometry. The rounded impeller leading edge exhibited as well lower wall frictional losses for the entire operating range of discharge.

Effect of the impeller blade outlet setting angle on the performance of the helical axial-flow multiphase pump

Effect of the impeller blade outlet setting angle on the performance of the helical axial-flow multiphase pump

Leakage vortices and energy characteristics of semi-open sewage pump with various blade tip alterations

As one of the most commonly used fluid machineries, sewage pumps play a critical role in various sectors, including urban construction, industry, and environmental protection. Considering the clog-resistant performance, the impeller usually uses a semi-open structure, giving rise to a tip structure that introduces leakage flow. This exacerbates the instability of flow within the pump, thereby impacting the overall performance and operational stability of sewage pumps. In this study, four distinct blade tip structure schemes are developed through a combination of numerical calculations and experimental validation. The Liutex–Omega vortex identification method is employed to scrutinize the initiation and development mechanisms of the leakage vortex system. A comprehensive analysis is conducted to explore the influence of the tip structure on both the energy characteristics and the internal flow dynamics of semi-open sewage pumps. It is found that the complex mixing effect of the leakage flow with the main flow is the primary source of energy loss within the semi-open impeller. Additionally, the characteristic angle of the leakage flow exhibits a high correlation with the energy dissipation characteristics of the impeller. Meanwhile, the impeller with a rounded tip exhibits the poorest performance, with the most substantial reductions in head and efficiency amounting to 44.17% and 36.11%, respectively, compared to the original impeller. Conversely, the impeller featuring a T-shaped tip demonstrates a maximum increase in the head of up to 7.25% under conditions of a large clearance size. This study not only contributes to the theoretical understanding of the unsteady flow within the semi-open impeller but also offers valuable insights for the optimized design of semi-open impeller sewage pumps, holding both theoretical and practical significance.

Performance prediction and optimization of hydrogenation feed pump based on particle swarm optimization – least squares support vector regression surrogate model

Due to high power consumption and low energy efficiency of the hydrogenation feed multistage pump, conducting structural optimization design and reducing energy losses for this pump is necessary. In this study, an optimization method based on the particle swarm optimization (PSO) algorithm and least squares support vector regression (LSSVR) surrogate model is proposed. The head and efficiency are taken as the optimization objectives of the multistage pump, and the optimization design of the two impellers is carried out. Through the optimization of the surrogate model, the head and efficiency of the multistage pump are increased by 3.99% and 2.91%, respectively. It is found that the optimized impeller has more stable flow characteristics than original impeller. Further, the entropy production method is introduced to analyze the energy loss of pump. The result shows that the pump optimized by PSO-LSSVR surrogate model can reduce 9% energy consumption under nominal flow rate. It is attributed to the inhibitory effect of the optimization scheme on the horseshoe vortex at leading edge and the wake vortex at trailing edge of impeller. This study provides a new idea for the optimization design of high efficiency and low energy consumption of multistage centrifugal pumps.

Analyzing the impact of blade geometrical parameters on energy recovery and efficiency of centrifugal pump as turbine installed in the pressure-reducing station

Improving renewable energy efficiency has received great attention globally by increasing demand for energy supplies and air pollution issues. The Soft Pressure Regulation System (SPRS) as a potential technology provides the possibility of regulating pressure and energy recovery in pressure-reducing stations. Pump as Turbine (PAT) is a good choice for installation in Water Distribution Network (WDN) pipelines due to its availability and economic benefits, and it can play a key role in decreasing startup time and return on investment. In this paper, the performance of centrifugal PAT under WDN conditions has been numerically and experimentally evaluated, and simulation validation was performed, too. Analyzing the work conditions of the pressure reduction station shows that the hourly flow rate trend changes considerably based on end-user demand. A major portion of the SPRS's operation time occurs in off-design conditions of the PAT, and efficiency is drastically decreased considering the lack of flow control tools. The effect of blade inlet angle, blade warp angle, blade curvature, and change of these parameters simultaneously was investigated to increase the high-efficiency working range. Losses resulting from flow separation and formation of vortices are significantly decreased by simultaneous change of blade geometrical parameters in the range of design point and higher flow rates (Q ≥ 1.0QBEP). Since the highest frequency of flow rate based on statistical analysis occurs in this range, the total power generation of SPRS improves significantly. The PAT efficiency with the improved impeller at part-load condition (0.8QBEP), design condition (QBEP), and over-load condition (1.2QBEP) is improved by 0.83 %, 2.69 %, and 6.71 % in comparison with the original impeller, respectively.

Enhancing mesenchymal stem cells cultivated on microcarriers in spinner flasks via impeller design optimization for aggregated suspensions

During the ex vivo expansion of umbilical cord-derived mesenchymal stem cells (hUCMSCs) in a stirred tank bioreactor, the formation of cell–microcarrier aggregates significantly affects cell proliferation and physiological activity, making it difficult to meet the quantity and quality requirements for in vitro research and clinical applications. In this study, computational fluid dynamic (CFD) simulations were used to investigate the effect of an impeller structure in a commercial spinner flask on flow field structure, aggregate formation, and cellular physiological activity. By designing a modified impeller, the aggregate size was reduced, which promoted cell proliferation and stemness maintenance. This study showed that increasing the stirring speed reduced the size of hUCMSC-microcarrier aggregates with the original impeller. However, it also inhibited cell proliferation, decreased activity, and led to spontaneous differentiation. Compared to low stirring speeds, high stirring speeds did not alter the radial flow characteristics and vortex distribution of the flow field, but did generate higher shear rates. The new impeller’s design changed the flow field from radial to axial. The use of the novel impeller with an increased axial pumping rate (Qz) at a similar shear rate compared to the original impeller resulted in a 43.7% reduction in aggregate size, a 37.4% increase in cell density, and a better preservation of the expression of stemness markers (SOX2, OCT4 and NANOG). Increasing the Qz was a key factor in promoting aggregate suspension and size reduction. The results of this study have significant implications for the design of reactors, the optimisation of operating parameters, and the regulation of cellular physiological activity during MSC expansion.Graphical

Performance and unsteady flow characteristic of forward-curved impeller with different blade inlet swept angles in a pump as turbine

As an economical energy recovery device, a pump as turbine (PAT) is widely used in micro hydropower and energy recovery fields. Compared with an original impeller, a special impeller with forward-curved blades can dramatically enhance a PAT's efficiency and broaden its high-efficiency range because the blade angles created by the latter more effectively match the PAT's operating mode. The shape of blade curve and sweep has obvious influence on the performance of a PAT. To investigate how the inlet swept angle of forward-curved blade influences the performance of PAT, five different forward-curved impellers with different inlet swept angle blades were designed and numerically investigated based on a verified computational fluid dynamics (CFD) method. The effects of blade inlet swept angles on the external characteristics, energy loss and unsteady characteristics of PAT are analyzed. Compared with the blade whose inlet swept angle is 0°, the maximum efficiency of back-swept PAT with swept angle of −8° increases by 0.58% while the head decreases by 0.49 m. However, the efficiency of forward-swept PAT of 8° reduces by 0.9%, and the head increases by 0.68 m. The maximum reduction rates of the main frequency amplitude of pressure pulsation in the volute, impeller and draft tube of back-swept PAT are 35.2%, 45.47% and 67.24%, respectively, indicating that the back-swept blade can contribute to improve the operation stability of PAT. Moreover, the vortex in PAT with back-swept blade is greatly improved under partial and design flow rate, which can improve the unsteady flow characteristics of PAT.

Investigation into Dynamic Pressure Pulsation Characteristics in a Centrifugal Pump with Staggered Impeller

For the centrifugal pump, the rotor–stator interaction (RSI) induces high-energy pressure pulsation, which directly affects the stability of systems and equipment. Therefore, this work proposes a new staggered impeller structure to suppress high-energy pressure pulsation in centrifugal pumps. The original impeller blade is divided into two layers and is staggered at 10°, 20° and 30° to form a staggered impeller. The dynamic pressure pulsation characteristics of both the original impeller and the staggered impeller are predicted using large eddy simulation (LES). The results indicate that the uniform staggered arrangement of blades can significantly reduce the pressure pulsation energy in the pump by 54.69% under the design conditions, while also achieving the best performance. Even under off-design conditions, the pressure pulsation energy can still be effectively suppressed by the staggered blades. The study of the time–frequency domain of the monitoring points near the tongue found that the phase difference in the pressure fluctuation caused by the RSI between the staggered impeller and the tongue prevents the superposition of pressure pulsation energy and efficiently suppresses it in the pump. The results can provide a reference for optimizing low-vibration-noise pump impellers in engineering applications.

원심 펌프의 임펠러에 대한 혹등고래 결절 형상 적용 및 최적화

In this study, bio-mimetic tubercle shapes of humpback whale are applied to the impeller of a commercial centrifugal pump based on RANS simulations and design optimization. In specific, a few geometric parameters of tubercles are employed as the design variables of the trailing and leading edges of the impeller. Design optimization is performed based on a sampling approach and the radial-basis artificial neural network. As the objective function, a combination of the turbulent kinetic energy (TKE) and pump efficiency is used based on the effects of tubercle shapes found in previous studies. Pump performance and flow fields are compared between the optimized and original impeller designs. The results show that the optimized tubercle design at the impeller trailing edge affects the vortical structures significantly. Tubercles generate counter-rotating vortices in wake region of the impeller, which leads to vortex breakdown and a decrease of turbulent fluctuation by about 25%. Also, a trade-off between the TKE and pump efficiency is observed. In contrast, the optimized tubercle design at the impeller leading edge results in relatively smaller (about 3%) reduction of the TKE. While the leading edge tubercles suppress flow separation at the suction side significantly, the effect is localized near the leading edge. For both leading and trailing edge optimization, the changes of the pump efficiency and head are found to be relatively minor.

The influence of blade trailing edge modification on the pressure pulsation inside a two-stage centrifugal pump

Adjusting the clearance between the rotor and the stator in the centrifugal pump is an effective measure to reduce the pressure pulsation. In this paper, we investigated the influence of blade trailing edge modification on the internal unsteady flow and the performance of a two-stage centrifugal pump with the V-type trailing edge (VTE) and elliptic trailing edge (ETE). The pressure pulsation on the spherical casing and the performance were analyzed based on the experimental results for the pump with the modified blade trailing edges of the cutting depths 1 mm, 2 mm and 2.5 mm. Also the unsteady flow in the pump was numerically simulated, and the velocity and the axial vorticity intensity were analyzed to evaluate the influence of the flow on the pressure pulsation and the performance of the pump. The results show that cutting the blade trailing edge will reduce the head and efficiency of the two-stage pump, and different outlet shapes under the same cutting depth have little effect on the performance. The modified impeller makes the high velocity areas at the blade outlet away from the spherical casing wall and reduces the pressure pulsation amplitude at the main frequency. At the design flow rate, the heads decrease by 7.3%, 9.8% and 11.3%, the efficiencies decrease by 2.8%, 3.5% and 4.0%, and the pressure pulsation amplitudes at the main frequency are reduced by 29%, 10.1% and 28.7% for the ETE1, ETE2, ETE2.5 blade compared with that of original impeller. Also, the heads decrease by 6.3%, 8.0% and 9.1%, the efficiencies decrease by 3.5%, 3.9% and 4.1%, and the pressure pulsation amplitudes at the main frequency are reduced by 3.2%, 11.7% and 38.1% for VTE1, VTE2, VTE2.5 blade. When the cutting depth is large, the trailing edge of the blade has a large vortex intensity. This may cause the energy loss and lead to the decrease of the efficiency and head. Considering the performance and unsteady pressure pulsation of the two-stage pump, the impeller with VTE1 blade has certain reference significance for engineering application.

Performance improvement of forward-curved impeller with an adequate outlet swirl using in centrifugal pump as turbine

Pump as turbine (PAT) is a type of economical energy recovery device that is widely used in micro-hydropower plants and energy recovery. A special impeller with forward-curved blades can dramatically improve the PAT's performance relative to an original impeller with backward-curved blades because the inlet angle created by the former more effectively matches volute outlet flow. The blade outlet angle is another important factor in energy conversion. To investigate the effects of blade outlet angle on the performance of a special impeller, four outlet velocity moments were chosen according to the same inlet velocity moment value vu1r1 (0.02vu1r1, 0, −0.02vu1r1, -0.04vu1r1, were used). Four special impellers with different blade outlet angles were modeled and simulated via verified computational fluid dynamics. The results show that, the highest efficiency among PATs at −0.02vu1r1 was higher than that at 0.02vu1r1 by 1.46%. A suitable negative outlet velocity moment also helps eliminate swirl at the impeller outlet caused by the asymmetric inlet velocity moment and helps reduce the formation of vortex in the draft tube. This further decreases hydraulic loss and improves the operating stability of PAT. This paper presents a method for determining the blade outlet angle of the special impeller of PAT.

Experimental Investigation on Improving Lifetime of Peripheral Pump Impeller under Cavitation Using Different Techniques

The industry is becoming more interested in peripheral pumps because they are inexpensive, have low specific speeds, and are small. One of the more serious problems that may occur with any pump is cavitation. That has a significant impact on pump components, particularly the impeller. This work presents a detailed experimental study on prolonging impeller lifespan under cavitation conditions by studying the effect of impeller surface finishing and coatings on its lifetime. For this purpose, seven impellers, in addition to the original one of the peripheral pump, had prepared and treated. Three impellers with three different levels of arithmetic surface roughness (Ra) were produced using a low-cost and customizable hand grinding procedure. And four impellers have been coated thermally with four different erosion-resistant composite materials. All of the impellers were cavitated for 300 minutes at normal and one at high water temperatures. The result showed that the mass loss percentages with the smallest (Ra) of 0.35µm, and coated with yellow epoxy were 84.86% and 48.50% lower than the original impeller, respectively. Thus, improving the quality of impeller surface finishing, and thermal coatings are excellent method for increasing the impeller's cavitation erosion resistance and thereby extending its lifetime.

Experimental Investigation on the Effect of the Staggered Impeller on the Unsteady Pressure Pulsations Characteristic in a Pump

High−energy pressure pulsation induced by rotor−stator interaction (RSI) is the primary source of flow−induced vibration noise in the pump, affecting the pump’s stability and system operation. In order to find an effective method to suppress the pressure pulsation in the pump caused by RSI, a new staggered impeller is proposed in this paper, which can significantly suppress the pressure pulsation energy. The unsteady pressure pulsation characteristic of the original impeller and the staggered impeller scheme are measured and analyzed under different working flow conditions. The results show that although the hydraulic performance of the model pump decreases to a certain extent when the staggered impeller is used, the pressure pulsation energy in the pump decreases significantly. Under 0.8QN–1.2QN working flow conditions, the energy suppression effect of the blade passing frequency (fbpf) amplitude is higher than 80% with the staggered impeller scheme. The Root Mean Square (RMS) values for distribution of pressure pulsation in different frequency bands varies greatly, and the pressure pulsation energy near the tongue is prominent. On a broader frequency band (0–6 fbpf), the pressure pulsation energy of the staggered impeller scheme is smaller than that of the original impeller scheme. With the expansion of the frequency band, the pressure pulsation energy decreased steadily, with a minimum decrease of 37.33%.

Influence of a complex impeller with tip clearance on the internal and external characteristics of a multiphase pump

With the exploitation of deep sea and desert oil fields, multiphase pumps have come into the public eye. However, due to the nature of the medium and operating environment, the performance of traditional multiphase pumps has diminished, leading to problems such as increased recovery cycles and rising costs. In order to obtain a high-head, high-reliability multiphase pump, this paper uses the model optimization method to design a complex pattern impeller. The best complex impeller with 17.25% increase in head was selected with the external characteristics as the optimization index, and a comparative analysis of the internal flow field was carried out between the complex impeller and original impeller when the inlet gas volume fraction was 10%. The results show that in the complex impeller, the short blade reduced the proportion of the high-speed zone, inhibited the appearance of the main blade suction surface low-speed zone, and significantly improved the return flow. The slope of the pressure boosting curve at the relative position 1.5–2.0 was increased, and the pressure boosting capacity was increased by 16.34 kPa. The short blade weakens the leakage movement while reducing the pressure effect on the main blade. In addition, the short blade not only improved the gas phase gathering but also reduced its size and made it closer to the main blade suction surface, which improved the uniformity of the gas phase distribution in the flow channel and also enhanced the inlet flow capacity. The results can provide a reference for future optimization and performance improvement of multiphase pump models.

Multi-Conditional Optimization of a High-Specific-Speed Axial Flow Pump Impeller Based on Machine Learning

In order to widen the range of high-efficiency area of a high-specific-speed axial flow pump and to improve the operating efficiency under non-design conditions, the parameters of the axial flow pump blades were optimized. An optimization system based on computational fluid dynamics (CFD), optimized Latin hypercube sampling (OLHS), machine learning (ML), and multi-island genetic algorithm (MIGA) was established. The prediction effects of three machine learning models based on Bayesian optimization, support vector machine regression (SVR), Gaussian process regression (GPR), and fully connected neural network (FNN) on the performance of the axial flow pump were compared. The results show that the GPR model has the highest prediction accuracy for the impeller head and weighted efficiency. Compared to the original impeller, the optimized impeller is forward skewed and backward swept, and the weighted efficiency of the impeller increases by 1.31 percentage points. The efficiency of the pump section at 0.8Qd, 1.0Qd, and 1.2Qd increases by about 1.1, 1.4, and 1.6 percentage points, respectively, which meets the optimization requirements. After optimization, the internal flow field of the impeller is more stable; the entropy production in the impeller reduces; the spanwise distribution of the total pressure coefficient and the axial velocity coefficient at the impeller outlet are more uniform; and the flow separation near the hub at the blade trailing edge is restrained. This research can provide a reference for the efficient operation of pumping stations and the optimal design of axial flow pumps under multiple working conditions.

Experimental study of centrifugal pump as turbine with S-blade impeller

As a hydraulic energy recovery device, pump as turbine(PAT) has been applied widely in the seawater desalination and petrochemical industry. In order to improve the hydraulic performances, the blade inlet angle was redesigned by analyzing the velocity triangle of PAT impeller inlet, and an S-blade was proposed. Then, A new S-blade impeller was obtained by optimizing the impeller in a real case of centrifugal pump as turbine application, and it was compared with the original impeller through experiments. The results show that the efficiency of the new S-blade impeller is around 3% higher than that of the original blade with the fixed flow rate and head. Under the fixed speed, the shaft power of the new S-blade impeller is higher than that of the original blade, and the maximum deviation is 0.75 kW. The study could have important directive significance to blade optimization of PAT.

Study on Impeller Configuration Strategy of Dredger Pump with Different Conveying Distance

For DN850 dredge pumps of 3,500 m3/h series cutter suction dredger, on the premise of not changing the impeller size, by changing the parameters of impeller blade to reduce the head of dredge pump, special new impellers for inboard pump and submerged pump are designed; The flow field of the dredge pump is analyzed by numerical simulation. There is no vortex in the impeller channel and near volute tongue, which indicates that the hydraulic performance is excellent; At the flow rate of 10,000 m3/h, compared with the original impeller, the head of the two pumps in series with new impellers is reduced by 23 m, and the efficiency is close to that before modification, reaching more than 85%; This paper analyzes the matching between the dredger pump and the pipeline under three kinds of common sandy mud. By comparing the unit power consumption and productivity, it obtains the suitable conveying distance range of special new impellers of dredger pumps, and forms the impeller configuration scheme of 3,500 m3/h series cutter suction dredger with different conveying distance, which provides guidance for dredging engineering.

Transportability Improvement of a Gas–Liquid Rotodynamic Pump Using the Two-Step Multi-Objective Optimization Strategy

The development of multiphase pumps is restricted because of low efficiency and poor mixing transportation capacity. In this study, a two-step multi-objective optimization design system for a multiphase pump is constructed using a three-dimensional (3D) design theory and multi-objective optimization techniques. The transportability improvement for the pump impeller is achieved by implementing the optimization variables of its geometry and blade loading and the optimization objectives containing the pump efficiency and gas uniformity. The optimal results of impeller geometry show that the blade wrap angle and control parameters of the hub have remarkable effects on the pump efficiency and gas uniformity. The optimal results of impeller blade loading show that the pump efficiency is improved if the impeller with large loading at the leading edge, large slope at the middle part, and large negative high-pressure edge angle. The gas uniformity is improved if the hub loading at the middle and trailing parts is larger than the shroud loading. Compared to the original test impeller, the pump efficiency with the impeller T-Opt1 and the gas uniformity at the impeller outlet are improved by 10.81% and 6.91%, respectively. The maximum fluctuation amplitudes in T-Opt1 and its corresponding guide vane are reduced by 0.61% and 67.76%, respectively.

Effect of trailing edge bending and sweeping on brake impeller of low-temperature turbo-expander

With the continuous development of low-temperature turbo-expanders, the rotation speed of the rotor is getting faster. The diameter of the impeller has become one of the factors that limit the rotation speed. In this article, a new idea to improve braking capability and reduce the diameter of the brake impeller is proposed. The brake impeller of a small low-temperature air turbo-expander test bench is used as a prototype, influence of the combination of circumferential bending and sweeping at the trailing edge of the brake impeller on the braking ability is studied. It is found that the braking ability is significantly improved. To simplify the description, the combination of a forward bending of 10° and a sweeping of 20° is called combination 1. For the current brake impeller, combination 1 is the most suitable. Compared with the original impeller, the braking power of combination 1 has increased by 99.6 W, an increase of 10.4 %. Forward bending and forward sweep substantially increase the wrap angle of the brake impeller, thereby increasing the air outlet speed and improving the braking ability, but at the expense of the flow stability of the brake impeller.