Multiparameter and multiobjective optimization design of centrifugal pump based on orthogonal method

For the centrifugal pump, additional splitter blades are sometimes necessary in order to improve the head and efficiency. On the other hand, the additional splitter blades will have effect on the cavitation performance due to the changes at the impeller inlet channel. In order to investigate this influence, three impeller schemes were proposed based on a model pump IS50-32-160, one without splitter blades and another two with splitter blades of different inlet diameters. Numerical simulations were carried out to investigate the characteristics of internal flow and the pump cavitation performances at different NPSHA with the CFD technique. The results show that the additional splitter blades will have some positive effect on the pump cavitation performance if the inlet diameter of the splitter blade is properly selected. The reason behind such improvement is that it helps to avoid the flow blocking at the impeller inlet and the vortex cavitation inside the blade passages effectively. For the pump model under our investigation, the cavitation performance reaches its best when the inlet diameter of the splitter blade is 0.725D2.

The aim of the current study is to investigate the effect of inlet blade angles on cavitation performance in a centrifugal pump. In order to reveal this relationship, both hub and shroud blade angles are considered and a two-phase three-dimensional computational fluid dynamics (CFD) study is carried out. Shear stress transport (SST) turbulence and Rayleigh–Plesset cavitation models are used in simulations. Inlet blade angles for both hub and shroud are changed and pump performance (head-discharge) and cavitation (head-inlet pressure) graphs are obtained for eight different designs. Afterward, numerical cavitation tests are conducted, required net positive suction head values of the each design are calculated, and variations are demonstrated. Results show that hub and shroud blade angle variations have no significant effect on the pump characteristic curves excluding for shroud blade angle at high discharge values. However, cavitation performance of the pump is excessively affected for both hub and shroud blade angle alterations. Increasing hub blade angle has slightly negative effect on cavitation performance of the pump. On the other hand, while increasing shroud blade angle from 20 deg to 30 deg have positive effect on cavitation performance, it is negatively affected from 30 deg to 50 deg.

In order to figure out the priority order of factors affecting centrifugal pump cavitation performance, the author carried out an orthogonal experiment on impeller geometric parameters which affects its cavitation performance, designed different impeller hydraulic models with the help of PCAD software, and used CFX software to conduct numerical stimulation calculation about its hydraulic and cavitation performance. The cavitation model used in this paper accurately predicted the centrifugal pump NPSH, in accordance with the experimental results of the prototype. The calculation result of the centrifugal pump cavitation performance was analyzed by the range analysis method. The influence of impeller inlet diameter, impeller exit width, outlet installing angle of impeller and blade numbers on centrifugal pump's cavitation performance weakens successively.

The non-uniform inflow caused by the elbow inlet is one of the main reasons for the low actual operation performance of a centrifugal pump. Orthogonal experiment and GA_PSO algorithm are used to improve the head and efficiency of a centrifugal pump with an elbow inlet based on the method combining numerical simulation and prototype experiment in this paper. The effects of the design parameters, including elbow inlet radius ratio, blade inlet angle, blade number, blade wrap angle, blade outlet angle, impeller outlet diameter, blade outlet width and flow area ratio, on the pump head and efficiency are studied in the orthogonal experiment. The blade inlet angle is the major factor to match the non-uniform inflow and reduce the flow loss in the impeller inlet to contribute to enhancing the pump performance and cavitation characteristics. The particle swarm optimization (PSO) algorithm is optimized by integrating the genetic algorithm (GA), which ensures that the PSO-calculation result avoids falling into the local optimization and the global optimal solution is obtained as quickly as possible. The centrifugal pump with an elbow inlet is optimally designed by the GA_PSO algorithm. According to the performance test results, the efficiency of the optimized pump is 4.7% higher than that of the original pump.

To improve the cavitation performance of the centrifugal pump, a new kind of centrifugal pump impeller with slot is proposed. The slot is on the impeller shroud near the suction side of the blade leading edge. So, the fluid with high energy in the impeller front side chamber is drained to the lowest pressure area. The jet flow would compensate the blade inlet flow with a certain energy. With numerical simulations, the pump’s inner flows for 5 different slot sizes and their hydraulic performances are compared with those of the prototype pump. The slot jet would result in the increase of the impeller flow rate and the volute area ratio, leading to the head decrease within the whole flow rate range. The slot jet can suppress the reverse flow remarkably at a low flow rate, and the pump efficiency is improved. The slot jet improves the pump cavitation performance effectively, especially at a low flow rate. To some extent, the smaller the slot size is, the better the pump cavitation performance is. The cavitation performance of the slot impeller with a size of 2 mm×1.75 mm is much better than that of the prototype impeller. Compared with the prototype impeller, the lowest pressure near the slot impeller blade inlet and even the pressure in all forepart regions are improved significantly. The slot impeller is shown to be effective in suppressing the cavitation, and the available net positive suction head is improved.

A high specific speed centrifugal pump is used in the situation of large flow and low head. Centrifugal pump parameters need to be optimized in order to raise its head and efficiency under off-design conditions. In this study, the orthogonal experiment design method is adopted to optimize the performance of centrifugal pump basing on three parameters, namely, blade outlet width b2, blade outlet angle β2 and blade wrap angle φ. First, the three-dimensional model of the centrifugal pump is established by CFturbo and SolidWorks. Then nine different schemes are designed by using orthogonal table, and numerical simulation is carried out in CFX15.0. The final optimized combination of parameters is b2 = 24 mm, β2 = 24°, φ = 112°. Under the design condition, the head and efficiency of the optimized centrifugal pump are appropriately improved, the increments of which are 0.74 m and 0.48%, respectively. However, the efficiency considerably increases at high flow rates, with an increase of 6.9% at 1.5 Qd. The anti-cavitation performance of the optimized centrifugal pump is also better than the original pump. The results in this paper can provide references for parameter selection (b2, β2, φ) in the centrifugal pump design.

In this paper, multi-objective optimization (MOO) of Al2O3-water nanofluid flow in microchannel heat sinks (MCHS) with triangular ribs is performed using Computational Fluid Dynamics (CFD) techniques and Non-dominated Sorting Genetic Algorithms (NSGA II). At first, nanofluid flow is solved numerically in various MCHS with triangular ribs using CFD techniques. Finally, the CFD data will be used for Pareto based multi-objective optimization of nanofluid flow in MCHS with triangular ribs using NSGA II algorithm. In the MOO process there are seven geometrical and non-geometrical parameters and the conflicting objective functions are to simultaneously maximize the amount of heat transfer and minimize the pressure drop. Five optimum designs are determined and discussed for both nanofluid and base fluid flows. Details of design variables for each of five optimum points are deeply discussed. It is shown that the achieved Pareto solution includes important design information on nanofluid flow in MCHS with triangular ribs.

To study the effect of blade wrap angle on energy performance and unsteady characteristics of the single-channel pump, a single-channel pump with specific speed of 140 was selected as experimental test model and three impeller models with blade wrap angle of 290°, 340° and 390° were respectively designed. The performance of different single-channel pumps with blade wrap angle of 290°, 340° and 390° respectively were tested. Based on the experimental study, the effect of blade wrap angle on the energy characteristics, head pulsation, pressure fluctuation and radial force of the single-channel pump was obtained and analyzed. The results show that with blade wrap angle increases from 290° to 390°, the maximum pump head and efficiency gradually increases and the maximum increase amplitude is 7.3% and 7.79% respectively. The minimum static pressure at impeller outlet under three schemes all occurs at 1.0Qd and bigger blade wrap angle can reduce the mixing loss at impeller outlet. With the increase of blade wrap angle, the head pulsation and pressure fluctuation all decrease gradually. The maximum eighth section under the small flow rate and under the big flow rate occurs at the volute second the section. A higher pressure fluctuation exists around volute tongue. The time-averaged radial force decreases as the blade wrap angle increases and its increase amplitude decreases as the flow rate increases. The research fruits can provide some reference and theoretical basis for the optimization of single-channel pumps.

A reverse running centrifugal pump is one of the attractive choices in micro-hydropower development and industrial pressure energy recovery. One of the main problems in utilizing pump as turbine (PAT) is that the performance of PAT is usually not ideal due to the impeller with the routine backward curved blades which do not match well with turbine running condition. A cost effective suitable way for solving this problem is to redesign impeller with forward curved blades from turbine working condition while the other components do not undergo any modifications. Blade inlet width is one of the main factors in impeller design. Therefore, research on the influence of blade inlet width on PAT performance is useful. In this paper, based on the constant velocity moment theory, the velocity moment at impeller inlet is acquired, firstly. Next, a relationship expression between blade inlet angle and the design flow rate is deduced. To perform research on blade inlet width influencing PAT’s performance with special impeller, three impellers which inlet widths are 13 mm, 16 mm and 19 mm, respectively, are designed by using ANSYS Bladegen software. Numerical simulation and analysis of the three PATs are performed using a verified computational fluid dynamics (CFD) technique. Comparison of three PATs’ performance curves obtained by CFD, we can find that the blade inlet width has obvious effect on the performance of PAT. The flow rate, required pressure head, generated shaft power, and efficiency at best efficiency point (BEP) increase with the increase of blade inlet width. The flow rates of three PATs at BEP are about 90 m3/h, 100 m3/h and 105 m3/h, respectively, when impeller inlet width varies from 13 mm to 16 mm and 19 mm. The BEP of three PATs shifts towards higher discharge and its high efficiency range becomes wider with the increase of blade inlet width. At above 100 m3/h discharge, the PAT efficiency increases in accordance with the increase of blade inlet width. And the hydraulic loss and turbulence kinetic energy loss within impeller decrease with the increase of blade inlet width. In order to improve efficiency, it is helpful to choose a relatively larger blade inlet width in the design of special impeller using in turbine mode of PAT.

The blade outlet angle, wrap angle, and number of blades of the impeller are optimized to increase the pumping efficiency of the automotive coolant pump while keeping the size constant. Three new variants were designed and the optimal one was selected for the comparison with the original scheme. The experiment was conducted to test the hydraulic performance of the optimized impeller. The results show that the energy characteristics of the optimized impeller are in reasonable agreement with the experimental data. The energy characteristics and internal flow details of original scheme and optimized scheme are analyzed and compared. It was found that increasing the wrap angle while decreasing blade outlet angle appropriately can improve the flow conditions and the pressure distribution in the impeller and the volute, especially at low flow rates. At the designed flow rate, increasing the wrap angle while decreasing the number of blades and blade outlet angle can significantly increase the efficiency of the pump. And the maximum efficiency of the optimized impeller is 4.8% higher than the efficiency of the original impeller. The results of the study can guide designers in optimizing an automotive centrifugal coolant pump and reduce energy consumption of the automotive cooling system.

The use of pumps as turbines has been gaining more and more attention in recent years. The present work mainly investigates the influence of blade wrap angle on the internal flow and pressure fluctuation characteristics of centrifugal pumps as turbines. Five different wrap angles (35°,45°, 55°, 65°, and 75°) for a forward-curved impeller were numerically analyzed under multiple operating conditions. The accuracy of numerical simulation was validated by experimental results. The results show that maximum efficiency is achieved with a blade wrap angle of 35°, and the highest efficiency flow point gradually decreases as the blade wrap angle increases. It is found by conducting entropy production theory analysis that the high-entropy production rate regions in PATs are concentrated in the volute tongue and impeller blade inlet regions, and that the entropy production rate at the impeller inlet region increases and then decreases as the blade wrap angle decreases. In addition, pressure pulsation was affected not only by dynamic and static interference but also by an irregular vortex around the impeller; its magnitude under Qt is higher than 0.8Qt for blade wrap angles of 55° and 75°. The primary frequency of pressure pulsation within the impeller is the axial frequency fn and its multiples, and the frequency with the largest amplitude is 3fn. The periodicity of vortices is closely related to the periodicity of pressure pulsation. And it is suggested that a PAT with a 35° blade wrap angle is advantageous for improving the stability of a turbine.

With the pressure decreasing, the process of cavitation in a centrifugal pump could be summarized as incipient cavitation, quasi-steady cavitation and unsteady cavitation. Quasi-steady cavitation is the condition that is between the incipient cavitation and unsteady cavitation in a centrifugal pump. Under this condition, the intensity of cavitation is relatively weak, and the head of the pump almost remains unchanged, but the cavitation exists, causing damage to the impeller by pitting and erosion. So it is important to investigate the quasi-steady cavitation. In this paper, both the numerical and experimental methods had been carried out to investigate the characteristics of quasi-steady cavitation. The internal flow in the pump, the performance of cavitation and the inlet and outlet pressure pulsation of the pump measured through experimental method have been studied under different NPSHa conditions. It was found that the head decreases about 0.77%-1.38% from non-cavitation condition and it could be regarded as the quasi-steady cavitation. Little change has been found from the internal flow between non-cavitation condition and quasi-steady cavitation condition. The period of inlet pressure pulsation changes from the time that the blade passes by to the period of shaft rotating with the development of cavitation. The dominant frequency of the inlet pressure pulsation is two times of shaft frequency whose amplitudes decrease firstly and then increase to a peak value, followed by a decrease to a low value in quasi-steady cavitation conditions. The dominant frequency of the outlet pressure pulsation is blade passing frequency whose amplitudes increase firstly and then decrease gradually with the decrease of NPSHa.

Based on the three-dimensional design platform, this article conducted parametrization of blade leading and trailing edge positions, and analyzed the influence of different position parameters on mixed-flow pump hydraulic performance and internal flow with model test and numerical simulation. The results showed that the hydraulic efficiency η of a mixed-flow pump increased slightly when the position parameter θh of the blade leading edge on the hub increased, and η increased significantly when the position parameter θt of the blade leading and trailing edge positions on the shroud increased. However, with θt increasing, the growth rate of η decreased. Numerical simulation has shown that by selecting a proper value of θt, the impeller energy conversion capacity can be effectively improved, and the distributions of static pressure and total energy can be more uniform in the flow passage. Meanwhile, with θt increasing, blade angle on the blade trailing edge decreased. Correspondingly, the absolute velocity in the outlet zone decreased, and the hydraulic loss in the outlet zone also decreased, which is beneficial to improving hydraulic efficiency of the mixed-flow pump. Within the value range of 7–9°, with different combinations of position parameter θt1 of the blade leading edge on the shroud and position parameter θt2 of the blade trailing edge on the shroud, the mixed-flow pump hydraulic efficiency η and blade wrap angle ϕ show a linear positive correlation, suggesting that an increase in ϕ could significantly improve impeller energy conversion capacity. Compared to θt1, θt2 has a more significant influence on ϕ and η. Thus, the value of θt2 should be carefully attended to during design process.

In engineering applications, design and manufacture of double-suction impeller are on the basis of single-suction impeller. However, there is a lack of clear view on the differences of hydraulic performance between single-suction centrifugal pump and double-suction centrifugal pump which has the same blades. In this paper, a single-suction centrifugal pump and double-suction centrifugal pump with the same blades are investigated respectively, and their hydraulic performances have been compared in terms of external characteristics, flow pattern, pressure fluctuation and cavitation characteristics. In operating range of 0.6Q0∼1.1Q0, results show that the efficiency of double-suction pump is 4.14% higher than that of single-suction pump stably, and the head of single suction pump is 3.5% higher than that of double-suction pump stably. Single-suction impeller and double-suction impeller have similar jet-wake structure in impeller outlet, but the amplitude of velocity of single suction impeller changes more sharply. In the vicinity of rated condition, the amplitude of pressure fluctuation of double suction pump is about half that of the single suction pump, and the cavitation performance of double suction pump and single suction pump are basically the same. These quantitative results show that pressure fluctuation characteristics and cavitation performance of single-suction pump and double-suction pump with the same blades have little difference in the vicinity of rated condition. Compared with single-suction pump, the head of double-suction pump has declined, while the efficiency has improved remarkably. The research results have significant guidance on excavating the potential of excellent hydraulic models and guiding the design of double-inlet multistage double-suction centrifugal pump.

Blade wrap angle is one of the main parameters of centrifugal pump, which has an important influence on the internal flow characteristic and pump performance. In this work, five impeller models with different blade wrap angles (85°, 95°, 105°, 115°, and 125°) are established on the condition of other impeller parameters remain unchanged, whose external characteristic, internal flow, and wear were analyzed by numerical simulation method. The results show that the influence of blade wrap angle on efficiency is more significant than head, has a certain effect on the internal flow field of the centrifugal pumps and effects the wear position of pressure surface. With the increasing of blade wrap angle, the pump efficiency increases companied by the pump head decreases slightly, the area of higher speed at the outlet of the impeller tends to decrease, the higher speed wake area at the end of the blade pressure surface breaks and shrinks, the vortex in the impeller passage is fewer and smaller, the turbulent kinetic energy and morphology of vortex inside the pump decreases gradually, and the wear rate of the flow passage components shows a pattern of first decreasing and then increasing.