Optimization and CFD performance analysis of an automotive coolant pump

In order to research the effect of the blade wrap angle and outlet angle on the hydraulic performance of the low-specific speed sewage pump, the Reynolds time-averaged Navier-Stokes equations was discretized based on the finite volume method, and the modified k-ε turbulence model were chosen in FLUENT. Numerical simulation of the internal flow within the centrifugal pump with the specific speed of 60 at different blade wrap angle and outlet angle is carried out. The analysis of the velocity and the turbulent kinetic energy distribution in different cases, and predicts the external characteristics of the several cases based on the loss analysis method. The study results show that the efficiency of pumps increase with decreasing the outlet angle and increasing the wrapping angle at the design of sewage pumps. According to the analysis, changing the blade outlet Angle has much more influence on the performance of the pump than changing the wrap angle.

The influence of inducer blades’ geometry on the propagation of cavitation instabilities was examined using three and four-bladed inducer, to develop the design criteria that can operate stably over a wide operation range. In industrial centrifugal pumps used for transporting liquefied natural gas at low flow rates and low NPSH, the self-excited oscillations caused by cavitation have been observed. In previous studies, both the effect of the number of inducer blades on pump performance and the effect of the blades’ outlet angle on cavitation instability phenomena were investigated. The main objective of this study was to investigate the effect of the configuration of blade number and outlet angle on the suppression of cavitation instability phenomena at low flow rates.

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.

The influence of blade outlet angle on the performance of centrifugal pump with high specific speed

In order to investigate the effect of blade design on pump performance, a CFD analysis was carried out, and the results were compared with experimental performance data of a low specific speed radial pump, which presents a good agreement. After model verification, the effect of impeller geometrical parameters includes blade outlet angle, wrap angle, and width at the exit, was investigated on the pump’s performance. Moreover, these parameters were chosen on three levels using an L9 orthogonal standard array of the Taguchi optimization method. The efficient levels of variables were calculated using the analysis of variance (ANOVA) method. The results revealed that impeller width at exit and blade outlet angle is the most effective pump shaft power and efficiency parameters. To minimize power, the optimal levels are the outlet angle of 27∘∘, wrap angle of 150∘∘, and width at the exit of 9 mm. Further, an outlet angle of 23∘∘, a wrap angle of 155∘∘, and a width at the exit of 9 mm lead to maximum pump efficiency. According to the validation simulations, an increase of 2.4% inefficiency and a minimum power of 3.9KW were achieved. The Overall Evaluation Criteria (OEC) technique revealed that considering 23∘∘, 160∘∘, and 9 mm for outlet angle, wrap angle, and width at the exit, minimum shaft power, and maximum pump efficiency will be achieved. ANOVA introduced width at the exit as the most governing parameter of pump performance characteristics.

In order to study the effect of different numbers of impeller blades on the performance of mixed-flow pump “saddle zone”, the external characteristic test and numerical simulation of mixed-flow pumps with three different impeller blade numbers were carried out. Based on high-precision numerical prediction, the internal flow field and tip leakage flow field of mixed flow pump under design conditions and stall conditions are investigated. By studying the vorticity transport in the stall flow field, the specific location of the high loss area inside the mixed flow pump impeller with different numbers of blades is located. The research results show that the increase in the number of impeller blades improve the pump head and efficiency under design conditions. Compared to the 4-blade impeller, the head and efficiency of the 5-blade impeller are increased by 5.4% and 21.9% respectively. However, the increase in the number of blades also leads to the widening of the “saddle area” of the mixed-flow pump, which leads to the early occurrence of stall and increases the instability of the mixed-flow pump. As the mixed-flow pump enters the stall condition, the inlet of the mixed-flow pump has a spiral swirl structure near the end wall for different blade numbers, but the depth and range of the swirling flow are different due to the change in the number of blades. At the same time, the change in the number of blades also makes the flow angle at 75% span change significantly, but the flow angle at 95% span is not much different because the tip leakage flow recirculates at the leading edge. Through the analysis of the vorticity transport results in the impeller with different numbers of blades, it is found that the reasons for the increase in the values of the vorticity transport in the stall condition are mainly impacted by the swirl flow at the impeller inlet, the tip leakage flow at the leading edge and the increased unsteady flow structures.

To enhance the hydraulic performance and operational stability of a full tubular pump (FTP), this study conducts a systematic investigation and optimization of the impeller structural parameters based on computational fluid dynamics (CFD) simulations and multi-parameter optimization techniques. The number of blades and hub ratio were selected as key geometric variables, and their effects on the head and efficiency characteristics were analyzed using a single-factor approach. The results indicate that increasing the blade number improves the head but shifts the best-efficiency point toward a lower flow rate. In contrast, decreasing the hub ratio deteriorates the low-flow performance while slightly improving the high-flow performance, exhibiting a nonlinear hydraulic response. Subsequently, a surrogate model was constructed using a radial basis function (RBF) neural network (NN) within the Isight platform, and a multi-objective optimization was performed employing the multi-island genetic algorithm (MIGA). Under the constraint of an approximately constant specific speed, the blade outlet angle and blade cascade solidity were identified as the dominant factors influencing head and efficiency. The optimized impeller demonstrated a remarkable improvement in overall efficiency, a more uniform distribution of the blade boundary vorticity flux (BVF), and a significantly improved internal flow structure.

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.

This work presents the influence of splitters on the performance of small-scale turbopumps for organic Rankine cycle applications numerically. Different design parameters, such as impeller diameter at the outlet, number of blades, blade angle at the trailing edge, and the length and location of the splitter blades, are studied for both shrouded and unshrouded impellers at tip clearance ratios of 0.05 and 0.10 (relative to blade height). The results suggest that splitter blades can increase impeller head coefficient and slip factors up to 10%–24% depending on the blade outlet angle. At the same time, the total efficiency is not influenced significantly. The CFD calculations predict that the placement of splitters in the middle of the blade channel leads to the maximum head coefficient for shrouded impellers. In contrast, for the tip clearance ratio of 0.10, a higher head coefficient is observed for placement closer to the suction side of the main blade. After that, different meridional profiles are studied to investigate their influence on the performance characteristics and mitigation of tip clearance effects. Profiles with a sharper change of cross-section area at the inlet rather than a linear change are found more advantageous, as higher head rise, total efficiency, and static efficiency are observed. In the end, the splitter blade profiles are optimized through techniques of design of experiments, leading to a 2.43% improvement in total efficiency. In contrast, the head rise remains constant, and static efficiency decreases by 0.49% for an impeller with a tip clearance ratio of 0.05.

As one of the core components of the fire-fighting water-supply system, the performance of a fire pump directly determines the extent of damage caused by the fire. Compared with conventional pumps, the design requirements of fire pumps not only need to ensure that the head of the pump is at 0Qd, 1.0Qd, and 1.5Qd and its efficiency is at 1.0Qd but also consider the cavitation performance at each flow rate, which presents a greater challenge for the design of high-performance fire pumps. By optimizing the design of a centrifugal fire pump with a specific speed of 24.7, numerical calculations were performed to obtain the best optimized scheme Y4. The results show that at the design flow rate the best optimized scheme improves the efficiency by 9.17% compared with the original scheme, and the head meets the design requirements of the fire pump while avoiding the hump phenomenon. Through a comparative analysis, it was found that the optimized scheme Y4 can reduce the pressure pulsations at the outlet of the pump and improve the cavitation performance at each flow rate. The experiment verifies that the head of the best optimized scheme at the design flow rate is 74.43m, the pump efficiency is 40.22%, and there is no hump in the head curve, which can meet the design and use requirements of the fire pump. The maximum reduction in the outlet pressure pulsations coefficient in the best optimized scheme was 47.12% on average. Compared with the original scheme, the critical net positive suction head (NPSHr) of the best optimized scheme was reduced by 21.5%, 17.6%, 15.7%, and 16.8%, respectively.

Geometrically, the single-blade centrifugal impeller, commonly used today as a sewage pump, is not axially symmetric. For this reason, the static pressure around the impeller fluctuates greatly when the impeller is rotating, and not only the radial thrust but also the axial thrust shows large fluctuations. Therefore, it is extremely important for the improvement of pump reliability to quantitatively grasp these fluctuating hydrodynamic forces. In this study, we investigated the unsteady hydrodynamic forces in a closed-type centrifugal pump with a single blade for different blade outlet angles using a numerical analysis that takes into account both experiment and the leakage flow. The results clearly showed the effect of the blade outlet angle on that act on the impeller. The root-mean-square value of the fluctuating component of the total radial thrust was roughly the same for whichever impeller at low flow rate, but at high flow rates, the value increased for impellers with larger blade outlet angles. Moreover, when the leakage flow rate increased with increasing static pressure around the impeller, such that the rear and front shroud parts were subject to high pressure, the absolute value of the axial thrust on both these parts increased.

The characteristics of the three-dimension flow field of the G4-73 centrifugal fan were numerically simulated based on the k-epsiv turbulence model with the Fluent, and then verified the simulating result by experiment. Taking the efficiency eta maximizing as a function goal, while the blade number and the angle of blade outlet as the variable quantities, the fan impeller parameters are optimized based on least squares method. The optimizing results showed that the performance of centrifugal fan was improved by lowering the energy loss which caused by the secondary flow vortex, the volute tongue, the wake-jet and the angle of attack. After the optimization, the total pressure and efficiency increased 3.7% and 0.5% respectively.

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.

Optimization design of centrifugal pumps involving multiple parameters and objectives is a complicated research topic. The orthogonal method is introduced in the present study to find a high efficiency and low cost way in the optimization process of a centrifugal pump. A orthogonal table designation L16(45) is established, in which 16 individuals of impellers are generated with five design parameters: blade wrap angle, blade angles at impeller inlet and outlet, blade leading edge position, and blade trailing edge lean varying at four levels for each parameter. To realize the multiobjective optimization of both pump efficiency and cavitation performance, an integrated factor considering the weight of two objectives is introduced. On the basis of validated computational fluid dynamics (CFD) technique, the range analysis gives the influence order of five parameters and also determines the value of each parameter. Finally, the optimal centrifugal pump is obtained with remarkable superiority on the efficiency of 3.09% rise and cavitation performance of 1.45 m promotion in comparison with the original pump.

An air compressor is the core component of the air supply system of a hydrogen fuel cell, which demands high efficiency and reliable stability in a wide operation region. In this work, a centrifugal air compressor for a hydrogen fuel cell is first designed and then measured experimentally. Furthermore, a test rig for assessing the aerodynamic performance of the centrifugal air compressor is established, which includes a pipeline, gas flowmeter, flow regulating valve, pressure transmitter, centrifugal compressor, controller, DC power supply and computer. Then, the orthogonal method is employed to conduct the aerodynamic performance optimization. Four optimization parameters—including blade number, blade angle at the inlet, blade angle at the outlet and wrap angle—are set with three levels. Nine compressor individuals are designed according to the orthogonal method, and then numerical simulation is implemented to confirm the aerodynamic performance and flow pattern. Results show that the blade number has the greatest influence on the compressor’s performance, and the blade angle at inlet is also very important. The optimal performance of the compressor improves compared to that of the baseline compressor; the efficiencies of the baseline compressor and optimal compressor are 81.3% and 83.8%, respectively, improving by 2.5%. The frequency domain of pressure fluctuation in the centrifugal compressor is related to the stator-rotor interaction. The peak value of pressure fluctuation amplitude occurs at the rotation frequency of 833 Hz and its harmonic frequency. In comparison with the baseline compressor, the pressure fluctuation amplitude of the optimal compressor is obviously reduced, especially near the volute tongue.