Investigation on the Effect of Impeller Design Parameters on Performance of a Low Specific Speed Centrifugal Pump Using Taguchi Optimization Method

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.

Research on the mathematical modelling of the starting torque of self-lubricating spherical plain bearings

The starting torque of self-lubricating spherical plain bearings (SSPBs) is a key parameter for evaluating the performance of bearings. Therefore, the starting torque of SSPBs should be controlled to within an allowable range. In this paper, the starting torque generation mechanism is analyzed, and the critical load for the separation of the liner from the outer spherical surface of the inner ring is determined. A mathematical model of the starting torque is established; the experimental and theoretical results of the starting torque are compared and analyzed, and then the accuracy of the mathematical model is evaluated by the deterministic coefficient R2. The research reveals that a critical load exists for the starting torque. Below the critical load, the starting torque is dependent on the outer spherical radius of the inner ring, bearing wrap angle, and liner parameters such as the compressive elastic modulus, friction coefficient, and precompression of the liner; however, the starting torque is independent of the radial load. Above the critical load, the starting torque is also dependent on the radial load. The research results provide a theoretical basis for the design and application of bearings.

Research on Performance of Variable-Lead Rotor Twin Screw Compressor

Twin-screw compressors are widely used in aerodynamics, refrigeration and other fields. The screw rotors are the core component of the screw compressor and affect the performance of the compressor. This paper focuses on variable-lead rotors. A thermal process simulation model considering leakage is established to calculate the efficiency of the compressor. Different lead change methods are compared by evaluating the contact line, exhaust port and simulation results. The results show that the compressor obtains better performance when the lead decreases rapidly on the discharge side. Furthermore, the effects of the wrap angle and internal volume ratio on variable-lead rotors are studied. The work provides a reference for the design of the screw compressor rotor.

Analysis of influence of guide vane wrap angle and blade number on propulsive performance of a water jet propulsor

In this paper, the propulsion performance of a screw mixed-flow jet propulsion pump is studied systematically. The optimum thrust performance is achieved by changing the geometrical dimensions of the guide vanes. Under the condition of keeping other parameters unchanged, the operating conditions of the pump can be effectively adjusted by changing the number of guide vanes and wrap angle. The focus of this paper is on the presentation and demonstration of a strategy that takes the number of guide vanes and wraps angle as the main research object and its propulsion efficiency as the main reference index to analyze the advantages and disadvantages of each working condition in detail. The CFD numerical simulation technology has been used for numerical calculation. The simulation results are compared with the experimental results, and the numerical calculation results are in good agreement with the experimental values. The results show that the kinetic energy of the propulsion pump increases with the number of guide vane blades and the angle of wrap angle. The increase of guide angle and the number of blades will reduce the overall propulsion efficiency of the propeller. Finally, a mathematical model of propeller efficiency with the number of guide vane blades and the angle coefficient of guide vanes is established.

Influence of Blade Wrap Angle on the Hydrodynamic Radial Force of Single Blade Centrifugal Pump

To investigate the effect of blade wrap angle on the hydrodynamic radial force of a single blade centrifugal pump, numerical simulation is conducted on the pumps with different blade wrap angles. The effect of the wrap angle on the external characteristics and the radial force of a single blade centrifugal pump was analyzed according to the simulation result. It is found that, with the increase of the blade wrap angle, the head and efficiency of the single blade centrifugal pump are improved, the H-Q curve becomes steeper, and the efficiency also increased gradually, while the high-efficiency area is narrowed. The blade wrap angle has a great effect on the radial force of the single blade centrifugal pump. When the blade wrap angle is less than 360°, the horizontal component of the radial force is negative and the value is reduced with the increase of the wrap angle of the blade. When the wrap angle is larger than 360°, the horizontal component of the radial force is positive and the value increases with the increase of the wrap angle. Under part-loading conditions, the radial force of the single blade pump is significantly reduced with the increase of the blade wrap angle. When the wrap angle is smaller than 360°, the radial force decreases with the flow rate increase. In the condition that the wrap angle is larger than 360°, the radial force increases with the flow rate increase.

Centrifugal pump performance enhancement: Effect of splitter blade and optimization

The shape of impeller blades of a centrifugal pump affects the best efficiency point (BEP), and splitter blades improve the pump performance at BEP. In this work, multiple parameters such as number of blades, length of splitter blade, splitter blade angle at hub, and wrap angle were modified to maximize head and minimize input power. The problem was solved by a numerical and experimental approach. Initially, an impeller was designed and tested in a laboratory setup. The same impeller was simulated in a computational fluid dynamics (CFD) solver, checked the accuracy of the CFD results, optimized by an in-house surrogate-based optimization code and finally the optimal designed manufactured and tested again. The mix and match of the splitter blade with the other parameters improved the pump performance i.e. head by 8.2% and overall efficiency by 3%. The improvement was due to the reduction in pressure fluctuations and uniform blade loading throughout the impeller blade span.

Analysis and development of a roots-type air compressor with fixed internal compression for fuel cell system

The air compressor is a key component in the polymer electrolyte membrane (PEM) fuel cell system and its performance has great impact on the electric power output from the system. Here, analysis was conducted firstly on the Roots-type compressor with fixed internal compression based on the volume reduction created by helical rotors. The built-in volume ratio variations with the wrap angle and the lobe numbers were calculated and discussed. Then a prototype of the Roots-type air compressor with 6 lobes was developed according to the outcomes of the research. The volumetric and isentropic efficiency of the prototype were measured under the discharge pressures from 0.11 MPa to 0.25 MPa while the rotation speeds from 10000 to 14000 rpm. Under the design conditions, the volumetric efficiency and isentropic efficiency of the Roots-type air compressor were 75.8% and 53.9% respectively. It was concluded that this kind of Roots-type air compressor is especially suitable for the fuel cell systems applied in the range extended electric vehicles.

Design and Analysis of Cam Wave Generator Based on Free Deformation in Non-Working Area of the Flexspline

Deformation stress of a flexspline under the action of a wave generator directly affects the service life of the flexspline and meshing quality of meshing pair. This study proposed a new deformation model for a flexspline, which incorporates forced deformation in the working area and free deformation in the non-working area, keeping the deformation shape unchanged during rotating. Based on this assumption of a deformation model, the mathematical model is further established, and the design approach of a cam wave generator is developed with the deflection curve of the ring structure. Then, a sample design with a double eccentric arc cam wave generator based on this deformation model is developed and analyzed in FEM. The results show that the deformation stress of the flexspline can be improved by relaxing the forced deformation in the non-working area, and the selected deformation shape can also remain unchanged during rotating. Moreover, the stress distribution and the maximum stress value could be improved with the variation of the combination coefficient, especially for the wrap angle.

Influence of surface roughness, friction coefficient, and wrap angle on clinching joint strength and its correlation with belt friction phenomenon

Clinching is an economical sheet joining technique that does not require any consumables. Besides, after its usage, the joints can be recycled without much difficulty, making clinching one of the most sustainable and eco-friendly manufacturing processes and a topic of high research potential. In this work, the influence of surface roughness on the load-bearing capacity (strength) of joints made by the mechanical clinching method in cross-tensile and lap-shear configuration is explored. Additionally, a correlating mathematical model is established between the joint strength and its surface parameters, namely, friction coefficient and wrap angle, based on the belt friction phenomenon. This correlation also explains the generally observed higher strength in lap-shear configuration compared to cross-tensile in clinching joints. From the mathematical correlation, through friction by increasing the average surface roughness, it is possible to increase the strength of the joint. The quality of the thus produced joint is analyzed by cross-sectional examination and comparison with simulation results. Experimentally, it is shown that an increment of >50% in the joint strength is achieved in lap-shear configuration by modifying the surface roughness and increasing the friction coefficient at the joint interface. Further, the same surface modification does not significantly affect the strength in cross-tensile configuration.