Blade Wrap Angle Impact on Centrifugal Pump Performance:Entropy Generation and Fluid-Structure Interaction Analysis

The centrifugal pump is a prevalent power equipment widely used in different engineering patterns,and the impeller blade wrap angle significantly impacts its performance.A numerical investigation was conducted to analyze the influence of the blade wrap angle on flow characteristics and energy distribution of a centrifugal pump evaluated as a low specific speed with a value of 69.This study investigates six impellermodels that possess varying blade wrap angles(95°,105°,115°,125°,135°,and 145°)that were created while maintaining the same volute and other geometrical characteristics.The investigation of energy loss was conducted to evaluate the values of total and entropy generation rates(TEG,EGR).The fluid-structure interaction was considered numerically using the software tools ANSYS Fluent and ANSYSWorkbench.The elastic structural dynamic equation was used to estimate the structural response,while the shear stress transport k–ωturbulence model was utilized for the fluid domain modeling.The findings suggest that the blade wrap angle has a significant influence on the efficiency of the pump.The impeller featuring a blade wrap angle of 145°exhibits higher efficiency,with a notable increase of 3.76%relative to the original model.Variations in the blade wrap angle impact the energy loss,shaft power,and pump head.The model with a 145°angle exhibited a maximum equivalent stress of 14.8MPa and a total deformation of 0.084 mm.The results provide valuable insights into the intricate flow mechanism of the centrifugal pump,particularly when considering various blade wrap angles.

Influence of Blade Wrap Angle on Centrifugal Pump Performance by Numerical and Experimental Study

The existing research on improving the hydraulic performance of centrifugal pumps mainly focuses on the design method and the parameter optimization. The traditional design method for centrifugal impellers relies more on experience of engineers that typically only satisfies the continuity equation of the fluid. In this study, on the basis of the direct and inverse iteration design method which simultaneously solves the continuity and motion equations of the fluid and shapes the blade geometry by controlling the wrap angle, three centrifugal pump impellers are designed by altering blade wrap angles while keeping other parameters constant. The three-dimensional flow fields in three centrifugal pumps are numerically simulated, and the simulation results illustrate that the blade with larger wrap angle has more powerful control ability on the flow pattern in impeller. The three pumps have nearly the same pressure distributions at the small flow rate, but the pressure gradient increase in the pump with the largest wrap angle is smoother than the other two pumps at the design and large flow rates. The pump head and efficiency are also influenced by the blade wrap angle. The highest head and efficiency are also observed for the largest angle. An experiment rig is designed and built to test the performance of the pump with the largest wrap angle. The test results show that the wide space of its efficiency area and the stability of its operation ensure the excellent performance of the design method and verify the numerical analysis. The analysis on influence of the blade wrap angle for centrifugal pump performance in this paper can be beneficial to the optimization design of the centrifugal pump.

Influence of Blade Outlet Angle on Inner Flow Field of Centrifugal Pump Transporting Salt Aqueous Solution

During transportation of salt aqueous solutions with centrifugal pump, crystallization phenomenon is frequently encountered. For this kind of two-phase flow, it is difficult to be accurately modeled since there are various medium properties and phase change characteristics. In view of experiment, several problems are hampering the implementation of precise measurement. Influences of blade outlet angle and medium temperature on crystallization rate were studied. Sodium sulfate solution was applied to simulate practical fluid in chemical industry. Particle image velocimetry（PIV） was employed to measure velocity distributions in rotating impeller. Crystallization processes in three impellers with different blade outlet angles were investigated. Relations among crystallization and flow parameters such as temperature and velocity were obtained. With the same blade wrap angle, when blade outlet angle is larger, diffusion of single flow passage gets stronger, relative velocity at blade outlet decreases and large scale vortex tends to appear near the blade working surface. For the impact of volume effect of particle phase on fluid viscosity, both liquid and solid phase velocities decrease with continual forming and growing of crystal particles. Velocity of solid phase is greater than that of liquid phase and its direction leans more closely to blade working surface. Solid particles tend to move towards blade working surface, as is more obvious in the impeller with large blade outlet angle. Therefore, collision between solid particles with stem part of blade working surface is more intensive in impeller with large blade outlet angle. Concerning transportation of salt aqueous solution, accurate PIV measurement is conducted in centrifugal impellers with different blade outlet angles. The results are useful and instructive in relevant engineering design and operation.

Influence of Blade Outlet Angles on Separation Performance of Guide Vane Type Axial Flow Cyclone Tube

The influences of the internal and external outlet angles on separation performance and flow field are compared and analyzed. Two arc functions are employed for controlling the internal and external angles. The separation process in the cyclone tube is calculated by using two-fluid model based on the Eulerian-Eulerian method.The results show that the structure with the internal outlet angle smaller than the external one is more beneficial to the separation performance. It is found that the small internal angle can help increase the swirl number,while the small external angle can help increase the friction coefficient. Several groups of numerical simulations are conducted for the air intake unit of the gas turbine in practice. When the internal outlet angle is 35° and the external outlet angle is 40°,the blade has sufficient cyclone strength and the separation rate of particles with diameters of 10—100 μm is between70%—98%. The small blade angle is more conducive to the separation of fine particles,leading to violent collision of large particles on the outer wall and reduction of separation efficiency. In addition,reducing the external angle is conducive to the discharge of large particles.

Influences of attack angle and mach number on aerodynamic characters of typical sections of extra-long blade in a steam turbine

On super-sonic or trans-sonic planar cascade wind tunnel of free jet intermittent type, wind blowing experiments were performed on the typical sections of stator and rotor blades in the last stage of ultra-ultra-critical steam turbine with extra-long blade of 1200mm. The influences of attack angle and Mach number on the aerodynamic performances of these sections of the blade profiles were verified, and their operating ranges were also specified.

Effects of blade sliding cutting angle and stem level on cutting energy of rice stems

Previous studies highlighted the significance of optimizing the cutting blade for crop harvesting and size reduction.This study investigated the effect of blade sliding cutting angle and stem level on cutting energy of single rice stem using a cutting apparatus that combined with texture analyzer.The cutting energy was determined for four blade angles.The results showed that the average cutting energy was the highest for cutting stem upper level and the lowest for cutting stem lower level.It was found that the peak cutting force per unit stem area decreased with blade sliding cutting angle increased.However,the least average cutting energy was 9.12 J/mm^(2) of 45°sliding angle when cutting without counter support blade and 32.3%less than that of 60°sliding angle.When cutting with counter support blade,the cutting energy per unit stem area varied from 6.57 to 12.54 J/mm 2 as the sliding angle varied from 0°to 60°,whereas the peak cutting force per unit stem area varied from 2.46 to 0.98 N/mm 2.It was concluded that the optimal sliding cutting angle was 45°without support blade and 30°with support blade,respectively.The experiments on rice stems in this study indicated that optimization of sliding cutting angle and stem level have a significant effect on cutting energy savings.Also this study emphasized the need to further investigate the effect of the case of more moisture content and cutting speed on the cutting energy to help in selection of optimum cutting speed and harvesting time.

Study on the Influence of Blade Outlet Backsweep Angle on Performance of Impeller

As an important parameter of compressor impeller, the design value of blade outlet backsweep angle has a great influence on the performance of impeller. In this paper, six impellers with blade outlet backsweep angle β2B equal to 0°, 10°, 20°, 30°, 40°, and 50° were designed to evaluate the influences of impeller backsweep angle β2B on the performance, characteristics of gas flow and equivalent stress using computational fluid dynamics (CFD) and finite element analysis (FEA). Results indicated that the performance curve for the outlet backsweep blade angle β2B of 50° has the largest stable operating range. The isentropic efficiency of the impeller with backsweep angle β2B equal to 40° is 16.8% - 25.9% higher than that of the impeller with backsweep angle β2B equal to 0°. When the blade outlet backsweep angle is 30°, the equivalent stress distribution of the impeller is more uniform, the maximum equivalent stress is the smallest.

Effect of Tip-Blade Cutting on the Performance of Large Scale Axial Fan

The effect of tip-blade cutting on the performance of a large scale axial fan was investigated using computational fluid dynamics(CFD)methods.Experiments verified the numerical simulations.The original fan was compared with the one with tip-cutting in terms of dimensionless characteristic and aerodynamic performance in tip region under the conditions of the maximum efficiency point and near-stall point.The results showed that double leakage flow occurred in tip clearance at maximum efficiency point and spillage of leakage flow from leading edge occurred in tip-blade region at near-stall point for the both two fans;and that tip-cutting with 6% of blade height could reduce the intensity of tip-leakage vortex and increase flow capacity in tip blade region,and hold the stall margin almost the same as the original fan.The maximum efficiency of the fan with tip-cutting was improved by1%,and the ability of total pressure rising was obviously greater than the original fan.

Development of Cutting Condition Monitoring System for ID-blade Saw Slicing Machine

The purpose of this study is focused on development of an online monitoring system for measuring and evaluating the cutting condition as the ID-blade saw is cutting a silicon ingot. First,the cutting experiments are carried out and the cutting signals during the blade slicing a six-inch ingot are measured by a 3-axes load sensor which is mounted on the top of the ingot. To evaluate the blade condition in slicing,a novel data processing method,combining the discrete Fourier transform(DFT) with the discrete Wavelet transform(DWT),is proposed in this paper for extracting the components due to the rotation of the blade and the cutting impedance. To validate the effect of the method,four ID-blades with three different types of the blade edge are used and discussed. The obtained results show that the component induced from the rotation and the component due to the blade slicing can be extracted efficiently by introduction of the proposed method. Furthermore,a simple online monitoring system,which consists of a 3-axes load sensor or acceleration sensor,DC cuts high-pass filter,and AD converter embedded microcomputer,is designed. The estimated cutting condition information obtained from the proposed monitoring system can be used as a feedback signal to the slicing machine for production of high quality wafer.

Cutting performance of saw blades with microtextured rougher and finisher sawteeth

The problems of severe sawtooth wear,harsh sawing noise,and low surface quality during the processing of circular saw blades need to be solved.To improve the cutting performance of TiC-based cermet saw blades,microtextures parallel to the cutting edge were fabricated on rough and fine sawteeth by laser machining.The cutting tests were performed on a sawing platform under lubricated conditions.Models of the sawing arc length and working sawtooth cutting force variations were developed for sawing steel pipes,and the accuracy of the sawing force model was verified experimentally.The results indicate that the variations in the sawing force are proportional to the sawing arc length.The circular saw blades with microtextures that did not penetrate the sawtooth rake face exhibited the lowest cutting force,sawing noise,and highest machined surface quality.Furthermore,the worn-out distance of the rougher and finisher sawteeth was reduced by approximately 7.4%and 44.1%,respectively,compared with conventional circular saw blades.The main failure modes of sawteeth were tip wear,rake face adhesion,and oxidative wear.In addition,the mechanism by which the textures improve the cutting and wear properties of TiC-based circular saw blades was discussed.This study provided a significant concept for enhancing the cutting performance of circular saw blades and improving the machined surface quality.

Effect of blade tilt angle on fluid flow characteristics in spray-blowing agitation composite process:a simulation

Aiming at the paddle tilt angle of the spray-blowing agitation composite process,the four-blade stirring and blowing composite desulfurization agitator was chosen as the research object,and the computational fluid dynamics numerical simulation was used to investigate the changes in flow field velocity,turbulent kinetic energy magnitude,and distribution caused by the blade tilt angle.Furthermore,the impact of blade tilt angle on the flow fragmentation behavior of individual bubbles and the coalescence process of multiple bubbles at different positions was studied.Under the same stirring and blowing process parameters,with the increase in the blade tilt angle of the agitator,the velocity of the flow field and the average turbulent kinetic energy inside the agitator decreased,and the bubble fragmentation speed decreased while the merging speed accelerated.The turbulent kinetic energy at the agitator bottom was greater when the blade tilt angle was 3.2°compared to when it was 13.2°,while the turbulent kinetic energy at the agitator upper part was relatively smaller.The results for single bubbles represented the state and trajectory of the bubble fragmentation process,and the results for multiple bubbles illustrated the state and trajectory of the bubble aggregation process.

Influence of Blade Thickness on Transient Flow Characteristics of Centrifugal Slurry Pump with Semi-open Impeller

As the critical component, the impellers of the slurry pumps usually have blades of a large thickness. The increasing excretion coefficient of the blades affects the flow in the impeller resulting in a relatively higher hydraulic loss, which is rarely reported. In order to investigate the influence of blade thickness on the transient flow characteristics of a centrifugal slurry pump with a semi-open impeller, transient numerical simulations were carried out on six impellers, of which the meridional blade thickness from the leading edge to trailing edge varied from 5-10 mm, 5-15 mm, 5-20 mm, 10-10 mm, 10-15 mm, and 10-20 mm, respectively. Then, two of the six impellers, namely cases 4 and 6, were manufactured and experimentally tested for hydraulic performance to verify the simulation results. Results of these tests agreed reasonably well with those of the numerical simulation. The results demonstrate that when blade thickness increases, pressure fluctuations at the outlet of the impeller become severe. Moreover, the standard deviation of the relative velocity in the middle portion of the suction sides of the blades decreases and that at the outlet of the impeller increases. Thus, the amplitude of the impeller head pulsation for each case increases. Meanwhile, the distribution of the time-averaged relative flow angle becomes less uniform and decreases at the outlet of the impeller. Hence, as the impeUer blade thickness increases, the pump head drops rapidly and the maximum efficiency point is offset to a lower flow rate condition. As the thickness of blade trailing edge increases by 10 mm, the head of the pump drops by approximately 5 m, which is approximately 10 % of the original pump head. Futhermore, it is for the first time that the time-averaged relative flow angle is being considered for the analysis of transient flow in centrifugal pump. The presented work could be a useful guideline in engineering practice when designing a centrifugal slurry pump with thick impeller blades.

Numerical Simulation of Axial Inflow Characteristics and Aerodynamic Noise in a Large-Scale Adjustable-Blade Fan

Numerical simulation are conducted to explore the characteristics of the axial inflow and related aerodynamic noise for a large-scale adjustable fan with the installation angle changing from−12°to 12°.In such a range the maximum static(gauge)pressure at the inlet changes from−2280 Pa to 382 Pa,and the minimum static pressure decreases from−3389 Pa to−8000 Pa.As for the axial intermediate flow surface,one low pressure zone is located at the junction of the suction surface and the hub,another is located at the suction surface close to the casing position.At the outlet boundary,the low pressure is negative and decreases from−1716 Pa to−4589 Pa.The sound pressure level of the inlet and outlet noise tends to increase monotonously by 11.6 dB and 7.3 dB,respectively.The acoustic energy of discrete noise is always higher than that of broadband noise regardless of whether the inlet or outlet flow surfaces are considered.The acoustic energy ratio of discrete noise at the inlet tends to increase from 0.78 to 0.93,while at the outlet it first decreases from 0.79 to 0.73 and then increases to 0.84.

Postprocessor development for ultrasonic cutting of honeycomb core curved surface with a straight blade

When ultrasonically cutting honeycomb core curved parts,the tool face of the straight blade must be along the curved surface’s tangent direction at all times to ensure high-quality machining of the curved surface.However,given that the straight blade is a nonstandard tool,the existing computer-aided manufacturing technology cannot directly realize the above action requirement.To solve this problem,this paper proposed an algorithm for extracting a straight blade real-time tool face vector from a 5-axis milling automatically programmed tool location file,which can realize the tool location point and tool axis vector conversion from the flat end mill to the straight blade.At the same time,for the multi-solution problem of the rotation axis,the dependent axis rotation minimization algorithm was introduced,and the spindle rotation algorithm was proposed for the tool edge orientation problem when the straight blade is used to machine the curved part.Finally,on the basis of the MATLAB platform,the dependent axis rotation minimization algorithm and spindle rotation algorithm were integrated and compiled,and the straight blade ultrasonic cutting honeycomb core postprocessor was then developed.The model of the machine tool and the definition of the straight blade were conducted in the VERICUT simulation software,and the simulation machining of the equivalent entity of the honeycomb core can then be realized.The correctness of the numerical control program generated by the postprocessor was verified by machining and accuracy testing of the two designed features.Observation and analysis of the simulation and experiment indicate that the tool pose is the same under each working condition,and the workpieces obtained by machining also meet the corresponding accuracy requirements.Therefore,the postprocessor developed in this paper can be well adapted to the honeycomb core ultrasonic cutting machine tool and realize high-quality and high-efficient machining of honeycomb core composites.

Experimental study of the effect of blade tip clearance and blade angle error on the performance of mixed-flow pump

The hydraulic performance test of the mixed-flow pump has been carried out through selecting different blade tip clearances and various blade angle errors.The ratio of the mixed-flow pump efficiency reduction and the blade tip clearance variation(η/δ) varies with the flow rate coefficient revealing a parabolic trend.An empirical equation has been developed for the mixed-flow pump model by parabolic fitting.For the same blade tip clearance variation δ,the mixed-flow pump efficiency reduction η increases rapidly as the flow rate rises.For any given flow rate,the efficiency,the head and the shaft power of the mixed-flow pump all decrease with the increase of the blade tip clearance.Among them,the efficiency reduction η varies approximately linearly with the blade tip clearance variation δ.When the angle of an individual blade of the mixed-flow pump has a deviation,the performance curves will move and change.These curves have consistent change directions with the performance curves under the condition of all the blades rotated at the same time,but have smaller offset and lower range of variation.When an individual blade angle error changes to ±2°,the optimal efficiency of the mixed-flow pump will have no significant difference.When the individual blade angle error increases to ±4°,the optimal efficiency will decrease by 1%.

Design of Bionic Saw Blade for Corn Stalk Cutting

The serrated incisors of grasshopper [Chondracris rosea rosea （De Geer）] possess an advantageous capacity for cutting plant fiber. Inspired by this special geometrical structure of incisors, bionic saw blade was designed and manufactured. MATLAB software digital image processing technology was used to obtain outer margin profile from stereomicroscope pho- tograph of the serrated incisors. The outer margin profile of incisors was fitted and expressed by six-order polynomial function. To compare the cutting capacity of bionic and traditional saw blades, the internodes of dry corn stalks were cut perpendicularly. Cutting force-deformation characteristics were obtained by universal testing machine. The results of cutting experiments show that the maximum cutting force of bionic saw blade was 128.26 N, which is 15.87% lower than 152.45 N of traditional saw blade; the average cutting force of bionic saw blade was 51.56 N, which is 28.17% less than 71.78 N of traditional saw blade. Meanwhile, the cutting energy consumption of bionic saw blade was 8.95 J, which is 12.85% less than 10.27 J of traditional saw blade. Overall, the bionic saw blade can lead to noticeable reduction of the cutting force and energy. These results will be helpful for designing cutting elements of corn stalk harvesting, biomass size reduction and other processing machinery.

The Effect of Blade Outlet Angle on Performance and Internal Flow Condition of Mini Turbo-Pump

Mini turbo-pumps having a diameter smaller than 100mm are employed in many fields;automobile radiator pump,ventricular assist pump,cooling pump for electric devices,washing machine pump and so on.Further,the needs for mini turbo-pumps would become larger with the increase of the application of it for electrical machines.It is desirable that the mini turbo-pump design is as simple as possible due to restriction to make precise manufactures.But the design method for the mini turbo-pump is not established because the internal flow condition for these small-sized fluid machineries is not clarified and conventional theory is not conductive for small-sized pumps.Three types of rotors with different outlet angles are prepared for an experiment and a numerical analysis.The performance tests are conducted with these rotors in order to investigate the effect of the blade outlet angle on performance and internal flow condition of mini turbo-pumps.It is clarified from the experimental results that head of the mini turbo-pump increases and maximum efficiency flow rate shifts to larger flow rate according to the increase of the blade outlet angle,however the maximum efficiency decreases with the increase of it.In the present paper,the performance of the mini turbo-pump is shown and the internal flow conditions are clarified with the results of the experiment and the numerical flow analysis.Furthermore,the effects of the blade outlet angle on the performance are investigated and high performance design with simple structure for the mini turbo-pump would be considered.

Development of swashplateless helicopter blade pitch control system using the limited angle direct-drive motor(LADDM)

It can be greatly beneficial to remove the swashplate of conventional helicopter, because the swashplate is usually complicated, aerodynamically resistive, and obstacle of more complex pitch control for improving performance. The present technologies for helicopter vibration reduction are usually narrow in effective range or requiring additional actuators and signal transfer links, and more effective technology is desired. Helicopter blade pitch control system, which is removed of swashplate and integrated high-frequency pitch control function for active vibration reduction, is likely the suitable solution at current technical level. Several potential implementation schemes are discussed, such as blades being directly or indirectly driven by actuators mounted in rotating frame and application of different types of actuators, especially implementation schemes of electro-mechanical actuator with or without gear reducer. It is found that swashplateless blade pitch control system based on specially designed limited angle direct-drive motor （LADDM） is a more practical implementation scheme. An experimental prototype of the finally selected implementation scheme has been designed, fabricated and tested on rotor tower. The test results show considerable feasibility of the swashplateless helicopter blade pitch control system using the LADDM.

Influence of Blade Outlet Angle on Performance of Low-specific-speed Centrifugal Pump

In order to analyze the influence of blade outlet angle on inner flow field and performance of low-specific-speed centrifugal pump, the flow field in the pump with different blade outlet angles 32.5°and 39° was numerically calculated. The external performance experiment was also carried out on the pump. Based on SIMPLEC algorithm, time-average N-S equation and the rectified k-ε turbulent model were adopted during the process of computation. The distributions of velocity and pressure in pumps with different blade outlet angles were obtained by calculation. The numerical results show that backflow areas exist in the two impellers, while the inner flow has a little improvement in the impeller with larger blade outlet angle. Blade outlet angle has a certain influence on the static pressure near the long-blade leading edge and tongue, but it has little influence on the distribution of static pressure in the passages of impeller. The experiment results show that the low-specific-speed centrifugal pump with larger blade outlet angle has better hydraulic performance.

The cooling performance of three-row compound angle holes on the suction surface of a rotating turbine blade

Experiments were carried out to study the effects of compound angle,hole arrangement,and blowing ratio on the film cooling performance of multiple rows of holes on the suction surface of a turbine blade.The turbine worked at rotational speed of 600 rpm corresponding to the rotational Reynolds number of 5.36
105.Three rows of cylindrical holes arranged in line or in stagger were drilled on the rotor blade suction surface at the streamwise location of 12.4%,17.8%,and 23.2%,respectively.Three compound angles,with the same streamwise angle of 45but different lateral deflection angles of 45,0,and45,were studied.The film cooling effectiveness was obtained using pressure sensitive paint(PSP)technique with average blowing ratios varied from 0.5 to 2.0.The results showed that the application of compound angle changes the jet direction in the near-hole region and makes the film spread laterally.Compared with the film cooling without compound angle,using positive and negative compound angle can improve overall average film cooling effectiveness by about 20%and 25%,respectively.The effects of the secondary flow also can be weakened.A stagger film trajectory arrangement can achieve more uniform film coverage with higher overall film cooling effectiveness.The film trajectory arrangement of a positive compound angle injection is determined by the combined effect of hole arrangement and blowing ratio.While,the film trajectory arrangement of a negative compound angle injection is almost the same as the hole arrangement and nearly does not change with the blowing ratio.