Attack Of Blades Research Articles

Coordination of energy loss and fish friendliness for a low-head tubular-pump blade based on a multi-objective optimization model

Tubular pumps and turbines are the water-to-electricity conversion devices widely used in pumped hydro storage systems for low heads and high flow rates. An ecological concern is the high proportion of fish injuries caused by the rotating blades. In this study, a tubular pump blade is retrofitted to balance the energy loss and fish friendliness through multi-objective optimization, combining computational fluid dynamics with a mathematical blade strike model. Sensitivity analysis identifies nine geometric variables out of thirteen for optimizing blade design. An approximation model is developed to implement optimization algorithm and achieve the objective function. By artificially assigning weights to targeted performance metrics, three scenarios are obtained: the optimal efficiency scheme (A), the optimal fish friendliness scheme (C) and the balanced scheme (B). Scheme C achieves a fish survival ratio of 100 % at multiple flow rates (for fish lengths of Lf/D=1/12), but results in a 6.4 % decrease in efficiency compared to scheme A. Additionally, a negative blade attack angle can improve flow pattern. Considerable reduction in fish mortality can be obtained by equipping the rotor with a larger size but lower shaft speed, while also limiting the fish size to pass through the pump running at a reduced flow rate.

Hydrokinetic hybrid vertical axis rotor performance at difference blade shape and angles of attack

We must invest in renewable energy research to combat pollution from fuel combustion and promote affordable energy. Hydrokinetic rotors produce mechanical torque using kinetic energy in rivers, canals, and ocean water. Hydrokinetic integrated Darrieus-Savonius rotors are a vertical axis type with good properties, but only a few researchers are interested in them. Only one Savonius rotor has the ability to self-prime, despite having poor performance but high torque. Darrieus rotors are effective but challenging to start. In order to find the best configuration, hydrokinetic integrated rotor performance is experimentally studied in this work. The study was conducted in a water flume at Egypt's National Water Research Centre, Hydraulics Research Institute (HRI). The number of Darrieus blades, Darrieus blade attack angles, and airfoil shape are studied and compared for four different NACA airfoils: NACA 012, 015, 018, and NACA 021. Semi-circular Savonius blades were employed in this work, the fact that the Savonios rotor in double-stage is always the best in terms of performance for an integrated rotor. The results showed that NACA 21 with a three-bladed Darrieus rotor and 15° angle of attack produced the highest power factor, as the maximum obtained value is 0.334 at a tip speed ratio of 1.8.

Identifying the influence of blade number and angle of attack on a breastshot type waterwheel micro hydroelectric power generator using ANOVA

This study focuses on optimizing the performance of micro-hydro power generation, specifically the breastshot type waterwheel. The limited availability of non-renewable energy sources and the high cost of developing renewable energy sources in the energy sector pose challenges, making it essential to find new energy sources and improve energy efficiency. The 2004–2022 national electricity plan aims to increase electricity access in rural areas, including remote regions like Bogor Regency, where access to electricity is limited. Many residents have constructed their own micro hydroelectric power generators, but their vulnerability to natural disasters is a concern. The study investigates the potential of breastshot waterwheel technology for micro hydroelectric power generation. The study involved testing a micro hydro power plant with 6, 8, and 10 blades and blade angles of 0°, 30°, and 45°. The current research focuses on performance optimization, including the use of ANOVA analysis to know the significant impact of blade number and angle on the waterwheel’s rotation. The maximum rotational speed was achieved with 10 blades and an angle of attack of 0°, 30°, and 45°, with respective speeds of 153.59 RPM, 155.84 RPM, and 164.95 RPM. The study indicates that the higher the number and angle of attack of blades, the greater the rotation of the breastshot type waterwheel. ANOVA tests showed that the number of blades had a significant impact on the waterwheel’s rotation, with an F-test value of 6.32 and a p-value of 0.012. On the other hand, the angle of attack of the blade had no significant impact, with an F-test value of 3.20 and a p-value of 0.067

Numerical simulation of the effect of atmospheric condition on the lightning strike for wind turbine

The risk of lightning exposure increases as wind turbine size increases, and lightning accidents have grown up to be a severe threat to wind turbines. The present paper focuses on the influence of the changes in atmospheric conditions around the rotating blade for the upward leader initiation. A 2D computational fluid dynamics model was established to obtain the air pressure distribution around the blades, and the simplified inception model was used to determine the initiation of the upward leader mechanism. In this paper, two significant factors of velocity and attack angle were studied. The results show that the trigger height is about an 11.2% difference for 120 m/s with the peak current of return stroke at 30 kA; the difference has reached about 28% for the attack angle of 10°. The research indicates that the area with higher air pressure is exposed to a greater risk of lightning strikes, and the probability of lightning strikes will increase as the blade attack angle increases.

Design and analysis of 5 MW horizontal axis wind turbine

The need of renewable energy sources is growing. Wind energy is the important sources of renewable energy. In the wind energy sector Horizontal axis wind turbines are the major devices used for the production of electricity. Blade is the most important part of HAWT. Lift force and drag force has an important role in the performance of a wind turbine. The main aim of this work is to make CFD analysis of optimum blade attack angle using k-e model. The moments are calculated for the blade angle varies 10 to 85 degree. The wind velocities considered for the study are 3 m/s, 12.5 m/s and 25 m/s. The result obtained from this simulation is the optimum blade attack angle where the maximum moment produced at the given wind velocities.

INVESTIGATION OF BLADE ATTACK ANGLE VALUE ON VERTICAL AXIAL WIND POWER PLANT

In this paper, the efficiency of the vertical-axial wind power plant at various wind speeds depending on the angle of attack of the rotor blades was investigated. The object of the investigation was a three-bladed Darrieus rotor. During the modeling we used the viscous gas flow model with averaging of turbulent characteristics (Reynolds-averaged Navier–Stokes equations for an incompressible fluid. These investigations would allow us to develop new principles for constructing vertical-axial wind turbines with a variable angle of attack of the blades in order to increase the energy efficiency of vertical-axis wind turbine.

A Computational Study about the Effect of Turbines Pitched Blade Attack Angle on the Power Consumption of a Stirred Tank

In this study, the stirring mechanism of shear-thinning fluids benefiting from four blades in turbulent flow is considered. The fluid is studied inside a stirred cylindrical tank with a flat bottom. The height of fluid is equal to the cylinder’s diameter and the impeller is positioned centrally. A CFD simulation has been carried out and three-dimensional turbulent flow is numerically analyzed using the Shear Stress Transport k-ω (k- ω SST) model. The parameters related to power consumption including attack angle and flow index were studied. The power consumed during the mixing of the shear thinning liquids under a specific Reynolds number and attack angle is less than that consumed when the fluid used is water, which is a Newtonian fluid. As the power law index decreases, the corresponding power consumption also declines. At a certain attack angle and power law index, an increase in the Reynolds number first significantly decreases power consumption; beyond a given range, the consumption plateaus. To validate the numerical simulation results, the findings derived on the basis of the power number used in this work were compared with the test results of other studies, and good agreement was observed.

Investigation of various airfoils for maximisation of lift in horizontal axis wind turbine - a case study

Wind energy can be considered to be one of the most reliable and sustainable energy sources of world. In India, more than 2,300 MW capacity of wind turbine power has been installed in 2014. This can be further increased by improving overall efficiency of wind turbines. The efficiency of wind turbine is governed by various geometric characteristics, and the airfoil of a blade is considered to be one of most influencing parameters. In the present work, HAWT is designed to provide electric power of about 10 KW that is to be used at authors' hometown (Rajkot). Different five airfoils with varying angle of attack of blades are modelled, and analysed to identify the most suitable airfoil for the optimum lift, and stall angle. The NACA 4412 was found to be the most suitable for providing optimum lift as well as stall angle. The prototype of all airfoils were also tested, and simulated for flow separation.

Determining the equation of surface of additional blade of a screw conveyor

Analysis of directions of upgrading screw conveyors, used for the transportation of chips and sludge, was performed. We conducted analysis of equations of determining critical rotation frequency of the screw, the values of which influences the angle of beginning of movement of material along the blade. Equations of the surface area of additional blade in a general form were analyzed. Using frontal dissection of the gutter, Authors analyzed equation of normal loop taking into account the angle of beginning of movement of material, affected by the angle of attack of the blade. The aim of the work is to obtain equation of the line of intersection of the screw surface and the surface area of additional blades, which possesses considerable value for carrying out calculations and designing constructive parameters of screw conveyors with improved performance for the transportation of metal chips. The formula for determining improved angle of beginning of movement of material along the surface of additional blade was obtained, which allows taking into account the impact of fluid angle. The dependency of equation of the blade surface in the polar coordinate system was described, which gave us the opportunity to develop equation of the line of intersection of the screw surface and the area surface in the parametric form. Authors theoretically substantiated positive impact of additional blades of screw conveyor on decreasing the lifting and driving force for moving the metal chips through the reduction of forces of internal friction of transported metal chips, which is achieved by partial removal by additional blades of the layer of chips from the general stream in the gutter of a screw conveyor. Mathematical dependency for determining effective angle of beginning of metal chips motion along additional blade of the screw’s spiral was obtained, and the law of its movement along the blade was established. We designed, manufactured and tested under laboratory and industrial conditions the prototype sample of a screw conveyor with different angles of attack of additional blades, which can be used in the process of designing similar conveyors for specific workshop conditions.

Mixing of complex fluids with flat and pitched bladed impellers: Effect of blade attack angle and shear-thinning behaviour

In the present work, results on the mixing of complex fluids by two-bladed stirrers are given; the method used was a numerical analysis. The fluids simulated have a shear thinning behaviour modelled by the Ostwald de Waele Law. The effects of inclined angle on the local and global mixing characteristics have been particularly determined. Also, the effects of Reynolds number and rheological behaviour are checked. To verify our computer simulations, some results have been compared with others experimental data and a satisfactory agreement was found.

Numerical Simulation Study on Propeller Slipstream Interference of High Altitude Long Endurance Unmanned Air Vehicle

In this paper,thecontrol equation of Multiple Reference Frame(MRF) as the propeller calculation model was present and analyzed, the propeller slipstream interference on HALE UAV was studied with three-dimensional numerical simulation. It is shown that the flow field of the MRF model is good consistent with true propeller flow, and MRF can accurately simulate aerodynamic interference on the aircraft. The stream traces on the V-tail surface were deflected and shrank, pressure distribution,Cmx and Cmzon V-tail surface was changed apparently too.Butslipstream had little effect on wing. The influence of propeller slipstream on the aerodynamic performance of the UAV at the status of taking off is biggest, become weaker at status of climbing and smallest at the status of cruising. The influence of propeller slipstream is enhanced with increment of propeller thrust and basically familiar in the same thrust between the two blade attack angle. The pressure drag on aft of UAV fuselage increased rapidly by the interference of propeller slipstream, leading aerodynamic performance of UAV become badly.

Theoretical and experimental study of agricultural spraying using CFD

This paper presents a computational fluid dynamics (CFD) application about the axial fan design used in an agricultural spraying system with a theoretical and experimental analysis of comparative results between the characteristic curves of a fan for several rotations and numerical results for the influence of blade attack angle variation and optimization of the spraying system, both for a same rotation. Flow was considered three-dimensional, turbulent, isothermal, viscous and non-compressible in a steady state, disregarding any influence of the gravity field. The average turbulent field was obtained from the application of time average where the turbulence model required for closing the set of equations was the k-E model. Resolution of all connected phenomena was achieved with the help of a fluid dynamics computer, CFX, which uses the finite volumes technique as a numerical method. In order to validate the theoretical analysis, an experiment was conducted in a circular section of a horizontal wind tunnel, using a Pitot tube for pressure readings. The main results demonstrate that the methodology used, based on CFD techniques, is able to reproduce the phenomenological behavior of an axial fan in a spraying system because results were very reliable and similar to experimentally measured ones.

Hydraulic Characteristic of Cooling Tower Francis Turbine with Different Spiral Casing and Stay Ring

Cooling tower Francis turbine stands between heat exchanger and sprayer of cooling water system in cooling tower, so the level dimension of spiral casing is small and the flow rate coefficient is high to 1.42. Its flow rate limits to cooling water discharge, output to fan, and head to energy-saving of cooling water system, so its specific speed is very low, hydraulic loss of spiral casing and stay ring is high to reduce hydraulic efficiency of water turbine. To increase the hydraulic efficiency, a pump casing and stay ring with no stay vane is designed. Through CFD simulation and test, hydraulic efficiency of water turbine with that spiral casing and stay ring is improved to 5%, hydraulic loss of casing and stay ring reduces from 13.7% to 3.41%, hydraulic loss of runner increases from 7.93% to 11.57%, and simulation result coincides with test. If that spiral casing and stay ring links to runner with no angle of blade attack, hydraulic loss of runner is about 7% and hydraulic efficiency reaches to 82%.

Numerical Simulation of Vortex Shedding and Lock-in Characteristics for a Thin Cambered Blade

In this paper, vortex-shedding patterns and lock-in characteristics that vortex-shedding frequency synchronizes with the natural frequency of a thin cambered blade were numerically investigated. The numerical simulation was based on solving the vorticity-stream function equations with the fourth-order Runge–Kutta scheme in time and the Chakravaythy–Oscher total variation diminishing (TVD) scheme was used to discretize the convective term. The vortex-shedding patterns for different blade attack angles were simulated. In order to confirm whether the vortex shedding would induce blade self-oscillation, numerical simulation was also carried out for blade in a forced oscillation. By changing the pitching frequency and amplitude, the occurrence of lock-in at certain attack angles was determined. Inside the lock-in zone, phase differences between the blade’s pitching displacement and the torque acting on the blade were used to infer the probability of the blade self-oscillation.

Effect of the attack angle on the roll and trailing vortex structures in an agitated vessel with a paddle impeller

The purpose of the present study is to observe the effect of the blade attack angle on the roll and trailing vortex structures in a stirred vessel via laser-Doppler velocimetry (LDV). In this investigation, four-bladed paddle impellers with four attack angles, which were 45 ∘ , 60 ∘ , 75 ∘ and 90 ∘ , respectively, were used. By synchronizing LDV with a rotary encoder coupled to the impeller shaft, angle-resolved measurements of all three velocity components were performed. This experimental method made it possible to capture the details of the vortical structure both behind the impeller blade and discharge region. Our study on the mean flow structure generated by three types of pitched blade turbines ( 45 ∘ , 60 ∘ , and 75 ∘ , respectively) found that a single trailing vortex was formed around each turbine blade. Roll-up of the vortex sheet issuing from the blade tip was also observed, which indicated a major roll of trailing vortex generation mechanism for each pitched blade turbine.

Gas—liquid mixing studies with multiple up‐ and down‐pumping hydrofoil impellers: Power characteristics and mixing time

AbstractAxial flow impellers with hydrofoil blades, APV‐B2, i. e., B2‐30 and B2‐45 (30° and 45° angle of attack of blades) have recently been designed, mainly for use in the up‐pumping mode, and some new results are reported here for single, dual and triple impeller configurations in the turbulent flow regime. The results are compared with dual Lightnin' A‐315's pumping downwards as they have traditionally been used and with dual radial flow Rushton turbines. The ungassed power numbers of the APV‐B2's are low, allowing these impellers to be used at large impeller‐to‐tank diameter ratios. The drop in Pg/P is lower with all combinations of APV‐B2 impellers, i. e., for single, dual and triple impellers when compared to other configurations tested. Torque fluctuations are less than those with single or dual down pumping axial hydrofoils. Mixing times measured using a decolourisation technique for dual and triple impeller configurations of APV‐B2 under unaerated and aerated conditions showed that the mixing times are much shorter than those for the dual Rushton turbine and similar to those found for dual down‐pumping A‐315's. Detailed mixing characteristics and flow patterns for the dual and triple APV‐B2's are also discussed.

Investigation of Rotor Noise Source Mechanisms with Forward Speed Simulation

The noise of a model propeller was measured with and without forward speed simulation in the open test section of a low-speed wind tunnel at velocities up to 60 m/s and blade tip Mach numbers up to 0.6. Compared to the static tests, even low wind velocities reduced the propeller noise by up to 20 dB. Strong sound radiation occurred due to interaction of the propeller blades with the wake of the supporting beam when the propeller was mounted as a pusher propeller. At wind velocities above 20 m/s, the high-frequency part of the propeller noise depends strongly on the angle of attack of the blades. At moderate angles of attack, laminar vortex shedding noise dominates the high-frequency sound radiation. This noise component could be eliminated by tripping the boundary layer on the suction surface of the blades. The frequencies of maximum noise radiation were predicted fairly well by existing theories. The laminar vortex shedding noise disappears at higher angles of attack of the propeller blades. If the angle of attack is further increased, strong braodband noise occurs which is generated probably by the turbulent boundary layer and local flow separations.