Blade Pressure Research Articles

A strongly coupled Eulerian Lagrangian method applied in unsteady 3D external flows around Wind Turbine rotors

This paper presents a hybrid CFD solver that couples a standard Eulerian approach that solves the compressible Navier-Stokes equations under a cell-centered finite volume discretization, with a Lagrangian one, based on particles representation which carry mass, pressure, dilatation and vorticity. The velocity field is calculated using the Helmholtz’s decomposition theorem. Computational performance is enhanced by employing the Particle Mesh (PM) technique in order to solve the Poisson equations for the scalar potential ϕ and the stream function ψ. Even though validated for 2D flows over airfoils, this specific solver is used for the first time in order reproduce the flow around a wind turbine rotor. The validation simulations concern axial flow over the wind turbine model rotor used in the New MEXICO experimental campaign. Results of the hybrid solver, presented as blade pressure distribution and axial flow velocities are compared against the ones produced by its pure Eulerian counterpart and experimental measurements. PM grids of up to 5 points per chord of the blade section at 75% radius have been used. Comparison with the standard Eulerian solver suggest that the produced blade loads are over-predicted by approximately 7% near the tip and 14% near the root. However, the calculated velocity field is much closer to the experimental measurements as compared to the one produced by the Eulerian approach, which is attributed to the reduced numerical diffusion of the Lagrangian-vorticity formulation.

Influence of Solid–Liquid Two-Phase Flow on Cavitation of Tubular Turbine Blades Under Combined Conditions

The influence of sediment media on the blade pressure and cavitation of a tubular turbine was investigated in this study. The Zwart–Geber–Belamri cavitation model and the shear stress transport k–w turbulence model were applied to numerically simulate and experimentally validate the full flow path of the tubular turbine under combined conditions for sediment particle sizes of 0.01 and 0.05 mm and concentrations of 1%, 1.5%, and 2%. The results show that the pressure of the blade increases with the sediment concentration. Cavitation mainly occurs between the blade shroud and the leading edge. The higher the sediment concentration, the lower the vapor volume fraction at the same sediment particle size. The presence of sediments inhibits further cavitation development, and the inhibition effect is significant. At the same concentration, the larger the particle size of the sediment, the lower the vapor volume fraction. Thus, the increase in the particle size inhibits cavitation, but the inhibition effect is not significant.

An experimental insight into dynamic characteristics and wear of centrifugal pump handling multi-size particulate slurry

The river water has a high sand content and the characteristics of mixed distribution of sand particles with different diameters. The effect of sand particles on the dynamic characteristics and wear of centrifugal pumps is an important issue when handling particulate slurry. The objective of this work is to establish the effect of flow rate and sand volume concentration variation on pump energy performance, outlet pressure pulsation, pump body vibration, and pump impeller wear. Experiments were conducted in a pilot plant test rig with five flow rates and three particle concentrations based on multi-size particulate slurry. It was observed that the head and efficiency of the centrifugal pump decrease with the increase of sand concentration, whereas the effect of small sand concentration on the energy performance of the pump is weak. The larger the flow rate of centrifugal pump, the lower the pressure pulsation and vibration intensity of pump body, but the more serious the impeller wear. When the sediment concentration increases, the pressure pulsation at the pump outlet and the vibration intensity of the pump body increase, and the impeller wear is more serious. In addition, with the increase of pump operation time, the outlet of blade pressure surface, the middle area of blade suction surface and the outlet area of impeller back shroud passage are seriously worn, and the outlet of blade pressure surface is the most serious.

Experimental and Numerical Analysis of Rotor–Rotor Interaction Characteristics inside a Multistage Transonic Axial Compressor

Serving as a key component of the core engine, the high-load axial compressor is expected to have high performance, which determines several critical parameter levels of the aero-engine. The unsteady effect on the performance induced by the interaction among different rotors should not be ignored during the design of a high-load compressor. The interaction between R1 (the first rotor row) and R2 (the second rotor row) rotors of a transonic axial compressor was measured in detail using high-frequency pressure fluctuation sensors, aiming to reveal the evolution and distribution characteristics of the R1 sweep effect inside the R2 passage. The results show that near choke and design points, the interaction between the R1 oblique shock wave at the leading edge and the high-pressure region on the blade pressure side triggers the R1-2BPF (blade passing frequency) disturbance, which is different from the traditional harmonic of the blade wake disturbance. A ‘long tail’ flow structure, which indicates the major influence of the R1 shock wave, fluctuation obviously reaches the exit of R1 and influences the upper part of S1 and R2. The combination of the R1-2BPF and the R1-1BPF (mainly caused by the R1 wake disturbance) influences the R2 flow field significantly, and both of them sharply grow at the middle and rear parts of the R2 passage where the strength of the two disturbances increases by 24% and 68%, respectively, compared to the leading edge of R2. Moreover, the circumferential non-uniformity of the R1-1BPF and R1-2BPF disturbances significantly increase at some locations of the R2 passage compared to the R1 exit, which is attributed to the relative clocking positions of the R1 and R2 blades.

Numerical study on flow and wear characteristics of dense fine particle solid–liquid two-phase flow in centrifugal pump

The solid–liquid two-phase centrifugal pump is one of the core power equipment of solid phase material hydraulic transportation, widely used in hydraulic engineering, petrochemical industry, marine metal mineral exploitation, urban sewage treatment, and other sectors of the national economy. There is a significant increase in the need to transport dense fine particle slurry in industrial production. Under this condition, the influence of particle parameters on the performance of the centrifugal pump is still not clear. In order to study the flow and wear characteristics of dense fine particle solid–liquid two-phase transported by an open impeller centrifugal pump, the Re-Normalization Group k − ε and dense discrete phase models in Fluent were used to describe the characteristics of the solid–liquid two-phase flow. The numerical model is validated with the experimental data of the pump’s performance. The study indicates that the particle size and concentration have great influence on the wear of the impeller. The wear of the blade pressure surface is the most serious. With the increase of particle concentration and size, the wear area expands to the leading edge and the upper surface of the blade. These results can provide supporting theories for the design of a dense fine particle solid–liquid two-phase medium conveying pump.

Influence of Gas Content on Performance Effect on Shunt Vane Type Aviation Fuel Pump

In order to study the flow law of shunt vane type aviation fuel pump under the condition of gas-liquid mixture transportation, based on the RNG K-ε turbulence model and the Euler-Euler non-uniformity model, using the ANSYS CFX software to calculate an aviation fuel pump under different gas content conditions, and analyzing the flow of the fuel pump and the pressure law of the blade pressure. The research shows that the gas phase is mainly distributed in the front section of the long blade suction surface and the back section of the short blade pressure surface. The increased gas content will result in increased liquid velocity in the pump, which makes the gas phase gradually develop towards the suction surface of long and short blades and diffuse to the impeller flow path. The gas content mainly affects the pressure surface load of the fuel pump blades. The pressure load curve fluctuates at the relative position of the short blade (0.5-0.6) and long blade (0.3-0.6) as well as at the end of the blade and decreases with the increase in gas content. The change of pressure fluctuation of the blade is mainly reflected at the junction of long and short blades, and the pressure fluctuation amplitude of the front section of the short blade and middle section of the long blade fluctuates greatly. With the increase in gas content, the pressure fluctuation amplitude at each monitoring point reduces. The research results can provide some reference for the design of aviation fuel pumps.

Flint Pressure Blade Technology in the Neolithic Northern Levant: Emergence of Specialized Tool Manufacture of Sickle Elements and Micro-drills

Flint Pressure Blade Technology in the Neolithic Northern Levant: Emergence of Specialized Tool Manufacture of Sickle Elements and Micro-drills

A comprehensive three-dimensional study on Darrieus vertical axis wind turbine with slotted blade to reduce flow separation

Aerodynamic performance of different designs of slotted blade of a straight blade Darrieus vertical axis wind turbine and their corresponding flow structure are precisely analyzed using three-dimensional numerical simulation. The slots aim to transfer flow from the blade pressure side to its suction side and eventually improve the blade output torque by procrastination of flow separation, especially at low tip speed ratios (TSRs). Investigations on slot width and blade height reveal that the slot should be wide enough to successfully pass flow to confront higher volume of flow separation in larger blades. Having changed the outflow location of the slot from 2C/3 to C/6 from the blade leading edge, the location of C/3 is found to be the best by noticeable alleviation in flow separation and suppressing its development toward the blade leading edge. As a result, significant improvement in average torque coefficient is achieved. This means that at TSRs of 0.5, 1.0, and 1.5, average torque coefficient increases for the slotted blade by 93.4%, 66.1%, and 10.5%, respectively. In addition, a delay of up to 15.5° occurs in the azimuth angle of torque coefficient peak with respect to that of the base blade (without slot).

A new generation of centrifugal pumps for high conversion efficiency

Centrifugal pumps are fundamental machines in our daily life. Indeed, they can be found everywhere, for instance, in domestic, civil, industrial, and agricultural fields. In the last years, the pump market has newly gained a boost coherently with the world demographic growth. Pumps are among the main responsible for electric energy consumption, therefore even a slight efficiency improvement (+1%) can be effective in contrasting the growth of the global Greenhouse Gas Emissions (at least −570 tCO2/day in Europe). For this reason, a new generation of centrifugal pumps is here proposed. In particular, the impeller has been redesigned improving the flow guidance inside the vanes and simultaneously reducing the number of blades, with the aim to increase the blade loading, reducing manufacturing costs, and enhancing the conversion efficiency with respect to conventional configurations. Furthermore, the new impeller design respects all the geometrical constraints of the corresponding conventional configuration, allowing its retrofit with a boost of performance. To reach these goals, a 1D in-house code has been developed implementing a Harmony Search Algorithm (HSA) for the selection of the most suitable design point (H and Q), and introducing two parameters for the blade loading evaluation, namely, the blade pressure coefficient (Cp,blade), computed locally along the impeller blade walls, and the blade lift coefficient (CL), achieving an optimal vane arrangement. Starting from a baseline centrifugal pump, the novel impeller has been designed, manufactured, and finally experimentally tested. The resulting new generation of centrifugal pumps actually proves to have a higher performance (maximum efficiency at BEP +1%), a flatter efficiency curve, and a monotone bending characteristic curve, while keeping unchanged the required Net Positive Suction Head (NPSH3%).

Performance of a Propeller Coated with Hydrophobic Material

Computational and experimental methods were used to study a propeller coated with hydrophobic material and a propeller with a conventional surface for comparison. In CFD simulations, the blade surface mesh was arranged in a way to set non-slip or free slip wall boundary conditions with different proportions to define the level of surface slip. The conventional and the hydrophobic material propellers defined by different surface slip rates were simulated under different advance speed coefficients and different rotational speeds. Propeller performance results, blade pressure, and the Liutex vorticity distribution were studied. An experimental platform was established to study the velocity field around the propeller using a Particle Image Velocimetry (PIV) device. The CFD calculation results were compared with the PIV results. It was found that the calculation results using a 75% surface slip rate were closer to the experimental results. The calculation results show that the propeller coated with hydrophobic material has improved thrust and efficiency compared with the propeller with conventional material. The hydrophobic material can significantly reduce the low-speed region downstream of the propeller hub. The hub and the tip vortices shown by the Liutex are also significantly reduced. Those changes help to improve the propulsion efficiency.

Design, development and multi-disciplinary investigations of aerodynamic, structural, energy and exergy factors on 1 kW horizontal-axis wind turbine

AbstractContinually increasing demand for energy, coupled with the need for clean environment, has made it mandatory to fall back on efficient conversion of energy from renewable sources. Wind energy is one of the most viable sources of renewable energy. A wind turbine blade, shaped as an airfoil with a streamlined cross-section, can be graded for its aerodynamic efficiency in terms of lift-to-drag ratio. Optimal design and analysis of blades with different airfoil sections is critical for efficient energy extraction. In this paper, computational fluid dynamics (CFD) is used to predict the aerodynamic efficiency of wind turbine blades. To set the basics right, a detailed review of aerodynamics of the 2D airfoils are undertaken: (a) NACA4412, (b) NACA23012 and (c) NACA63215 airfoils. Additionally, a numerical study on structural analysis for a 1-kW horizontal-axis wind turbine blade using finite element analysis (FEA) to assess the initial failure of NACA 63215 airfoil internal structure after optimization was conducted. In the internal structure of the blade, a single spar was included to make the structure more efficient in bending. Structural optimization resulted in bringing the weight down from an initial weight of 5.6 kg to a final design weight of 1.1 kg, i.e. a net saving of more than 4 kg. In addition stress levels in the model also improved with the failure indices turning toward unity. Optimized structural thicknesses in terms of glass fiber-reinforced plastic (GFRP) layers were found within safe limits. From FEA study and based on the von Mises stress distribution on the pressure and suction sides of wind turbine blade from root to tip, the initial failure was found to occur in the overlap edge of root region when the equivalent stress reached to the ultimate stress of the tip region. It was found that a well-designed GFRPs wind turbine blade is very efficient compared with metals/alloys.

Supersonic compressor cascade flow control using plasma actuation at low Reynolds number

To control the supersonic compressor cascade flow at low Reynolds numbers, this paper describes the use of nanosecond dielectric barrier discharge (NS-DBD) plasma actuation for flow control, and presents the results of large-eddy simulations conducted to investigate the corresponding flow control effects. NS-DBD plasma actuation on both the blade pressure surface and suction surface induces a distorted flow structure (DFS) within the blade passage. In the case of NS-DBD plasma actuation on the blade pressure surface, the influence of the DFS on the flow is suppressed by a shock wave. Even so, the DFS can still trigger the instability in the shear layer between the separated flow and the mainstream flow. Shock-wave-induced large-scale flow separation on the blade pressure surface is then suppressed, and the overall total pressure loss of the blade passage is reduced by 7.4%, despite the increased shock wave loss from the reduced flow blockage within the blade passage. In the case of NS-DBD plasma actuation on the blade suction surface, the DFS is less effective in suppressing the shock-wave-induced small-scale flow separation on the blade suction surface. However, the DFS on the blade suction surface enhances the shock wave oscillations within the blade passage, and this suppresses the flow separation on the blade pressure surface.

Transonic Turbine Blade Tip Heat Transfer with Pressure Side Film Cooling

Investigated are spatially resolved distributions of surface adiabatic film cooling effectiveness and surface heat transfer coefficients for a transonic turbine blade tip, with a unique and innovative film cooling arrangement, wherein a single row of five film cooling holes, located on the pressure side of the blade very near to the blade tip, provides thermal protection to the blade tip. The blade tip contains a squealer rim, and a squealer recess region. The present tip gap magnitude is 1.2% of the true blade span. When blade upper pressure side data are considered, heat transfer coefficient ratio variations are due, in part, to a horseshoe-shaped vortex structure, which forms around each film cooling jet, and then advects downstream. Spatially resolved distributions of surface adiabatic film cooling effectiveness show that the coolant advects to the upper edge of the blade pressure surface, along the pressure side rim, over the squealer recess region, and then sometimes collects in a substantial manner along portions of the suction side rim. As a result, local effectiveness values are generally higher on the suction side rim relative to pressure side rim values when compared at a particular value of blowing ratio.

Film cooling performance of blade pressure side with three-row film holes under rotating condition

Film cooling is an essential cooling method for high-temperature components of turbines. The film cooling performance on the pressure side of turbine blades with three-row film holes is investigated experimentally and numerically at a rotating speed of 600 rpm. Three test models composed of two types of hole arrangement (in-line and staggered) and two compound angles (β = 0° and 45°) are studied at five blowing ratios (M = 0.5, 0.75, 1.0, 1.25, and 1.5). The film trajectories on the pressure side are short, dissipate quickly, and deflected to the upper and lower sides. Upstream of the pressure side, the coolant coverage is poor near the tip due to the rotating effect, and no coolant is ejected near the hub at low M due to insufficient internal pressure. The best film cooling performance is at M = 0.75 for all three models in this study. Because of the large row space, the difference in film cooling effectiveness (η) between cases with the in-line and staggered arrangement is not significant at M = 0.5. When M ≥ 0.75, η is generally higher for the case with the staggered arrangement. Furthermore, the case with β = 45° shows a higher η than cases with β = 0°

Numerical simulation of the influence of mixed sand on erosion characteristics of centrifugal pump

PurposeThe purpose of the paper is to predict the erosion rate of the components of centrifugal pump under certain operating condition to identify the maximum erosion area and to discuss the factors affecting them. This helps to optimize design and estimate service life.Design/methodology/approachIn the paper, the Eulerian–Lagrangian approach method coupled with the erosion model to investigate the mixed sand characteristics on erosion characteristics of centrifugal pump flow-through wall. The hydraulic performance and wear characteristics experiment of the pump is used to verify the accuracy of the numerical simulation.FindingsThe blade erosion area mainly occurs near the blade inlet and the trailing edge of the pressure surface, the main erosion area of the impeller back shroud is near the outlet of the flow passage and the main erosion area of the volute is near the tongue and the I section. With the change of the average diameter and density of sand particles, the average erosion rate on different flow-through walls is positively correlated with the average mass concentration to a certain extent. However, for different sand shape factors, there is little correlation between the average erosion rate and the average mass concentration. In addition, compared with other erosion areas, the increase of average sand particle diameter and density has the greatest impact on the total erosion rate of blade pressure surface, while the shape of sand particles has a greater impact on the total erosion rate of each flow-through wall of centrifugal pump.Originality/valueIn this work, according to the characteristics of the mixed distribution of different sand diameters in the Yellow River Basin, the erosion characteristics of centrifugal pumps used in the Yellow River Basin are studied. The numerical calculation method for predicting the wall erosion of centrifugal pump is established and compared with the experimental results. The results can provide reference for optimizing design and increasing service life.

STONE TOOL FUNCTIONS, HOUSEHOLD ACTIVITIES, AND FORMATIVE LITHIC ECONOMIES IN NORTHERN TLAXCALA, MEXICO

AbstractHigh-magnification use-wear analyses create datasets that enable microeconomic studies of lithic consumption and household activities that complement macroeconomic studies of lithic production and exchange to collectively improve our reconstructions of ancient economies. In recent decades, compositional and technological analyses have revealed how certain obsidian sources and lithic technologies were exploited, produced, and exchanged in Mexico's central highlands region during the Formative period (1500b.c.–a.d.100). This article presents use-wear analyses of 275 lithic artifacts from four sites in northern Tlaxcala—Amomoloc (900–650b.c.), Tetel (750–500b.c.), Las Mesitas (600–500b.c.), and La Laguna (600–400b.c.and 100b.c.–a.d.150)—to compare household activities with lithic technologies and evaluate their roles in regional economies. Blades were used for subsistence and domestic crafting; maguey fiber extraction for textile production increased over time, especially in non-elite households. The preparation and consumption of meat acquired by hunting and other methods increased slightly over time, and bipolar tools were used as kitchen utensils. Bloodletting was practiced with two variations of late-series pressure blades, but these and other tools were neither exchanged as nor used to craft prestige goods, often viewed as driving forces of Formative economies in Mesoamerica.

Centrifugal Compressor and Bell mouth Air Intake Preliminary Design for Micro Turbojet Engine

This paper presents a design of centrifugal compressor and air intake for micro turbojet engine of 200 N thrust. Because of the small size of the micro turbine engines the air intake is designed in the form of bellmouth air intake in order to capture the needed amount of mass flow rate (0.45 kg/s). The function of the air intake is to deliver the air to the entry of the centrifugal compressor. The air intake has been drawn with start-up motor to take in the consideration the effect. The centrifugal compressor was designed to deliver 3.8 pressure ratio with efficiency about 77%. The compressor impeller was built with 7 main blades and 7 splitters in order to reduce the effect of slip at the exit of the impeller due to pressure difference between pressure and suction side of the main blade. Diffuser of 13 vanes also was designed to increase the static pressure, direct the flow to the combustion chamber and decrease the flow velocity before to enhance the combustion process. The structural integrity for impeller was validated using ANSYS software for aluminum alloy 7075-T6; 7075651. In addition, the aerodynamic analysis was investigated using NUMECA software. The most important findings of the extensive analysis were; the impact of air intake on compressor performance is very crucial. It add an increment in efficiency and pressure ratio, it should be taken in consideration in early design stage of the compressor. The highest performance characteristics of compressor were achieved by accurate design optimization of impeller-diffuser interaction.

A NOVEL DESIGN OF PERISTALTIC CARBON NANO PUMP AND AN ANALYSIS OF HELIUM FLOW

A novel nano-scale pump that can transport atoms or small molecules with a peristaltic motion is designed. It is proven by molecular-dynamics simulations that the introduced nano-pump design works properly. The designed nano-pump consists of one main carbon nanotube named the flow tube and two rotors where multi-walled carbon nanotubes are attached. The pumping of helium atoms by the designed peristaltic carbon nano-pump is investigated by molecular-dynamics simulations. For varying rotor speeds and blade counts, time-averaged velocity, temperature, and pressure results of pumped helium atoms are calculated, and relationships between them are modeled as polynomial surfaces. The results showed that rotor frequency increases the velocity of helium linearly and the temperature and pressure of helium non-linearly. Furthermore, the blade count of the proposed mechanism does not substantially affect the velocity as per the previous studies in the literature.

Performance and wake analysis of horizontal axis tidal current turbine using Improved Delayed Detached Eddy Simulation

This paper presents the results of hydrodynamic performance and wake assessment for a horizontal axis tidal current turbine. The three-dimensional instantaneous flow field is resolved utilizing the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model and polyhedral mesh. The rotor rotation is simulated by employing the sliding mesh approach. The simulation results using turbulence model of k-ω Shear Stress Transport are also presented for comparison. The simulated thrust and power coefficients and wake characteristics are validated against published experimental results. It is shown that the performance and wake velocity predicted by IDDES are closer to the experimental values than those predicted by k-ω Shear Stress Transport model. In determining the pressure coefficient, only IDDES captures the time-varying fluctuations pertaining to blade generated turbulence. The oscillations in phase-averaged performance coefficients are substantially larger for IDDES because the inflow turbulence in this model is more realistically resolved using Synthetic Eddy Method. The IDDES predicts more detailed vortex structures which has impact on accurate determination of blade pressure distribution, energy dissipation rate and downstream flow field. It is demonstrated that the IDDES model is capable to satisfactorily simulate the hydrodynamics of a horizontal axis tidal current turbine.

Influence of inlet gas volume fraction on energy conversion characteristics of multistage electric submersible pump

A local-regional power loss analysis method based on multiphase computational fluid dynamics (CFD) simulation results is proposed in this study. This method is used to investigate the energy conversion characteristics of a three-stage electric submersible pump under high inlet gas volume fraction (IGVF) conditions. Results show that the input power and effective power increase first and then decrease along the streamline. When IGVF increases from 0% to 14.5%, the total input power and total effective power decrease by 32.4% and 56.2%, respectively. In particular, the input power and effective power in R4 drop by 62% and 67%, respectively. The high gas volume fraction (GVF) area on the blade pressure surface near the impeller inlet causes the power decrease in R4. However, the input power in R6 increases by 47.5%. This condition is due to a jet flow near the impeller outlet causes the vortex and high GVF area in R6, thereby leading to a high liquid velocity area along the radial direction near the pressure surface of the impeller blade. The kinetic energy of the fluid in the jet region increases rapidly in accordance with Bernoulli equation and is converted into pressure energy in the vortex area. The total power loss increases quickly with IGVF. The power loss near the impeller outlet area at 14.5% IGVF is ten times higher than that of 0% IGVF condition and five times higher than that of 5% IGVF condition. This condition is caused by the large air pockets accompanied by vortices in the area. This work provides a theoretical basis for the design and optimization of the multiphase pump.