scholarly journals Design and Performance Analysis of Blades Based on the Equal–Variable Circulation Method

2021 ◽  
Vol 9 ◽  
Author(s):  
D. Liang ◽  
C. Song ◽  
S. Liang ◽  
S. Wang ◽  
Y. Li ◽  
...  
Keyword(s):  
Design Method ◽  
Axial Flow ◽  
Aerodynamic Performance ◽  
Low Flow ◽  
Improve Performance ◽  
Flow Rates ◽  
Circulation Method ◽  
Blade Tip ◽  
New Type ◽  
And Performance

With the aim of improving the aerodynamic performance of axial turbomachinery, a new type of blade is designed using the equal–variable circulation method. Taking an axial flow fan as the research object, this article describes the development of a new type of turbomachinery by changing the design method and producing a blade with forward sweep. The aerodynamic performance of the fan is simulated and compared with the experimental data. The numerical results show that the equal circulation design method improves the aerodynamic performance of the blade roots, while the variable circulation design method enhances the aerodynamic performance of the blade tips. By adopting the equal–variable circulation design method, the total pressure of the experimental fan is increased by about 4%, while the efficiency remains unchanged. Forward-swept blades with an equal–variable circulation design also improve performance over the conventional blades by changing the center-of-gravity stacking line. At low flow rates, the efficiency of the experimental fan can be increased by 7.5%, and the working range of the flow is expanded. Under high flow rates, the restriction of the blade tip on the airflow is decreased and the fluidity is slightly reduced.

Compressible Simulation of Flow and Sound Around a Small Axial-Flow Fan With Flow Through Casing Slits

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Hiroshi Yokoyama ◽  
Katsutake Minowa ◽  
Kohei Orito ◽  
Masahito Nishikawara ◽  
Hideki Yanada
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Aerodynamic Performance ◽  
Design Flow ◽  
Low Flow ◽  
Axial Fan ◽  
Flow Rates ◽  
Blade Tip ◽  
Flow Through ◽  
Design Flow Rate

Abstract Small axial fans are used for cooling electronic equipment and are often installed in a casing with various slits. Direct aeroacoustic simulations and experiments were performed with different casing opening ratios to clarify the effects of the flow through the casing slits on the flow field and acoustic radiation around a small axial fan. Both the predicted and measured results show that aerodynamic performance deteriorates at and near the design flow rate and is higher at low flow rates by completely closing the casing slits compared with the fan in the casing with slits. The predicted flow field shows that the vortical structures in the tip vortices are spread by the suppression of flow through the slits at the design flow rate, leading to the intensification of turbulence in the blade wake. Moreover, the pressure fluctuations on the blade surface are intensified, which increases the aerodynamic sound pressure level. The suppression of the outflow of pressurized air through the downstream part of the slits enhances the aerodynamic performance at low flow rates. Also, the predicted surface streamline at the design flow rate shows that air flows along the blade tip for the fan with slits, whereas the flow toward the blade tip appears for the fan without slits. As a result, the pressure distributions on the blade and the torque exerted on the fan blade are affected by the opening ratio of slits.

scholarly journals Investigation of the Flow Field in the Vicinity of an Axial Flow Fan During Low Flow Rates

2014 ◽  
Author(s):  
Francois G. Louw ◽  
Theodor W. von Backström ◽  
Sybrand J. van der Spuy
Keyword(s):  
Flow Field ◽  
Numerical Simulations ◽  
Flow Rate ◽  
Axial Flow ◽  
Operating Conditions ◽  
Design Flow ◽  
Low Flow ◽  
Axial Flow Fan ◽  
Free Vortex ◽  
Flow Rates

Large axial flow fans are used in forced draft air cooled heat exchangers (ACHEs). Previous studies have shown that adverse operating conditions cause certain sectors of the fan, or the fan as a whole to operate at very low flow rates, thereby reducing the cooling effectiveness of the ACHE. The present study is directed towards the experimental and numerical analyses of the flow in the vicinity of an axial flow fan during low flow rates. This is done to obtain the global flow structure up and downstream of the fan. A near-free-vortex fan, designed for specific application in ACHEs, is used for the investigation. Experimental fan testing was conducted in a British Standard 848, type A fan test facility, to obtain the fan characteristic. Both steady-state and time-dependent numerical simulations were performed, depending on the operating condition of the fan, using the Realizable k-ε turbulence model. Good agreement is found between the numerically and experimentally obtained fan characteristic data. Using data from the numerical simulations, the time and circumferentially averaged flow field is presented. At the design flow rate the downstream fan jet mainly moves in the axial and tangential direction, as expected for a free-vortex design criteria, with a small amount of radial flow that can be observed. As the flow rate through the fan is decreased, it is evident that the down-stream fan jet gradually shifts more diagonally outwards, and the region where reverse flow occur between the fan jet and the fan rotational axis increases. At very low flow rates the flow close to the tip reverses through the fan, producing a small recirculation zone as well as swirl at certain locations upstream of the fan.

Design and Development of a Radial Turbine for Low Flow Turbocharging

2019 ◽  
Author(s):  
Dhinagaran Ramachandran ◽  
Srinivasa Rao Billa ◽  
Balamurugan Mayandi ◽  
Perumal Balappan ◽  
Shyamaprasad Kanthila ◽  
...  
Keyword(s):  
Transient Response ◽  
Mass Flow ◽  
Aerodynamic Performance ◽  
Low Flow ◽  
Angle Distribution ◽  
Turbine Wheel ◽  
Structural Requirements ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Low Mass

Abstract The scope of this study is to develop a turbocharger turbine wheel with improved aerodynamic performance at low mass flow rates and with reduced inertia for better transient response. The contrasting effect of geometrical shape and size parameters on the objectives of aerodynamic performance and transient response gives rise to the need to explore the design space for the best design having good trade-off between the multi-objective requirements. The search for an optimum aerodynamic design is a challenge due to structural requirements as well. A turbine wheel that is best suited for the current application is selected from the library as a baseline and this wheel is further optimized to meet the targets. Preliminary screening allowed the identification of parameters having major impact on the objectives and these results have been used to train a Response Surface (RS). Further, in the interest of reducing computational cost, a virtual optimization algorithm based on the RS has been employed to predict optimum design within the design constraints. The optimum designs thus obtained are validated with Computational Fluid Dynamics simulations for flow performance and Finite Element solver for satisfying structural requirements. This approach has allowed for application-based design of turbine wheel for instance, by changing key parameters like blade angle distribution, number of blades, axial length, blade height and width. An inertia reduction up to 10% has been obtained while retaining the performance at low mass flow rates.

Distortion Tolerance: By Design Instead of by Accident

1969 ◽  
Author(s):  
C. E. Langston
Keyword(s):  
Adverse Effects ◽  
Peak Pressure ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Chord Length ◽  
Individual Stage ◽  
Inlet Distortion ◽  
Blade Tip ◽  
And Performance ◽  
Selection Of

A variety of techniques are available today that may be employed by the compressor designer to minimize the adverse effects of inlet distortion. The effects of individual stage rotor matching and blade chord length have been qualitatively indicated by isolated airfoil data. These effects have been verified through testing of several multistage axial flow compressors. Matching of early compressor stages well below their peak pressure ratio has been shown to significantly reduce the sensititivty of the entire compressor-to-inlet distortion. Careful selection of blade geometry by the designer may be used to provide a favorable balance between distortion tolerance and performance. In addition, increases in rotor blade chord length and use of honeycomb blade tip shrouds have been shown to further reduce the compressor’s sensititivity to distortion. Finally, the association of inlet distortion with turbulence is established. This association assures the designer that accommodations made for time-average spatial distortion will be effective in combating the adverse effects of inlet turbulence.

A Comparison of Actuator Disc Models for Axial Flow Fans in Large Air-Cooled Heat Exchangers

2016 ◽  
Author(s):  
Michael B. Wilkinson ◽  
Francois G. Louw ◽  
Sybrand J. van der Spuy ◽  
Theodor W. von Backström
Keyword(s):  
Heat Exchangers ◽  
Three Dimensional ◽  
Axial Flow ◽  
Velocity Profiles ◽  
Low Flow ◽  
Disk Model ◽  
Flow Rates ◽  
Fan Performance ◽  
Actuator Disk ◽  
Performance Results

The performance of large mechanical draft air-cooled heat exchangers is directly related to fan performance which is influenced by atmospheric wind conditions, as well as the plant layout. It is often necessary to numerically model the entire system, including fans, under a variety of operating conditions. Full three-dimensional, numerical models of axial flow fans are computationally expensive to solve. Simplified models that accurately predict fan performance at a lesser expense are therefore required. One such simplified model is the actuator disk model (ADM). This model approximates the fan as a disk where the forces generated by the blades are calculated and translated into momentum sources. This model has been proven to give good results near and above the design flow rate of a fan, but not at low flow rates. In order to address this problem two modifications were proposed, namely the extended actuator disk model (EADM) and the reverse engineered empirical actuator disk model (REEADM). The three models are presented and evaluated in this paper using ANSYS FLUENT. The models are simulated at different flow rates representing an axial flow fan test facility. The resulting performance results and velocity fields are compared to each other and to previously simulated three dimensional numerical results, indicating the accuracy of each method. The results show that the REEADM gives the best correlation with experimental performance results at design conditions (ϕ = 0.168) while the EADM gives the best correlation at low flow rates. A comparison of the velocity profiles shows that none of the three models predict the radial velocity distribution at low flow rates correctly, however the correlation improves at flow rates above ϕ = 0.105. In general the upstream velocity profiles, where reversed flow occurs through the fan, are poorly predicted at low flow rates. At the flow rates above ϕ = 0.137 the correlation between the velocity profiles for the simplified modes and the three dimensional results is good.

Suppression of Cavitation in Inducers by J-Grooves

2006 ◽  
Vol 129 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Young-Do Choi ◽  
Junichi Kurokawa ◽  
Hiroshi Imamura
Keyword(s):  
High Speed ◽  
Leading Edge ◽  
Design Flow ◽  
Low Flow ◽  
Axial Pressure ◽  
Flow Rates ◽  
New Device ◽  
Axial Pressure Gradient ◽  
Blade Tip ◽  
Suction Performance

Cavitation is a serious problem in the development of high-speed turbopumps, and an inducer is often used to avoid cavitation in the main impeller. Thus, the inducer often operates under the worst conditions of cavitation. If it could be possible to control and suppress cavitation in the inducer by some new device, it would also be possible to suppress cavitation occurring in all types of pumps. The purpose of our present study is to develop a new, effective method of controlling and suppressing cavitation in an inducer using shallow grooves, called “J-Grooves.” J-Grooves are installed on the casing wall near the blade tip to use the high axial pressure gradient that exists between the region just downstream of the inducer leading edge and the region immediately upstream of the inducer. The results show that the proper combination of backward-swept inducer with J-Grooves improves the suction performance of the turbopump remarkably, at both partial flow rates and the design flow rate. The rotating backflow cavitation occurring at low flow rates and the cavitation surge which occurs near the best efficiency point can be almost fully suppressed by installing J-Grooves.

HAWT Rotor Design and Performance Analysis

2009 ◽  
Author(s):  
Emrah Kulunk ◽  
Nadir Yilmaz
Keyword(s):  
Performance Analysis ◽  
Computer Program ◽  
Wind Turbine ◽  
Design Method ◽  
Aerodynamic Performance ◽  
Horizontal Axis Wind Turbine ◽  
Rotor Design ◽  
And Performance ◽  
Bem Theory ◽  
Blade Element

In this paper, a design method based on blade element momentum (BEM) theory is explained for horizontal-axis wind turbine (HAWT) blades. The method is used to optimize the chord and twist distributions of the blades. Applying this method a 100kW HAWT rotor is designed. Also a computer program is written to estimate the aerodynamic performance of the existing HAWT blades and used for the performance analysis of the designed 100kW HAWT rotor.

Design and Experimental Research of Self-Suction Sprinkler Irrigation Jet Pump

2011 ◽  
Author(s):  
Jianrui Liu ◽  
Xiaoke He ◽  
Weidong Shi ◽  
Qiqin Su
Keyword(s):  
Design Method ◽  
Sprinkler Irrigation ◽  
The Self ◽  
National Standard ◽  
Average Weight ◽  
Pump Efficiency ◽  
Jet Pump ◽  
Working Mechanism ◽  
New Type ◽  
And Performance

A new type of self-suction sprinkler irrigation jet pump was presented in this paper. A jetted self-priming set with Venturi Tube was installed in the inlet of the pump, and the self-priming performance was improved. The valve of the jetted self-priming set shut off when the pump self-priming was finished and the pump efficiency was increased. The design method, working mechanism and structure of the pump were introduced. The experiment results of the jet aerator of the pump, the self-shutoff of the reflowing valve and performance were obtained. The results showed that the self-priming performance of the pump was principal concern with the size of the jet aerator and the pump efficiency was increased as the reflowing valve automatically closing. The efficiency of the pump is higher by 5.3%∼8.9% and the time of the self-priming is shorter by 25∼73s and the average weight is lighter by 16% than the national standard, which indicates that comprehensive technical index is on the top of international level.

Lift and Drag Characteristics of an Air-Cooled Heat Exchanger Axial Flow Fan

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Francois G. Louw ◽  
Theodore W. von Backström ◽  
Sybrand J. van der Spuy
Keyword(s):  
Heat Exchanger ◽  
Lift Coefficient ◽  
Axial Flow ◽  
Design Flow ◽  
Low Flow ◽  
Axial Fan ◽  
Flow Rates ◽  
Blade Element Theory ◽  
Lift And Drag ◽  
Air Cooled Heat Exchanger

Actuator-disk models (ADMs) use blade element theory to numerically simulate the flow field induced by axial fans. These models give a fair approximation at near design flow rates, but are of poor accuracy at low flow rates. Therefore, the lift/drag (LD) characteristics of two-dimensional (2D) sections along the span of an air-cooled heat exchanger (ACHE) axial fan are numerically investigated, with the future prospect of improving ADMs at these flow conditions. It is found that the blade sectional LD characteristics are similar in shape, but offset from the 2D LD characteristics of the reference airfoil (NASA LS 413 profile) at small angles of attack (αatt<5deg). A deviation between these characteristics is observed at higher angles of attack. The blade sectional lift coefficients for αatt>5deg always remain lower compared to the maximum lift coefficient of the reference airfoil. Conversely, the blade sectional drag coefficients are always higher compared to that of the reference airfoil for αatt>5deg.

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