scholarly journals Effect of Rotor Spacing and Duct Diffusion Angle on the Aerodynamic Performances of a Counter-Rotating Ducted Fan in Hover Mode

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1338
Author(s):  
Woo-Yul Kim ◽  
Santhosh Senguttuvan ◽  
Sung-Min Kim
Keyword(s):  
Steady State ◽  
Numerical Model ◽  
Figure Of Merit ◽  
Aerodynamic Performance ◽  
Power Coefficient ◽  
Flow Conditions ◽  
Thrust Coefficient ◽  
Ducted Fan ◽  
Aerodynamic Performances ◽  
Rotor Model

The aerodynamic performance of a counter-rotating ducted fan in hover mode is numerically analyzed for different rotor spacings and duct diffusion angles. The design of the counter-rotating fan is inspired by a custom-designed single rotor ducted fan used in a previous study. The numerical model to predict the aerodynamic performance of the counter-rotating ducted fan is developed by adopting the frozen rotor approach for steady-state incompressible flow conditions. The relative angle between the front and the rear rotor is examined due to the usage of the frozen rotor model. The results show that the variation of thrust for the different relative angles is extremely low. The aerodynamic performances are evaluated by comparing the thrust, thrust coefficient, power coefficient, and figure of merit (FOM). The thrust, thrust coefficient, and FOM slightly increase with increasing rotor spacing up to 200 mm, regardless of the duct diffusion angle, and reduce on further increase in the rotor spacing. The duct diffusion angle of 0° generates about 9% higher thrust and increases the FOM by 6.7%, compared with the 6° duct diffusion angle. The duct diffusion angle is highly effective in improving the thrust and FOM of the counter-rotating ducted fan, rather than the rotor spacing.

scholarly journals Optimization of aerodynamic performance for co-axial rotors with different rotor spacings

2018 ◽  
Vol 10 (4) ◽  
pp. 362-369
Author(s):  
Yao Lei ◽  
Yuxia Ji ◽  
Changwei Wang
Keyword(s):  
Power Consumption ◽  
Aerodynamic Performance ◽  
Separation Distance ◽  
Power Coefficient ◽  
Axial Thrust ◽  
Thrust Coefficient ◽  
Hover Performance ◽  
Power Loading ◽  
Blade Tip ◽  
Aerodynamic Interference

In this article, attempts are made to study the aerodynamic performance of co-axial rotors with different rotor spacings in hover. A custom-designed experimental platform with seven rotor spacings ( z/D = 0.16, 0.19, 0.23, 0.26, 0.29, 0.33 and 0.38) is applied to measure the hover performance, i.e. co-axial thrust and power consumption, and to optimize the aerodynamic configuration of the co-axial system. The experimental errors in thrust coefficient, power coefficient and power loading calculated through ‘Kline-McClintock equation’ are less than 2%. Additionally, the streamline distribution and pressure of blade tip at different rotor spacings obtained from numerical simulations are presented to visualize the effects of aerodynamic interference between the top and bottom rotor. Results show that the aerodynamic performance of a co-axial rotor with the specific rotor configure and speed range can be indeed improved by changing the rotor spacing, and the optimal performance is obtained with a rotor spacing of 0.19. Also, the magnitude of aerodynamic interference related to the axial separation distance has demonstrated to be beneficial on the total thrust and power consumption. For the same disc loading, a decrease in rotational speed results in an increase in power loading especially for z/D = 0.19. It is also found that the bottom rotor does affect the performance of the top rotor at smaller rotor spacings, whereas the effect is significantly reduced as the rotor spacing increases.

scholarly journals Comparative analysis of numerical computational techniques for determination of the wind turbine aerodynamic performances

2020 ◽  
pp. 175-175
Author(s):  
Bojan Peric ◽  
Aleksandar Simonovic ◽  
Milos Vorkapic
Keyword(s):  
Wind Turbine ◽  
Pressure Coefficient ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Numerical Approach ◽  
Power Coefficient ◽  
Future Research ◽  
Computational Techniques ◽  
Thrust Coefficient ◽  
Aerodynamic Performances

The purpose of this paper is to explore and define an adequate numerical setting for the computation of aerodynamic performances of wind turbines of various shapes and sizes, which offers the possibility of choosing a suitable approach of minimal complexity for the future research. Here, mechanical power, thrust, power coefficient, thrust coefficient, pressure coefficient, pressure distribution along the blade, relative velocity contoure at different wind speeds and streamlines were considered by two different methods: the blade element momentum (BEM) and computational fluid dynamics (CFD), within which three different turbulence models were analyzed. The estimation of the mentioned aerodynamic performances was carried out on two different wind turbine blades. The obtained solutions were compared with the experimental and nominal (up-scaled) values, available in the literature. Although the flow was considered as steady, a satisfactory correlation between numerical and experimental results was achieved. The comparison between results also showed, the significance of selection, regarding the complexity and geometry of the analyzed wind turbine blade, the most appropriate numerical approach for computation of aerodynamic performances.

scholarly journals Aerodynamic Performance Characterization of Slotted Propeller: Part B Effect of Angle

2019 ◽  
Vol 11 (4) ◽  
pp. 155-170
Author(s):  
Aravind SEENI
Keyword(s):  
Rotational Speed ◽  
Aerodynamic Performance ◽  
Von Mises Stress ◽  
Power Coefficient ◽  
Small Scale ◽  
Propeller Blade ◽  
Static Structure ◽  
Thrust Coefficient ◽  
Advance Ratio ◽  
Von Mises

In this paper, designs of slotted propeller blade were discussed numerically, in terms of aerodynamic performance and static structural analysis. Baseline APC Slow Flyer 10’ x 7’ small scale propeller blade was modified by including slots along the propeller blade. Numerical analysis has been done to determine the influence of slots angle towards thrust coefficient, power coefficient and efficiency. Simulations were performed by using ANSYS Fluent implementing k-ω turbulence model and Multiple Reference Frame to incorporate rotational speed of the propeller. The analyses were conducted at a fixed rotational speed, with variance of advance ratio. Initial slotted design is set at 180 degree and the angles were changed with 10-degree interval, ranging from 180 degree to 90 degree. The results were compared with available experimental data. For the slotted design, the result shows that inducing slots do not always lead to improvement in propeller blade performance. Improvement in thrust coefficient with the range of 0.267% to 2.71% can be seen for low advance ratio for most of slot angles. However, a significant increase in power coefficient can be observed which reduces the overall efficiency of the propeller blade. For stress and deformation, ANSYS Mechanical Static Structure was used to determine maximum Von-Mises stress, maximum Von-Mises strain, and total deformation. The analyses were conducted by using 60% long strand fiber glass reinforced nylon 6 Natural. The blade is more suitable to operate at higher velocity. At lower operational velocity, the blade tends to experience material failure as the stress exceeds stress at break.

A New Multi-Objective Evolutionary Algorithm for Optimizing the Aerodynamic Design of HAWT Rotor

2014 ◽  
Author(s):  
Ekhlas M. Alfayyadh ◽  
Sadeq H. Bakhy ◽  
Yasir M. Shkara
Keyword(s):  
Genetic Algorithm ◽  
Aerodynamic Performance ◽  
Power Coefficient ◽  
Aerodynamic Design ◽  
Thrust Coefficient ◽  
Blade Element Momentum Theory ◽  
Multi Objective ◽  
Momentum Theory ◽  
Bem Theory ◽  
Blade Element

This paper presents a new multi-objective evolutionary algorithm (MOEA) for optimum aerodynamic design of horizontal-axis wind turbines (HAWT). The design problem is set to find the blade shape such that optimizing multi-objective at different airfoil profiles. Combined Blade Element Momentum (BEM) theory and two different algorithms (Genetic (GA) and Enumeration) are used. Flow around subsonic airfoils is analyzed using XFOIL software. WINDMEL III wind turbine is selected to improve its aerodynamic performance with different airfoil profiles technique of National Renewable Energy Laboratory (NREL) family. Employing Genetic Algorithm embodied in Blade Element Momentum theory to calculate power, thrust and starting torque coefficients that are the fitness function. Another method, Enumeration method, is used to enhance evolutionary method results. The optimum solution acquired from combination of Genetic Algorithm and Blade Element Momentum theory of three blades configuration increased power coefficient by (25.8 %) and thrust coefficient by (16.6%). Enumeration method results increased power coefficient by (13.8%), while thrust coefficient decreased by (0.2%) from the original design. In general, the evolutionary method of combined GA and BEM theory with different airfoil profiles technique improved the turbine aerodynamic performance, and the results are in good agreement with other published papers.

Total Pressure Correction of a Sub-Miniature Five-Hole Probe in Areas of Pressure Gradients

2012 ◽  
Author(s):  
J. Town ◽  
A. Akturk ◽  
C. Camcı
Keyword(s):  
Pressure Measurement ◽  
Measurement Errors ◽  
Total Pressure ◽  
Pressure Gradients ◽  
Pressure Data ◽  
Flow Conditions ◽  
Complex Flow ◽  
Ducted Fan ◽  
The Difference ◽  
Best Fit

Five-hole probes, being a dependable and accurate aerodynamic tools, are excellent choices for measuring complex flow fields. However, total pressure gradients can induce measurement errors. The combined effect of the different flow conditions on the ports causes the measured total pressure to be prone to a greater error. This paper proposes a way to correct the total pressure measurement. The correction is based on the difference between the measured total pressure data of a Kiel probe and a sub-miniature prism-type five-hole probe. By comparing them in a ducted fan related flow field, a line of best fit was constructed. The line of best fit is dependent on the slope of the line in a total pressure versus span and difference in total pressure between the probes at the same location. A computer program, performs the comparison and creates the correction equation. The equation is subsequently applied to the five-hole probe total pressure measurement, and the other dependent values are adjusted. The validity of the correction is then tested by placing the Kiel probe and the five-hole probe in ducted fans with a variety of different tip clearances.

The Comparison of Aerodynamic Performance Data Acquired From Thermal Measurements and a Torquemeter on a Compressor Impeller

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Natalie R. Smith ◽  
Timothy C. Allison ◽  
Jason C. Wilkes ◽  
Christopher Clarke ◽  
Michael Cave
Keyword(s):  
Steady State ◽  
Heat Loss ◽  
Performance Metrics ◽  
Aerodynamic Performance ◽  
Performance Data ◽  
Testing Time ◽  
Southwest Research Institute ◽  
Significant Difference ◽  
Thermal Measurements ◽  
Isentropic Efficiency

Full-thermal heat-soak of machinery is vital for acquiring accurate aerodynamic performance data, but this process often requires significant testing time to allow all facility components to reach a steady-state temperature. Even still, there is the potential for heat loss in a well-insulated facility, and this can lead to inaccurate results. The implementation of a torquemeter to calculate performance metrics, such as isentropic efficiency, has two potential advantages: (1) the method is not susceptible to effects due to thermal heat loss in the facility, and (2) a torquemeter directly measures actual torque, and thus work, input, which eliminates the need to fully heat-soak to measure the actual enthalpy rise of the gas. This paper presents a comparison of aerodynamic performance metrics calculated both from data acquired with thermal measurements as well as from a torquemeter. These tests were conducted over five speedlines for a shrouded impeller in the Southwest Research Institute Single Stage Test Rig facility. Isentropic efficiency calculated from the torquemeter was approximately 1–2 efficiency points lower than the isentropic efficiency based on thermal measurements. This corresponds to approximately 0.5–1 °C in heat loss in the discharge collector and piping. Furthermore, observations from three full-thermal heat-soak points indicate the significant difference in time required to reach steady-state performance within measurement uncertainty tolerances between the torque-based and thermal-based methods. This comparison, while largely suspected, has not yet been studied in previous publications.

The Comparison of Aerodynamic Performance Data Acquired From Thermal Measurements and a Torquemeter on a Compressor Impeller

2018 ◽  
Author(s):  
Natalie R. Smith ◽  
Christopher Clarke ◽  
Timothy C. Allison ◽  
Michael Cave ◽  
Jason C. Wilkes
Keyword(s):  
Steady State ◽  
Heat Loss ◽  
Performance Metrics ◽  
Aerodynamic Performance ◽  
Performance Data ◽  
Testing Time ◽  
Southwest Research Institute ◽  
Significant Difference ◽  
Thermal Measurements ◽  
Isentropic Efficiency

Full-thermal heat-soak of machinery is vital to acquiring accurate aerodynamic performance data, but this process often requires significant testing time to allow for all facility components to reach a steady state temperature. Even still, there is the potential for heat loss in a well-insulated facility, and this can lead to inaccurate results. The implementation of a torquemeter to calculate performance metrics, such as isentropic efficiency, has two potential advantages: 1) the method is not susceptible to effects due to thermal heat loss in the facility, and 2) a torquemeter directly measures actual torque, and thus work, input, which eliminates the need to fully heat-soak to measure the actual enthalpy rise of the gas. This paper presents a comparison of aerodynamic performance metrics calculated both from data acquired with thermal measurements as well as from a torquemeter. These tests were conducted over five speedlines for a shrouded impeller in the Southwest Research Institute Single Stage Test Rig facility. Isentropic efficiency calculated from the torquemeter was approximately 1–2 efficiency points lower than the isentropic efficiency based on thermal measurements. This corresponds to approximately 0.5–1°C in heat loss in the discharge collector and piping. Furthermore, observations from three full-thermal heat-soak points indicate the significant difference in time required to reach steady state performance within measurement uncertainty tolerances between the torque-based and thermal-based methods. This comparison, while largely suspected, has not yet been studied in previous publications.

Drawing of Tubes

1980 ◽  
Vol 47 (4) ◽  
pp. 736-740 ◽  
Author(s):  
D. Durban
Keyword(s):  
Exact Solution ◽  
Steady State ◽  
Radial Flow ◽  
Material Behavior ◽  
Wall Friction ◽  
Flow Rule ◽  
Flow Conditions ◽  
Steady State Flow ◽  
Linear Hardening ◽  
Von Mises

The process of the tube drawing between two rough conical walls is analyzed within the framework of continuum plasticity. Material behavior is modeled as rigid/linear-hardening along with the von-Mises flow rule. Assuming a radial flow pattern and steady state flow conditions it becomes possible to obtain an exact solution for the stresses and velocity. Useful relations are derived for practical cases where the nonuniformity induced by wall friction is small. A few restrictions on the validity of the results are discussed.

The Effect of Stator-Rotor Hub Sealing Flow on the Mainstream Aerodynamics of a Turbine

2006 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Steady State ◽  
Entropy Generation ◽  
Flow Rate ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Flow Conditions ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Mainstream Flow ◽  
Flow Interactions

An investigation into the effect of stator-rotor hub gap sealing flow on turbine performance is presented. Efficiency measurements and rotor exit area traverse data from a low speed research turbine are reported. Tests carried out over a range of sealing flow conditions show that the turbine efficiency decreases with increasing sealant flow rate but that this penalty is reduced by swirling the sealant flow. Results from time-accurate and steady-state simulations using a three-dimensional multi-block RANS solver are presented with particular emphasis paid to the mechanisms of loss production. The contributions toward entropy generation of the mixing of the sealant fluid with the mainstream flow and of the perturbed rotor secondary flows are assessed. The importance of unsteady stator wake/sealant flow interactions is also highlighted.

scholarly journals Double multiple stream tube theory coupled with dynamic stall and wake correction for aerodynamic investigation of vertical axis wind turbine

2020 ◽  
Vol 23 (4) ◽  
pp. 771-780
Author(s):  
Anh Ngoc VU ◽  
Ngoc Son Pham
Keyword(s):  
Wind Turbine ◽  
Shape Function ◽  
Vertical Axis ◽  
Transformation Method ◽  
Aerodynamic Performance ◽  
Dynamic Stall ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Stream Tube ◽  
Aerodynamic Investigation

This study describes an effectively analytic methodology to investigate the aerodynamic performance of H vertical axis wind turbine (H-VAWT). An in-house code based on double multiple stream tube theory (DMST) coupled with dynamic stall and wake correction is implemented to estimate the power coefficient. Design optimization of airfoil shape is conducted to study the influences of the dynamic stall and turbulent wakes. Airfoil shape is universally investigated by using the Class/Shape function transformation method. The airfoil study shows that the upper curve tends to be less convex than the lower curve in order to extract more energy of the wind upstream and generate less drag of the blade downstream. The optimal results show that the power coefficient increases by 6.5% with the new airfoil shape.

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