scholarly journals Power Coefficient Analysis of Double-blade Half-rotating Impeller Tidal Turbine Operating at Yaw

2021 ◽  
Vol 242 ◽  
pp. 03008
Author(s):  
Cong Liu ◽  
Xiaoyi Wang ◽  
Xiaofeng Yu ◽  
Yuhua Zhang ◽  
Zhizhen Qiu ◽  
...  
Keyword(s):  
Flow Direction ◽  
Power Coefficient ◽  
Flow Angle ◽  
Tidal Turbine ◽  
Rotating Impeller ◽  
New Type ◽  
Grid Technique ◽  
Tidal Current Turbine ◽  
Yaw Angle ◽  
Resistance Performance

The double-blade half-rotating impeller tidal turbine (DHITT) is a new type of vertical shaft tidal current turbine with lift and resistance performance. The power coefficient of the DHITT is affected by the flow direction. In order to research the power coefficient (CP) of the DHITT under different flow direction, the optimal attack flow angle of a half-impeller turbine was explored, and the fluctuation of power coefficient of the DHITT operating at yaw was analyzed based on the optimal attack flow angle. The unsteady flow of the turbine was simulated by overlapping grid technique, and the fluctuation of the turbine’s power coefficient under different flow directions was analyzed, which was verified by experiments. The results have demonstrated that the power coefficient at the optimal angle of attack is 0.53. As the yaw angle greater than 30º, the power reduction is nearly 40%, but the average efficiency loss is only 3.7% in the range of -3º to 3º.

scholarly journals Performance and wake characteristics of a tidal turbine under yaw

2018 ◽  
Vol 1 (1 (Aug)) ◽  
pp. 41-50 ◽  
Author(s):  
P. Modali ◽  
N. S. Kolekar ◽  
A. Banerjee
Keyword(s):  
Center Of Mass ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Thrust Coefficient ◽  
Tip Vortices ◽  
Downstream Distance ◽  
Tidal Turbine ◽  
Yaw Angle

In tidal streams and rivers, the flow of water can be at yaw to the turbine rotor plane causing performance degradation and a skewed downstream wake. The current study aims to quantify the performance variation and associated wake behavior caused by a tidal turbine operating in a yawed inflow environment. A three-dimensional computational fluid dynamics study was carried out using multiple reference frame approach using κ-ω SST turbulence model with curvature correction. The computations were validated by comparison with experimental results on a 1:20 scale prototype for a 0° yaw case performed in a laboratory flume. The simulations were performed using a three-bladed, constant chord, untwisted tidal turbine operating at uniform inflow. Yaw effects were observed for angles ranging from 5° to 15°. An increase in yaw over this range caused a power coefficient deficit of 26% and a thrust coefficient deficit of about 8% at a tip speed ratio of 5 that corresponds to the maximum power coefficient for the tested turbine. In addition, wake propagation was studied up to a downstream distance of ten rotor radius, and skewness in the wake, proportional to yaw angle was observed. At higher yaw angles, the flow around the turbine rotor was found to cushion the tip vortices, accelerating the interaction between the tip vortices and the skewed wake, thereby facilitating a faster wake recovery. The center of the wake was tracked using a center of mass technique. The center of wake analysis was used to better quantify the deviation of the wake with increasing yaw angle. It was observed that with an increase in yaw angle, the recovery distance moved closer to the rotor plane. The wake was noticed to meander around the turbine centerline with increasing downstream distance and slightly deviate towards the free surface above the turbine centerline, magnitude of which varied depending on yaw.

scholarly journals Measurement Drift in 3-Hole Yaw Pressure Probes From 5 Micron Sand Fouling at 1050° C

2019 ◽  
Author(s):  
Edward J. Turner ◽  
Matthew F. Bogdan ◽  
Tyler M. O’Connell ◽  
Wing F. Ng ◽  
Kevin T. Lowe ◽  
...  
Keyword(s):  
Flow Direction ◽  
Significant Risk ◽  
Road Dust ◽  
Maximum Error ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Flow Angle ◽  
Cylindrical Probe ◽  
Flow Characterization ◽  
Yaw Angle

Abstract The present paper focuses on the resilience of 3-hole pressure probes to hot sand fouling in turbomachinery environments. These probes are utilized inside jet engine hot sections for diagnostics and flow characterization. Ingestion of sand and other particulates pose a significant risk to hot section components and measurement devices in gas turbine engines. In this study, wedge, cylindrical, and trapezoidal probes were exposed to hot section turbine aerothermal conditions of 1050°C and 65–70 m/s flow velocity and fouled with 0–5 μm Arizona Road Dust (ARD). Sand accumulated more rapidly on the surface of the trapezoidal and cylindrical probe geometries than on the surface of the wedge probe geometry. Probe calibrations following sand fouling were performed in an ambient temperature, open air, calibration jet at Mach 0.3 and 0.5. Calibration curves using non-dimensional coefficients were used to assess probe error in yaw angle due to sand fouling. Probe error was based on each probe’s ability to accurately measure flow direction over a flow angle range of [−10°, 10°]. On average, the probes displayed greater error at Mach 0.5 than Mach 0.3. The wedge probe performed the best after sand fouling and displayed a maximum error of less than ±2° in yaw angle. In contrast, the cylindrical probe performed the worst after sand fouling and displayed maximum errors of more than ±8° in yaw angle. Transient response did not change notably with sand fouling.

Measurement Drift in 3-Hole Yaw Pressure Probes From 5 µm Sand Fouling at 1050 °C

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Edward J. Turner ◽  
Matthew F. Bogdan ◽  
Tyler M. O’Connell ◽  
Wing F. Ng ◽  
Kevin T. Lowe ◽  
...  
Keyword(s):  
Flow Direction ◽  
Significant Risk ◽  
Road Dust ◽  
Maximum Error ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Flow Angle ◽  
Cylindrical Probe ◽  
Flow Characterization ◽  
Yaw Angle

Abstract The present paper focuses on the resilience of 3-hole pressure probes to hot sand fouling in turbomachinery environments. These probes are utilized inside jet engine hot sections for diagnostics and flow characterization. Ingestion of sand and other particulates pose a significant risk to hot section components and measurement devices in gas turbine engines. In this study, wedge, cylindrical, and trapezoidal probes were exposed to hot section turbine aerothermal conditions of 1050 °C and 65–70 m/s flow velocity and fouled with 0–5 µm Arizona Road Dust (ARD). Sand accumulated more rapidly on the surface of the trapezoidal and cylindrical probe geometries than on the surface of the wedge probe geometry. Probe calibrations following sand fouling were performed in an ambient temperature, open air, calibration jet at Mach 0.3 and 0.5. Calibration curves using nondimensional coefficients were used to assess probe error in yaw angle due to sand fouling. Probe error was based on each probe’s ability to accurately measure flow direction over a flow angle range of [−10 deg, 10 deg]. On average, the probes displayed greater error at Mach 0.5 than Mach 0.3. The wedge probe performed the best after sand fouling and displayed a maximum error of less than ±2 deg in yaw angle. In contrast, the cylindrical probe performed the worst after sand fouling and displayed maximum errors of more than ±8 deg in yaw angle. Transient response did not change notably with sand fouling.

Numerical Simulation of a Farm of Vertical Axis Marine Current Turbines

2010 ◽  
Author(s):  
Anders Goude ◽  
Olov A˚gren
Keyword(s):  
Flow Direction ◽  
Computational Cost ◽  
Vortex Method ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Total Power ◽  
Flow Angle ◽  
Higher Power ◽  
Zigzag Pattern ◽  
Marine Current

For commercial applications of marine current turbines, it can be useful to build several turbines close to each other in a farm, similar to wind turbine parks. To create a good farm configuration, the turbines’ mutual interaction needs to be studied. Here, to obtain detailed information, several turbines were simulated together using a 2D vortex method. To limit the computational cost, the vortex method was combined with known profile section data for the blades. First, a single turbine was compared against two turbines in close proximity. The two turbines were tested both with equal and opposite rotational direction, and the two blade pitch angles 0 and 3 degrees were tested. For both a single turbine and the two turbine case, a 3 degree pitch angle gave higher power coefficients than 0 degrees. The differences between 3 and 0 degrees were more significant for the single turbine. In all cases, the two turbine system had higher power coefficient per turbine than the single turbine. A five turbine park was simulated with three different combinations, one with all turbines on a row, and two with a zigzag pattern, where the difference was that the last simulation had larger turbines than the other two. For 0 degrees incident flow angle, the turbines on the row obtained the highest power coefficient, while the larger turbines in zigzag pattern obtained higher total power. The case with the turbines on the row was most insensitive to changes in flow direction, and for a 30 degree change, the row produced the highest total power as well. By locating the turbines inside a channel, all turbines obtained higher power coefficients, and the increase was largest for the large turbines, which blocked the channel to a larger extent.

Influence of the Blade-Spoke Connection Point on the Aerodynamic Performance of Darrieus Wind Turbines

2016 ◽  
Author(s):  
Alessandro Bianchini ◽  
Francesco Balduzzi ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari
Keyword(s):  
Wind Turbines ◽  
Design Parameter ◽  
Flow Direction ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Common Solution ◽  
Curvature Effects ◽  
Flow Curvature ◽  
Low Incidence

The assessment of robust CFD techniques is casting new light on the aerodynamics of airfoils rotating around an axis orthogonal to flow direction, with particular reference to flow curvature effects and stall mechanisms. In particular, Darrieus wind turbines’ designers are taking profit from these new discovers to improve the aerodynamic design of the rotors, in view of an increase of the overall efficiency and a reduction of the structural stresses on the blades. A controversial design parameter for Darrieus turbines, especially in case of small-size rotors, is represented by the location of the blade-spoke connection along the chord. The most common solution is indeed to place the connection at approximately airfoil’s quarter chord, i.e. where the pressure center is commonly located for low incidence angles. In some cases, however, the blade is connected at middle chord due to symmetry or aesthetic reasons. In some small turbines, innovative designs have even disregarded this parameter. Even if one can argue that the blade connection point is about to have some aerodynamic effects on the turbine’s performance, the real impact of this important design parameter is often not fully understood. The present study makes use of extensive CFD simulations on a literature case study, using a NACA 0021 airfoil, to assess the influence of the blade-spoke connection point. In particular, the differences in terms of power coefficient curve of the turbine, optimal tip-speed ratio, torque profiles and stresses on the connection are analyzed and discussed. Detailed flow analyses are also shown for azimuthal positions of particular interest. Results on the selected case study showed that the middle-chord blade-spoke connection point seems to guarantee a higher performance of the rotor, even if additional solicitation is applied to the connection itself. It is further shown that the same performance can indeed be obtained with the airfoil attached at quarter chord and properly pitched. By doing so, the stresses are contained and the performance is maximized.

Optimization of a Horizontal Axis Tidal Current Turbine by Multi-Objective Optimization

2019 ◽  
Author(s):  
Takumi Nagataki ◽  
Ko Kurokawa ◽  
Reiko Yamada ◽  
Daisaku Sakaguchi ◽  
Yusaku Kyozuka
Keyword(s):  
Tidal Current ◽  
Swirling Flow ◽  
Operating Conditions ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Design Parameters ◽  
Navier Stokes Equation ◽  
Baseline Design ◽  
Tidal Current Turbine ◽  
Current Turbine

Abstract A global search optimization system is applied to the design of a horizontal axis tidal current turbine with shroud. 11 design parameters of the turbine blade and 4 design parameters of the shroud casing are considered for the optimization using a genetic algorithm. In order to reduce the simulation cost, a neural network is applied as the meta-model of the RANS (Reynolds-averaged Navier–Stokes) equation solver. Multi-objectives of the power coefficient at different tip speed ratios are applied to cover a wide operating range of the turbine. The CFD (Computational fluid dynamics) for optimization is validated experimentally for the case of a baseline design, and an optimum design is proposed. In this paper, a static structural analysis has been performed, and its robustness is confirmed under several operating conditions. Furthermore, internal flow of the optimized turbine is discussed in detail. It is found that the optimized blade generates a swirling flow and suppresses flow separation at the diffuser wall. The wide angle of the diffuser successfully achieves a high pressure recovery ratio and results in a high level of suction at the inlet of the turbine. It is found that the high-performance tidal turbine is possible to design if both the blade and the shroud diffuser are optimized at the same time.

Displacement-Based Assessment of Seismic Resistance for Transfer Structure with Haunching Braces

2011 ◽  
Vol 243-249 ◽  
pp. 557-562
Author(s):  
Wei Sheng Liang ◽  
Jian Cai
Keyword(s):  
Seismic Resistance ◽  
Engineering Practice ◽  
Seismic Events ◽  
Feature Based ◽  
New Type ◽  
Beam Type ◽  
Plastic Displacement ◽  
Transfer Structure ◽  
Displacement Based ◽  
Resistance Performance

The beam-type transfer structure has recently been well adopted in multi-purpose buildings. A new type of transfer structure with haunching braces is introduced in this paper through static elasto-plastic analysis of example structure with specific focus on its unique feature. Based of the deformation damaged criteria, seismic resistance performance for transfer structure with haunching braces is assessed. The results indicate that elastic and elasto-plastic displacement of structure under minor, medium and major seismic events designed against 7 degree seismic fortification intensity satisfy the requirement of the current standards, the structure’s damage status under minor and medium seismic events is Almost Intact and the structure’s damage status under major seismic events is Minor Damage. It can provide reference for engineering practice.

scholarly journals Measurement of Flow Pattern Within a Rotating Stall Cell in an Axial Compressor

2006 ◽  
Author(s):  
J. Lepicovsky ◽  
E. P. Braunscheidel
Keyword(s):  
Flow Direction ◽  
Flow Behavior ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Pressure Probe ◽  
Ensemble Averaging ◽  
Flow Angle ◽  
High Frequency Response ◽  
Actual Flow ◽  
Design Speed

Effective active control of rotating stall in axial compressors requires detailed understanding of flow instabilities associated with this compressor regime. Newly designed miniature high frequency response total and static pressure probes as well as commercial thermoanemometric probes are suitable tools for this task. However, during the rotating stall cycle the probes are subjected to flow direction changes that are far larger than the range of probe incidence acceptance, and therefore probe data without a proper correction would misrepresent unsteady variations of flow parameters. A methodology, based on ensemble averaging, is proposed to circumvent this problem. In this approach the ensemble averaged signals acquired for various probe setting angles are segmented, and only the sections for probe setting angles close to the actual flow angle are used for signal recombination. The methodology was verified by excellent agreement between velocity distributions obtained from pressure probe data, and data measured with thermoanemometric probes. Vector plots of unsteady flow behavior during the rotating stall regime indicate reversed flow within the rotating stall cell that spreads over to adjacent rotor blade channels. Results of this study confirmed that the NASA Low Speed Axial Compressor (LSAC) while in a rotating stall regime at rotor design speed exhibits one stall cell that rotates at a speed equal to 50.6% of the rotor shaft speed.

Simulating Characteristics of Vaneless Diffusers Using Neural Networks

2020 ◽  
pp. 29-42
Author(s):  
Y.B. Galerkin ◽  
A.G. Nikiforov ◽  
O.A. Solovyeva ◽  
E.Y. Popova
Keyword(s):  
Neural Networks ◽  
Mathematical Models ◽  
Dynamic Characteristics ◽  
Flow Direction ◽  
Similarity Criteria ◽  
Relative Width ◽  
Flow Angle ◽  
Gas Dynamic ◽  
Vaneless Diffusers ◽  
Two Parameters

To calculate flow parameters of a vaneless diffuser of the centrifugal compressor stage, it is sufficient to determine the loss coefficient and the flow direction at the outlet. The paper presents the results of modeling the characteristics of these two parameters using neural networks and CFD methods. To obtain mathematical models, ANSYS calculation data was used for vaneless diffusers with a relative width of 0.014–0.1, relative outlet diameter of 1.4–2.0, inlet flow angle of 10–90° and velocity coefficient of 0.39–0.82, with the Reynolds number being in the range of 87 500–1 030 000. A comparison with the theory showed the regularity of gas-dynamic characteristics, and comparison with well-known experiments showed the correspondence of the flow structure. In order to improve the accuracy of simulation using neural networks, various recommendations on the preparation and processing of the initial data were collected and tested: identification of conflict examples and outliers, data normalization, improving the quality of the neural network training under the insufficient amount of sampling, etc. The application of the aforementioned recommendations significantly improved the accuracy of simulation. A simulation experiment based on neural models for studying the influence of dimensions, diffuser shape and similarity criteria on the diffuser gas dynamic characteristics made it possible to verify physical adequacy of the mathematical models, obtain new data on energy conversion processes and produce a set of recommendations on the optimal design of vaneless diffusers.

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