Performance Optimization for Cycloidal Hydrokinetic Turbine With Augmentation Duct for Harvesting Riverine Energy

With the increased demand for developing renewable energy, hydro energy has attracted more attention since it is reliable and easy to acquire. In this area, the cycloidal turbine has been recently studied and applied to ocean energy for its stable and efficient output. Compared to the ordinary vertical/horizontal axis turbine with fixed pitch angle blades (e.g., Darrieus turbine), the cycloidal turbine can maximize the extracted power efficiency by keeping the optimized angle of attack for the blades. Meanwhile, the cycloidal turbine provides a potential solution to solve the problems of self-starting and seasonal flow variations. Introducing an augmentation duct is considered as a method to further increase the incoming flow velocity of the turbine. Inspired by the design of the wind tunnel, a convergent-divergent design of the augmentation duct is developed. One is noted that the dimensions of the augmentation duct are essential to the performance of the duct. In this study, a convergent-divergent augmentation duct is developed based on a 3-blade cycloidal hydro-turbine, operated at a 2 m/s river. Computational fluid dynamic (CFD) analysis with sliding unstructured mesh is applied to investigate the extent how the dimensions of the duct affect the flow velocity to the turbine as well as the extracted power efficiency.

Fault Diagnosis of Horizontal Axis Turbine with Different Twist Angle to Reduce Stress under Failure Thrust Force

Five types of configurations of tidal turbine blade including validation model have been considered with different profile tidal turbine blade with twist angle of 9, 10, 10.5, 11, 11.5 and 12 degrees. An optimized model of tidal turbine blades is developed. The simulation of the optimized model i.e. 12 degree twist angle gives minimum value of stress and deformation at different loads i.e. 441, 271, 272 and 610N which has optimized and converged result compared to respected models of tidal turbine blade, it has also been observed that stress and deformation was reduced at static load of 610N in 12 degree twist angle tidal turbine blade with the Zylon, Kevlar and CFRP material, thus the observed fault is diagnosed in this present research work. The configuration of optimized model gives maximum convergence on all parameters amongst all the configurations used.

Hydrodynamic Analysis of Horizontal Axis Tidal Current Turbine under the Wave-Current Condition

To take advantage of the high tidal current velocity near the free surface, the horizontal axis turbine is installed, which inevitably causes hydrodynamic characteristics to effect the turbine by the waves. In this article, we established a numerical calculation method for the hydrodynamic load of a horizontal axis turbine under wave-current conditions. Based on the numerical calculation results, the hydrodynamic loads were decomposed and the influence rules of wave parameters and blade tip immersion depth on the hydrodynamic load were obtained. The study found the following: (1) the multi-frequency fluctuations based on the rotation frequency and incident wave frequency occurred in instantaneous values of the axial load coefficients and energy utilization ratios, and the fluctuation amplitude decreased with the increase of the blade tip immersion depth; (2) the fluctuation amplitude, according to rotation frequency, changed less with the increase of wave period and wave height, and was smaller according to wave frequency; (3) the fluctuation amplitude based on wave frequency increased linearly with the increase of wave height and wave period. The research results can provide the basis and reference for the design and engineering application of tidal current power station.

The effects of shape and size on duct-augmented horizontal axis turbine performance

This article seeks to contribute to knowledge on duct-augmented turbines by investigating the influence of the key geometric parameters of the duct on the turbine performance: (i) duct expansion angle and length, (ii) position of the duct relative to the rotor and (iii) added geometric features to the duct. A new analytic model is proposed for the duct-augmented turbine and used for the investigation. The proposed analytic model used in this study was developed with existing momentum and blade element analysis methodologies serving as its basis. Using the proposed analytic model, the duct length is found to be more influential on the duct turbine system performance than the duct expansion angle. In addition, the performance can be enhanced by addition of a flange to the duct trailing edge. The study also highlights that the optimum rotor location within a duct is slightly behind the minimum duct area.

Estimating the stability of a bed protection of a weir-mounted tidal turbine

Coastal infrastructure, such as bridges and storm surge barriers with weirs, provides an attractive location for harvesting renewable energy using tidal turbines. Often stone layers are applied downstream of coastal infrastructure to protect the sea bed from erosion. However, little is known about the potential effect of tidal energy extraction on the stability of this granular bed protection. This paper describes a study of the flow conditions influencing the stability of the bed protection downstream of a weir-mounted tidal turbine, using hydrodynamic data of an experimental test. The analysis indicates that the flow recirculation zone downstream of a weir may become shorter and flatter due to the presence of a horizontal-axis turbine. As a result, energetic turbulence eddies can transport more horizontal momentum towards the bed – hence the reason a heavier bed protection may be required for granular beds downstream of weirs when a turbine is installed. This information is essential when designing safe bed protections for coastal infrastructure with tidal turbines.

Numerical investigation of the effects of immersion on the efficiency of a tidal helical turbine

In the current study, a two-phase simulation of a tidal helical turbine was performed that contrasts with previous studies in two ways. First, the current research simulated the turbine in different states of immersion in water, whereas previous studies simulated turbines mostly in single-phase conditions and full immersion in water. Second, the present study used a horizontal-axis turbine, whereas previous research employed a vertical-axis helical turbine or Darrius turbine. In this study, a simulation was conducted using the volume of fluid method in ANSYS Fluent 18. Results indicated that the complete immersion of the turbine in water generated a high torque, thereby reducing the efficiency of the device. To determine the conditions with the highest efficiency, immersion rates of 100%, 75%, 50%, and 25% in water were examined, and a configuration with best power coefficient ( C p = 0.175 in TSR = 0.47) was found in 25% immersion. In immersion rate of 25%, resistant pressure on blades was minimum.