Investigation of aerodynamic interaction between the balloon and the ducted wind turbine in airborne configuration

An aerodynamic analysis is presented in the current work, which estimates the separation distance between the balloon and the turbine in an airborne wind energy system (AWES). The stability of the structure of AWES depends on the aerodynamic interaction between the turbine and the balloon. A minimum gap must be maintained between the balloon and the wind turbine to reduce the interaction between the balloon and the turbine assembly. Three cases of AWES have been studied with a separation gap of 5 m, 10 m, and 16 m to estimate the minimum distance of separation between the balloon and the turbine. The aerodynamic interaction details suggest that a minimum distance of 13 m needs to be maintained between the turbine and the balloon to avoid the interaction between the balloon and turbine. Steady-state simulations of the rotor are run for various wind conditions to evaluate the efficiency of the duct-mounted configuration. The ducted turbine configuration saw a 7.4% increase in torque than the inducted turbine for a wind speed of 5 m s−1. A torque increase of 17.85% was observed when the separation distance was increased to 16 m from earlier 10 m.

A Comparative Study on the Hydrodynamic-Energy Loss Characteristics between a Ducted Turbine and a Shaftless Ducted Turbine

The shaftless ducted turbine (abbreviated as SDT), as an extraordinary innovation in tidal current power generation applications, has many advantages, and a wide application prospect. The structure of an SDT resembles a ducted turbine (abbreviated as DT), as both contain blades and a duct. However, there are some structural differences between a DT and a SDT, which can cause significant discrepancy in the hydrodynamic characteristics and flow features. The present work compares the detailed hydrodynamic-energy loss characteristics of a DT and a SDT by means of computational fluid dynamics (CFD), performed by solving the 3D steady incompressible Reynolds-averaged Navier-Stokes (RANS) equations in combination with the Menter’s Shear Stress Transport (SST k−ω) turbulence model and entropy production model. The results show the SDT features a higher power level at low tip speed ratio (TSR) and a potential reduction in potential flow resistance and disturbance with respect to the DT. Moreover, a detail entropy production analysis shows the energy loss is closely related to the flow separation and the reverse flow, and other negative flow factors. The entropy production of the SDT is lessened than that of the DT at different TSR. Unlike the DT, the SDT allows a large mass flow of water to leak through the open-center structure, which plays an important role in improving the wake structure and avoiding the negative flow along the central axis.

Maximal power per device area of a ducted turbine

The aerodynamic design of a ducted wind turbine for maximum total power coefficient was studied numerically using the axisymmetric Reynolds-averaged Navier–Stokes equations and an actuator disc model. The total power coefficient characterizes the rotor power per total device area rather than the rotor area. This is a useful metric to compare the performance of a ducted wind turbine with an open rotor and can be an important design objective in certain applications. The design variables included the duct length, the rotor thrust coefficient, the angle of attack of the duct cross section, the rotor gap, and the axial location of the rotor. The results indicated that there exists an upper limit for the total power coefficient of ducted wind turbines. Using an Eppler E423 airfoil as the duct cross section, an optimal total power coefficient of 0.70 was achieved at a duct length of about 15 % of the rotor diameter. The optimal thrust coefficient was approximately 0.9, independent of the duct length and in agreement with the axial momentum analysis. Similarly independent of duct length, the optimal normal rotor gap was found to be approximately the duct boundary layer thickness at the rotor. The optimal axial position of the rotor was near the rear of the duct but moved upstream with increasing duct length, while the optimal angle of attack of the duct cross section decreased.

Maximal power per device area of a ducted turbine

The aerodynamic design of a ducted wind turbine for maximum total power coefficient was studied numerically using the axisymmetric Reynolds-averaged Navier-Stokes equations and an actuator disc model. The total power coefficient characterizes the rotor power per total device area, rather than the rotor area. This is a useful metric to compare the performance of a ducted wind turbine with an open rotor and can be an important design objective in certain applications. The design variables included the duct length, the rotor thrust coefficient, the angle of attack of the duct cross-section, the rotor gap, and the axial location of the rotor. The results indicated that there exists an upper limit for the total power coefficient of ducted wind turbines. Using an Eppler E423 airfoil as the duct cross-section, an optimal total power coefficient of 0.69 was achieved at a duct length of about 15 % of the rotor diameter. The optimal thrust coefficient was approximately 0.9, independent of the duct length and in agreement with the axial momentum analysis. Similarly independent of duct length, the optimal normal rotor gap was found to be approximately the duct boundary layer thickness at the rotor. The optimal axial position of the rotor was near the rear of the duct, but moved upstream with increasing duct length, while the optimal angle of attack of the duct cross-section decreased.

Performance Evaluation of Axial Flow Wind Turbine Integrated with The Condenser

This study investigated the application of an axial flow wind turbine integrated with a condenser. The exhaust air from condenser was used to drive the wind turbine by a ducted turbine system. There were two parameters varied in this work: the blade number and the blade pitch angle. The blade number used was two blades, five blades, and ten blades, while the blade pitch angles were 5°, 10°, 15°, 20°, 30°, and 45°. The diameter of the wind turbine was 495 mm. The model of the condenser had a fan diameter of 600 mm and the range of the average air velocity of 2.01 m/s - 7.86 m/s. The maximum mechanical power was 10.72 W for air velocity of 7.86 m/s. The maximum power coefficient recorded was 0.38 for the tip speed ratio of 1.3 on the blade number of five blades and a pitch angle of 10°. The maximum exhaust air energy recovery was 13.64% of the power consumption of the condenser fan.

Wind Catcher Technology: The Impact of Tower Cross Section and Turbine on Wind Power Harnessing

This research explores utilizing distributed wind turbines in the built environment computationally. The targeted wind turbine design is an unconventional ducted turbine, called Wind Tower technology that its operation and performance metrics have been studied in earlier works in the team. Wind Tower is an established architectural technology that operates by catching wind and directing it into buildings, providing natural ventilation to support HVAC systems, and thus reducing cooling costs in urban environments. Wind power has long struggled to meet expectations in built (urban) environments. By combining wind towers at different cross sections with wind turbines, one might develop a device which provides natural ventilation and produces power in spite of a hostile wind environment. The preliminary results suggest that the maximum potential for a wind tower-turbine combination appears to be 700-1.46 kW under idealized conditions with a 4 m/s site dominant wind speed. This suggests that wind towers might be viable for power harvesting in both remote and grid connected regions. Further analysis suggested that additional turbine performance enhancements are needed to bring the turbine real power production closer to that ideal.

Design and Optimization of a Ducted Marine Current Savonius Turbine for Gun-Barrel Passage, Fiji

Marine current energy is a reliable and clean source of energy. Many marine current turbines have been designed and developed over the years. Placement of an appropriately designed duct or shroud around the turbine significantly improves the turbine performance. In the present work, a ducted Savonius turbine (DST) is designed and optimized and its performance analysis carried out. The components of DSTs are simple and easily available and can be manufactured in developing countries like Fiji. A scaled-down model of 1/20 of a DST was fabricated and tested in a water stream at a velocity of 0.6 m/s and the results were used to validate the results from a commercial computational fluid dynamics (CFD) code ANSYS-cfx. Finally, a full-scale DST was modeled to study the flow characteristics in the turbine and the performance characteristics. The maximum efficiency of the turbine is around 50% at the tip speed ratio (TSR) of 3.5 and the maximum shaft power obtained is 10 kW at the rated speed of 1.15 m/s and around 65 kW at a freestream velocity of 2.15 m/s. The stress distribution on the ducted turbine was also obtained.