Diffuser augmented wind turbines: Review and assessment of theoretical models

Bontempo, R.; Manna, M.

doi:10.1016/j.apenergy.2020.115867

Cited by 53 publications

(27 citation statements)

References 82 publications

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“…Therefore, the development of aeroelastic simulation methods has become necessary to follow the modern design approach that is based on current design standards and guidelines. Theoretical studies on previous aerodynamics analyses are well summarized in Bontempo and Manna [6]. The Betz model [7] is a classical model for DAWTs and has been extended to several other models.…”

Section: Introductionmentioning

confidence: 99%

Diffuser Total Efficiency Using Generalized Actuator Disc Model and Its Maximization Method

et al. 2021

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The diffuser total efficiency was formulated and defined based on the generalized actuator disc model for the index of the efficiency of the diffuser-alone of the diffuser-augmented wind turbines. An optimization method to maximize the diffuser total efficiency was developed using a genetic algorithm and axisymmetric computational fluid dynamics. A case study was conducted for a 10% chord-to-diameter ratio, 2% thickness-to-chord plate, and the crest position at 50% chord of the diffuser. The optimal result showed a diffuser total efficiency of 1.087. Furthermore, 1392 (=48 population × 29 generations) simulation cases of the optimization process showed that high diffuser total efficiency appears at a low-drag coefficient, high-lift coefficient, and 15–25% low diffuser height-to-chord ratio.

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Section: Introductionmentioning

confidence: 99%

Diffuser Total Efficiency Using Generalized Actuator Disc Model and Its Maximization Method

et al. 2021

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“…Similarly, some experimental studies replace turbines with screens of different porosity to study DWTs at various rotor loadings (Igra, 1981;Gilbert and Foreman, 1983). Most simplified theoretical models of DWTs indicate that the optimal power output is achieved at a thrust coefficient of 8/9 similar to open wind turbines ( van Bussel, 2007;Jamieson, 2008;Bontempo and Manna, 2020). Bontempo and Manna (2020) reviewed various theoretical models of ducted wind turbines and concluded that they are all equivalent and that their apparent differences are due to different choices of flow parameters used to characterize the effect of the duct (e.g., the exit pressure coefficient, Foreman et al, 1978; or extra back pressure velocity ratio, van Bussel, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Most simplified theoretical models of DWTs indicate that the optimal power output is achieved at a thrust coefficient of 8/9 similar to open wind turbines ( van Bussel, 2007;Jamieson, 2008;Bontempo and Manna, 2020). Bontempo and Manna (2020) reviewed various theoretical models of ducted wind turbines and concluded that they are all equivalent and that their apparent differences are due to different choices of flow parameters used to characterize the effect of the duct (e.g., the exit pressure coefficient, Foreman et al, 1978; or extra back pressure velocity ratio, van Bussel, 2007). They also show that these models are insufficient in predicting the optimal design of ducted turbines as they neglect the dependence of the flow parameters on the thrust coefficient.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, Aranake and Duraisamy (2017) use a penalty function to avoid large values of the thrust coefficient, and the axial location of the rotor, the chord length of the duct cross section, and the rotor gap were not introduced as design variables. In most studies, a high-lift airfoil with the suction side inside the duct is used as the cross section of the duct (de Vries, 1979). A high-lift airfoil shape creates circulation and thereby increases the mass flow rate through the duct.…”

Section: Introductionmentioning

confidence: 99%

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Maximal power per device area of a ducted turbine

2021

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Abstract. 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.

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“…The second is diffuser-augmented wind turbines (DAWTs). Surrounding the turbine rotor by a diffuser is a seemingly simple modification which induces more airflow through the blades, and hence produces more power, but the optimum design is not known (Bontempo and Manna, 2020). Small DAWTs are now commercially available (Evans et al, 2020).…”

mentioning

confidence: 99%

Grand Challenges in Wind Energy Research

Wood

2020

Front. Energy Res.

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This is a brief summary of the author's views on the important future directions of wind energy research. It is impossible for a single researcher to provide a comprehensive review of a multidimensional subject but the recent publication of excellent and extensive multi-authored reviews, in 2019 (Veers et al., 2019) and 2016 (Van Kuik et al., 2016), is taken as justification for a more personal account. The author, moreover, is an engineer and will not cover issues associated with the societal context of wind energy. These range from the many aspects of noise which will be briefly mentioned here, to the intrusion of large wind turbines on isolated rural life (Aeon). One of the most important conferences in wind energy is the "Torque" series. Torque 2020 was to be held at the Technical University of Delft at the end of May but was eventually run electronically in October. It had seven themes which are listed below in decreasing order of the number of abstracts accepted for oral or poster presentation:

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Diffuser augmented wind turbines: Review and assessment of theoretical models

Cited by 53 publications

References 82 publications

Diffuser Total Efficiency Using Generalized Actuator Disc Model and Its Maximization Method

Diffuser Total Efficiency Using Generalized Actuator Disc Model and Its Maximization Method

Maximal power per device area of a ducted turbine

Grand Challenges in Wind Energy Research

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