Michal Kulak, Michal Lipian and Karol Zawadzki
This paper aims to discuss the results of the performance study of wind turbine blades equipped with winglets. An investigation focusses on small wind turbines (SWTs), where the…
Abstract
Purpose
This paper aims to discuss the results of the performance study of wind turbine blades equipped with winglets. An investigation focusses on small wind turbines (SWTs), where the winglets are recalled as one of the most promising concepts in terms of turbine efficiency increase.
Design/methodology/approach
To investigate a contribution of winglets to SWT aerodynamic efficiency, a wind tunnel experiment was performed at Lodz University of Technology. In parallel, computational fluid dynamics (CFD) simulations campaign was conducted with the ANSYS CFX software to investigate appearing flow structures in greater detail.
Findings
The research indicates the potential behind the application of winglets in low Reynolds flow conditions, while the CFD study enables the identification of crucial regions influencing the flow structure in the most significant degree.
Research limitations/implications
As the global effect on a whole rotor is a result of a small-scale geometrical feature, it is important to localise unveiled phenomena and the mechanisms behind their generation.
Practical implications
Even the slightest efficiency improvement in a distributed generation installation can promote such a solution amongst energy prosumers and increase their independence from limited natural resources.
Originality/value
The winglet-equipped blades of SWTs provide an opportunity to increase the device performance with relatively low cost and ease of implementation.
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Michal Kulak, Maciej Karczewski, Pawel Lesniewicz, Krzysztof Olasek, Bas Hoogterp, Guillaume Spolaore and Krzysztof Józwik
This paper aims to provide the results of investigations concerning an influence of the tyre with longitudinal grooves on the car body aerodynamics. It is considered as an…
Abstract
Purpose
This paper aims to provide the results of investigations concerning an influence of the tyre with longitudinal grooves on the car body aerodynamics. It is considered as an important aspect affecting the vehicle aerodynamic drag.
Design/methodology/approach
To investigate a contribution of grooved tyres to the overall vehicle drag, three wind tunnel experimental campaigns were performed (two by Peugeot Société Anonyme Peugeot Citroen, one at the Lodz University of Technology). In parallel, computational fluid dynamics (CFD) simulations were conducted with the ANSYS CFX software to enable formulation of wider conclusions.
Findings
The research shows that optimised tread patterns can be derived on a single tyre via a CFD study in combination with a controlled experiment to deliver designs actively lowering the overall vehicle aerodynamic drag.
Practical implications
A reduction in the aerodynamic drag is one of ways to decrease vehicle fuel consumption. Alternatively, it can be translated into an increase in the maximum travel velocity and the maximum distance driven (key factor in electric vehicles), as well as in a reduction of CO2 emissions. Finally, it can improve the vehicle driving and steering stability.
Originality/value
The tyre tread pattern analysis on isolated wheels provides an opportunity to cut costs of R&D and could be a step towards isolating aerodynamic properties of tyres, irrespective of the car body on which they are applied.
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Krzysztof Olasek, Maciej Karczewski, Michal Lipian, Piotr Wiklak and Krzysztof Józwik
A solution to increase the energy production rate of the wind turbine is proposed by forcing more air to move through the turbine working section. This can be achieved by…
Abstract
Purpose
A solution to increase the energy production rate of the wind turbine is proposed by forcing more air to move through the turbine working section. This can be achieved by equipping the rotor with a diffusing channel ended with a brim (diffuser augmented wind turbine – DAWT). The purpose of this paper is to design an experimental stand and perform the measurements of velocity vector fields through the diffuser and power characteristic of the wind turbine.
Design/methodology/approach
The experiments were carried out in a small subsonic wind tunnel at the Institute of Turbomachinery, Lodz University of Technology. An experimental stand design process as well as measurement results are presented. Model size sensitivity study was performed at the beginning. The experimental campaign consisted of velocity measurements by means of particle image velocimetry (PIV) and pneumatic pitot probe as well as torque and rotational velocity measurements.
Findings
Characteristics (power coefficient vs tip speed ratio) of the bare and shrouded wind turbine were obtained. The results show an increase in the wind turbine power up to 70-75 per cent by shrouding the rotor with a diffuser. The mechanisms responsible for such a power increase were well explained by the PIV and pneumatic measurement results revealing the nature of the flow through the diffuser.
Research limitations/implications
Experimental stand for wind turbine rotor testing is of a preliminary character. Most optimal methodology for obtaining power characteristic should be determined now. Presented results can serve as good input for choice of stable and reliable control system of wind turbine operational parameters.
Practical implications
A 3 kW DAWT is being developed at the Institute of Turbomachinery, Lodz University of Technology. Aim of the study is to design a compact and smart wind turbine optimised for low wind speed conditions. Developed wind turbine has a potential to be used as an effective element within a net of distributed generation, e.g. for domestic use.
Originality/value
Research carried out is the continuation of theoretical study began in 1970s. It was also inspired by practical solutions proposed by Japanese researchers few years ago. Presented paper is the summary of work devoted to optimisation of the DAWT for wind conditions in the region. Original solution has been applied, e.g. for experimental stand design (3D printing application).
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Extensions/applications/revisions of the Marxian vision ofsocialism can broadly be categorized into two polar strands: thecentralized and the decentralized strands of socialist…
Abstract
Extensions/applications/revisions of the Marxian vision of socialism can broadly be categorized into two polar strands: the centralized and the decentralized strands of socialist economic systems. Explores the main postulates of a decentralized version of a socialist economic system as provided by Kautsky, Luxembourg, Bernstein, Bukharin and Lange. The centralized strand of socialist economic systems has been elaborated drawing mainly from the writings of Lenin, Trotsky, Dobb, Sweezy and Baran.