Publications

>> Active Aerodynamic Control of Wind Turbine Blades with High Deflection Flexible Flaps.

AIAA Conference Proceedings January 7, 2010

Authors: G. Pechlivanoglou, J. Wagner, C. N. Nayeri, C.O. Paschereit

Publication and Conference Presentation at: 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Orlando, FL, USA

 

>> The Effect of Distributed Roughness on the Power Performance of Wind Turbines.

ASME Conference Proceedings (ISBN 978-0-7918-3872-3) June 18, 2010

Authors: G. Pechlivanoglou, S. Fuehr, C.N. Nayeri, C.O. Paschereit

Publications and Conference Presentation at ASME IGTI Turbo Expo 2010, Glasgow, Scotland

 

>> Fixed Leading Edge Auxiliary Wing as a Performance Increasing Device for HAWT Blades. 

Conference Proceedings DEWEK 2010 November 2010

Authors: G. Pechlivanoglou, C.N. Nayeri, C.O. Paschereit

Conference Presentation and Publication: DEWEK 2010, Bremen, Germany

 

>> Flow Control Using Plasma Actuators at the Root Region of Wind Turbine Blades

Conference Proceedings DEWEK 2010 November 2010

Authors: O. Eisele, G. Pechlivanoglou, C.N. Nayeri, C.O. Paschereit

Conference Publication and Presentation: DEWEK 2010, Bremen, Germany

 

>> Integration of a WT Blade Design Tool in XFOIL/XFLR5Conference Proceedings DEWEK 2010 November 2010

Authors: D. Marten, G. Pechlivanoglou, C.N. Nayeri, C.O. Paschereit

Conference Presentation and Publication at DEWEK 2010, 17-18 November, Bremen, Germany

QBlade Open Source Software: http://fd.tu-berlin.de/en/research/projects/wind-energy/qblade/


>> Performance optimization of Wind Turbine Rotors with Active Flow Control

Conference Proceedings ASME IGTI Turbo Expo 2011 June 2011

Authors: G. Pechlivanoglou, C.N. Nayeri, C.O. Paschereit

The paper presents the methodical investigation and evaluation of various AFC solutions by means of extensive literature research and several numerical simulations. The best performing AFC solutions are studied and evaluated in a second step experimentally with constant chord wind tunnel wing sections under steady and unsteady conditions. After these two-dimensional investigations, more realistic configurations are studied in a third phase. This phase includes the integration of the investigated AFC solutions in two different custom wind turbine blade design proposals.

 

>> Experimental Investigation of Dynamic Load Control Strategies using Active Microflaps on Wind Turbine Blades

EWEA 2011 Scientific Proceedings March 17, 2011

Authors: O. Eisele, G. Pechlivanoglou, Christian Navid Nayeri, Christial Oliver Paschereit

A control system consisting of a force sensor, a controller and the microflap as an actuator was designed and tested in the wind tunnel. For this purpose a test wing with constant cross section, based on the dedicated wind turbine airfoil AH 93-W-174 was equipped with a trailing edge microflap with a flap-chord of 1.6%c.Measurements were accomplished at the large wind tunnel of the Herman Föttinger Institute (HFI) of the TU-Berlin. Wind gusts were simulated by varying the angle of attack of the airfoil model with a maximum angular velocity of 2.2°/s. The microflap could be deflected simultaneously with a deflection speed of approximately 300°/s.

>> PERFORMANCE OPTIMIZATION OF WIND TURBINE ROTORS WITH ACTIVE FLOW CONTROL PART 2: ACTIVE AEROELASTIC SIMULATIONS

ASME IGTI Turbo Expo Proceedings June 2012

Authors: G. Weinzierl, George Pechlivanoglou, C.N. Nayeri, C.O. Paschereit

This paper presents the continuation of the research efforts of the authors in the direction of the development of ”smart blades” for the wind turbines of the future. Results from previous research work is further in combination with a newly developed simulation code in order to assess the performance of Active Flow Control (AFC) elements implemented on modern wind turbine blade structures. Parametric investigations have been conducted in order to identify the optimal configuration of various AFC elements. These are tested under identical bound-ary conditions to define an overall optimal solution. The results of the research project show that the Active Gurney Flap is the element with a highest probability for the fastest implementation on wind turbine blades for load alleviation purposes. The most promising however overall solution is the Flexible Trailing Edge Flap. With its high control authority and relatively high regulation speed is able to significantly vary the aerodynamic performance of wind turbines.

>> VORTEX GENERATORS FOR WIND TURBINE BLADES: A COMBINED WIND TUNNEL AND WIND TURBINE PARAMETRIC STUDY

ASME IGTI Turbo Expo June 2012

Authors: H. M. Vahl, G. Pechlivanoglou, C.N. Nayeri, C.O. Paschereit

Vortex generators (VGs) are passive flow control device that are commonly employed to prevent flow separation on wind turbine blades. They mitigate the damaging fatigue loads resulting from stall while increasing lift and consequently lead to rotor torque increase. This work summarizes a comprehensive research project aimed at optimizing the sectional as well as the full rotor-blade aerodynamics using VGs.The effects of chordwise position, spanwise spacing and VG size were studied with force balance measurements of a 2D wing section.  Particle Image Velocimetry measurements were conducted at various chordwise positions to provide insight into the interaction between adjacent streamwise vortices. The experimental aerodynamic performance curves of the optimal VG configuration were used to project their effect on wind turbine blade aerodynamics. 

>> Single and Multi-Element Airfoil Performance Simulation Study and Wind Tunnel Validation

EUROMECH 2012 - Springer April 2, 2011

Authors:  O. Eisele, G. Pechlivanoglou

The focus of the present investigation is to evaluate the capability of modern state of the art codes to simulate the aerodynamic behavior of typical wind turbine airfoils. Two airfoils were selected. The AH93-W-174 [1] with a thickness of 17.4% as a representative for relatively thin airfoils in the outer region and the relatively thick DU 97-W-300 [8] with a thickness of 30% as a representative for rather thick airfoils in the inner region of wind turbine blades. The third test case was a multi-element configuration composed of the DU-97-W-300 as the main airfoil and a slat based on the NACA 22 airfoil. For all configurations aerodynamic simulations with different levels of complexity were accomplished. First simulations were carried out with the panel code XFOIL and the Euler code MSES. Furthermore steady state RANS computations were conducted by the use of the open source code OpenFOAM

>> THE PATH TOWARDS THE FUTURE "SMART WIND TURBINE" DESIGN

Proceedings of Renewable Energy 2030 - Expert's Visions, Oldenburg, Germany October 1, 2012

Authors: G. Pechlivanoglou

Wind turbines are being constantly developed with a rapid increase in size and capacity. The continuous upscaling however leads to significant design, manufacturing, transportation and operation challenges. Someof the largest and most heavily loaded components of wind turbines such as the blades are at the limits of their material and design properties. Current large wind turbine blades, bearings and other heavily loaded components suffer from extreme and fatigue loads. Meanwhile wind turbine control systems have reached a limited range of load and power management, therefore new concepts need to be developed. Active flow control (AFC) solutions are consequently becoming very attractive. Such concepts can offer accurate and fastaerodynamic response and therefore achieve a significant load reduction. The latest developments and theresearch efforts of the authors in this field described in this paper as well as the performance of some of theinvestigated solutions. Some of the critical aspects of AFC concepts are also outlined.

>> QBlade: Open Source Horizontal and Vertical Axis Wind Turbine Design and Simulation

Poster at Renewable Energy 2030 - Expert's Visions, Oldenburg, Germany October 1, 2012

Authors:  J. Wendler, D. Marten, G. Pechlivanoglou, C. N. Nayeri, C. O. Paschereit

>> GEOTHERMAL WIND TURBINE COOLING

Proceedings of Renewable Energy 2030 - Expert's Visions, Oldenburg, Germany October 1, 2012

Authors: G. Pechlivanoglou, H. Sader

The current paper presents an alternative cooling system for modern wind turbines. The proposed system utilizes a ground loop heat exchanger in order to dissipate the excess heat of a wind turbine to the ground.The excess thermal load is transferred from the nacelle to the foundation of the wind turbine via a working fluid through appropriate piping. The proposed system achieves a high quality performance with respect to wind turbine cooling and at the same time gives the opportunity to utilize the, otherwise lost, excess heat of wind turbines for additional useful purposes thus increasing the overall system efficiency.

>> EXPERIMENTAL & NUMERICAL INVESTIGATION OF INFLOW TURBULENCE ON THE PERFORMANCE OF WIND TURBINE AIRFOILS

Proceedings of ASME IGTI Turbo Expo 2013 ASME/IGTI, 2013, San Antonio, Texas, USA June 3, 2013

Authors: O. Eisele, G. Pechlivanoglou, C. N. Nayeri, C. O. Paschereit

Wind turbine blade design is currently based on the combination of a plurality of airfoil sections along the rotorblade span. The two-dimensional airfoil characteristics are usually measured with wind tunnel experiments or computed by means of numerical simulation codes. The general airfoil input for the calculation of the rotorblade power characteristics as well as the subsequent aerodynamic and aeroelastic loads are based on these two-dimensional airfoil characteristics. In this paper, the effects of inflow turbulence and wind tunnel test measurement deviations are investigated and discussed, to allow considerations of such effects in the rotorblade design process.

>> Active stall control solutions for power regulation and load alleviation of large wind turbines

Conference on Modelling Fluid Flow (CMFF’12) The 15 th International Conference on Fluid Flow Technologies Budapest, Hungary September 4, 2012

Authors: G. Pechlivanoglou, C. N. Nayeri, C. O. Paschereit

Large wind turbine blades suffer from the effects of high fluctuating aerodynamic loads, which lead to extreme load and power peaks. The existing blade pitch systems are required to operate reliably for several million cycles through the lifetime of the turbine. At the same time they are expected to be fast enough to adapt the blade positions to the current wind regimes. The pitch rates, however, are also limited by the structural integrity and torsional stiffness of the blades thus creating a very complex system control problem. The current paper proposes the use of active stall control elements on the blades forload alleviation and partial power regulation.Vertical and inclined spoilers as well as inflatable stall ribs are parametrically investigated in the wind tunneland tested on virtual blade simulations.

>> DEVELOPMENT OF A FLEXIBLE TRAILING EDGE FLAP AND SYSTEM INTEGRATION CONCEPT FOR WIND TURBINE BLADES

Conference Proceedings DEWEK 2012 November 7, 2012

Authors: J. Fischer, G. Weinzierl,  G. Pechlivanoglou, J. Wagner

This paper describes the design of a flexible trailing edge flap and its system integration for an exemplary 250kW prototype test turbine with a forward look to a multi megawatt approach. Necessary requirements forthe envisioned system are derived by aerodynamic simulations as well as general system studies. The development of the flap system is documented from the points of structural design of the flap and the choice of suitable actuators in connection with the system integration. A wind tunnel test model equipped with the flap prototype was built for aerodynamic and mechanical investigations in the wind tunnel facilities of HFI/ISTA at the Berlin Institute of Technology. Steady state wind tunnel tests were conducted.

>> QBLADE: AN OPEN SOURCE TOOL FOR DESIGN AND SIMULATION OF HORIZONTAL AND VERTICAL AXIS WIND TURBINES

International Journal of Emerging Technology and Advanced Engineering February 2013

Authors:  J. Wendler, D. Marten, G. Pechlivanoglou, C. N. Nayeri, C. O. Paschereit

The software QBlade is developed as an open source framework for the simulation and design of wind turbines. QBlade utilizes the Blade Element Momentum (BEM) method for the simulation of horizontal axis-and a Double Multiple Stream tube (DMS) algorithm for the simulation of vertical axis wind turbine performance. For the design of custom airfoils and the computation of airfoil lift- and drag coefficient polars the viscous-inviscid coupledpanel method code XFOIL is integrated within the graphical user interface ofQBlade. Additionally a module for the extrapolation of airfoil polars, beyond the stall point, for a 360° rangeofangles of attack is integrated. The resulting functionality allows the use of QBlade as a comprehensive toolfor wind turbine design. QBlade is constantly being maintained, validated and advanced with newfunctionality. This paper describes the software and its modules, at the current state, in theory andapplication.

>> DEVELOPMENT AND APPLICATION OF A SIMULATION TOOL FOR VERTICAL AND HORIZONTAL AXIS WIND TURBINES OF WIND TURBINE AIRFOILS

Proceedings of ASME Turbo Expo 2013: Turbine Technical Conference and Exposition June 3, 2013

Authors:  J. Wendler, D. Marten, G. Pechlivanoglou, C. N. Nayeri, C. O. Paschereit

A double-multiple-streamtube vertical axis wind turbine simulation and design module has been integrated within the open-source wind turbine simulator QBlade. QBlade also contains the XFOIL airfoil analysis functionality, which makes the software a single tool that comprises all functionality needed for the design and simulation of vertical or horizontal axis wind turbines. The functionality includes two dimensional airfoil design and analysis, lift and drag polar extrapolation,rotor blade design and wind turbine performance simulation.The QBlade software also inherits a generator module, pitch and rotational speed controllers, geometry export functionality and the simulation of rotor characteristics maps. Besides that,QBlade serves as a tool to compare different blade designs and their performance and to thoroughly investigate the distribution of all relevant variables along the rotor in an included post processor. The benefits of this code will be illustrated with two different case studies. The first case dealswith the effect of stall delaying vortex generators on a vertical axis wind turbinerotor. The second case outlines the impact of helical blades and blade number on the time varying loads of a vertical axis wind turbine.

>> VORTEX GENERATORS FOR WIND TURBINE BLADES: WIND TUNNEL TESTS, FIELD SIMULATIONS AND STRUCTURAL ANALYSIS

Proceedings of the Conference on Wind Energy Science and Technology, RUZGEM 2013 October 3, 2013

Authors: G. Pechlivanoglou, S.Vey, O.Eisele, T.P. Philippidis,  Christian Navid Nayeri, C.O. Paschereit

This paper presents wind tunnel and field investigations on the aerodynamic effects of Vortex Generators(VGs) on wind turbine performance. Field results validate the aerodynamic simulations with respect to the expected energy production benefits of VGs on wind turbines.Additionally structural analysis simulations were performed in order to assess the effect of additional loading due to VGs on the blade structure. The results of the simulations show that the additional loading due to VGs has very low impact on the blade structure, significantly lower than its design load levels.