DESIGN, ANALYSIS AND DEVELOPMENT OF A NACELLE MAIN LOAD FRAME FOR A 500KW WIND TURBINE
Ahmet Selim Pehlivan
Mechatronics Engineering, M.Sc. Thesis, 2012
Assoc. Prof. Mahmut F. Akşit (Thesis Supervisor), Assoc. Prof. Ali Koşar, Asst.Prof. Güllü Kızıltaş, Asst.Prof. İlyas Kandemir, Asst.Prof. Murat Makaracı
Date &Time: August 6th, 2012 – 11:00
Place: FENS G029
Keywords: Nacelle, bedplate, finite element analysis, static stress and deflection, fatigue, topology optimization, joint design, modal analysis.
Wind energy is gaining increasing momentum over the last two decades, and wind energy business is one of the most attractive renewable energy sectors. Several wind turbine designs are available in the industry, and developing a wind turbine for continuous commercial electricity production is one of the challenging engineering problems in today’s world. This work involves design, analysis and development of a nacelle main load frame for a 500kw wind turbine as part of the national wind turbine development project (MILRES) of Turkey. Starting from conceptual design complete static and dynamic analyses were conducted including the crane loads on the nacelle bedplate. Conceptual and detail design work were conducted using commercially available 3D solid modeling code SOLIDWORKS. Structural analyses such as stress and strain calculations, and modal analyses of the main load frame were performed using the finite element method. A hybrid (cast iron main base and weld formed steel extension) structure has been developed to improve stiffness while controlling overall weight. A bolted joint assembly was designed for cast base and steel extension interface. Analytical joint and bolting calculations were confirmed by finite element simulations of the assembled bedplate structure. An iterative design approach has been used. Design and analysis iterations were done to improve functionality, weight, and stress levels. For an optimum stress and weight design solution, topology optimization methods were applied to the structure in order to minimize weight while maintaining design safety limits and stiffness of the structure. Topology optimization stage was conducted by commercially available codes OPTISTRUCT and ANSYS shape optimization module. The optimization work resulted over 40% reduction in weight. The analysis results for optimized geometry indicated sufficiently high design safety margins for all design load combinations. Overall, an optimum Nacelle bedplate design has been developed achieving high safety factors with minimum weight.