Structural development and optimization of rotor blades for wind turbines Lessons from the aerospace industry. Josef Mendler Christoph Katzenschwanz

Transcription

1 Structural development and optimization of rotor blades for wind turbines Lessons from the aerospace industry Josef Mendler Christoph Katzenschwanz ACENTISS

2 Design Study of Segmented Rotor Blades Motivation The size of the rotor blades increase because wind energy converters will earn more energy by larger systems Transport of blades with a length of 50 or more meters is difficult and therefore expensive Manufacturing of large blades needs big moulds resulting in large investments Automated manufacturing processes are needed to produce the increasing number of rotor blades The number and the variety of wind energy converters increase which demands for an efficient design method Is a segmented blade the right answer? ACENTISS

3 Content 1. System requirements in the aerospace and wind-energy sectors 2. Design, Materials and Manufacturing processes 3. Aerospace and Wind Energy Common objectives in Process Development 4. Structural development of rotor blades in the scope of optimization procedures ACENTISS

4 Requirements on Aircrafts and Wind-Energy Installations Requirements from the Airlines Damage tolerant structure: Simple to inspect and repair Good corrosion prevention Long inspection intervals Simple inspection methods Low priced spare parts Requirements from the Suppliers Weight saving Optimization of supplier costs Provision of well-implemented customer service Maturity of the production process Application of new technologies for product improvement Requirements from the WEI operator Damage tolerant, robust structure: Simple to inspect and no repair needed Good corrosion prevention Long inspection intervals Visual inspection methods Low priced spare parts Requirements from the WEI supplier Maturity of the production process Optimization of supplier costs Provision of well-implemented customer service (Supply Chain Logistics) Application of new technologies for product improvement Similar requirements exist for aircrafts and wind energy installations ACENTISS

5 Significant load cases Manoeuvring loads (mass forces) Lateral and vertical gusts Aerodynamic loads on the ground (Hydraulics at limit of travel) Cabin pressure, emergency evacuation equipment Ground loads during taxiing, push-back and braking Ground loads from hard landings Asymmetrical landing loads Vibration characteristics Landing with retracted landing gear Recovery of aircraft after missing the runway Thermal loads -60 C to C Lightning strike, hail and bird strike Tire damage, turbine damage Tail strike Aerodynamic forces (steady, unsteady-stochastic) Mass forces (Centrifugal-, Inertial-, Coriolis forces) Environmental conditions (temperature, icing, lightning protection, soil conditions, sound emissions) Vibration of rotor, power train, Aircraft structures and the rotor blades are designed due to Static strength Fatigue Stiffness (Stability, Vibration) ACENTISS

6 Content 1. System requirements in the aerospace and wind-energy sectors 2. Design, Materials and Manufacturing processes 3. Aerospace and Wind Energy Common objectives in Process Development 4. Structural development of rotor blades in the scope of optimization procedures ACENTISS

7 Evolution of Composite Technology at Airbus + rudder + spoilers + airbrakes fairings radome A300/B2 + elevators + VTP box + dry HTP box + LG doors + flaps A310/200 A310/300 + ailerons + wet HTP box + J-nose + monolithic nacelle + keel beam, + rear bulkhead + monolithic elevator skin A ACENTISS A A /500 A

8 Manufacturing techniques for composite structures Manual Lay Up Automated Placement Automated Tape / Fibre Placement Laying Filament Tape Winding Manufacturing techniques for composite structures Thermoforming Hydroforming Pultrusion Resin Transfer Moulding (Massive Mould) Liquid Resin Infusion (Single Side Mould) ACENTISS

9 Joining technology Co-Curing Co-Bonding Joining of Composite-Structures Joints (Fastening elements) Welding Cold-Bonding ACENTISS

10 Aspects for Designing Segmented Rotor Blades Design Separate part design, acceptable integration level Composite-suitable design methods Manufacturing quality (Weight tolerance, quality) Materials Hybrid Design methods Semi-finished components (Preforms) Material costs Manufacturing processes Part and automated production Reproducibility with acceptable build quality Competitive cost levels ACENTISS

11 Content 1. System requirements in the aerospace and wind-energy sectors 2. Design, Materials and Manufacturing processes 3. Aerospace and Wind Energy Common objectives in Process Development 4. Structural development of rotor blades in the scope of optimization procedures ACENTISS

12 Common Objectives in Product Development Aerospace Wind energy Performance Optimization goal is Robustness Application of the most suitable solution Use of similar to identical tools and processes, but for different objectives Safety Qualities such as Reliability dominate the Economics ACENTISS

13 Content 1. System requirements in the aerospace and wind-energy sectors 2. Design, Materials and Manufacturing processes 3. Aerospace and Wind Energy Common objectives in Process Development 4. Structural development of rotor blades in the scope of optimization procedures ACENTISS

14 Design Study of Segmented Rotor Blades As part of a development project, the effects of segmented design on the properties of a rotor blade will be analysed With the help of optimization methods, different solution concepts are investigated and optimized with regard to the requirements The loft geometry of the blade is taken from Aeolus II (diameter = 80m). Design improvements from further studies to an Aeolus III blade are incorporated Different automated manufacturing methods are investigated to find potential for cost reductions The chance of improving the development process with respect to development time and quality using optimisation methods will be tested ACENTISS

15 Design Study of Segmented Rotor Blades ACENTISS

16 Finite Element Analysis of a Rotor Blade ACENTISS

17 Finite Element Analysis of a Rotor Blade Aerodynamic loads are modelled on basis of a vortex panel method calculation The material used for the blade is Glass Fibre Reinforced Plastic (GFRP) to be comparable to the Aeolus II blade. Mixed material (CFRP- GFRP) analyses will follow. Constraints to be considered in the optimisation are static deformation (bending and torsion), static strength fatigue (simplified criteria by strain levels) modal frequencies In the design process the free size optimisation of Optistruct is used to develop the composite lay up ACENTISS

18 Finite Element Analysis of a Rotor Blade In a first step a free size optimisation is started Three different design domains have been selected skin ribs and web of the spar Objective: Minimise (mass) Constraints: Modal frequency Static displacement (deflection and torsion) Strain constraint ( and ) ACENTISS

19 Free Size Optimisation The design variables are the thickness of each ply of the composite material This ply distribution will be determined for each element in the design domain individually The user needs not to define all design variable individually. A single command is sufficient and all the design variables are created by Optistruct To neglect the effects of the stacking sequence the SMEAR option on the PCOMP card is used Minimum thickness and percentage of each direction can be defined Coupling of ±45 layers is possible ACENTISS

20 Optimisation History Objective Function mass mass modal freq. modal freq. deflection modal freq. rotation deflection Normalised Constraint Iteration ACENTISS

21 Optimisation History 3.5E E E-03 strain 5.0E E E E Iteration 15 active strain constraints at the end of the optimisation strain constraints are needed ACENTISS

22 Layup of Skin After Free Size Optimisation 0 ± ACENTISS

23 Layup of Web After Free Size Optimisation should belong to the flange 0 ± Ribs reduce to minimum thickness as no constraint is highly affected ACENTISS

24 Output of Optistruct for the Individual Plies An outcome of the free size optimisation of the rotor blade Optistruct offers the possibility to export individual plies The user can define how many layers should be written (PARAM,FSTOSZ,YES,number) Complete skin as one 0 layer Flange of the spar (redefinition needed due to manufacturing constraints) Flange of the spar (holes and borders of the flanges have to be adopted by hand) ACENTISS

25 Output of Optistruct for the Individual Plies The resulting cuts of the plies of the FSTOSZ parameter need to be redefined in most cases Hypermesh should provide more efficient methods to redefine the plies Helpful methods could be different colouring of the elements of a component if they belong to the ply ore not easy selection method to add or remove elements to the ply filling of holes Filling of holes smoothing the boundary For the rotor blade we have then defined the plies on basis of the free shape optimisation without the usage of the FSTOSZ parameter ACENTISS

26 Conclusion and Outlook Segmented rotor blade Further analyses are needed to find an appropriate design for a segmented rotor blade For a segmented blade an automated manufacturing process will be necessary to be cost efficient Optistruct The composite free size optimisation (step 1) is a straight forward process to find a suitable design for rotor blades Before the second step of the optimisation (sizing) the individual plies have to be modified in most cases This step should be further improved within Hypermesh ACENTISS

27 Thank you for your attention ACENTISS GmbH Dr. Christoph Katzenschwanz Research & Technology, Innovations Einsteinstrasse 28a Ottobrunn Germany Web ACENTISS