Application of CAD for Designing Or Fabrication of Parts with Complex Shapes

Introduction

Wondering if students or engineers living in the 21st century consider themselves fortunes as a lot of problems which previously solved by scholars, engineers, programmers from the past, simplified the solutions and consolidate into various tools to make solving some of the problems easier than ever. With the help of all these tools, engineers or students nowadays are able to solve problems more effectively, productively and more innovative.

Computer-Aid Design software is one of those tools. This leads us to the following case study report which will show an example of the process of design, simulate and modelling a wind turbine blade by a design team with the application of Computer-Aid Design software, engineering knowledge and simulation software. The design team mentioned in the following report are a team of personnel from the reference report.

Design of wind turbine blade

The reason of choosing win turbine blade as a case study example is because of its complexity on not only shape but also involve heavy simulation on a designed model for performance and calculation on how to manufacture and bring the designed product to live. CAD (Computer-Aid Design) program are able to produce 2D and 3D sketches which used in the manufacturing process and simulation.

The creation process required high accuracy and reliability works performed as it involves a large number of variants and calculation for the surface profile, working parameter for the specific working environment and material for the turbine blade. For an example quote from reference documents, “For a 3D object with m types of materials and n number of variations for each material, the modelling space is E3 x nm dimensional. That is to say, for a turbine blade made of modestly three constituent materials with volume fraction 2% as the resolution, there are 1. 25 x 105 possible designs even with geometry assumed to be the same. Due to such heavy computation involved, this approach becomes practically very challenging even with the advanced computational power”.

The first step of the design process for a turbine blade involves choosing the aerofoil profiles for the blade. The selection is based on constraint from the environment, budget, requirements from the regulation and performance. Based on the information above mentioned, the calculation was done which involve calculation for the force that generated in the aerodynamic profile and lifting 4 forces produced by the aerodynamic blade profile.

The design team later perform an analysis on the designed aerofoil profiles with a WIATRAK 1. 1 software with a set of wind speed and required span of the rotor. Forces generated in an aerodynamic profile with various symbol which used for calculation Shape and forces generated are determined by the aerodynamic profiles and which can be found on Aerospace Institutes. Details parameters of aerodynamics profiles can be downloaded from Aerofoil Investigation database.

The design team utilize those data to create the blade model. This further improve the accuracy of the data collected. Based on geometry which calculated in the CAD software a 3D model of the blade will be created. For its creation, Solidworks software is used by the design team. It allows the team to create a 3D model from an existing 2D aerodynamic profile which chosen from the Aerospace Institutes Database in the earlier stage.

Simulation to proof out the chosen aerodynamic profile

Based on the provided working environment and constraint by manufacturing technology, the design team then further evaluate the performance of the chosen turbine blade profiles, size 5 and shape on simulation software WIATRAK 1. 1 From the simulation result, the team are able to collect data including forces generated with various wind speed and angle of attack with respect to specific aerodynamic profile.

From the collected data, the team may determine to continue with the design or re-design it to get better performance. This simulation reduced a large amount of time which consume to produce prototype and perform wind tunnel experiment. It’s extremely helpful when one trying to compare various ideas and selection of aerodynamic profiles for the turbine blade.

Modelling of the wind turbine blade in Cad system

One of the research team consist of Xiaoping Qian and Deba Dutta presented an approach to design for design heterogeneous turbine blade based on physic based modelling method back in 2001. The approach using a B-spline tensor representation for heterogeneous object to shorten the computational time, a diffusion process and finate element method for the design process. This method helps designer to get better understanding on material property variation during different circumstances. But in this case study, the design team based on the calculated geometric and analytic parameters, a 3D model of a given blade will be created.

The process starts with the creation of the aerodynamic profile curve. This size of the curve is adapted to the first section of the blade which is located nearest to the rotor’s axis. Next, based on the knowledge of the parameters of the last section of the blade and its angle of incidence, its geometry is created on the surface at the distance equal to the given length of the blade. Having the two characteristic sections, when creating a given solid, it is possible to create the required section of the blade when connecting the two surfaces.

The last part is the creation of connection between the blade and the rotor. This element was constructed in a schematic manner in order to visualize its existence. It is not the subject of the research and shall not be subjected to machining. The prepared 3D model was visualized on 4 projection planes in sketch view and realistic view. The first visualization shows the construction lines of the element, the existing angle changes and the support structure, and the next visualization shows the general view of the geometry of the construction and its factual appearance.

Conclusion

From the above case study on a design team designing a wind turbine blade, observation can be made that how various CAD software helps on designing, simulation, evaluate and modelling and provide accurate, reliable data to prevent catastrophic failure during design and later stage and reduce waste from prototyping, testing and analysis. Without the assistance of CAD software, thousands of hours might require to calculate how much force generated by different aerodynamic profiles curve and error might occur easily during the early stage of design.