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Weight reduction of a unison ring: a study of composite materials and its potential in design of future variable bleed valve systems
2008 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This Master Thesis was accomplished during the period 20th August 2007 to 18th of January 2008 at Volvo Aero Corporation. The Master Thesis was the final moment in the MSc programme in Mechanical Engineering at LuleƄ University of Technology. During the development of a new aero engine family a new Variable Bleed Valve system (VBV-system) was designed, the second phase of this design was to reduce the weight of the components by considering alternative materials and methods of manufacture: thus improving Specific Fuel Consumption (SFC). Several concepts were discussed with regards to the VBV- system and one of these was to replace some of the existing metallic (Aluminum & Titanium) components with a composite alternative and the unison ring was considered to be a prime candidate for this study. The challenge in using composites is the complexity of the material. Different mechanical properties and performance can be achieved by different numbers of layers, fiber orientations and choice of fiber and matrix. In order to use composites, a full understanding of the mechanical behavior of the unison ring is required. This resulted in a review study of the existing unison ring. The most important task was to investigate how changes in the unison ring stiffness could affect the opening and closing of the 10 VBV doors, located in the Fan Hub Frame. With the results given in the review study, a concept generation (including basic laminate theory) was made to determine the final concept design. From the concept generation, it was determined that the unison ring should be designed as a sandwich, with composite laminates on top and bottom. Between the two composite laminates foam or honeycomb should be used. The composite material was chosen to be a standard aerospace composite, which are based on long fiber reinforcements (carbon) with epoxy matrix. Most of the fibers are orientated along the unison ring, to keep both tensile stiffness (AE) and bending stiffness along the unison ring as high as possible. To ensure that the composite laminate was fiber dominated, at least 10% of the fibers and a maximum of 60% of the fibers were oriented in four different directions. The research performed in this study has been a limited concept study, therefore more studies are needed before a final design can be achieved.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Composites, Unison ring, Weight reduction, Variable Bleed, Valve System
Keyword [sv]
URN: urn:nbn:se:ltu:diva-45976ISRN: LTU-EX--08/011--SELocal ID: 39e3bdad-1989-4d79-bac0-ec06ba1a2037OAI: diva2:1019283
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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