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Evaluation of 3D rotordynamics capabilities within NX nastran
2010 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In today's industry, companies within the jet engine industry are trying to make their product development more effective. One way is to use product models to enable upfront evaluation through simulation. To model the dynamic behaviour of rotors, mainly beam and shell elements are used in the common rotor-dynamics software. As the geometry becomes more complex, 3D rotor-dynamics can be used to solve vibration problems as well as the interactions with bearings and the non-rotating structure. This 3D-modelling could also give a more realistic post-processing than the current software in the market and the dynamics of the whole engine could be assessed. To try to solve these rotor-dynamics problems, NX7 was used, a commercial CAD/CAM/CAE software developed by Siemens PLM software. The solver used is NX Nastran Rotor-Dynamics. The main interest in this choice (with the 3D capabilities) is that both the CAD and CAE will be performed on the same platform and adjustments can be done faster if some problems in meshing or modelling occur. The aim of this Master's thesis is thus to develop a whole engine with the Computer Aided Design capabilities of NX7 and investigate the possibilities of doing rotor-dynamics analyses with NX Nastran Rotor Dynamics. First of all, simpler models were studied to validate the analyses and more complicated elements were added piece by piece until all the problems are solved to build the whole engine and analyse it. The results presented in this Master's thesis reveals several aspects of rotordynamics analysis. First of all, a section is dedicated to the mode shapes of the rotor for several common models. Then plots of Campbell diagram are shown and compared with theoretical results. Finally, a mass unbalance analysis is performed for all types of rotor and the displacement and rotation response are plotted for some particular nodes. These displacement curves are also compared with the Campbell diagrams to check if the simulation are run properly. The main problem in this Master's thesis is that the program is today too undeveloped for efficient 3D modelling of rotors. Indeed, it was found that rotating and stationary parts could not be coupled in the Campbell diagram. Also a lot of commands and execution needs to be done manually and the possibilities of post-processing have to be developed to facilitate an effective evaluation of the results.

Place, publisher, year, edition, pages
Keyword [en]
Technology, 3D, FEM, NASTRAN, Rotordynamics
Keyword [sv]
URN: urn:nbn:se:ltu:diva-44947ISRN: LTU-PB-EX--10/020--SELocal ID: 2af80a8a-7823-440c-bef0-aa96e8a7fb48OAI: diva2:1018226
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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