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Abstract

The seriousness of the rotor vibration problem demands a reasonably accurate knowledge of natural frequencies and their mode shapes at the design stage. This thesis is concerned with the vibrational characteristics of rotor blades of complex geometrical configurations. A discreteelment method is developed to study the vibrational characteristics of both rotating and non-rotating rotor blades, which includes complexities such as pretwist angle, shear centre being off-set from centroid, variable mass densities and abrupt changes in blade geometry like sweep back.

The blade is idealised into a number of discreteelements and the theory is developed along the engineering beam theory. Both flapping loads and centrifugal loads are taken into consideration. ‘The unit load method is used in developing the flexibility matrix. ‘The loads are assembled to form an eigenvalue problem. A programme called VTRI was written in Fortran IV language and this programme makes use of the library subroutines for establishing the eigenvalues and eigen ~ vectors of the dynamic matrix. On the University ICL 1905 computer the programme uses 46K of core storage. A maximum run time of 3 minutes and 34 seconds was needed for a ten element idealisation.

In total 62 different cases were run on the computer to include as many variations as possible and the natural modes of vibration and the mode shapes established. Comparison with known exact solutions and other investigators’ results, where available, shows the accuracy to be good, especially for the lower modes. A considerable increase in accuracy of results has been achieved when the number of elements was increased to 20. The accuracy of the technique with respect to frequency and mode shapes and the results obtained have been encouraging. A few concluding remarks have been presented and certain suggestions were indicated for future work,

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TL Motor vehicles. Aeronautics. Astronautics
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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