Objective
1. Structural Internal Rotor Damping
The measurements conducted on several representative test rotors under rotating and non-rotating conditions established the quantity of internal damping present in the various test rotors. The procedure developed identified instability of the rotor without the test arrangement itself becoming unstable, and this measurement technique is believed to have wider application.
The theoretical work identified the existence of an 'optimum value' of internal damping and a better understanding of the nature of the instability.
By modelling the friction damping in the rotor using a dedicated finite element, it was possible to stimulate accurately the damping characteristics observed in the test specimens.
2. Rotor Stability, Fluid-Clearance Forces
Software was prepared to predict the linear dynamic rotor forces generated in labyrinth seals and bearings, from which dynamic coefficients can be derived.
3. Labyrinth Seal Stability
The predictive software was produced and validated by the experimental rig test and industrial gas turbine seal evidence.
A dimensionless parametric study was conducted which gave some design pointers and criteria for preliminary stability assessment.
The rig tests showed that the importance of some of the major controlling parameters.
4. Rotor Whirl Characteristics due to Light Casing Rubs
Contact between a rotor and a stator, as encountered in turbomachinery and in magnetic bearing suspensions, can lead to violent vibrations.
Rub-induced reverse whirl has been demonstrated and characterised on a magnetic bearing rig representative of aero-engine rotor dynamic conditions.
Theoretical methods have been developed which are in qualitative agreement with the test results, but which highly overestimate the severity of the response at each condition.
The measurements of the contact interaction between a steel rotor and its stator ring made of graphite show that, during the whirl motion, the whirl velocity increases until it locks onto the first elastic natural frequency of the rotor, rigidly supported at both ends, and that it usually increases only slightly from then on before, finally, it breaks down as a consequence of the energy dissipation.
Light contact in steam turbine rotor/stator systems is likely to be benign in all cases in which the stability limit is not close to rated speed.
5. Flexible Bladed Disc-Casing, Severe Interaction
The theoretical analysis and rig demonstration show clearly that the hypothesised phenomenon does exist and should be considered at the design stage when assessing critical speeds and reducing clearances in new engine designs.
The analytical model is validated quantitatively by the experimental results.
Stability can be increased by imposed non-axisymmetry on the stator, and - to some degree - by adding damping to the system.
The thermodynamic efficiency of many high performance rotating machines is strongly dependant upon very small running clearances between the high speed rotor and its casing. For steam and gas turbines, large fuel savings can be achieved if the radial clearances are reduced but there are also severe implications for mechanical integrity. Instabilities may occur, either of the whole rotor casing system or the immediate dynamically flexible components, due either to coupling through the working fluid or rubbing due to physical contact. In both cases, current analysis methods are unavailable or inadequate and this project seeks to develop new methods capable of providing more competitive design prediction tools. As a basis for predicting rotor stability it is essential to have an improved model of the rotor structural damping (Task 1).
For fluid coupling, the project is to develop improved prediction methods for the fluid destabilising forces influencing the whirl of the rotor as a whole (Task 2), together with the dynamic stability predictions for high performance labyrinth seals (Task 3). For the case where significant mechanical rubbing contact occurs, the project investigates the influence of the main controlling parameters on the whole rotor whirl stability (Task 4), together with the dynamic interaction between a dynamically flexible casing and simulated bladed rotor (Task 5).
The above five items form the work tasks for the project. The deliverables are : verification of mechanisms, improved/new analytical models, design criteria/information and user software routines.
Fields of science (EuroSciVoc)
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
- natural sciences computer and information sciences software
- engineering and technology environmental engineering energy and fuels
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Coordinator
BS12 7QE Filton
United Kingdom
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