Rotor behaviour determination

Abstract

A method of resolving vibration behaviour of a rotor assembly having a plurality of rotor blades. The method including generating a computational model of the rotor by discretization of the rotor geometry and assigning parameter values representative of a plurality of physical characteristics of the rotor. An artificial parameter feature is applied to each rotor blade such that the parameter values for the artificial parameter feature substantially depart from the physical characteristics of the rotor. A vibration response is calculated for the rotor or blade thereof for the applied artificial parameter features and compared to a predetermined vibration response so as to determine a value of the artificial parameter feature which results in a calculated vibration response that substantially matches the predetermined vibration response.

1 . A method of resolving vibration behaviour of a rotor assembly having a plurality of components, the method comprising:
 obtaining a measured vibration response for the rotor;   generating a computational model of the rotor by discretization of the rotor geometry and assigning parameter values representative of a plurality of physical characteristics of the rotor;   applying a localised artificial parameter feature to each component of the rotor such that the parameter value for said artificial parameter for each component departs from   the physical characteristics of said rotor;   calculating a vibration response for the rotor or component thereof for said applied artificial parameter features;   comparing the calculated vibration response against the measured vibration response so as to determine a value of the artificial parameter feature which results in a calculated vibration response that substantially matches the measured vibration response; and,   modifying one or more components of the rotor in dependence on the determined artificial parameter values.   
     
     
         2 . A method according to  claim 1 , wherein the artificial parameter feature comprises an artificial mass. 
     
     
         3 . A method according to  claim 1 , wherein the artificial parameter feature comprises a spring element or damping parameter. 
     
     
         4 . A method according to  claim 1 , wherein the determining of the artificial parameter value comprises determining a discrepancy between the calculated vibration response and the measured vibration response. 
     
     
         5 . A method according to  claim 4 , comprising comparing the discrepancy to a threshold discrepancy and accepting the artificial parameter values if the discrepancy falls within the threshold discrepancy. 
     
     
         6 . A method according to  claim 4 , comprising comparing the discrepancy to a threshold discrepancy and, in the event that the discrepancy falls outside of the threshold discrepancy, iteratively updating the artificial parameter values, recalculating the vibration response and determining a discrepancy between the recalculated vibration response and predetermined vibration response. 
     
     
         7 . A method according to  claim 4  comprising determining the sensitivity of the calculated vibration response or discrepancy to the value of the artificial parameter feature and updating the value of the artificial parameter feature based upon said sensitivity. 
     
     
         8 . A method according to  claim 1  comprising repeating the determination of a value of the artificial parameter feature for each component. 
     
     
         9 . A method according to  claim 1 , wherein the generating a computational model comprises generation or importing of a finite element model. 
     
     
         10 . A method according to  claim 1 , comprising amending one or more further parameter values to accommodate the localised artificial parameter feature. 
     
     
         11 . A method according to  claim 10 , wherein the one or more further parameter values comprises a density or modulus value for each blade. 
     
     
         12 . A method according to  claim 1 , wherein the artificial parameter value for a first component of the rotor differs from the artificial parameter for a second or further component of the rotor. 
     
     
         13 . A method according to  claim 1  comprising determining individual vibration characteristics of each component such as natural frequency or damping based upon the output component models and associated artificial parameter features. 
     
     
         14 . A method according to  claim 1  wherein obtaining said measured vibration response comprises taking physical measurements of the vibration response for a rotor sharing the same geometry as that of the computational model. 
     
     
         15 . A method according to  claim 1  wherein the determining of the artificial parameter values comprises iteratively adjusting the artificial parameter values and calculating an updated vibration profile to be compared with said measured vibration profile for each iteration. 
     
     
         16 . A method according to  claim 1 , wherein a value for the artificial parameter is applied to a corresponding specified location on each component. 
     
     
         17 . A method according to  claim 16 , wherein a value for the artificial parameter is applied to a point location or finite element on each component. 
     
     
         18 . A method according to  claim 1 , wherein modifying one or more components comprises modifying the location of one or more components of the rotor. 
     
     
         19 . A method according to  claim 1 , wherein modifying one or more components comprises modifying the mass and/or stiffness of the component. 
     
     
         20 . A method according to  claim 1 , wherein the rotor comprises a bladed rotor assembly and the components comprise rotor blades. 
     
     
         21 . A method of analysing a vibration characteristic of a rotor having a plurality of components, the method comprising:
 generating a computational model of the rotor by discretization of the rotor geometry and assigning parameter values representative of a plurality of physical characteristics of the rotor;   applying an artificial localised parameter value to each component of the rotor;   calculating a vibration response of the rotor for said applied artificial parameters; and,   comparing the vibration response of the rotor against a predetermined vibration response so as to determine artificial parameter values for each of the components which result in a calculated vibration response which approximates or substantially matches the predetermined vibration response.   
     
     
         22 . A data carrier comprising machine readable instructions for operation of one or more computer processors to:
 calculate a vibration response for a rotor comprising a plurality of components from a computational model of the rotor, said model comprising a discretization of the rotor geometry and accompanying parameter values representative of a plurality of physical characteristics of the rotor;   wherein the model comprises an artificial localised parameter value applied to each component of the rotor; and,   iteratively compare the calculated vibration response of the rotor against a predetermined vibration response and determine an artificial parameter value for each of the components which results in a calculated vibration response which approximates or substantially matches the predetermined vibration response.