Vibration Analysis of Turbomachinery Blades Using Dedicated Discretization and Twisted Beam Theory

A method of discretizing the stiffness and mass properties of beam segments of turbine or compressor blades is presented. The theory encompasses both the modification of beam bending and torsional stiffnesses due to pretwist and the coupling of bending and torsional deformation with axial deformation occasioned by pretwist. Examples show that accurate prediction of vibration frequencies for blades possessing substantial pretwist can be obtained by discretization on to a quite modest number of degrees of freedom. Some comparisons of prediction accuracy with Finite Element and other methods are included.