Study the Thermal Effect of Twin Spool on the Dynamic Response and Whirl Orbit Using the Combined Finite Element – Transfer Matrix Method

Abstract

A study of the thermal effect on the critical speed and on the distribution of both the lateral and axial vibrations along the Dual rotor – system are considered . Differal thermal distributions and their influence on the critical speed and on the distribution of lateral amounts of vibration (eign mode) are adopted .The rotatingsystem is assummed to be made of two coaxial rotor under the effect ofgyroscopic moments ; The bearings are represented by their linearized dynamic properties known as the stiffness and damping coefficients .The props that support the Dual rotor are modeled with elastic springs and dashpots ; The study is considered the effects of the thermal distribution on the Dual rotor system for constant temperarture of the two rotors linear distribution on the critical speeds of the two shafts , eigen mode (Deflection , Slope , Shear force , Bending moment)and on the values of whirl orbit (major and minor axis , phase angle) .The combined Finite element – Transfer matrix (F.E.T.M) technique was implemented to idealized the mathematical model of the rotating system .This technique is convenient in computer programming .Another computer programs were developed in Fortran language and a program Matlab 6.5 and Ansys 11 to simplify the work and to embrace the theoretical analysis . From this research it has been found that the temperature affects the critical speeds and the distribution of the lateral amounts of vibration . The eigen mode (Deflection , Slope , Shear force ,Bending moment) and the value of whirl orbit (major and minor axis , phase angle) depends on the thermal distribution , rank of the critical speed and values of the rotating speed of the dual shafts.