The transient response of a point-mass rotor supported i n turbulent and hydrostatic bearings under a variety of external loadc are preflow, externally pressurized fluid film bearings is presented. The equasented. Transient responses based on a n approximate model which lions of motion are solved numerically with local linearization at uses constant rotordynamic f m e coeflicienls are also included and each integration time step. The bearing reaction f m e s are calculated shown to compare well with the full nonlinear responses. The nonporn the numerical solution of unsteady bulk-flow equations includlinear model needs small time steps with large execution times, while ing fluid inertia, turbulence, variable fluid properlies and thermal the simple linear model provides reliable resulh i n a minute fraction energy transport. Examples fbr the transient response of damper seals of time. A x , AY = rotor accelerations [m/s2] C = radial clearance function [m] c~ = fluid specific heat u/kg 'K] Cxx, CXY. CYX, CYY = damping force (linear) coefficients [Ns/ml c d = orifice discharge coefficient D = 2 R; bearing diameter [m] Dx(r) 9 D Y (~) =journal (rotor) center displacements in inertial coordinates [m] do = orifice diameter [m] = turbulent flow friction factors at journal and bearing surfaces 1,. 1 = bearing axial leng~h, recess axial length [ml M = point rotor mass [kg] Mxx, MXY, M Y X , MYY = bearing (linear) inertia force coefficients [kg] p, p, = fluid pressure, recess pressure [~/ m~] 9, = external supply pressure [~/ m~) Re = (RC/p)*; nominal circumferential flow Reynolds number RJ3 RB = flow Reynolds numbers relative to journal and bearing surfaces ' j 7 rt J a,+j = 0.001375 bM = 500,000 , CM = lo4. x. Y eM = 3.0 Fx, I.; = bearing fluid film forces along {X,Y} axes 1, 1, [Nl 7; 7; H = C + D x ( t ) cos0 + D y ( t ) sine; film u thickness [m] ' -J.xP uY H, = recess depth [m] Kxx, KXY. KYX. Kw = bearing (linear) force stiffness coefficients "x. "Y [N/ml W X ( I ) , W Y ( I ) 147 = roughness depths atjournal and bearing surfaces [m] = (Re, %) circumferential and axial flow coordinates = time coordinate [s], initial time [s] = temperature, supply temperature [OK] = rotor imbalance displacement [m] = bulk-flow velocities in circumferential ( x ) and axial (y) directions [m/s] =journal (rotor) velocity components [m/s] = external loads applied on rotor [N] Downloaded by [Ryerson University Library] at 02:01 06 June 2016 I 3 7.