AUTOMATED ANALYSIS OF TIME TRANSIENT RESPONSE IN NONLINEAR ROTOR BEARING SYSTEMS Luis San Andres

Transcription

1 TRC 32513/1519X5 Year II AUTOMATED ANALYSIS OF TIME TRANSIENT RESPONSE IN NONLINEAR ROTOR BEARING SYSTEMS Luis San Andres Mast-Childs Professor Qing Liu Research Assistant May 2014

2 Why a Transient Response Analysis? All Rotor Bearing Systems (RBS) undergo unsteady or transient forcing loading: Start and shut down events: influence of load and rotor speed on transient behavior Sudden events: blade loss simulations (large imbalances), maneuver loads Support excitation: earthquake, engine motions and noise Beyond the threshold speed of instability: whirl frequency and limit cycle (orbit size) Highly NL rotating machines: turbochargers, rotors on foil bearing systems, electrical submersible pumps (ESP) Trend in RBS design & analysis: conduct more & more preliminary studies (using fast virtual tools) to anticipate any upsetting event to costly systems. 2

3 Work Finished in : Added click & run worksheets: multiple cases, multiple loading conditions, multiple bearing configurations, efficient storage of data Save time in waiting for transient response calculation Post-processing tools: analyze tons of data (thousands of data points), make FFTS and waterfalls, filter responses to obtain 1X and any other sub or supersynchronous motions, filtered mode shapes at selected frequencies, etc. Save time in diagnosing & troubleshooting 3

4 Overview of Work in Year II Nonlinear bearing models XLTRC 2 : short length journal bearing. Need more bearing models: realistic configurations In year II ( ) Developed a realistic NL bearing model for Pressure dam journal bearing multiple-pad (lobe) journal bearing Integrated model in XLTRC 2 4

5 Bearing Geometry Nomenclature c: pad clearance c m : assembled clearance e : journal eccentricity r p =c-c m : preload, θ Bearing center Pad center Note: angle θ origin starts from - X axis r p =0, cylindrical pad r p =c, journal and pad contact l r p Y e journal Film thickness: p h c e cos e sin r cos( ) X Y p p t Pad with preload X 5

6 Reynolds Equation Nomenclature P : film pressure h : film thickness : viscosity, fn (T) : journal speed c : pad clearance rp : pad preload P 12 2 t Film thickness: 3 h h h h c e cos e sin r cos( ) X Y p p ex, ey: journal eccentricity Boundary conditions: Pad leading edge, θ= l. P = P S (supply pressure) trailing edge, θ t. P = P a = 0 (ambient pressure) Pad sides, z= +/- ½ L, P=P a (ambient) Film pressure P> P cav (oil cavitation pressure) Solution method: FE method for pressure 6

7 Code Input User Interface Bearing with identical pads Bearings with uniform pads # of Bearings with Uniform Pad ( max = 10 ) 2 BEARING # Number of pads on bearing Pad 1 - leading edge Preload (dimensionl ess) Pad 1 - offset (% arc length) From To Station Rotor Bearing Axial Radial Pad 1 - arc Ambient Supply Cavitation Viscosity at Station # # Diameter Length Clearance length pressure pressure pressure Tsupply Density - - m m m - degrees degrees - -- bar bar bar centi-poise kg/m E E Step 1: input number of bearings # of Bearings with Uniform Pad ( max = 10 ) 2 Step 3: input pad geometry Rotor Diameter Bearing Axial Length Radial Clearance Number of pads on bearing Pad 1 - arc length Pad 1 - leading edge Preload (dimensionl ess) Pad 1 - offset (% arc length) m m m - degrees degrees E E Step 2: input bearing location BEARING # From Station # To Station # Step 4: input lubricant property Ambient Supply Cavitation Viscosity at pressure pressure pressure Tsupply Density bar bar bar centi-poise kg/m Step 5: click button 7

8 Code Input User Interface Bearing with different pads Bearings with nonuniform pads # of Bearings with Uniform Pad ( max = 10 ) 1 BEARING # 1 From Station # - 1 Pad Information Dam or Grv Arc Length Dam or Grv Axial Length To Station # - 2 Pad leading edge Arc length Offset clearance preload Rotor Diameter m degrees degrees -- m -- degrees m m Bearing Axial Length m E E+00 Number of pads on bearing m E E+00 Ambient pressure bar E E+00 Supply pressure bar 0.00 Cavitation pressure bar 0.00 Viscosity at Tsupply centi-poise Density kg/m Step 3: input pad geometry Step 1: input number of bearings Step 4: click button From Station # - 1 Dam or Grv Depth Step 2: input bearing & lubricant information To Station # - 2 Rotor Diameter m Bearing Axial Length m Number of pads on bearing m 3 Ambient pressure bar 0.00 Supply pressure bar 0.00 Cavitation pressure bar 0.00 Viscosity at Tsupply centi-poise Density kg/m Dam or Grv Arc Dam or Grv Axial Dam or Grv Pad leading edge Arc length Offset clearance preload Length Length Depth degrees degrees -- m -- degrees m m E E E E E E+00

9 Integrating into XLTRC 2 Functions to solve NL model XLPressDm.dll Input: bearing #, rotor/bearing XLPressDmDLL(IBEAR, RPM1,RPM2, speeds, X1, X2, Y1, relative Y2, VX1, VX2, displacement, VY1, VY2, FX1, FY1, TORQ1, TORQ2) difference in velocities bw/ two stations) Output: reaction force, torque XLTRC 2 Use pressure dam bearing option in XLTRC2: input in NLConn worksheet STN 1 STN 2 TYPE NL Text # of # # Default / UserDef OPTION Coeffs Coeff1 1 0 Default 5 Pressure Dam Bearing Default 5 Pressure Dam Bearing 1 2 Define bearing type Input bearing number

10 Closure Years I & II Develop a click & run tool to save time in multiple-case transient response prediction Develop post-processing tools for data analysis: FFTs, waterfalls Add generic journal bearing model into XLTRC 2 Forthcoming: Examples in XLTRC 2 of rotor-journal bearing system NL transient responses. Need student willing to work & finish. 10

11 NL Transient Response Analysis Questions (?) 11