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Modeling and Analysis of Elevated Skid Mounted High Speed Compressor Structure

Modeling and Analysis of Elevated Skid Mounted High Speed Compressor Structure. GT STRUDL User’s Group Presentation Atlanta, GA June 24-26,2009 Jonathan Guan, P.E. Houston, Texas Jonathan.guan@jacobs.com 832-351-6847.

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Modeling and Analysis of Elevated Skid Mounted High Speed Compressor Structure

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  1. Modeling and Analysis ofElevated Skid Mounted High Speed Compressor Structure GT STRUDL User’s Group Presentation Atlanta, GA June 24-26,2009 Jonathan Guan, P.E. Houston, Texas Jonathan.guan@jacobs.com 832-351-6847

  2. Modeling and Analysis ofElevated Skid Mounted High Speed Compressor Structure Topic Outline • Design Overview • Preliminary Design • Dynamic Properties • Geometry Modeling • Dynamic Analysis • Beyond Moore’s Law

  3. Design Overview Project Assignment: To Design a Recycle Compressor with: Power: 10,000 HP Speed: 7,242 to 11,522 rpm Equipment Weight Compressor: 30.8 Kips Steam turbine: 54.0 Kips Skid: 31.3 Kips Piping: 6.0 Kips Total Machine + Skid WT = 122 Kips

  4. Design Overview Study Design Data Study Soil Report Start Preliminary Design Request for More Geotech./Vendor Info Generate Dynamic Impedance Derive Excitation Force Create Geometry Model Perform Dynamic Analysis Check Criteria No Fine Tune Foundation Geometry Yes Detail Design Foundation

  5. Design Overview • Design Criteria: The basic goal in the design of a machine foundation is to limit its motion to amplitudes that neither endanger the satisfactory operation of the machine nor disturb people working in the immediate vicinity. (Gazetas 1983)

  6. Preliminary Design • Purpose: • To initialize the foundation dimension and arrange columns • To create the finite element model for dynamic analysis • Based on: • Rule of thumbs • Vendor data • Soil Report • Piping layout • Modeling Tool: • Other Software May Be Used to Create the Model.

  7. Preliminary Design FrameWorks Model: Steam Turbine-Compressor Skid. Steam Condenser

  8. Preliminary Design Using FrameWorks 3D model to obtain the foundation center of gravity:

  9. Preliminary Design Concrete Foundation Only Equipments + Foundation

  10. Dynamic Properties In Veletsos Model, the Dynamic Impedance Expressed as: Dynamic Equilibrium Equation:

  11. Dynamic Properties • The classic single lumped mass machine-foundation-soil system with circular foundation on elastic half-space summarized by Richart, Woods, Hall (1970): A Frequency Independent Model, Applied for 0 < a0 <1.0 a0: Dimensionless frequency.

  12. Dynamic Properties Dimensionless frequency, a0 Where: ω: machine speed – equipment; R: foundation radius – foundation; Vs: shear wave speed – soil.

  13. Dynamic Properties Dynamic Stiffness: Dynamic Damping: Dynamic Ratio: Critical Damping: (translational) (rotational)

  14. Dynamic Properties Veletsos’ Model – Dynamic Stiffness and Damping Coefficients: b1 to b4 in expression above are dimensionless functions of μ. Given by Veletsos for different type of soils.

  15. Dynamic Properties • Veletsos Model, kx & cx to Frequency Relation in Horizontal Mode: • cx is independent of a0 ,or the frequency. • kx in sandy soil is kind of sensitive to a0 ,or the frequency.

  16. Dynamic Properties • Veletsos Model, kθ & cθ to Frequency Relation in Rocking Mode: • cθ is independent of a0 ,or the frequency. • kθ in clay soil is very sensitive to a0 ,or the frequency.

  17. Dynamic Properties • Veletsos Model, kz & cz to Frequency Relation In Vertical Mode: • cz is independent of a0 ,or the frequency. • kz in clay soil is very sensitive to a0 ,or the frequency.

  18. Dynamic Properties Dynamic Stiffness and Damping Coefficients:

  19. Dynamic Properties At The Speed: f = 7242 Hz:

  20. Dynamic Properties At The Speed: f = 11522 Hz: Changes less than 0.2% Changes less than 0.2% .

  21. Dynamic Properties Equivalent Foundation Radius: (The Original Veletsos’ Studies Was on Circular, Massless Disk)

  22. Dynamic Properties Evaluation of Static Stiffness of Circular Footing on Inhomogeneous Half-space (Werkle and Waas):

  23. Seismic Downhole Survey

  24. Seismic Downhole Survey P-Wave: S-Wave:

  25. Seismic Downhole Survey

  26. Seismic Downhole Survey • To Determine Soil Moduli from in-situ testing data: • For soils that are not close to saturation, μ can be obtained: • Empirical Correlations for Vs (Imai 1977): N, standard penetration number, however, the reliability of such relations is very low, and they should only be used, if necessary, for preliminary when seismic survey is not done.

  27. Seismic Downhole Survey

  28. Dynamic Properties

  29. Dynamic Properties Dynamic Unbalance Forces: • The Dynamic Equilibrium Equation: GTSTRUDL Harmonic Load Command: Where: Sf = 2.0, service factor for centrifugal compressor. The amplitude of a harmonic forcing function of the Harmonic Loading Condition in GTSTRUDL: (B = C = 0)

  30. Dynamic Properties • Industrial Standard:

  31. Dynamic Properties • Calculating Amplitude of Harmonic Force: UNIT LBS FEET SEC CYCLE HARMONIC LOADING 2 'FREQUENCY FROM 7,000RPM TO 12,000RPM-IN PHASE' JOINT LOAD SIN FREQ FROM 120.0 TO 200.0 AT 1.0 1 2 FORCE Y A 0.00024 PHASE 0.0 3 4 FORCE Y A 0.00060 PHASE 0.0 $ 1 2 FORCE X A 0.00024 PHASE 0.0 3 4 FORCE X A 0.00060 PHASE 0.0 END OF HARMONIC LOAD $

  32. Geometry Modeling Tabletop with Skid Finite Element Modeling: Tabletop mass c.g. elevation Plate elements continuity violation Compressor skid How to Set the Elevation? The dilemma of modeling to accurate mass elevation or column length? Model with Plates and Beams

  33. Geometry Modeling Why Foundation Modeled as Linear Instead of Nonlinear Elastic ? For the small strains (less than about 0.005%) usually induced in the soil by a properly designed machine foundation, shear deformations are the result of particle destortion rather than sliding and rolling between particles, such deformation is almost linearly elastic. STATUS SUPPORT JOINT - 1029 TO 1041 BY 2 1042 TO 1054 BY 2 - 1085 TO 1097 BY 2 1098 TO 1110 BY 2 - 1141 TO 1153 BY 2 1154 TO 1166 BY 2 - 1197 TO 1209 BY 2 1210 TO 1222 BY 2 - 1253 TO 1265 BY 2 1266 TO 1278 BY 2 - 1309 TO 1321 BY 2 1322 TO 1334 BY 2 - 1365 TO 1377 BY 2 1378 TO 1390 BY 2 - 1421 TO 1433 BY 2 1434 TO 1446 BY 2 – ……………………………………. JOINT RELEASES MOMENT X Y Z 1029 TO 1041 BY 2 1042 TO 1054 BY 2 - 1085 TO 1097 BY 2 1098 TO 1110 BY 2 - 1141 TO 1153 BY 2 1154 TO 1166 BY 2 - 1197 TO 1209 BY 2 1210 TO 1222 BY 2 - 1253 TO 1265 BY 2 1266 TO 1278 BY 2 - 1309 TO 1321 BY 2 1322 TO 1334 BY 2 - 1365 TO 1377 BY 2 1378 TO 1390 BY 2 - 1421 TO 1433 BY 2 1434 TO 1446 BY 2 – ……………………………………… FORCE X Z KFY 720 DAMPING 0.70 $ JOINT RELEASES MOMENT X Y Z 3102 TO 3112 BY 2 3115 TO 3127 BY 2 - FORCE X Y KFZ 12960 DAMPING 0.4 $ JOINT RELEASES MOMENT X Y Z 2020 TO 2568 BY 56 2652 TO 3100 BY 56 - FORCE Y Z KFX 10080 DAMPING 0.40 Physically Similar to Shock Absorber Maxwell Model For Vibration of Viscoelastic Foundation

  34. Geometry Modeling Dynamic Stiffness and Damping Distribution:

  35. Geometry Modeling • Convert Skid Beam, W18X97 to a Modulus of Elasticity Equivalent Solid Element: W18X97 Properties: Ix = 1910 in4 Iy = 220 in4 A = 28.5 in2 Equation shall satisfy: Es·Isx = Ee·Iex(1) (Stiffness in y-y is not critical) y x x y Note: E of Filled Epoxy Grout can be ignored. It’s only 1/3 of Regular concrete.

  36. Geometry Modeling Skid Modeled in Solid Elements: Converted Steel Frame Elements Filled Grout Elements Exhaust Opening

  37. Dynamic Analysis Mode Shape: Mode: 56 Freq: 146.7 c/sec. As expected, one of the typical mode shape shows that the table top remain rigid while large deflection observed at columns and base slab. The vibrating energy has been absorbed by the columns and base slab.

  38. Dynamic Analysis • Velocity (in vertical Y) vs Frequency, Out of Phase Load Case. • Machine frequency range: 120 cps to 200 cps. • Max vertical velocity found at joint 101, Vy=0.032 in/sec, within the “Very Good” range.

  39. Dynamic Analysis • Acceleration (in X dir.) vs Frequency, Out of Phase Load Case. • The criteria to make sure machine parts at attachment point not overstressed. • Max Horizontal Acceleration found at joint 8128, ax=60.0 in/sec2, < 0.2g.

  40. Beyond Moore’s Law Multiple Core Processors

  41. Beyond Moore’s Law GTSTRUDL Job Monitoring on a Intel Duo Core CPU at 1.86Ghz CPU No. 1 Fully Occupied by GTSTRUDL CPU No. 2 Not Reached by GTSTRUDL

  42. Beyond Moore’s Law • Finite Element Dimension Limit: • It is usually recommended that the maximum dimension of an element should not exceed λ/8 (G. Gazetas). • λ=V/f • =762ft/s/[120, 192](c/s) • =[4’,6.35’] • λ/8=[0.5’, 0.8’]. • Try: Element with Horizontal Dimension: 1’x1’ • Resulting the Tabletop with • 4373 solid elements; • 7024 joints; • 21,000 DOF.

  43. Beyond Moore’s Law • Dynamic System Solution Implement Comparison: • Dynamic Model Consist of 4373 solid elements and 7024 joints, about 21,000 degree of freedoms. • Max. Velocity and Acceleration Calculated with the Compressor Speed from 120 – 200 cycle/sec. at 1.0 cycle/sec. step. GTSTRUDL V29.0 Dynamic Speed Report for the Design Example

  44. Modeling and Analysis ofElevated Skid Mounted High Speed Compressor Structure QUESTIONS? Jonathan Guan, P.E. Jacobs Engineering Houston, Texas Jonathan.guan@jacobs.com 832-351-6847

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