Vibration Characteristics of 50 Hz, 120 MW Gas Turbine

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Emil Dalton
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1 THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS 345 E. 47 St., New Yrk, N.Y IGT-4 The Sciety shall nt be respnsible fr statements r pinins advanced in papers r in discussin at meetings f the Sciety r f its Divisins r Sectins, r printed in its publicatins. Discussin is printed nly if the paper is published in an ASME Jurnal. Papers are available frm ASME fr fifteen mnths after the meeting. Printed in USA. Cpyright 985 by ASME Vibratin Characteristics f 5 Hz, 2 MW Gas Turbine Mitsubishi Heavy Industries,Ltd., Japan ATSUO OKUBO, Takasag Machinery Wrks, Hyg YOSHITAKA MORI, Pwer Systems Headquarters, Tky YOSHIKAZU NADAI, Pwer Systems Headquarters, Tky HIROSHI KANKI, Takasag Technical Institute, Hyg ABSTRACT This paper describes the vibratin analysis technlgy f MW-7D Gas Turbine which was develped by Mitsubishi Heavy Industries, Ltd. fr 5 Hz utilities. MW-7D is the highest perfrmance gas turbine available with a firing temperature f,54 C fr base lad peratin. It is emplyed by the,9 MW cmbined cycle plant, ne f the largest f its kind in the wrld, and the plant began cmmercial peratin at half f the ttal capacity f,9 MW in December, 984. The plant was designed t supply base lad electric pwer generatin by burning imprted liquefied natural gas (LNG) fuel. This paper describes the general descriptin f the cmbined cycle plant and the vibratin characteristics f MW-7D Gas Turbine. MW-7D is emplyed by the,9 MW cmbined cycle plant, in Japan, ne f the largest f its kind in the wrld, and cnfirmed t achieve high reliability and high perfrmance. The rtrdynamics analysis technlgy which has develped by Mitsubishi Heavy Industries, Ltd. ver years has applied t design the rtr vibratin characteristics f MW-7D Gas Turbine. Especially, this paper describes the fllwing advanced technlgy. () Analysis f critical speed and respnse characteristics taken int cnsideratin with rtr as well as bearing and vibratin characteristics f casing system. (2) Lw sensitivity design applied by the analysis (). (3) Accurate analysis f field vibratin characteristics with the cmputer aided balancing system. INTRODUCTION Mitsubishi Heavy Industries, Ltd. has develped MW-7D Gas Turbine fr 5 Hz utilities based upn the 6 Hz W-5D under license frame Westinghuse Electric Crpratin, U.S.A. with the latest advanced technlgy in rder t crrespnd t the need fr saving energy. MW-7D Gas " Turbine has a firing temperature f,54 C fr base lad peratin and it is designed t achieve an elevated gas temperature by abut C higher than thse f existing gas turbines. MW-7D is designed n the basis f MW-7B which went int service in 975 t incrprate the latest advanced design practice prven by peratinal experience f W-5D, a 6 Hz machine, fr upgraded perfrmance in service in the U.S.A., Mexic and Saudi Arabia. GENERAL DESCRIPTION OF MW-7D GAS TURBINE Backgrund f Develpment. Mdel MW-7D Gas Turbine is a 5 Hz machine develped by Mitsubishi Heavy Industries, Ltd. with the latest advanced technlgy (firing temperature f,54 C fr base lad peratin) and it is designed t achieve an elevated gas temperature by abut C higher than thse f existing gas turbines. The MW-7D is designed n the basis f MW-7B which went int service in 975 t incrprate the latest advanced design practice prven by peratinal experience f MW-5D, a 6 Hz turbine, fr upgraded perfrmance. The "Law f similarity" design technique is nrmally used fr cnversin frm a 6 Hz turbine t a 5 Hz turbine. One designed by this technique is basically the same in perfrmance and strength as the basic machine is. Furthermre the scale-up f MW-7D was accmplished applying a design technique based n the same turbine blade length methd. Despite its larger size that methd makes MW-7D safe in terms f strength. Specificatins and Characteristics. This advanced gas turbine features a simple structure f an pen Presented at the 985 Beijing Internatinal Gas Turbine Sympsium and Expsitin Beijing, Peple's Republic f China September -7, 985 Dwnladed Frm: n 2/5/27 Terms f Use:

2 cycle, single shaft and tw bearing supprt type. The cmpressr has 9 axial stages and a pressure rati f 4. Other features are 8 multi-can type cmbustrs with a high firing temperature f,54 C and axial turbines in fur stages with air-cled blades in the high temperature stages. Specificatins f MW-7D Gas Turbine are shwn in Table, and the cnstructin and features are presented in Fig.. Table Basic specificatin f MW-7D Gas Turbine Cmpressr N. f stages 9 Pressure rati 4 Air flw 443 kg/s N. f bleeds 3 Turbine N. f stages 4 Gas temperature,54 C Air cled statinary vanes Rw and 2 Air cled-rtating blades Rw and 2 Cmbustr Type and N. Can type, 8 Ignitin type Spark discharge Rtr Type Speed Overall length Weight bladed (tns) Tw bearing supprt 3, rpm 9.9 meters 55 tns Design Imprvements. The MW-7D gas turbine features the fllwing imprvements, based n perating experience with mre than 2 units f large capacity gas turbines by Mitsubishi Heavy Industries, Ltd. and Westinghuse Electric Crpratin aimed at achieving high perfrmance and high perating availability; Cmpressr Imprved cycle efficiency by increased pressure rati. Imprved element efficiency prvided by reinfrced inter-stage sealing. Increased surge margin prvided by ptimizing blade lad distributin in each stage. Cmbustr Decreased NOx emissin using a premix cmbustin system. Lwered and unifrm wall temperature f cmbustr basket with imprved air cling. Turbine Effective air cling f the rtating blades and statinary vanes in the high temperature first and secnd stages. Decreased cling lss achieved by imprving the turbine cling air system. Decreased lss f exhaust gas flw achieved by lnger blades in the last stage.. Output shaft 5. Cmpressr 9. Turbine 2. Thrust bearing 6. Cmbustr. Tangential strut 3. Bearing (inlet side) 7. Cmbustr basket. Bearing (exhaust side) 4. Inlet guide vane (IGV) 8. Transitin piece Features f cnstructin Tw bearing supprting structure fr ease f alignment Atmspheric bearings withut need fr high-pressure seals Cld end cupling design fr stability f the utput shaft end Turbine supprt structure (tangential strut) fr hlding the rtr shaft High-perfrmance, axial flw exhaust structure Air cling system fr ht parts reliability Variable I.G.V. fr imprving thermal efficiency at partial lad Lw-NOx, premix type cmbustr Fig. Cnstructin f Mitsubishi MW-7D 2 Dwnladed Frm: n 2/5/27 Terms f Use:

The statinary vanes in the first stage f the turbine, which are expsed t the highest gas temperature, are cled by film cling and by pin-fin cling fr the rear edges, in additin t cnventinal duble

3 The statinary vanes in the first stage f the turbine, which are expsed t the highest gas temperature, are cled by film cling and by pin-fin cling fr the rear edges, in additin t cnventinal duble insert cling, s as t lwer the metal temperature. The vane cling structure is shwn in Fig. 2. VIBRATION ANALYSIS OF ROTOR-BEARING-CASING SYSTEM Mdeling f System. It is the mst imprtant pint fr the rtrdynamics analysis that the supprting structure is adequately mdeled r nt. Especially fr a gas turbine which has relatively light and flexible structure, the dynamic interactin between rtr and casing is essential t cnsider the vibratin behavir f rtr system. The typical mdeling f the bearing supprt structure is summarized in Table 2. The gas turbine is crrespnding t type E (the mst cmplicated case). Table 2 Simplified mdels f the bearing supprt MODEL CONDITION EXAMPLES A K. As rrt`rt Pin Jint r. Hard Pedestal Light Pedestal Lw Damping Pedestal Supprted Pedestal Small Machine O KZ, Damper Natural frequency is very high. Hard Pedestal n Hard K M,p ik) Mass Damper One natural frequency is lw. Usual Large Machine Fig. 2 First stage statinary vane cling structure f MW-7D turbine Shp Test. The first unit f Mdel MW-7D was cupled t a generatr and lad absrbing equipment (Fig. 3), and subjected t a mnth-lng full lad test at the factry. In additin t the rdinary measurements, special measurements were made at 6 temperature pints and 7 pressure pints t cnfirm its mechanical characteristics and reliability. Full lad perfrmance, partial lad perfrmance, and perfrmance with IGV (cmpressr inlet guide vane) variatin, which is an imprtant factr fr a cmbined cycle plant, were measured during the shp test. Measured results indicated that the gas turbine perfrmance satisfies the design requirements. O,(w.) Elp6) c 2...,(i,) I I Frequency Dependent Mass Damper Cmmn Supprt Structure Cmplex Supprt Interactin between pedestals must be cnsidered. Cmplex Supprt f Large Machine Gas Turbine, Heavy Rtr n Steel Bed Cnsidering the characteristics f gas turbine structure the rtrdynamics techniques has been established in recent ten years as shwn in Fig. 4. As summarized in Fig. 4, the mdeling f rtr is cnfirmed by many test data f rtr free-free exciting test, and the casing system is mdeled by measured dynamic characteristics f similar machine. The dynamic characteristics f the il film bearing is theretically analyzed and tested by special test system. Fig. 3 Shp test arrangement 3 Dwnladed Frm: n 2/5/27 Terms f Use:

4 Mdeling f Rtr System Vibratin Analysis f Rtr System Rtr Free-Free Exciting Test Vibratin Exciting Test f Casing System Mdeling Estimatin f Gas Turbine Casing System Develpment f Cmputer Prgram System fr Rtr - Bearing-Casing Cupled Vibratin Analysis VIBRATION ANALYSIS OF MW-7D GAS TURBINE Rtr Vibratin Characteristics. T cnfirm the vibratin characteristics f rtr itself, the vibratin characteristics f rtr in nn rtating cnditin is tested in free-free bundary cnditin, like shwn in Fig. 6. The measured mechanical impedance is shwn in Fig. 7 bttm pints f the curve are crrespnding t natural frequencies. Cmparisn and Estimatin Between Measured and Calculated Valves Establishment f Mdeling f Rtr System Applicatin fr New Mdel Rtr Vibratin Analysis f Existing Machine Cmparisn and Estimatin Between Measured and Calculated Values Establishment f Analysis Methd fr Rtr- Bearing-Casing Cupled Vibratin Applicatin fr New Mdel Estima n f New Mdel Fig. 4 Flw f vibratin analysis f gas turbine Rtr-Bearing-Casing Cupled Vibratin Analysis. Fig. 5 shws the summary f the cmputer prgram system fr Rtr-Bearing-Casing cupled system vibratin analysis. The analysis is based n transfer matrix analysis and including the pints f rtrdynamics analysis i.e.; crss cupled bearing cefficients and gyrscpic effects etc. e Fig. 6 Free-free test f MW -7D rtr 7 9 CASING SYSTEM ANALYSIS ll 4., ail As,ntt rt,, Ileng pck t f,,,,,n, [If i _,. f i'fl 7)7/7 Sta Ide n,etan C -II spt, / Unbalart,, u whip sta EMt 6 fund -m static dell, cn static a ur ltg Critical apced gt tnd= r,tt. r 3 DIMI I -, Rtr ttd,,,,, mde, Cupling,,,FIC, & r-,,,,.t, - unbltlce 2,, 5e rt 3 mde, Plt tr Ottntt S..64 Rtr rt,,,,, tt7,,t, amplitude mud Tr Gltg,,,, t checked v, I whttl Et,, r nt lt V- kt SI WI(, {I-,,,table),,,,,,,.- I() :/. UE ' " U Hz , 65.8 H Frequency (Hz) E ^e,t ar d,agrat Fig. 7 Measured mechanical impedance j ktc7f Rt r, g Fig. 5 Cmputer prgram system The natural mdes measured and calculated are shwn in Fig. 8, and the figure shws gd agreement, and it was prved that the applied mdeling methd has sufficiently gd accuracy. 4 Dwnladed Frm: n 2/5/27 Terms f Use:

5 let mde Measured 33.3 Hz Calculated 34.9 Hz.. Measured -- Calculated Lateral Vibratin Analysis Cmbined Casing and Rtr Rtr mde shape at 9 rpm 2nd mde fa Measured 65.8 Ilz Calculated 69.4 Hz el, fy,,,,m 3rd mde Measured.2 Hz Calculated 2.8 Hz Casing mde shape at 9 rpm Fig. 8 Natural mdes Vibratin Exciting Test f MW-7D Casing System. The casing system is excited by electr-hydraulic exciter. The example f measured mechanical impedance is shwn in Fig. 9. The curve shws that there is n sharp resnance in the regin f perating speed (5 Hz). I_I ltliti-(iiatikifilluc 4 Lateral Vibratin Analysis Cmbined Casing and Rtr Rtr mde shape at,85 rpm ' 8 ' Hnzntal r , A ppiwg7 -.. (.,,, Hz)., i 3,, \ (2 -(2)\ 7. 4 Hz r er... 4,,, i Arwt- iiiillillre : n / Vpia... II.\ / MAVIIIistv. Ifilland=illI Casing mde shape at,85 rpm Frequency ',Hz ) 5 Fig. 9 Measured mechanical impedance Vibratin Analysis f Cmplete Gas Turbine Unit. The rtr-bearing-casing vibratin characteristics are analyzed by the cmputer prgram as described in abve sectin. Fig. shws the calculated mde shapes. The figure shws the heavy dynamic cupling between rtr and casing. I t' titan Fig. Calculated mde shapes 5 Dwnladed Frm: n 2/5/27 Terms f Use:

6 Vibratin Measurement f Gas Turbine in Shp Test. The designs f new gas turbine are verified by full lad shp test. The measurement f vibratin was perfrmed by cmputer aided balancing system which was develped by Mitsubishi Heavy Industries, Ltd. This system has the functins f n-line multichannel vibratin mnitring and ptimum balancing weights calculatin. Fig. shws the cmputer aided balancing system in the shp test. Fig. 2 shws the typical shaft vibratin data f MW-7D Gas Turbine. The data shws the smth running f the unit fr all speed and lad range. The cmbined cycle plant cnsists f six gas turbines, six heat recvery steam generatrs (HRSG), and tw steam turbines, as shwn in Fig. 3. i Gatihed LNG. f. Gas racvery S C Fig. 3 Cmbined cycle plant cnfiguratin Fig. Cmputer aided balancing system # Bearing Shaft Vibratin Amplitude 25 Each gas turbine is paired with an HRSG. Three pairs are cmbined with each steam turbine fr a ttal f tw sets. The main particulars f MW-7D Gas Turbine which plays the main rle in the plant are shwn in Table Table 3 Specificatins f MW-7D Gas Turbine /4 2/4 3)4 4 '/4 Speed (rpm) Lad 5, #2 Bearing Shaft Vibratin Amplitude Type Pwer utput Turbine inlet pressure Turbine inlet temperature Speed Single shaft, pen cycle type 33, kw (at an ambient temperature f - C) 3.5 kg/cm 2,54 C (based lad perating) 3, rpm A /4 2/4 3/4 4/4 Speed (rpm) Lad Fig. 2 Typical shaft vibratin FIELD VIBRATION TEST RESULTS OF,9 MW COMBINED CYCLE PLANT General Descriptin f Cmbined Cycle Plant. Thku Electric Pwer Cmpany Inc. planned cnstructin f Higashi Niigata Thermal Pwer Statin N. 3, and the plant is ne f the largest cmbined cycle plants in the wrld with a pwer utput f,9 MW. The cmbined plant was cnfirmed t be a highly reliable and high perfrmance plant by varius field tests. The plant began cmmercial peratin at half part f the plant equivalent t half the ttal capacity f,9 MW in December, 984, and it keeps cntinuus peratin. The anther half part f the plant is under cnstructin nw, and it is scheduled t begin cmmercial peratin in Octber, 985. Vibratin Measurements and Mnitring System. As this plant has six gas turbine generatr units and tw steam turbine generatr units, the new cmputer aided balancing system (versin up system frm Fig. ) is adpted t reduce the time and cst f vibratin measurements and analysis. The system has capability f n-line vibratin mnitring f eight rtating machinery in cntinuus peratin and vibratin analysis f ne unit which is in starting up r shut dwn peratin. 6 Dwnladed Frm: n 2/5/27 Terms f Use:

7 Results f Vibratin Measurement, Fig. 4 and Table 4 shw the shaft vibratin level in base lad peratin. The vibratin level f the units are very lw and average value is nly 2 pm (peak t peak). Fig. 5 shws the typical vibratin data during shut dwn peratin, and there is n sharp resnance peak in all speed range. TOTAL EVALUATION OF THE GAS TURBINE VIBRATION One f the authrs published the new critical speed evaluatin methd and the philsphy f the methd (s called Q-factr design) is applied fr the design f MW-7D Gas Turbine. Fig. 6 shws the calculated and measured critical speed and Q-factr n the mdified design criteria. The figure shws the fairly gd agreement between measured and calculated values and lw sensitivity f vibratin f the unit is verified. 3 5 Gas Tu ist (Calcu:ated) Gas Turbine, st / Generatr st / tideasurecii ( Calculated) SENSITIVE FAIR Gas Tairbine Casing /I ( Measured) Fig. 4 Shaft vibratin level in base lad peratin 4 3 Generatr 2nd ',Calculated) Gas Turbine 2d ( Calculated) Table 4 Measured shaft vibratin level at base lad (Output 22 MW, Speed 3 rpm) Unit: mp -,, 3, 4, Rtating Speed (rpm) _, # Turbine Cmpressr H, #2# 3 Generatr #4 E 5 x #5.-- Fig. 6 Q-factr n the mdified design criteria Measured Pints # X Y #2 XY #3 X Y #4 #5 X Y X Y ! Average 3 27 I ( All average 23m p-p) x X DIrf.5t in Y - Directin UN 3-2 G /d ) # BR G r) e Side) r, CONCLUSION This paper described the practical vibratin analysis and the estimatin methd in rtating rtrs. As described abve sectin, MW-7D Gas Turbine has gd vibratin characteristics as a result f accumulated technical level and experiences. The lw sensitive design was verified by many data. REFERENCES 25 -e S 5 5 ia it@ S i' x X - Di /dictin Y - Directin q #2 BRG (Cmpressr Side). Yamakawa, A., Araki, R., and Sait, I., "Design and Cnstructin f Gas-Steam Cmbined Cycle Plant fr Higashi Niigata Thermal Pwer Statin N. 3" 983 Tky Internatinal Gas Turbine Cngress. 2. Shiraki, K., and Kanki, H., "A New Vibratin Criteria fr High Speed Large Capacity Turbmachinery" 8th Turbmachinery sympsium, Shiraki, K., Kanki, H., Inagasaki, T., and Kawasaki, H., "New Criteria fr Critical Speed f Rtating Machinery" Mitsubishi Heavy Industries Technical Review Vl. 6, N. 2, 979. Fig. 5 Speed-shaft vibratin amplitude diagram 7 Dwnladed Frm: n 2/5/27 Terms f Use:

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