GUIDELINE FOR FIELD TESTING OF GAS TURBINE AND CENTRIFUGAL COMPRESSOR PERFORMANCE

Transcription

1 GUIDELINE FOR FIELD TESTING OF GAS TURBINE AND CENTRIFUGAL COMPRESSOR PERFORMANCE RELEASE.0 Augut 006 Ga Machinery Reearch Council Southwet Reearch Intitute

2 Thi page i intentionally left blank.

3 GUIDELINE FOR FIELD TESTING OF GAS TURBINE AND CENTRIFUGAL COMPRESSOR PERFORMANCE RELEASE.0 Author: Klau Brun, Ph.D., SwRI Marybeth G. Nored, SwRI Indutry Adviory Committee: Rainer Kurz, Solar Turbine Principal John Platt, BP Robert Arnold, Duke Energy Don Cruan, Columbia Ga Tranmiion William Couch, El Pao Corporation

4 Thi page i intentionally left blank.

5 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance RELEASE.0 Foreword Field teting of ga turbine and compreor ha become increaingly common due to the need to verify efficiency, power, fuel flow, capacity and head of the ga turbine package upon delivery. The performance tet of the ga turbine and compreor in the field i often neceary to aure that the manufacturer meet performance prediction and guarantee a cutomer return on invetment. Economic conideration demand that the performance and efficiency of a ga turbine compreor package be verified at the actual field ite. The field environment i not ideal and meaurement uncertaintie are neceary to characterize the validity of a performance tet. A the working field environment hift further from the ideal cae, the uncertaintie increae. Previou field tet have hown that the compreor efficiency uncertainty can be unacceptably high when ome baic rule for proper tet procedure and tandard are violated. Thi guideline applie to a typical ga turbine and centrifugal compreor. The motivation for conducting a field tet i baed on one of the following objective: The manufacturer i required to verify performance of the ga turbine and compreor to the cutomer. To the manufacturer, the field tet provide a baeline for the ga turbine and compreor at the ite of delivery to compare to the factory performance tet, although the field tet accuracy may be inherently lower. In addition, the field performance tet i the final validation from the manufacturer to the cutomer of the guaranteed performance. The uer need to verify performance of the ga turbine and compreor. Baeline performance data i obtained from the initial field performance tet. The baeline tet can be ued for comparing and monitoring the health of the ga turbine-driven compreor package in the future. The uer or manufacturer need to ae performance of the ga turbine or compreor becaue of degradation concern. Baed on the field tet reult, a performance recovery program may be initiated. The uer require calibration of an intalled hitorical trend monitoring ytem. The field tet i ued to provide initial calibration of the ytem baed on the firt performance of the ga turbine and compreor. The uer need to determine the operating range of the intalled equipment after an upgrade, retage, or phyical ytem change. In thi cae, the urge point may alo need to be re-aeed. The following guideline i a uggeted bet practice for field teting of ga turbine and centrifugal compreor. Specific conideration at a field ite may require deviation from thi guideline in order to meet afety requirement, improve efficiency, or comply with tation operating philoophy. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page i

6 Thi page i intentionally left blank. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page ii

7 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance RELEASE.0 TABLE OF CONTENTS 1. Purpoe and Application Performance Parameter Centrifugal Compreor Flow/Flow Coefficient Centrifugal Compreor Head/Head Coefficient Centrifugal Compreor Efficiency Ga Turbine Power Centrifugal Compreor Aborbed Power (Ga Turbine Power Output) Ga Turbine Heat Rate and Efficiency Ga Turbine Exhaut Heat Rate Turbocompreor Package Efficiency Equation of State Determination of Surge Point and Turndown Similarity Condition Tet Preparation Pre-Tet Meeting Pre-Tet Operation and Intrumentation Checkout Pre-Tet Equipment Checkout Pre-Tet Information Tet Stability Safety Conideration Meaurement and Intrumentation Meaurement of Preure Meaurement of Temperature Meaurement of Flow Meaurement of Ga Compoition Meaurement of Rotational Speed Meaurement of Torque Meaurement of Generator Power Tet Uncertainty Ideal Field Tet Condition For Reducing Uncertaintie Effect of Non-Ideal Intallation on Uncertainty Interpretation of Tet Data Data Reduction and Checking Uncertaintie Generation of Performance Curve from Recorded Data Point Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page iii

8 6.3 Standardized Uncertainty Limit Uing Redundancy to Check Tet Meaurement and Uncertainty Effect of Fouling on Tet Reult Analyi of Meaured Reult Other Field Teting Conideration Determination of Influential Tet Parameter Field Teting of Compreor Under Wet Ga Condition Reference APPENDICES APPENDIX A Determination of Ga Turbine Power APPENDIX B Equation of State Model APPENDIX C Uncertainty Analyi for Independent Variable Meaurement APPENDIX D Similiarity Calculation for Wet Ga Condition APPENDIX E Equation of State Model Comparion of Predicted Performance Data APPENDIX F Application of Compreor Equation for Side Stream Analyi Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page iv

9 LIST OF FIGURES Figure 1. Location of Tet Intrumentation for Centrifugal Compreor... Figure. Location of Tet Intrumentation for Ga Turbine... Figure 3. Enthalpy/Preure Change During Compreion and Expanion Proce (Edmiter and Lee, 1984)...6 Figure 4. Typical Compreor Surge Line on Compreor Performance Map...11 Figure 5. ASME PTC 10 Recommended Intallation Configuration for Preure and Temperature Meaurement... Figure 6. Short-Coupled Intallation for a Turbine Meter (AGA-7, Rev. 3)...6 Figure 7. Cloe-Coupled Intallation for a Turbine Meter (AGA-7, Rev. 3)...7 Figure 8. Sampling Method with Pigtail a Recommended in API MPMS Chapter Figure 9. Example of Tet Uncertainty Range...41 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page v

10 LIST OF TABLES Table 1 Table Suggeted Application for Equation of Stage Uage...10 ASME PTC 10 Acceptable Deviation in Tet Parameter for Similarity Condition...13 Table 3 Aement of Stability of Compreor During Pre-Tet Criteria Table 4 Aement of Stability of Compreor During Pre-Tet Criteria...18 Table 5 Aement of Stability of Ga Turbine During Pre-Tet...18 Table 6 Typical Uncertaintie in Preure Meaurement (hown a percent of full cale)...1 Table 7 Recommended Depth of Thermowell...3 Table 8 Table 9 Table 10 Typical Uncertaintie in Temperature Meaurement (hown a percent of full cale)...4 ISO 5167 Recommended Intallation Length for Orifice Flow Meter...5 In-Practice Achieveable Uncertainty for Meaured Tet Parameter...3 Table 11a Example of Total Uncertainty Calculation for Compreor in Near Ideal Cae SI Unit...35 Table 11b Example of Total Uncertainty Calculation for Compreor in "Near Ideal" Cae Englih Unit...35 Table 1a Table 1b Ideal Intallation for Ga Turbine Total Uncertainty Calculation SI Unit...36 Ideal Intallation for Ga Turbine Total Uncertainty Calculation Englih Unit...36 Table 13 Effect of Non-Ideal Temperature or Preure Meaurement...38 Table 14 Table 15 Non-Ideal Intallation Effect on Compreor Uncertainty...38 Non-Ideal Intallation Effect on Ga Turbine Uncertainty...39 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page vi

11 Definition of Symbol: A = cro-ectional area of pipe C = dicharge coefficient for orifice flow meter D tip = tip diameter of compreor E = velocity of approach factor EHR = exhaut heat rate H = head for compreor, either actual or ientropic HR = ga turbine heat rate LHV = fuel ga heating value, a determined through thermodynamic analyi Ma = Machine Mach number N = haft peed in rpm [ω = πn / 60] P = haft power P = total (tagnation) preure of ga at uction or dicharge ide P tat = tatic preure at uction or dicharge ide Q = volumetric flow rate on uction or dicharge ide of compreor SM% = urge margin of compreor a % of deign flow rate for fixed peed T = temperature of ga at uction or dicharge ide TD% = turndown of compreor a % of deign flow rate for contant head U = velocity of ga W = ma flow through the compreor Z = compreibility of ga at uction or dicharge condition c p = pecific heat at contant preure d = bore diameter of orifice meter f = Schultz correction factor for real ga behavior h = enthalpy of ga at uction, dicharge or ientropic condition k = ientropic exponent Δp = differential preure meaured acro orifice plate η = efficiency ϕ = flow coefficient γ = ratio of pecific heat ρ = denity of ga determined at uction or dicharge condition τ = meaured torque from the turbine haft v = pecific volume of ga at uction, dicharge or ientropic condition ψ = head coefficient ω = haft peed in radian per econd [rad/ec] Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page vii

12 Subcript: m = mechanical efficiency = ientropic condition P = polytropic condition C = compreor GT = ga turbine TC = turbocompreor package FG = fuel ga propertie = uction ga d = dicharge ga di = dicharge ga, ientropic condition in = input to ga turbine out = output to ga turbine/input to compreor A = denity of air E = exhaut air temperature f = fuel flow to the ga turbine GT = volume flow of air at ga turbine exhaut tip = tip diameter or tip peed for compreor blade tat = tatic Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page viii

13 Definition 1 : 1. Abolute Preure: The preure meaured above a perfect vacuum.. Gage Preure: The preure meaured with the exiting barometric preure a the zero bae reference. 3. Differential Preure: The difference between any two preure meaured with repect to a common reference (i.e., the difference between two gage preure.) 4. Total (Stagnation) Preure: An abolute or gage preure that would exit when a moving fluid i brought to ret, and it kinetic energy i converted to an enthalpy rie by an ientropic proce from the flow condition to the tagnation condition. In a tationary body of fluid, the tatic and total preure are equal. 5. Abolute Temperature: The temperature above abolute zero, tated in degree Rankine or Kelvin. Rankine temperature i the Fahrenheit temperature plu degree; Kelvin i the Celiu temperature plu degree. 6. Total (Stagnation) Temperature: The temperature that would exit when a moving fluid i brought to ret, and it kinetic energy i converted to an enthalpy rie by an ientropic proce from the flow condition to the tagnation condition. In a tationary body of fluid, the tatic and total temperature are equal. 7. Denity: The ma of ga per unit volume, equal to the reciprocal of the pecific volume. The denity i a thermodynamic property determined from the abolute total preure and temperature at a point in the fluid uing an equation of tate. 8. Capacity: The rate of flow, determined by delivered ma flow rate divided by inlet ga denity. 9. Preure Ratio: The ratio of abolute total dicharge preure to abolute total uction preure. 10. Machine Mach Number: The ratio of the blade tip velocity at the firt impeller diameter to the acoutic velocity of the ga at the uction condition. 11. Stage: A ingle impeller and it aociated tationary flow paage. 1. Compreor Surge Point: The capacity below which the compreor operation become aerodynamically untable. 13. Ientropic Compreion: A reverible, adiabatic compreion proce. 14. Polytropic Compreion: A reverible, non-adiabatic compreion proce between the total uction preure and temperature and the total dicharge preure and temperature. 15. Ga Power: The power tranmitted to the ga in a compreor, equal to the product of the ma flow rate compreed and the ga work. 16. Shaft Power: The power delivered to the compreor haft by the ga turbine, alo known a brake power. Shaft power i equal to ga power plu mechanical loe. 17. Mechanical Loe: The total power conumed by frictional loe in integral gearing, bearing and eal. 18. Equation of State: An equation or erie of equation that functionally relate the ga thermodynamic propertie, uch a preure, temperature, denity, compreibility, and pecific heat. 1 Definition for referenced term in Field Tet Guideline are baed upon ASME Performance Tet Code (PTC) , Performance Tet Code on Compreor and Exhauter. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page ix

14 Thi page i intentionally left blank. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page x

15 Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance RELEASE.0 1. PURPOSE AND APPLICATION The following guideline i intended to erve a a reference for field teting of ga turbine and centrifugal compreor performance. Thi guideline applie to any party conducting a field tet of a ga turbine or centrifugal compreor (manufacturer, uer company, or third-party). It i intended to provide the mot technically ound, yet practical procedure for all apect of conducting field performance tet of ga turbine and centrifugal compreor. The condition at the field ite often cannot be a cloely controlled a in a factory environment. The pecific ite condition of a particular tet may dictate that the tet procedure deviate from thi guideline or the ideal intallation decribed. Thi doe not preclude a field ite tet. Nonethele, when a particular tet deviate from the intallation requirement or other tet procedure, the deviation will affect the tet uncertainty and hould be accounted for in the uncertainty analyi, a recommended in thi guideline. The tandard that are ued a reference for thi guideline are ASME PTC , Performance Tet Code on Compreor and Exhauter, ASME PTC -1997, Performance Tet Code on Ga Turbine, ISO 314, Ga Turbine Acceptance Tet, and ISO 5389, Turbocompreor Performance Tet Code.. PERFORMANCE PARAMETERS The following even performance parameter generally decribe the performance of a ga turbine and centrifugal compreor. Thee parameter are commonly ued in acceptance teting, teting to determine degradation of the machine, and operational range teting. The primary meaurement required in order to calculate thee parameter are dicued in Section 4.0. The uncertainty calculation are dicued in Section 5.0. Accounting for the effect of non-ideal intallation on uncertainty i alo dicued in Section 5.0. Performance Parameter: 1. Centrifugal Compreor Flow/Flow Coefficient. Centrifugal Compreor Head/Head Coefficient 3. Centrifugal Compreor Efficiency 4. Centrifugal Compreor Power Aborbed 5. Ga Turbine Full Load Output Power 6. Ga Turbine Heat Rate (thermal efficiency) 7. Ga Turbine Exhaut Heat Rate The following tet data mut be meaured to determine the above performance parameter. Figure 1 and how the general meaurement arrangement for the required tet intrumentation on the compreor and ga turbine. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 1

16 Ambient Air - Patm Preure at Meter Q Pm Tm Suction Preure Suction Temperature P T Centrifugal Compreor Pd Dicharge Preure Dicharge Temp Td Flow Rate* Temperature at Meter Sample Line / Ga Chromatograph* Speed of Rotation * Flow Rate Meaurement and Ga Sample may be on uction or dicharge ide. Suction ide i recommended. Figure 1. Location of Tet Intrumentation for Centrifugal Compreor Ambient Air: - Temperature -Atmopheric Preure - Relative Humidity Exhaut Ga Outlet P out Preure H in T in P in Burner Ga Turbine Inlet Air Relative Humidity Inlet Air Temp Inlet Preure Fuel Flow Fuel Ga Compoition Shaft Speed Fuel Figure. Location of Tet Intrumentation for Ga Turbine Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page

17 Centrifugal Compreor Tet Meaurement : Suction Temperature Suction Preure Dicharge Temperature Dicharge Preure Flow Through Compreor (*Preure, temperature alo required at the flow meaurement point) Suction or Dicharge Ga Compoition Barometric Preure Speed of Rotation Impeller Diameter Uptream and Downtream Piping arrangement Pipe Diameter (uptream and downtream) Ga Turbine Tet Meaurement: Engine Inlet and Ambient Temperature Barometric Preure Power Turbine Speed Ga Generator Speed Fuel Flow (*Preure, temperature alo required at flow meaurement point for fuel ga) Fuel Ga Compoition Inlet and Exhaut Preure Lo Relative Humidity of Inlet Air Water/Steam Injection Rate Important Note: For the remainder of thi document, all preure and temperature ued for performance and uncertainty calculation are abolute total (tagnation) value unle otherwie noted..1 Centrifugal Compreor Flow/Flow Coefficient The actual flow through the centrifugal compreor (Q) hould be meaured by a flow-meauring device, uch a a volumetric flow meter (ultraonic, turbine, etc.), a differential preure device (orifice meter, annubar, etc.), or a nozzle. If an orifice meter i ued (typical of many intallation), the ma flow rate equation i: W π = CE d Δpρ 4 (.1) * Note the dicharge coefficient, C, i determined from the RG equation (a tated in AGA Report No. 3). The dicharge coefficient i dependent on the flow meter Reynold Number. The actual uction volumetric flow i given by: Q W = (.) ρ The requirement apply to each compreor or each compreor ection in a compreor train. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 3

18 The flow coefficient ued for imilarity comparion i: Q Q ϕ = = (.3) π π 3 Dtip U tip Dtip ω 4 4 * Note the flow coefficient ue the actual volumetric flow rate through the compreor at uction condition. * For a multi-tage compreor, the tip diameter may be defined a the firt impeller diameter or a geometric average for all tage diameter. When comparing flow coefficient for multi-tage machine, the definition of tip diameter hould be verified.. Centrifugal Compreor Head/Head Coefficient Compreor head and efficiency are commonly defined baed on either ientropic or polytropic ideal procee. Both definition are appropriate for performance comparion a they provide a ratio of the actual enthalpy difference (head) to the ideal (ientropic or polytropic) enthalpy difference acro the compreor. The ientropic proce aume a reverible adiabatic proce without loe (i.e., no change in entropy). The polytropic proce i alo a reverible proce, but it i not adiabatic. It i defined by an infinite number of mall ientropic tep followed by heat exchange. Both procee are ideal, reference procee. The compreor actual head (H), ientropic head (H*), and polytropic head (H P ) are determined from the meaurement of preure and temperature on the uction and dicharge ide and the calculation of enthalpy and pecific volume uing an equation of tate (EOS) model. The head are calculated from the enthalpie aociated with each tate from the EOS a follow: Ientropic head: H* hd h = h( pd, ) h( p, T ) = (.4) Actual head: H = h h = h p, T ) h( p, T ) (.5) d ( d d * Note that h d * i the enthalpy aociated with the dicharge preure at the uction entropy,, becaue the entropy change i zero in an ientropic proce. All enthalpie hould be directly determined from the EOS. Ientropic enthalpy can alo be for etimation purpoe (auming ideal ga behavior): h d k 1 k P d c p Td = c p T P (.6) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 4

19 Similarly, Polytropic head i determined from: S S n n S d P P P P f P P n n H P P ν = (.7) The polytropic exponent, n P, i defined a: d S d P P P n ν ν ln ln = (.8) The ientropic exponent, k, i defined a: * ln ln d d P P k ν ν = (.9) For equation (.7), the Schultz Polytropic Head Correction Factor, f, i defined a: [ ] d d d P P k k h h f ν ν = 1 (.10) For performance comparion, it i beneficial to ue non-dimenional head and flow coefficient (ϕ from equation (.3) and from equation.11.13) rather than actual head and flow. P ψ ψ ψ,, Ientropic head coefficient: * * * = = ω ψ D tip H U H (.11) Actual head coefficient: = = ω ψ D tip H U H (.1) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 5

20 Polytropic head coefficient: ψ P = P P H H = U Dtip ω (.13).3 Centrifugal Compreor Efficiency The ientropic efficiency i calculated from the ientropic and actual head: H * ψ * η* = = H ψ (.14) The polytropic efficiency i calculated baed upon the polytropic head and the polytropic exponent, n P, a defined in equation (.8): η P = P H H P n Pd P n ( 1) P = h d n P n P h 1 1 f Pν (.15) The compreion proce for a typical centrifugal compreor and the aociated enthalpy change are hown on a P-h diagram in Figure 3 for 100% methane ga mixture. An actual proce i compared to the ientropic tate. METHANE Preure-Enthalpy Diagram Ientropic compreion Actual compreion Preure Enthalpy Figure 3. Enthalpy/Preure Change During Compreion and Expanion Proce (Edmiter and Lee, 1984) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 6

21 .4 Ga Turbine Power Four method exit for determining ga turbine power. Thee are: 1. Direct torque coupling meaurement. Direct generator power meaurement 3. Indirect driven centrifugal compreor haft power meaurement 4. Indirect ga turbine heat balance meaurement The direct meaurement method (1) and () either uing a torque-meauring coupling (ee Section 4.6) or the input power from the generator (ee Section 4.7) will normally yield the lowet uncertainty. Uing the driven centrifugal compreor haft power to determine ga turbine haft output power will uually yield a higher uncertainty but i a widely ued and acceptable method, if properly performed. The ga turbine heat balance method yield the highet meaurement uncertainty and i generally not recommended. See Appendix A for a complete dicuion of the indirect approache. If the torque (τ) i meaured uing a torque coupling, then the haft power (P) developed by the ga turbine i calculated a: P = τ ( πn ) (.16) If ga turbine power i determined for an electric power generation application, the ga turbine haft output power can be imply determined from the meaured electric power at the generator terminal, the generator efficiency, and the gearbox efficiency (ee Section 4.7). Indirect method are more complex and are decribed in ection.5 and Appendix A..5 Centrifugal Compreor Aborbed Power (Ga Turbine Power Output) The aborbed power for the compreor (P c ) can be directly ued to determine the ga turbine haft output power, if no gearbox i preent. Otherwie, the gearbox power loe mut be included to determine ga turbine haft output power. Compreor aborbed power i calculated uing the compreor uction ga condition and the actual head (enthalpy change) a follow: P C = P η = ρ Q H (.17) out m If the driven compreor i rated for le power than the ga turbine output power, the full load power of the ga turbine cannot be determined uing thi approach..6 Ga Turbine Heat Rate and Efficiency If the ga turbine haft output power i known (or determined from the driven equipment or heat balance method), then the ga turbine efficiency i determined by dividing the ga turbine haft output power by the fuel energy flow rate. Pout η GT = (.18) W (LHV) f Similarly, the ga turbine heat rate i imply the reciprocal of the efficiency, or: Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 7

22 W f ( LHV ) HR = (.19) P out A heat rate i often expreed in mixed unit, the appropriate unit converion may need to be applied. The actual fuel ga compoition hould be ued to determine the lower heating value (LHV) of the fuel. If the fuel ga temperature i greater than 0ºC (36ºF) above the ambient temperature, the fuel ga enible heat hould be added to the equation above a uch: Pout η GT = (.0) W LHV + ( ρ c T) ) f ( P FG W f ( LHV + ( ρ cp T) HR = P out FG ) (.1) Senible heat repreent the energy introduced into the combutor in the form of thermal heat contained in the fuel..7 Ga Turbine Exhaut Heat Rate The ga turbine exhaut heat rate i often important for combined cycle or cogeneration application. Exhaut heat rate i the remaining energy in the exhaut flow of the ga turbine, or: GT ( he hr EHR = W ) (.) In equation. h R i a mutually agreed reference enthalpy. Direct meaurement of the ma flow i not recommended to determine the ga turbine exhaut heat rate becaue of the difficulty of accurately performing thi meaurement without a large preure differential. In addition, tet uncertaintie will be high due to the flow meaurement and temperature meaurement uncertaintie. An energy balance of the ytem may be ued to etimate the ga turbine exhaut heat rate, a decribed in Appendix A under method 4..8 Turbocompreor Package Efficiency The turbocompreor package efficiency (η TC ) may be calculated baed upon the previou value. Namely, the total package efficiency i the product of the ga turbine, gearbox, and compreor efficiencie: η = η η η η (.3) TC c GB GT M, compreor Note the compreor efficiency, η C, may be defined a either the ientropic or polytropic efficiency. For compreor drive, the package efficiency may alo be calculated a the compreor ientropic ga power divided by the fuel energy rate into the ga turbine: ρ Q H * η TC = (.4) W LHV f Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 8

23 Note that equation (.4) doe not work for the calculation of efficiency if polytropic head i ued intead of ientropic head. If equation (.4) i ued to define the package efficiency, an agreement about the treatment of recirculation and leakage loe mut be made to aure that thee loe are addreed properly in the turbocompreor package efficiency..9 Equation of State In the field performance tet of the compreor and turbine, the correct determination of the thermodynamic propertie of the ga (uch a enthalpy, entropy, and denity) play a critical role. The meaured quantitie (uch a preure, temperature, and compoition) are ued a input to an equation of tate (EOS) to determine thermodynamic propertie. The enthalpy change i ued to determine the head and the ientropic or polytropic efficiency of a compreor. The choice of the EOS ued in calculating enthalpy and denity affect the accuracy of the reult and need to be conidered in the uncertainty calculation. The poible equation of tate commonly ued in the ga indutry are: Redlich-Kwong (RK), Soave- Redlich-Kwong (SRK), Peng-Robinon (PR), Benedict-Webb-Rubin (BWR), Benedict-Webb-Rubin- Starling (BWRS), and Lee-Keler-Plocker (LKP), and AGA-10. The final election of the equation of tate to be ued in the field tet hould depend on the applicability of the particular equation of tate model to the ga and temperature encountered along with the proce of interet. Equation of tate model accuracy may depend upon the application range and the ga mixture at the ite (Sandberg, 005; Kumar et al., 1999). The conitent application of the equation of tate throughout the planning, teting, and analyi phae of the field tet i imperative. The choice of which EOS to ue mut be agreed upon before the tet. It i recommended to ue the EOS for tet data reduction that wa alo ued for the performance prediction. Thi procedure i alo recommended in ISO 5389 to avoid additional tet uncertaintie. The election of a particular EOS can have an important effect on the apparent efficiency and aborbed ga power. An added uncertainty of 1 to % can be incurred on the performance reult if the EOS i inconitently applied (Kumar et al., 1999). The formulation of the variou EOS i given in Appendix B..9.1 Application of Equation of State Generally, it i not poible to elect a mot accurate EOS to predict ga propertie, ince there i generally no calibration norm to tet againt for typical hydrocarbon mixture. All the frequently ued EOS model (RK, BWR, BWRS, LKP, SRK, PR) can predict the propertie of hydrocarbon mixture accurately below 0 MPa for common natural ga mixture. Outide thi preure range, deviation between the EOS model of 0.5 to.5% in compreibility factor Z are common, epecially if the natural ga contain ignificant amount of diluent. Becaue derivative of the compreibility factor (Z) mut be ued to calculate the enthalpy difference (i.e., head), the head deviation can be larger than the compreibility factor for different EOS. Table 1 provide uage uggetion for the variou EOS model baed on application. For normal hydrocarbon ga mixture (uch a pipeline quality ga) with diluent content (combined CO and N ) below 10%, all equation of tate hown in Table 1 provide accurate reult. Beyond thi range, Table 1 provide ome general recommendation on the mot applicable EOS. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 9

24 Table 1. Suggeted Application for Equation of Stage Uage Type of Application Typical hydrocarbon ga mixture, tandard preure and temperature, low CO and N diluent (< 6% total). Air mixture. High-preure application (>3000 pi). High CO and N diluent (10-30%) and/or high hydrogen content gae. High hydrogen content gae (>80% H ) Non-hydrocarbon mixture: ethylene, glycol, carbon dioxide mixture, refrigerant, hydrocarbon vapor, etc. Typically Ued EOS Model All EOS Model may be ued for thi application: Redlich-Kwong (RK), Soave-Redlich-Kwong (SRK), Peng Robinon (PR), Benedict-Webb-Rubin-Starling (BWRS), Benedict-Webb-Rubin (BWR), Lee-Keler- Plocker (LKP), AGA-10 BWRS, BWR, LKP BWRS, LKP PR, LKP, SRK Specific EOS model deigned for particular application or chemical mixture will reult in greater accuracy. The literature hould be conulted for the particular ga and application. A further comparion of the variou EOS model i provided in Appendix E. The calculated enthalpie for variou EOS model at different tate are ued to calculate ientropic efficiency and compreor power for two compreor operating cae..10 Determination of Surge Point and Turndown The low limit flow on a compreor i the urge point. Oftentime, rotating diffuer tall can further limit the compreor operating range due to aerodynamically induced vibration. The urge point i cutomarily ued a the lower flow limit for turndown determination. During a urge event, the flow field within the compreor collape, and the compreor head and flow rate drop uddenly. Surge i uually a udden and ometime catatrophic event and full urge hould be avoided. The turndown of a centrifugal compreor i the allowable operating range between the deign point and the urge line at any given peed for a fixed compreor head. It i determined from the difference between deign flow rate and the minimum flow rate at which the compreor i aerodynamically table a a percentage of the deign point flow rate at the ame head, a follow: TD % = 100 ( Q Q ) / Q Head = contant (.5) deign urge deign The urge margin i defined a the difference between deign flow rate and minimum flow rate a a percentage of the deign flow rate, for a fixed peed (N), a follow: SM % = 100 ( Q Q )/ Q Speed = contant (.6) deign urge deign The determination of the compreor urge point hould be conducted with extreme caution at relatively low preure differential and operating preure (i.e., low energy ) condition. Thu, urge point teting hould be at operating condition that correpond to low energy condition. If incipient urge tet mut Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 10

25 be performed at high head condition, thee tet hould be preceded by tet at low energy condition in order to characterize the compreor behavior and intrument output of incipient urge. Prior review of the compreor dynamic tet report to identify limiting vibration level may alo be valuable to avoid damaging compreor internal during the tet. Surge point teting conducted on a factory tet tand will often produce different reult than teting at a field intallation becaue the piping configuration and other intallation detail do affect the minimum table flow. Significant ga compoition change will alter the performance map of the compreor and lead to erroneou prediction of head and flow. Thu, urge teting can be important to etablih the correct urge line in the field. An example of a typical compreor urge line at variou compreor peed i hown in Figure 4 a the lower operational boundary of the compreor. 1.3 Compreor Curve - Surge Line and Operational Boundarie MAX SPEED Preure Ratio SURGE LINE 100% RPM 95% RPM 90% RPM 85% RPM Surge Line Surge Control MINIMUM SPEED LIMIT STONEWALL LIMIT Inlet Volume Flow Figure 4. Typical Compreor Surge Line on Compreor Performance Map There are a number of intrument reading that can provide an indication that the compreor i approaching it urge point; however, for each compreor geometry and operating condition, thee indication may be of varying magnitude or ometime may not occur at all. Thu, it i difficult to identify a ingular intrument reading that hould be utilized for the identification of incipient urge. In general practice, there are five indication that hould be monitored: 1. A marked increae in flow fluctuation in the uction and dicharge piping. An increae in uction or dicharge preure pulation 3. An increae in haft vibration (both axial and radial direction) 4. A decreae in head a flow i decreaed 5. An audible indication from the compreor of a ignificant operating change A urge i a udden and ignificant event, identifying the urge from the compreor operating noie can be dangerou, a the compreor may already be in full urge. Uing increaed vibration a the criterion to determine the urge point will be coniderably more inaccurate than other method (Kurz and Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 11

26 Brun, 005) due to variation in the mechanical reponivene of different compreor ytem. However, the increaed vibration can be due to the onet of talled flow rather than full urge. Alo, not all compreor have their urge point correponding to the maximum head for a fixed peed line. A good method to determine the urge line i by meauring flow and preure fluctuation on the compreor uction and dicharge piping. A thee fluctuation occur at a higher frequency range, preure tranducer and flow meter with a good dynamic repone mut be utilized (linear to at leat 100 Hz). If the dynamic tranducer are intalled at a ditance uptream or downtream from the compreor, the ignal may be delayed. Thu, the urge line hould alway be approached lowly, by carefully throttling uction or dicharge flow while maintaining compreor peed. It i recommended that the urge line i determined for a minimum of three different compreor peed line..11 Similarity Condition Generally, available field tet condition will deviate from pecified tet condition ued in the factory tet or previou teting of the ga turbine/compreor package. Thu, imilarity condition are ued to adjut for difference in the tet condition in order to match the flow characteritic for the machine under different tet condition. The imilarity variable that mut be calculated are provided in Section.11.1 and.11. to follow For the Centrifugal Compreor To compare performance data for a centrifugal compreor between predicted performance and actual tet data, the non-dimenional parameter for head and flow mut be ued. Namely, predicted performance, factory tet data, and field tet reult hould be normalized uing the head coefficient (Ψ) and the flow coefficient (ϕ) that were given previouly in Section.1 and.. By matching thee coefficient, the data can then be directly compared (a long a the Machine Mach number, ientropic exponent, and volume flow ratio are imilar a dicued below). Thi comparion of non-dimenional head and flow eliminate the requirement to tet the compreor at the identical peed a the factory tet (or other baeline tet of the unit) during the field tet. To vary ϕ and ψ during the tet, the compreor peed and actual head mut be adjuted. In addition to the head and flow coefficient for thermodynamic imilarity, the machine Mach number, ientropic exponent, and volume/flow ratio hould be maintained a cloely a poible to the comparion tet value to maintain aerodynamic imilarity. Machine Mach number: Ma = k U Z RT = π D tip k Z N RT (.7) Ientropic exponent: vδp k = pδv (.8) Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 1

27 Volume Flow Ratio: Q Q d Tet Q = Q d Actual (.9) In general, ingle- and two-tage compreor may allow deviation up to 10% from the Machine Mach number and ientropic exponent. For machine with multiple tage or high Machine Mach number (> 0.8), a 10% deviation in the Machine Mach number or ientropic exponent may lead to unacceptable deviation in the data et. Thu, a direct comparion between data et hould not be made unle the Machine Mach number and ientropic exponent are the ame, in uch cae. If the tet data how unexplainable deviation from the predicted performance, a deviation in the Machine Mach number may be the caue. An alternative approach to matching compreor performance data i provided by ASME PTC 10 but i generally written for factory teting rather than field teting. ASME PTC 10 allow deviation in the tet and deign cae for inlet preure, inlet temperature, pecific gravity, peed, capacity, and inlet ga denity (ee Table ). Namely, if the flow coefficient and head coefficient remain the ame a in the comparative (factory) tet, the velocity triangle at the inlet and outlet of each tage of the compreor will remain the ame. Thi i alo known a the Fan Law. Deviation in the tet within the limit given in Table will require only a correction uing the Fan Law. The volume ratio hown in equation (.9) hould alo remain the ame. The volume ratio may be kept contant by maintaining the Mach number and ientropic exponent (within 10%) over the machine. Table. ASME PTC 10 Acceptable Deviation in Tet Parameter for Similarity Condition Condition Acceptable Deviation (%) Inlet Preure 5 Inlet Temperature 8 Specific Gravity Speed Capacity 4 Inlet Ga Denity 8 If the intent i to compare identical compreor, ψ and ϕ can be implified to Q/N and H/N a hown by the Fan Law Proportionality below. Fan Law Proportionality: Q N ; H N ; 3 P N, where: Q = actual volumetric flow rate, acfm N = rotational peed, rpm H = head, ft-lb/lb P = power, ft-lb/min However, if the tet condition are coniderably different and outide the limit of ASME PTC 10 (Table ) or the Mach number difference or ientropic exponent difference i outide the acceptable range (a dicued above), the Fan Law Proportionality i no longer valid. It i recommended in thi cae that Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 13

28 the compreor manufacturer deign oftware be ued to recalculate compreor performance a well a the head and flow coefficient curve at the changed condition. Both the actual head and flow and/or the head coefficient and flow coefficient can be utilized to verify compreor performance. The compreor manufacturer hould inform the uer of the EOS model ued in recalculating the compreor performance..11. For the Ga Turbine For the ga turbine, the mot important parameter affecting the performance are engine inlet temperature, ga turbine peed and ambient preure. To a leer extent, fuel ga compoition and relative humidity may alo influence the performance characteritic. The achievement of imilarity condition for the ga turbine i more difficult than for the ga compreor becaue of the ga turbine enitivity to ambient condition. ASME PTC (1997) recommend that actual ga turbine performance curve hould be ued to correct the actual tet data. However, thee curve are often not available, particularly for older machine Full Load Operation The recommended method of correcting the meaured performance of the turbine i to ue ISO tandard or actual performance curve or the manufacturer oftware. In addition, the teting partie hould agree on the acceptable departure limit for the ga turbine parameter under tet prior to the actual field teting. The procedure for correcting the ga turbine to imilarity condition i a follow: 1. Determine full load power and heat rate for actual ambient condition and turbine peed.. Ue the map or the performance program to calculate the performance of a nominal engine at the ame condition a in (1). 3. Calculate the percent difference between the tet reult in (1) and () above, for power and heat rate. 4. Ue the map or the performance program to calculate the performance of the nominal engine under deired new condition. 5. Apply the percent difference for power and heat rate calculated under (3) to reference value in (4) to yield engine performance under deired new condition Part Load Operation The following procedure for correcting the ga turbine to imilarity condition at part load operation applie: 1. Determine part load heat rate for defined ambient condition and turbine peed.. Ue the map (if available for part load operation) or the performance program to calculate the performance of a nominal engine at the ame condition a in (1). 3. Calculate the percent difference between the tet reult in (1) and () above for heat rate. 4. Ue the map (if available for part load operation) or the performance program to calculate the performance of the nominal engine under deired new condition. 5. Apply the percent difference for heat rate calculated under (3) to reference value in (4) to yield engine performance under deired new condition. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 14

29 3. TEST PREPARATION A field tet agenda or plan hould be prepared prior to the tet a thi i an eential part of tet preparation. The plan hould include field condition and equipment layout, intrument to be ued and their location, method of operation, tet afety conideration, and the preure, temperature and flow limit of the facility. Piping and tation layout hould be made available. Any deviation from normal operation that may be neceary to conduct the tet hould alo be provided. The field tet agenda hould include a dicuion of the following: 1. The method of data reduction.. The elected approach for determining the tet uncertainty. 3. The acceptance criteria (pecified in term of maximal uncertainty allowable). 4. The equation of tate to be ued for all calculation in the tet. 5. The ue of ientropic or polytropic calculation (either may be ued for accurate thermodynamic performance characterization.). Tet preparation hould alo include a dicuion on poible operating condition and operational limitation. In many cae, a pecified operating point can only be maintained for a limited period of time (for example, becaue the pipeline operation depend upon the teted package) or at fixed ambient condition (if the neceary ga turbine power i only available on cold day). Becaue intrumentation i part of the overall tation deign, the requirement for intallation of tet intrumentation need to be communicated early. The election and calibration of the tet intrumentation i important. Generally, the intrument upplied for monitoring and protection of the package are not accurate enough to meet the tringent requirement neceary for a field tet (redundant meaurement requirement, mall uncertainty margin, detailed enor location placement, and the effect of improper flow meaurement). Whenever poible, calibrated laboratory quality intrumentation hould be intalled for the tet. (Refer to Section 4.0.) The accuracy of the intrument and the calibration procedure hould be uch that the meaurement uncertainty i reduced to the bet attainable uncertainty under ideal condition (ee Section 5.1). 3.1 Pre-Tet Meeting A meeting between the tet engineer, the partie involved (upplier, operator, etc.) and the cutomer to dicu tet procedure and the ituation on ite hould be conducted in advance of the performance tet. The ite P&ID, Site Layout and Mechanical Intallation Drawing diagram hould be obtained (if available) and ued in preparation for the performance tet. During the pre-tet meeting, the partie hould reach an agreement on the tet purpoe, tet procedure, afety requirement, reponibilitie during the tet, availability of neceary operating condition, and acceptance condition. 3. Pre-Tet Operation and Intrumentation Checkout The following item hould be checked during the pre-tet checkout: A. The tet engineer hould verify that the unit ha been proven uitable for continuou operation. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 15

30 B. The tet engineer hould note if a ga compreor tart-up trainer i intalled in the inlet pipe. If o, the trainer hould be checked for cleanline, either by ue of a differential preure gauge, direct inpection, or by borecope inpection. C. Sufficient ga hould be available for proper operation of the ga compreor. D. All intrumentation hould be calibrated in the range in which it will be operated during the tet. Check all intrument reading for temperature, preure, flow, torque, and peed to aure that the enor are functioning properly. Verify data acquiition ytem operation prior to tarting the field performance tet. E. All RTD or thermocouple ued in the tet hould ue pring load type fitting, or when neceary, the thermowell will be erviced with oil or other approved heat tranfer material. F. If thermowell are ued during the tet and a large portion of the thermowell i expoed to the atmophere, the area around the expoed portion hould be inulated to preclude the ambient air from affecting the temperature reading. G. Check inertion depth of thermowell. H. Where preure tap involve tubing run, the tubing hould be checked for leak. I. The proper number of capable peronnel hould be on ite to enure that all the data can be recorded in a reaonable amount of time. 3.3 Pre-Tet Equipment Checkout Prior to running the field performance tet, the following hould be performed: Wah the ga turbine compreor thoroughly. Clean air inlet filter panel (if neceary). Verify fuel and ite load to aure continuou operation of the unit and full-load condition a required at the time of the tet. Perform a viual walk-through of the turbine compreor package to eliminate any ource of hot air ingetion or recirculation. Conult with ga control on tation operation. Check if ga cooling i available and if recirculation of ga i an option during field tet. Notify all partie of time frame for tet. 3.4 Pre-Tet Information The following information hould be obtained a a reult of the tet preparation and pre-tet meeting: Impeller diameter. Predicted performance curve for compreor (or exiting tet curve). Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 16

31 Flow meter information: Pipe ID, orifice bore or beta ratio (for orifice meter), K-factor (for turbine or vortex hedding meter), flow coefficient (for annubar or nozzle) caling frequency, configuration log (for ultraonic meter or to adjut turbine or ma flow meter). Engine performance data, uch a factory tet data and predicted performance. Manufacturer Engine Performance Map or their electronic repreentation. Piping geometry between compreor and tet intrumentation. 3.5 Tet Stability In order to obtain teady tate condition, the ga turbine and compreor hould be tarted prior to the initiation of the tet (compreor require at leat 30 minute of heat oak time, ga turbine require between 1 to hour of heat oak time). The field tet hould be performed when the ga turbine and compreor operating condition have reached teady tate and the operating condition hould tay contant during each tet point. Power fluctuation hould not occur during the performance teting. A it i very difficult to determine fuel ga compoition variation during the hort tet interval, it i important to enure that the fuel and proce ga compoition will remain unchanged for the duration of the teting period for each tet point. Multiple ga ample of the proce ga and fuel ga mut be taken for each tet point if the ga compoition ignificantly change (heating value change of more than 1.0%) in between tet point. Temperature meaurement will epecially be affected by any intability during the tet. Temperature probe reach equilibrium through relatively low heat tranfer and heat oaking, while the ytem operating condition vary at much fater rate. The heat toring capacity of the compreor and ytem piping will need adequate time to reach equilibrium after any operating condition have changed. It i, thu, critical to maintain extended table operating condition prior to beginning the tet in order to reach thermal equilibrium and meaure accurate ga temperature. Regardle of the aumption of teady tate tet operation, any variation in meaured parameter during the tet interval hould be accounted for in the uncertainty calculation. Note that an increae in preure ratio due to drift during the tet will caue an increae in the temperature a well, though the temperature change will lag behind the preure change. Refer to Section 5.0 on uncertainty for more dicuion of unteady condition and drifting condition during a tet. Thee added uncertaintie due to drift during the tet interval are in addition to non-ideal effect dicued in Section Compreor Steady State The compreor hould be operated for at leat 30 minute prior to the tet or until table reading are reached. Steady tate i achieved if all of the compreor meaurement lited in Table 3 apply during a 10-minute interval. Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 17

32 Table 3. Aement of Stability of Compreor During Pre-Tet Criteria 1 Tet Reading Suction Temperature Dicharge Temperature Suction Preure Dicharge Preure Compreor Speed Compreor Flow Maximum Allowable Variation During 10-min Interval + 1ºC (+ 1.5ºF) + 1ºC (+ 1.5ºF) + 1% of Average Value + 1% of Average Value + 10 rpm + 1.0% of Average Value Alternatively, the following performance condition hown in Table 4 hould be atified: Table 4. Aement of Stability of Compreor During Pre-Tet Criteria Tet Reading Efficiency Head Shaft Power Maximum Allowable Variation During 10-min Interval Fluctuation < + 0.5% of Average + 0.5% of Average Value + 1% of Average Value 3.5. Ga Turbine Steady State Before reading are taken for any individual tet point, ga turbine teady tate operating condition mut be achieved. The ga turbine mut be heat oaked according to manufacturer pecification. If manufacturer pecification are not available, ga turbine hould be heat oaked for at leat 1 hour for aeroderivative ga turbine and mall ga turbine (<10,000 hp), and hour for large ga turbine (>10,000 hp), or until table operation (per Table 5) have been reached. To verify tability of the ga turbine, the parameter given in Table 4 hould be checked. Three to ten data point of each parameter over a 10-minute period hould be recorded to verify tability. If the ga turbine ha reached equilibrium, each of the parameter in Table 5 will fall within the tability criteria provided. Table 5. Aement of Stability of Ga Turbine During Pre-Tet Tet Reading Turbine Inlet Temperature Or Ambient Temperature Ga Producer Speed Shaft Load Firing Temperature Power Turbine Speed Fuel Flow Maximum Allowable Variation During 10-min Interval + 1 ºC (+ 1.5 ºF) + 1% Average Speed + 1% Average Load + 5 ºC (+ 9 ºF) + 10 rpm + % Average Flow Generator Line Voltage + 1% Guideline for Field Teting of Ga Turbine and Centrifugal Compreor Performance Page 18