A New Approach of Gas Turbine Component Matching for Electrical Power Generation Al-Hamdan, Qusai; Ebaid, Munzer

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1 UHI Research Database pd download summary A New Approach o Gas urbine Component Matching or Electrical ower Generation Al-Hamdan, Qusai; Ebaid, Munzer ublished in: International Journal o Mechanical Engineering and Applications ublication date: 017 ublisher rights: Copyright 017 Authors retain the copyright o this article. his article is an open access article distributed under the Creative Commons Attribution License ( which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. he re-use license or this item is: CC BY he Document Version you have downloaded here is: ublisher's DF, also known as Version o record he inal published version is available direct rom the publisher website at: /j.ijmea Link to author version on UHI Research Database Citation or published version (AA): Al-Hamdan, Q., & Ebaid, M. (017). A New Approach o Gas urbine Component Matching or Electrical ower Generation. International Journal o Mechanical Engineering and Applications, 5(4), 14-. DOI: /j.ijmea General rights Copyright and moral rights or the publications made accessible in the UHI Research Database are retained by the authors and/or other copyright owners and it is a condition o accessing publications that users recognise and abide by the legal requirements associated with these rights: 1) Users may download and print one copy o any publication rom the UHI Research Database or the purpose o private study or research. ) You may not urther distribute the material or use it or any proit-making activity or commercial gain 3) You may reely distribute the URL identiying the publication in the UHI Research Database ake down policy I you believe that this document breaches copyright please contact us at RO@uhi.ac.uk providing details; we will remove access to the work immediately and investigate your claim. Download date: 06. Oct. 018

2 International Journal o Mechanical Engineering and Applications 017; 5(4): doi: /j.ijmea ISSN: X (rint); ISSN: (Online) A New Approach o Gas urbine Component Matching or Electrical ower Generation Munzer S. Y. Ebaid 1, Qusai Z. Al-Hamdan 1 Department o Mechanical Engineering, Faculty o engineering, hiladelphia University, Amman, Jordan Aircrat Engineering Department, erth College, University o the Highlands and Islands, erth, Scotland, UK address: mebaid@philadelphia.edu.jo (M. S. Y. Ebaid), qusai.al-hamdan.perth@uhi.ac.uk (Q. Z. Al-Hamdan) o cite this article: Munzer S. Y. Ebaid, Qusai Z. Al-Hamdan. A New Approach o Gas urbine Component Matching or Electrical ower Generation. International Journal o Mechanical Engineering and Applications. Vol. 5, No. 4, 017, pp doi: /j.ijmea Received: February 7, 017; Accepted: March 7, 017; ublished: August 4, 017 Abstract: Gas turbines are oten required to operate at dierent power levels and under varying environmental conditions. But by the nature o the thermodynamic processes in the engine, it is not possible to obtain the same level o eiciency within the entire range o operation. hereore, depending on the particular application, or example or power generation, the rotational speed would be constant and dictated by the electrical generating machine. Gas turbine engine consists o various components which are linked together in such a way that there exists a mechanical and thermodynamic interdependence among some components. his means that some operational compatibility (matching) between components will be required or a steady state or equilibrium operation. he steady state o gas turbine engine or power generation can be achieved by the matching o its compressor and turbine. he usual approach o matching the compressor and the turbine is usually based on using an iterative procedure to determine the turbine operating points which are then plotted on the compressor characteristics. he draw back o this process is being laborious and time consuming. he new approach developed overcomes this by superimposing the turbine perormance characteristics on the compressor perormance characteristics while meeting the components matching conditions. his can be done by introducing a new mass low dimensionless parameter. Superimposing the turbine map on the compressor map cannot be totally accepted until both maps axes (the abscissa and the ordinate) are identical. his paper explains the new approach adopted to a single shat gas turbine engine. heoretically, the developed techniques can be applied to other gas turbine engines. Keywords: Gas urbine O-Design, Gas urbine erormance, Component Matching 1. Introduction Gas turbines are oten required to operate at dierent power levels and under varying environmental conditions. But, it is not possible to obtain the same level o power output and eiciency within the entire range o operation. he gas turbine may be designed or optimised operation at given power level and speciied conditions. he power level and expected thermal eiciency are chosen to correspond to those conditions under which the engine operates or most o its lie. he values o the characteristic parameters at that point are termed as the design point. Usually, a set o independent variables, which exclusively determine the perormance o the engine, will be associated with this region (envelope). For a ixed geometry engine, these may be chosen as pressure ratio, turbine inlet temperature, rotational speed and air mass low rate. his set is complete but not unique. he gas turbine engine consists o various components, which are linked together in such a way that there exists a mechanical and thermodynamic interdependence among some components. his means that some operational compatibility (matching) between components will be required or a steady state or equilibrium operation. his requirement reduces the range o the operating conditions or the components. But it is possible to deine a subset o the engine s operating envelope such that every point in this subregion is an equilibrium working point. hese working points can be mapped on the respective components characteristics. he design point values are elements o this region, which yield the best thermal eiciency. Any point in the region

3 15 Munzer S. Y. Ebaid1 and Qusai Z. Al-Hamdan: A New Approach o Gas urbine Component Matching or Electrical ower Generation other than the design point represents an o-design condition. he o-design problem may thereore be stated as the determination o a point in this region that corresponds to some speciied conditions at which the equilibrium criteria would be satisied but at reduced value o thermal eiciency. Since the operating points o the individual components can be determined by using the given values o some characteristic parameters, the o-design problem reduces to computing the values o these parameters, which would satisy the equilibrium criteria. his procedure is demonstrated in the analysis given hereater.. Matching rocedure Several researchers presented dierent methods or matching gas turbines components in the open literature. Among them the work by Flack [1] in which he presented a method o matching gas turbine components or an aeroderivative power generation gas turbine as an exercise or students in the classroom. Matching is accomplished by simultaneously solving the matching closure equations along with the component maps (either mathematical models or graphical data). Also, he claimed that this method is a tool in which a student can select components to optimize the overall perormance and can predict o-design perormance o a power generation unit. Kong et al. [] work were on uzzy logic and they used the uzzy approaches or searching optimal component matching point in gas turbine perormance simulation. Gugau and Roclawskip [3] have used an optimization sotware or producing the matching maps that its turbine and compressor (turbocharger) to the internal combustion gasoline engine, and keeps uel consumption low at all engine speeds. soutsanis et al. [4] developed a novel compressor map generation method, with the primary objective o improving the accuracy and idelity o the engine model perormance prediction. A new compressor map itting and modelling method is introduced to simultaneously determine the best elliptical curves to a set o compressor map data. he coeicients that determine the shape o compressor maps curves have been analyzed and tuned through a multi-objective optimization algorithm in order to meet the targeted set o measurements. he proposed component map generation method is developed in the object oriented Matlab/Simulink environment and is integrated in a dynamic gas turbine engine model. he accuracy o this method is evaluated or o-design steady state and transient engine conditions. he proposed compressor map generation method has the capability to reine current gas turbine perormance prediction approaches and to improve modelbased diagnostic techniques. Considering a simple radial gas turbine used or electrical power generation application schematically showed in igure 1. he perormance o the compressor and the turbine are completely known by their characteristics maps as shown in igure and igure 3. he data used in producing theses plots were taken rom actual tests experiments on type 01 C. A.V compressor and inward radial turbine itted with a nozzles casing provided by Bhinder [5]. In this radial gas turbine engine, the component s matching should meet the ollowing conditions: i. he compressor shat speed = the turbine shat speed, Nc = Nt = N ii. he gas mass low through turbine is the sum o the air mass low through compressor and the uel mass low, g = a + iii. Assuming that the pressure loss in the combustion chamber is a constant small percentage ζ cc o the combustion chamber inlet pressure, = ζ ( ) 03 1 cc 0 iv. Inlet and exhaust pressure losses are too small and can be ignored, 04 = 01 Figure 1. Schematic diagram o simple radial gas turbine engine.

4 International Journal o Mechanical Engineering and Applications 017; 5(4): It should be noted that the second condition is subject to modiication in that it is common practice to bleed air rom the compressor at various stations to provide cooling air or bearings and turbine blade cooling. Quiet oten it is suiciently accurate to assume that the bleed air equals the uel low, and thereore the mass low is the same throughout the compressor and the turbine. i. e. g = a = Figure. General Compressor Characteristics map. Figure 3. urbine Characteristics map.

5 17 Munzer S. Y. Ebaid1 and Qusai Z. Al-Hamdan: A New Approach o Gas urbine Component Matching or Electrical ower Generation he steady state or equilibrium operation o this gas turbine engine can be achieved by the matching o its compressor and turbine. Matching the compressor and the turbine can be done by superimposing the turbine perormance map on the compressor map while meeting the components matching conditions. his matching procedure is schematically shown in igure 4. Figure 4. Compressor-turbine matching procedure. Superimposing the turbine perormance map on the compressor map can be achieved by applying the usual procedure o using iterative process Res. [6, 7, 8] which is a long process or by applying the new approach o making both map s axes (the abscissa and the ordinate) being identical. he main diiculty here is that o temperatures: 01 or the compressor and 03 or the turbine are dierent. he procedure to overcome this problem was solved by introducing a new dimensionless parameter named as the mn ɺ matching parameter. he derivation o this dc01 parameter is described in the ollowing section..1. he Centriugal Compressor Based on igure shown previously which illustrates the general compressor characteristics map. he mass a Cpa01 low dimensionless parameter represents d c 01 the abscissa part o igure. he proposed matching an dimensionless parameter is derived by dc01 multiplying the mass low dimensionless parameter with dcn the dimensionless speed parameter as shown C in Eqn. 1: a Cpa o1 dcn an = d d co 1 Cpao1 co 1 he ordinate i.e. the pressure ratio parameter o o1, remains unchanged. Once these transormations had been made, the compressor characteristics map was plotted again in terms o these new parameters as shown in igure 5. It should be noted that the characteristics map does not change much. pa 01 (1)

6 International Journal o Mechanical Engineering and Applications 017; 5(4): o satisy the compressor-turbine matching conditions speciied previously, i.e. g = a = and 04 = 01. hen the developed matching parameter o the turbine is equal to the developed matching parameter o the compressor. i.e. N g d c 04 an = d c 01 (3) (3) Figure 5. Centriugal compressor map ater transormation... he Radial urbine Based on igure 3 shown previously, which illustrates the general turbine characteristics map. he mass low g Cpg03 dimensionless parameter represents the d 03 abscissa part o igure 3. he proposed matching g N dimensionless parameter is derived by dc04 multiplying the mass low parameter with the dimensionless speed parameter, turbine pressure ratio and the ratio o the turbine rotor diameter to compressor impeller diameter as shown in Eqn. : g Cpg 03 dtn 03 dt gn = () d t03 Cpg03 04 dc dc04 For the turbine pressure ratio parameter, the ordinate axis o the turbine characteristics map or matching is transormed into the pressure ratio across the compressor as shown in Eqn. 4: Note that: And = 04 1 ξcc cc 0 (4) = (1 ξ ) (5) = (6) Once these transormations had been made, the turbine characteristics map was plotted again in terms o these new parameters as shown in igure 6. Figure 6. Radial turbine map ater transormation.

7 19 Munzer S. Y. Ebaid1 and Qusai Z. Al-Hamdan: A New Approach o Gas urbine Component Matching or Electrical ower Generation.3. Compressor-urbine Matching It can be seen rom the graphical plots o compressor and turbine perormance maps that the abscissa and the ordinate o these maps are identical. hereore, it is clear that the turbine map could be superimposed on the compressor map to produce a complete compressor-turbine matching map as shown in igure 7. Figure 7. Complete compressor-turbine matching map. 3. Results and Discussion he resulting matching map shown in igure 7 is a very useul tool in predicting the overall perormance o matched components, i.e. the gas turbine design and o-design perormance. Using the compressor-turbine dimensionless speed intersection points, where the speed is the same ( Nc = Nt ), the turbine inlet temperatures 03 o the gas turbine speed can be easily calculated based on the speed d N parameter S = rom igure 7. or any speed. he C pa 03 turbine inlet temperature 03 lines o 750 K and 1000 K were computed and drawn in Figure 8. It can be seen that the changes o constant o3 lines at various pressure ratios are linear and showed divergence at higher values o speed and pressure ratios. he area between these two lines represents the accepted working range or the gas turbine engine. Figure 8. Constant turbine inlet temperatures 03.

8 International Journal o Mechanical Engineering and Applications 017; 5(4): 14-0 At any point within the matching range, the ollowing parameters listed in able 1 are computed according to Eqns. (7-13) given by [9, 10]. able 1. erormance parameters o gas turbine engine. Compressor power, W c urbine power, W t Speciic uel consumption Compressor torque, τ c SFC urbine torque, τ t Net output torque, τ net Gas turbine thermal eiciency, η gt Net power output, W net W γ a 1 γ a 01 0 c = acpa 1 η c (7) 01 where = a W = (1 + ) acpgηt γ g 1 γ g 04, where m = ɺ a (8) Wnet = W Wc (9) SFC 3600 = W W c (10) d τ c 3 c o1 1 1 = π η c d C c N a o1 1 a d C a o1 o 1 o o 1 γ a 1 γ a 1 (11) 1 γ g 1 1 m g Cg γ τ 3 g d N ɺ o o 4 = η π g o3 o3 o3 d C d gt ( 3 4 ) ɺ ( 1) C ( ) gcpg o o macpa o o η = g pg o3 o (1) (13) For a power generation driven by radial gas turbine engine, let's consider any running line, or example, the line o speed rpm was extracted rom igure 7, or clarity, it is depicted in igure 9. Figure 9. Matching characteristics o the design speed line at rpm. It can be seen that all the matching values o the engine components at the design speed are known and are used to predict the engine perormance such as thermal eiciency, speciic uel consumption and engine torque at design and o-design

9 1 Munzer S. Y. Ebaid1 and Qusai Z. Al-Hamdan: A New Approach o Gas urbine Component Matching or Electrical ower Generation conditions. Based on the graphical analysis, the above parameters can be calculated within the speciied working range. he output results are plotted as shown in igure 10 and igure 11 which provides important inormation about the perormance o the gas turbine at design and o design points. Figure 10. Variation o engine torque at design and o design conditions rpm. Figure 11. Variation o engine thermal eiciency and SFC at design and o- design conditions at rpm. 4. Concluding Remarks Applying this new approach leads to the determination o the operating range (envelope) and running line o the matched components. Also, the proximity o the operating points to the compressor surge line (how close the operating points to the surge line) is presented. However, it was concluded that the maximum operating point occurs at the maximum turbine inlet temperature ( o3). he most important it can be concluded rom this work whether the gas turbine engine is operating in a region o adequate compressor and turbine eiciencies. Finally, this method saves time and work eort compared to the usual iterative process. Nomenclature C γ Speciic heat at constant pressure Ratio o speciic heat w, W η τ LCV F d N ξ S o Mass low rate Speciic work output, work output ressure emperature Eiciency orque Lower caloriic value Fuel to air ratio Diameter Rotational speed Loss o stagnation pressure urbine dimensionless speed parameter Subscripts 1. Compressor inlet. Compressor exit 3. urbine inlet 4. urbine exit Stagnation

10 International Journal o Mechanical Engineering and Applications 017; 5(4): 14- g gt a c cc t Gas Gas turbine Air Compressor Combustion chamber urbine Fuel air ratio [4] soutsanis E., Meskin N., Benammar M., Khorasani K., An Eicient Component Map Generation Method or rediction o Gas urbine erormance ASME urbo Expo 014: urbine echnical Conerence and Exposition Volume 6: Ceramics; Controls, Diagnostics and Instrumentation; Education; Manuacturing Materials and Metallurgy, Düsseldor, Germany, June 16 0, 014. [5] Richard. C. Harman Gas turbine Engineering. First Edition, Reerences [1] Flack R., component matching analysis or a power generation gas turbine: classroom applications, ASME urbo Expo 00: ower or Land, Sea, and Air, Vol. 1: urbo Expo 00, Amsterdam, he Netherlands, June 3 6, (00), [] Kong C., Ki J., Kang M., Fuzzy approaches or searching optimal component matching point in gas turbine perormance simulation, J. Eng. Gas urbines ower, Vol. 16, issue 4, (004), [3] Gugau M., and Roclawski, H., On the Design and Matching o urbocharger Single Scroll urbines or ass Car Gasoline Engines, J. Eng. Gas urbines ower, Vol. 136, Issue 1, (014). [6] Walsh, and Fletcher,. Gas urbine erormance [7] Cohen, H. Rogers, G F C and Saravanamutto, H. I. H. Gas urbine heory. Second Edition, 197. [8] Bhinder F. S., Design parameters o centripetal turbine in nonsteady low hd thesis, King s college, London, March, [9] Ebaid, M. S. Y. Design and construction o small gas turbine to drive a permanent magnet high speed Generator. hd hesis, University o Hertordshire, 00. [10] Al-Hamdan, Q. Z. M. Design criteria and perormance o gas turbines in a combined power and power (C) plant or electrical power generation hd hesis, University o Hertordshire, 00.