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Generalized High Speed Simulation ofGas Turbine Engines

NANAHISA SUGIYAMAAero-Engine Division

National Aerospace LaboratoryChofu, Tokyo, Japan

ABSTRACTThis paper describes a real-time or faster-than-real-time simu-lation of gas turbine engines, using an ultra high speed, multi-processor digital computer, designated the AD100. It is shownthat the frame time is reduced significantly without any lossof fidelity of a simulation. The simulation program is aimed ata high degree of flexibility to allow changes in engine configu-ration. This makes it possible to simulate various types of gasturbine engines, including jet engines, gas turbines for vehiclesand power plants, in real-time. Some simulation results for anintercooled-reheat type industrial gas turbine are shown.

INTRODUCTIONModern gas turbine engines are becoming more and morecomplex in engine cycles and geometries, for higher perfor-mance and multi-mission requirements. This has resulted ina trend toward a variable geometry or a variable cycle engine,which has numerous variable geometry features, such as vari-able nozzle and variable stator vane, to obtain the optimumperformance over a wide range of operating conditions. Cor-respondingly, the requirements for engine control systems arebecoming more and more severe due to the complexity of thestatic and dynamic behavior of such an engine.

Real-time simulation of a gas turbine engine plays an im-portant role in developing control systems. It is useful in de-sign, evaluation and testing of the systems, and also is help-ful in good technological understanding of complicated engineperformance. In addition, since the representative simulationcan predict engine performance, especially dynamic charac-teristics, over the whole range of operating conditions at thedesign phase of an engine development program, it providesan effective tool to develop an engine itself.

All-digital simulation is generally preferred because of the

precision of computation, flexibility, repeatability and oper-ation with a stored program. In a gas turbine simulation,the major part of computation is the generation of nonlin-ear multivariable functions. All digital computation is bestsuited to this function generation task. To realize real-timesimulation using the digital computer, the frame time of dig-ital computation must be short enough to maintain dynamicaccuracy. Increasing complexity of functional relations, asnoted above, causes the frame time to be long. Conversely,increasing importance of engine dynamics at high frequenciesrequires shorter frame times. Because of these facts, ultra highspeed computation is needed for real-time digital simulationof modern gas turbine engines. Due to the current remarkableprogress in digital hardware, this short frame time becomespossible, even for a detailed engine model.

This paper describes a hardware and software method torealize real-time or faster-than-real-time simulation of gas tur-bine engines, using an ultra high speed, multi-processor digitalcomputer, designated the AD100, which is designed specifi-cally for high-speed simulation of continuous dynamic systems.It is shown that the frame time is reduced significantly with-out any loss of fidelity of a simulation. The simulation pro-gram is aimed at a high degree of flexibility to allow changesin engine configuration. This makes it possible to simulatevarious types of gas turbine engines, including jet engines, gasturbines for vehicles and power plants, in real-time. Some sim-ulation results for an intercooled-reheat industrial gas turbineare shown.

REQUIREMENTS FOR GAS TUR-BINE SIMULATIONThere are a number of requirements for gas turbine enginesimulation. First of all, the simulation must represent ac-curately the static and dynamic performance of an engine

'Presented at the Gas Turbine and Aeroengine Congress and ExpositionJune 11-14, 1990Brussels, Belgium

Copyright 1990 by ASME

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over the whole range of operating conditions, in order toserve as a realistic model. Thus there is a need for a wide-range, detailed mathematical model and an accurate comput-ing method. Highly detailed engine simulations have beendeveloped and implemented using a large scale digital com-puter (Sellers and Daniele, 1975, Fishbach and Caddy, 1975,Palmer and Yan, 1982, Fishbach and Gordon, 1988) and ahybrid computer (Szuch, 1974a). The validity of such simu-lations have been examined by comparing results with actualengine data. However, these simulations could not satisfy therequirement of real-time operation and were used for detailedstudy of steady state and transient performance on an off-linebasis.

In the case of simulations involving interaction with actualsystems, such as the engine controller, real-time operation isan essential requirement. This has been accomplished with thehybrid computer for particular engines (Szuch et al., 1974b,1975) and, currently, ultra high speed digital computers havebecome available for this purpose. A major problem encoun-tered in gas turbine simulation is to generate a large number ofnonlinear multivariable functions required to describe enginecomponent performances and properties of gas. All digitalcomputation, due to its accuracy and reliability, is best suitedto this function generation task and, hence, the frame timeof digital computation is a limiting factor for real-time opera-tion. Since the frequency range of interest in control problemis approximately 0-30 [Hz], the frame time should be around1 [msec] for real-time operation (Gilbert, 1966).

For realistic interaction with the real world external to thesimulator, an interface which provides suitable signals becomesnecessary. This can provide a facility for connection with ac-tual system hardware as well as monitoring devices such as agraphical display, which is helpful in gaining intuitive insightinto complicated engine dynamics. This interface is furnishedby A/D and D/A converters in the digital simulation.

Usually, modeling methods are more or less based on enginecomponent performance and associated conservation equa-tions. Component performance data can be obtained from de-sign studies or estimates from existing engines, prior to enginehardware availability; the data is then updated when compo-nent test and engine test data become available. Therefore,updates in engine data should be easily made without disturb-ing the entire simulation. The fact that the simulation can pre-dict engine performance based on design data or componenttest data suggests usefulness of the simulation in developmentof the engine.

Finally, it is desirable that the simulation method be appli-cable to a wide variety of gas turbine engines to reduce effec-tively the man-hours for development of the simulation. Sincemost engines consist of several common components and canbe modeled by proper interconnection of these components,a systematic procedure in a block diagram form is possible,where each block corresponds to one type of engine compo-nent. Simulation of a particular engine, then, is realized byconnecting these common components. The purpose of thiswork is to develop the simulation method which satisfies theabove requirements.

COMPUTATIONAL MODULES

AD100 and ADSIMFig.1 shows the basic architecture of the AD100. Five func-

tional processors, i.e., communication and control processor(COM), arithmetic and logic processor (ALU), multiplier pro-cessor (MUL), storage processor (STO), and function memoryunit -(FMU) are interfaced to the PLUSBUS, which transferdata to and from the memory unit and the processors usinga 25 [nsec] bus cycle time. A large number of A/D and D/Achannels are controlled by COM processor and are used to con-nect the simulator with external actual hardware. To accom-plish the required computational tasks, the functional proces-sors operate in parallel and execute instructions in a 100 [nsec]period synchronized to the bus cycle. The high data rate onthe PLUSBUS, high speed of the processors, parallelism andpipelining of the computation, and arithmetic ability suited tofunction generation and numerical integration, all contributeto high speed simulation. Especially, computational efficiencyfor function generation is remarkable. Execution times for 1,2, 3, and 4 variable function generation are 0.5, 0.9, 1.7 and3.6 [sec], respectively. Since 80% of computational burdenin gas turbine simulation is multivariable function generation,this feature is highly effective to realize real-time or faster-than-real-time simulation.

In the AD100 system, variables and constants are repre-sented by 65-bit floating point numbers, comprised of a 12-bitexponent and a 52-bit significant fraction. Hence the computa-tional precision is comparable to double precision arithmetic ina general purpose digital computer. This bit length is enoughto avoid round-off problems in summing up the derivative termin numerical integration for a stiff system (Gilbert and Howe,1978).

ADSIM is a FORTRAN-like simulation language for theAD100 system and its source code is very close to mathemat-ical equations. The user can use high-speed computational,data logging and I/O capabilities through the ADSIM lan-guage without knowledge of the hardware. A generalized gasturbine simulation program developed here is written by theADSIM language. In coding the many calculations needed insimulation, the traditional approach uses a series of additionand multiplication with minimum memory storage. However,the function generation approach is more efficient with avail-ability of large, low cost, high-speed memories (Gilbert andHowe, 1977). For example, the calculation of flow function

to A/D and D/A to Host Computer

Fig.1 Architecture of the AD100

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COMP (compressor module)1. inlet temp. Ti 1. air flow rate W2. inlet pressure Pi 2. outlet enthalpy ho3. inlet fuel/air fz 3. outlet fuel/air fo

z 4. inlet steam/air xi 4. outlet steam/air xo5. outlet pressure Po 5. compressor power P,6. rotor speed N7. stator angle a1. inlet relative pressure Pr; = Grt (Ti, f;, xi)2. inlet enthalpy hi = Ght(Ti, fi.x;)3. corrected inlet temp. 0 = TZ/T,4.corrected inlet pressure 6 = Pi/P,

.3 5. corrected rotor speed N* = N/f

0 6. presure ratio 7r = Po/PicL, 7. outlet relative pressure Pro = 7rPrt

8. corrected air flow rate W* = Fj c (lr, N*, a c )0 9. adiabatic efficiency t7 = Fec (7r, N*, ac )

10. isentropic enthalpy hso = Ghr (Pro, fi, Xi)11. enthalpy rise Oh = (h, o -12. outlet enthalpy ho = h; + Oh13. air flow rate W =W*6/f14. compressor power PP = WOh15. outlet fuel/air ratio fo = fi16. outlet steam/air ratio xo = xi

V a ^PiT{z

PWhjo

V fi J O`'' xt N xoP^

Fig.2(a) Compressor Module

through a nozzle;

Gwn = 7r7 (1 - it I )

(1)7-1is efficiently evaluated by considering it as a two variable func-tion of 7r and ry, storing the appropriate table, and using func-tion generation.

Computational Modules for Engine ComponentsAlthough there exist various types of gas turbine engines

according to their missions, all such engines consist of a rela-tively small number of basic components. A simulation modelof a complete engine can be obtained by tying together sev-eral sub-models of these basic components. Such componentsare:(1) compressor, for compressor and fan,

(2)turbine, for high- and low-pressure turbine,(3) duct, for connecting duct,

(4) bleed, for air bleed from compressor and turbine coolingair bleed,

(5) combustor, for main-combustor and reheat-combustor,

(6) intercooler, for water injection intercooler,

TURB (turbine module)1. inlet temp. Tti 1. gas flow rate W2. inlet pressure Pi 2. outlet enthalpy h03. inlet fuel/air fz 3. outlet fuel/air fo4. inlet steam/air xi 4. outlet steam/air x0

Z3 5. outlet pressure PO 5. turbine power Pt6. rotor speed N 07. stator angle at8. cooling air flow W19. coefficient 13cI1. inlet relative pressure Pr; = Grt(Ti, fl, xi)2. inlet enthalpy h = Ght(T1, fz.xti)3. corrected inlet temp. 0 = TtilT,,4. corrected inlet pressure 6 = PP/P,5. corrected rotor speed N* = N/\/6. presure ratio Ir = Pt/Po7. outlet relative pressure Pro = Pri/7r

r3 8. rrrrected gas flow rate W* = Fj t (7r, N*, at )9. adiabatic efficiency = Fet (x, N*, at )10. isentropic enthalpyP PY h = G f x )eo hr (P roe z^ z

Q. 11. enthalpy drop Oh = (hi - h, 0 )7712. outlet enthalpy ho = hti - Oh13. gas flow rate W = W*b/\14. turbine power Pt = Oh(W + /31W1)15. outlet fuel/air ratio fo = fti16. outlet steam/air ratio xo = xi

N

atPP;WTi ho{tT " XOf^ ox^ N

Pt 147c1, /'cl

Fig.2(b) Turbine Module

(7) nozzle, for main and bypass nozzle,

(8)inlet, for air inlet,(9) volume, for intercomponent volume, and

(10) rotor, for high- and low-pressure rotor.

Mathematical models, computational procedures andschematic diagrams for four representative components, i.e.,(1) compressor, (2) turbine, (9) volume and (10) rotor mod-ule, are shown in Fig.2(a)-(d). Mathematical models adoptedhere are highly detailed models and include no simplificationsto reduce computing time and memory storage. Descriptionsfor the rest of the components are omitted due to limitationsof space.

Components (1) to (8) are static elements and are mod-eled as lumped parameter systems represented by performancemaps, constant coefficients, and thermo- and aero-dynamicrelations. Compressor and turbine performance maps aretreated as 3-variable functions to take into account the ef-fect of such variable geometry features as the variable inletguide vane, variable stator vane, variable fan pitch and vari-able turbine areas. Also nozzle area and bleed valve area can

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VOL (volume module)1. incoming flow-1 Wit 1. temperature T2. enthalpy-1 hil 2. pressure P3. fuel/air-1 fir 3. fuel/air ff4. steam/air-1 xi1 ^. 4. steam/air x5. incoming flow-2 Wi2 5. rel.humidity b6. enthalpy-2 hi27. fuel/air-2 fi28. steam/air-2 Xi2 1. temperature Tv i9. outgoing flow-1 Wo l v 2. pressure Pi10. outgoing flow-2 W0211. outgoing flow-3 W0312. outgoing flow-4 Woo13. volume V1. incoming gas flow Wi n, = Wi i + Wi22. outgoing gas flow Wout = Wol + W02 + Wm + W043. air/gas ratio-1 gl = 1/(1+ fil + xi1)4. air/gas ratio-2 g2 = 1/(1 + fie + xi2)5. amount of fuel F = Wiifii9i + Wi2fi2926. amount of steam X = Wi1xii91 +Wi2xi2927. amount of air A = Wi n - F - X

2 8. fuel/air ratio f = F/A9. steam/air ratio x, = X/A10. enthalpy h = Ght (T0 , f0 ,x)11. relative humidity c = Grx (Tv , P,,, x)12.gas constant R = Gr (fv ,x)13. stored mass r (minit = P=v V/Ti v /G(0i r , 0))

m = ,l (Win - Wout ) dt14. stored energy (ut = Gut(Ti3O))

u = ( 1 /m) f(Wtithh). +Wfi2hi2 - Wosi.thv)dt15. temperature TT = Gtu (u, f,,, x)16. pressure P = mRTv /V

Wi lif

i lT r WoiPv I_

xil fv '^Wo2I VWi2

xv' Wo3

hiefit

l v) -- - o4

xiz

Fig.2(c) Volume Module

be treated as independent variables (or constants) to makethese controllable.

Components (9) and (10) are dynamic elements. Rotordynamics, which is a ruling factor in transient behavior ofan engine, is represented by the equation of conservation ofangular momentum. Volume dynamics is represented by theequations of conservation of mass and energy. Pressure andtemperature are assumed to be uniform throughout each vol-ume. Volumes are introduced between successive engine staticcomponents where a volume capacitive effect is considered tobe important, or where it is desirable to avoid iterative computation.

Fig.3 shows inputs and outputs for the computational mod-

ROTOR (rotor module)1. compressor power-1 PP1 1. rotor speed N2. compressor power-2 PP23. compressor power-3 P, 3 a4. compressor power-4 Pc45. turbine power-1 PtI6. turbine power-2 Pt2 1. rotor speed Ni7. turbine power-3 Pt38. turbine power-4 Pt49. moment of inertia I10. mechanical eff. s7/2

ti

1. excess power Q - (Ptl i- Pt2 1- Pt3 -f Pt4

O -- Pc 1 - 'c2 - Pc3 - Pc4) 71m

GL 2. rotational speed N = (60/2sr) 2 (1/I) (Q/N)dt

,.y Pcl Pct Pc3 Pc4 Ptl Pt2 Pt3 Pt4N

I ' Y1m

Fig.2(d) Rotor Module

ules. For gas path components, i.e., (1) to (9), the variableson the left side of each block are variables to and from theupper stream component, and the variables on the right sideare to and from the down stream component. Also the vari-ables on the top of each block are to and from rotor dynam-ics and the variables on the bottom are control variables andconstants specific to the component. It should be noted thatthere is a uniformity in input and output variables throughoutthe static modules, (1) to (7), and that the dynamic modules,(9) and (10), can be easily connected to the static modules.'Note that each computational module assumes the maximumpossible number of input variables to allow for the maximumcapability of the module. If some of these inputs do not existor are not necessary to consider, they should be set to zeroor to a constant value. This structure of the computationalmodules can permit a wide variety of interconnection of themodules and, hence, can be applied to various types of engines.

Argument data required to perform necessary computa-tions in a module consists of (i) input variables, (ii) constants,and (iii) data tables for multivariable function generation.Computational results from a module include not only enginevariables which are used for input variables to other compu-tational modules, but also variables which are useful for mon-itoring and recording of simulation results (ref. Fig.2). Ac-cording to the mathematical models and the computationalprocedures, each component of (1) to (10) is coded in theADSIM language in the form of a computational module, orsubroutine.

Execution TimeFig.4 shows the execution time for each computational

module, measured by running the program on the AD100. Fora. specific gas turbine engine simulation, the main program is

'Although the inlet module, (8), is static, it is connected to the staticmodules exceptionally.

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PP N

Pi'J(1) 4P0

Xs COMP rX0xi xo

h,a,

rPi-(2 ) ^PoY

TURBx^ X"

ho

(Q, Wei) a t

Pi - (3) - Po ' (4) F',1, Puz; 1 ,,3Ti Ti

xt DUCT xo xi i5I,i:'F,l; x.

a o

W W W1, W2, W3 W1, W2,{'1'3h h,

(R

P = 0.4769 5.5319 5.3387 1.3415 0.8867 0.8646 0.1052 0.1013 0.1003 0.4867 MPaT = 77.6 459.5 1300.0 836.8 735.0 1171.0 609.4 15.0 15.0 198.7 C

AirHP Main HP

IP Reheat LP Exhaust Intake LP LoadComp. Comb. Turb. Turb. Comb. Turb. Duct Duct Comp. 122MW

8850 pm 3000rpmcoo-:ng_air

---"---- G = 233kg/s G = 220kg/sW fL = 4.38kg/s Wf,. = 2.95kg/s

Ww i = 10.44kg/s

Inter-Cooler

Fig.6 Configuration of Intcrcooled-Reheat Type Industrial Gas Turbine

time does not exceed the limit needed to maintain the desireddynamic accuracy, it is possible to simulate several engines si-inultaneously. This capability may be useful for the study ofthe multi-engine balancing problem, where the performance ofengines is not identical.

SIMULATION OF INTERCOOLED-REHEAT TYPE INDUSTRIAL GASTURBINETo illustrate the capability of the simulation program, anintercooled-reheat type industrial gas turbine engine is con-sidered here, because it has a very complicated configurationand it makes full use of the capability of the program devel-oped here. Engine component performance data and someoverall performance data for this engine is available.

Engine ConfigurationFig.6 shows the schematical configuration and heat balance

of intercooled-reheat type industrial gas turbine (Takeya andOhteki, 1983 and 1984). HP compressor and HP turbine areon one shaft, while LP compressor and IP/LP turbines are onthe other shaft driving 120MW class electric power generator.LP compressor is a 10-stage axial compressor with variablestator vane to control air flow rate. Intercooler is a waterinjection type cooler to cool down the air from the LP com-pressor outlet. This contributes to reduce the HP compressordriving power and NOx level in exhaust gas. HP compressoris a 14-stage axial compressor with variable inlet guide vane.For turbine cooling, rotor balancing and starting bleed, airbleed ports are located at 6th, 8th, 11th and 14th stage of HPcompressor. The main combustor is a cannular type combus-tor burning LNG. Gas condition at combustor outlet reaches1573K (1300C) and 5.5Mpa at the 120MW rated load. TheHP and IP turbines are 2-stage axial turbines with air cooledblades. The reheat combustor is a cannular type and reheatsthe gas to 1473K (1200C). This contributes to increasing thepower output of the 4-stage axial LP turbine. The reheat

and intercooling processes are very effective in increasing thethermal efficiency of the engine. The gas temperature at theexhaust duct is 882K (609C), which is relatively high consid-ering a bottoming cycle. The thermal efficiency of the gasturbine obtained by experiments is 34% at 93MW load. Thethermal efficiency of a combined cycle with a steam turbine asa bottomig cycle is estimated at more than 50%.

ModelingSince the LP and HP compressors can be modeled by the

compressor module, the HP, IP and LP turbines by the turbinemodule, the main- and reheat-combustors by the combustormodule, intercomponent volumes by the volume module, etc.,the schematic configuration in Fig.6 can be diagrammed asshown in Fig.7. This is accomplished by simply replacing theengine components with the computational modules and in-troducing the volume module between the static engine com-ponents. Note that the HP compressor is divided into fourcompressors in order to take into account the interstage airbleed effect. There exists eight major control variables, con-stituting a multi-variable control system. The total number ofusages of each module, summarized in Fig.7, is almost twiceas many as the jet engine case in Fig.5.

Referring to Fig.7, the simulation program is easily ob-tained by just calling computational modules sequentially fromengine entrance to exhaust. To avoid complication of symbolsfor a large number of variables, self-evident and systematic as-signment of symbols is desirable. For example, the symbols areconstructed from the letter(s) indicating some physical mean-ing and the number(s) defining engine station numbers or en-gine components.

Component Performance Data and Gas TablesNext, the function data for component performance map

must be set up. ADSIM accepts a rectangular grid data ta-ble form for function generation. Usually, component per-formance data are given in this form and, hence, the codingis straightforward. The radial interpolation method (Szuch,1974a), or skewed grid interpolation method, is widely usedfor function generation of compressor performance to improve

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HP Compressor Main Combustor Reheat Combustor LP CompressorStator Angle Fuel Flow Fuel Flow Stator Angle

Bleed Valve-1 Area Bleed Valve-2 Area Intercooler

O : Control Variables Water Flow

Computational Module No. of UsageC : Compressor 5T : Turbine 3B Combustor 2D :Duct 3I : Intercooler 1

BL : Bleed 5R :Rotor 2V Volume 13L :Load 1

Estimated frame time = 1.1906 msec

Fig.7 Block Diagram of Intercooled-Reheat Type Industrial Gas Turbine Simulation

accuracy with a small number of data points and to avoidthe difficulty of interpolation in the neighborhood of a surgeline, beyond which function values are not defined. However,this method is not attractive using the AD100, where large,low-cost and high speed memories are available, because moreefficient interpolation methods are possible with such a largedata memory. Thus, to fully exploit the speed advantage ofthe AD100, function values must be defined at a large num-ber of arbitrarily spaced grid data points. The data memoryrequirements are still reasonable and well within the AD100capability.

Engine component performance data is changed frequentlyas more realistic data becomes available. Usually the initialcomponent performance data is obtained from design studiesin the early phase of an engine development program. This isfollowed by several data iterations based on experimental datain the later phase. These iterations can be easily done withoutdisturbing the entire simulation.

In addition to component performance data, gas propertydata is also required. This data is available in rectangulargrid data table form, using the gas table generation softwaredeveloped by the author which calculate properties of a gas atan arbitrary temperature, fuel/air ratio, steam/air ratio andH/C ratio of fuel. It is assumed that H/C ratio for LNG fuelis 3.696. Then most gas table data are 3-variable functions.

Function data tables required in this simulation are sum-marized in Fig.8. Since the size of the data tables in Fig.8,or the numbers and ranges of independent variables, influ-ence accuracy of the simulation, they must be chosen care-fully. Roughly speaking, larger numbers of data points resultin higher accuracy. Although static operating ranges are ob-tained easily from steady state analysis, it is not so easy todetermine dynamic operating ranges. It is obvious that, if areference variable for function generation goes out of specified

range, even if only during one calculation frame, the simulationis invalid. Hence, wider operating ranges should be assumedat first for variables whose dynamic operating ranges are notcertain and then, with the observation of simulation results,the ranges should be narrowed to improve simulation accuracy.

Size of the SimulationThe size of this simulation is summarized in Fig.9. The

frame time of this simulation is estimated as 1.1906 [msec] byusing equation (2) as shown in Fig.7. In this engine, com-ponent performance of turbines and parts of compressors arerepresented by two-variable functions, because the variable ge-ometry is not included. After these program modifications, theframe time can be reduced to 1.0538 [msec]. This is two timesfaster than the AD10, the older version of the AD100, and ap-proximately 50 times faster than a VAX8250. The simulationrequires a total of 27 function data sets, i.e., data for 10 three-variable, 15 two-variable and 2 one-variable functions. Thesenumbers are not equal to the number of usages of functiondata, because some function data, such as the properties ofgas, is used several times in one cycle of computation. Totalaccess of function data is 124 times in this example. The to-tal number of function data is around 30,000. Since the datamemory capacity is 2,000,000 words (64-bit) in the functionmemory unit, FMU in Fig.1, this is not very serious. The totalnumber of ADSIM source code lines are approximately 4,200and man-hours for coding is approximately one month.

CONCLUSIONA generalized programming method for real-time digital sim-ulation of gas turbine engines using the AD100 has been de-scribed. The frame time of digital computation is reduced sig-nificantly compared to simulation with conventional general-

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No. of State Variables 28No. of Control Variables 8No. of Algebraic Variables 244No. of Function Data Points 30,000No. of Function Tables

3-variable Functions 102-variable Functions 151-variable Functions 2

No. of Function Calls3-variable Functions 572-variable Functions 411-variable Functions 26

Frame Time [msec] 1.0538Speed Comparison

AD100 1.0AD 10 2.0

VAX8250 single precision 42.0VAX8250 double precision 54.7

ADSIM source code linesdynamic model part 1, 200component map part ,-- 1,900gas table part -

1,100

Fig.9 Size of the Simulation

Name Size CallLP-compressor flow Ff1.(7r1c, Nlc , cat,) 33 x 33 x 4 1LP-compressor efficiency

Felc(7rtc, NNc , cq c ) 33 x 33 x 4 1HP-compressor-1 flow Ffhcl(1nc^l, Nhcl,nhcl) 33 x 33 x 3 1HP-compressor-1 efficiency Fehc1( 7rhcl, Nhcl, nhcl) 33 x 33 x 3 1HP-compressor-2 flow FJhc2(1rhc2iNhc2) 33 x 33 1

n HP-compressor-2 efficiency Fehc2(lrhc2, Nhc2 ) 33 x 33 1HP-compressor-3 flow F1h03(lncC3, Nhc3) 33 x 33 1HP-compressor-3 efficiency Fehc3 ( 7ncc3, N, 3 ) 33 x 33 1HP-compressor-4 flow Ffhc4 (?fhc4 Nh`c4) 33 x 33 1HP-compressor-4 efficiency Fehc4( 7the4, Nhr,4 ) 33 x 33 1HP-turbine flow F1ht(lrht, NNt) 24 x 6 1HP-turbine efficiency Feht ( 7rht, Nht) 24 x 6 1IP-turbine flow Fjit (- it, Nit) 23 x 4 1IP-turbine efficiency Feit (irit, N,') 23 x 4 1

LP-turbine flow Fflt(7rjt,Njt) 26 x 4 1LP-turbine efficiency Feit(zrjt, Nit) 26 x 4 1Enthalpy (Temp.) Ght(T, f, x) 33 x 4 x 4 20Relative press. (Temp.)

Grt(T, f, x) 33 x 4 x 4 8Enthalpy (Relative press.)

Gh, (P,., f, x) 33 x 4 x 4 8Specific heat ratio (Temp.) Gyt (T, f, x) 33 x 4 x 4 5Temp. (Enthalpy) Gth(h, f, x) 33 x 4 x 4 5Temp. (Internal energy)

Gtu (u, f, x) 33 x 4 x 4 7Internal energy (Temp.)

Gut (T, f) 33 x 4 7Gas constant Gr (f, x) 4x4 7Flow function G,,,,l ( -y, 7r) 65 x 9 15

Enthalpy of water Ghtw (T.) 5 1

Saturated press. G(T) 4 4 25

Fig.8 Function Data Summary

purpose digital computers. Even allowing for the detailedmodel and the flexible programming method, the simula-tion can be accomplished at real-time or faster-than-real-timespeeds. For a intercooled-reheat type industrial gas turbine,the frame time time is 1.0538 [msec] and the engine dynamicsare considered to be valid for frequencies up to 30 [Hz]. Theprogram is highly flexible. Specifically, it can simulate a widevariety of gas turbines, including future engines characterizedby numerous variable geometry features.

BIBLIOGRAPHY`AD100 Hardware Reference Manual" and "ADSIM Ref-

e' ence Manual", Applied Dynamics International, Ann Arbor,Michigan, 1988.

Fishbach, L. H. and Caddy, M. J., "NNEP - TheNavy/NASA Engine Program", NASA TM X-71857, 1975.

Fishbach, L. H. and Gordon, S., "NNEPEQ - ChemicalEquilibrium Version of the Navy/NASA Engine Program",NASA TM 100851, 1988.

Gilbert, E. G., "Dynamic Error Analysis of Digital andCombined Analog-Digital Computer Systems", Simulation,Vol.6, No.4, pp 241-257, 1966.

Gilbert, E. O. and Howe, R. M., "An Expanded Role forFunction Generation in Dynamic System Simulation", Proc.1977 Summer Computer Simulation Conference, Chicago, July

18-20, pp 305-308, 1977.Gilbert, E. O. and Howe, R. M., "Design Consideration in

a Multi-processor Computer for Continuous System Simula-tion", AFIPS, National Computer Conference, 1978.

Palmer, J. R. and Yan Cheng-Zhong, "TURBOTRANS A Programming Language for the Performance Simulation ofArbitrary Gas Turbine Engines with Arbitrary Control Sys-tems", ASME 82-GT-200, 1982.

Sellers, J. F. and Daniele, C. J., "DYNGEN A Programfor Calculating Steady-State and Transient Performance ofTurbojet and Turbofan Engines", NASA TN D-7901, 1975.

Szuch, J. R., "HYDES A Generalized Hybrid ComputerProgram for Studying Turbojet or Turbofan Engine Dynam-ics", NASA TM X-3014, 1974.

Szuch, J. R. and Bruton, W. M., "Real-Time Simulationof the TF30-P-3 Turbofan Engine Using a Hybrid Computer",NASA TM X-3106, 1974.

Szuch, J. R. and Seldner, K., "Real-Time Simulation ofF100-PW-100 Turbofan Engine Using The Hybrid Computer",NASA TM X-3261, 1975.

Takeya, K and Ohteki, Y., "Technical Problems on Ad-vanced Reheat Gas Turbines Under the Moonlight Project",1983 Tokyo International Gas Turbine Congress, 83-TOKYO-IGTC-117, 1983.

Takeya, K, Ohteki, Y. and Yasui, H, "Current Status ofAdvanced Reheat Gas Turbines AGTJ-100A, (Part-3) Exper-imental Results of Shop Tests", ASME paper 84-GT-57, 1984.

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