Indian Journal of Engineering & Materials Sciences Vol. 12, October 2005, pp. 389-397 Flow analysis in a model can-type gas turbine combustor Abhishek Jain', Sidharth Chaudhary", S N Singh'" & Lajpat Rai" "Department of Mechanical Engineering, bDepartment of Applied Mechanics Indian Institute of Technology, New Delhi 110 016, India Received J 3 August 2004; accepted J 5 July 2005 Flow analysis has been carried out in a model can-type gas turbine combustor using a commercial computational fluid dynamics (CFD) code. The code has been validated against the experimental results quoted in the literature and part of the present study. The comparison has shown that CFD code can be effectively used to carry out parametric investigations on the complete combustor model for the combustor design. IPC Code: F15D The gas turbine engine is a very complex device. Its high power to weight ratio has made it the propulsion system of choice for aircraft applications. A gas turbine engine is also used extensively in the oil, gas, power and process industries. The three major areas of use of gas turbine combustors are civil aviation, military aviation and mechanical power applications. The performance of the gas turbine is expressed in various general parameters. One of the important parameter is the outlet temperature distribution that is tailored to maximize the life of the turbine blades and nozzle guide vanes'. From the point of view of flow analysis, uniform flow should also be ensured at the outlet of the combustor to maximize the life of the turbine blades. For achieving these objectives, the flow in the annulus is crucial as it feeds air to the liner at various stages. Improved aerodynamics of gas turbine combustors has also become important in view of the emission control. Gas turbine combustor design has historically depended on the use of empirical correlations and trial and error approaches. Experimental measurements of flow properties in real combustor geometries have been very limited. This is due to the highly hostile environment and the difficulties of accessing the flow field with diagnostic probes. Computational fluid dynamics (CFD) is showing great potential as a design tool for combusting systems as it can be used to simulate the combustor geometry and flow field. The numerical solution can provide detailed information of all flow properties being modeled across the entire flow field, *For correspondence (E-mail: [email protected]) whereas experimental measurements can only provide flow properties in the region where measurements are possible. Hence, today validated CFD codes can become the prime tool for combustor design. The studies for combustor flow modeling in general have been in the liner. Researchers using coaxial jets have carried out numerical predictions for swirl flows for confined co-axial jets having axi-symmetric geometries. Novice et aZ. 2 used standard k-c model to predict flow with re-circulation zones. Jones and McGuirk 3 have used standard k-e model to calculate the dissipation of Reynolds stresses for the problem of a round turbulent jet discharging into a confined cross flow and found only fair agreement in 3-D model. Habib and Whitelaw 4 and Correa' have found that standard k-e model predicts flow well for non- swirling flows as compared to swirling flows. Singh et aZ. 6 have also used k-e turbulence model to predict flow in dump confinement for contra swirling jets in co-axial mode. Kautmos and McGuire have done prediction in a sector of an annular combustor using standard k-t: model in realistic geometries and found reasonable agreement with measurements. Rizk and Mongia" have simulated turbulence and combustion by two-step chemical reaction. Karki et aZ. 9 have also carried out significant work in 3-D model combustor geometries. Lee et aZ. ID have compared the predictions by standard k-t: model with RSM turbulence models and found not much difference in predictions between the two models. Predictions have also been done for studies in simplified liner geometries with transverse jets. McGuirk and Palma 11 and Zhou 12 have also predicted mixing parameters at the outlet of an
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Indian Journal of Engineering & Materials SciencesVol. 12, October 2005, pp. 389-397
Flow analysis in a model can-type gas turbine combustor
Abhishek Jain', Sidharth Chaudhary", S N Singh'" & Lajpat Rai""Department of Mechanical Engineering, bDepartment of Applied Mechanics
Indian Institute of Technology, New Delhi 110 016, India
Received J3August 2004; accepted J5 July 2005
Flow analysis has been carried out in a model can-type gas turbine combustor using a commercial computational fluiddynamics (CFD) code. The code has been validated against the experimental results quoted in the literature and part of thepresent study. The comparison has shown that CFD code can be effectively used to carry out parametric investigations onthe complete combustor model for the combustor design.
IPC Code: F15D
The gas turbine engine is a very complex device. Itshigh power to weight ratio has made it the propulsionsystem of choice for aircraft applications. A gasturbine engine is also used extensively in the oil, gas,power and process industries. The three major areasof use of gas turbine combustors are civil aviation,military aviation and mechanical power applications.The performance of the gas turbine is expressed invarious general parameters. One of the importantparameter is the outlet temperature distribution that istailored to maximize the life of the turbine blades andnozzle guide vanes'. From the point of view of flowanalysis, uniform flow should also be ensured at theoutlet of the combustor to maximize the life of theturbine blades. For achieving these objectives, theflow in the annulus is crucial as it feeds air to the linerat various stages. Improved aerodynamics of gasturbine combustors has also become important inview of the emission control. Gas turbine combustordesign has historically depended on the use ofempirical correlations and trial and error approaches.Experimental measurements of flow properties in realcombustor geometries have been very limited. This isdue to the highly hostile environment and thedifficulties of accessing the flow field with diagnosticprobes. Computational fluid dynamics (CFD) isshowing great potential as a design tool forcombusting systems as it can be used to simulate thecombustor geometry and flow field. The numericalsolution can provide detailed information of all flowproperties being modeled across the entire flow field,
whereas experimental measurements can only provideflow properties in the region where measurements arepossible. Hence, today validated CFD codes canbecome the prime tool for combustor design.
The studies for combustor flow modeling in generalhave been in the liner. Researchers using coaxial jetshave carried out numerical predictions for swirl flowsfor confined co-axial jets having axi-symmetricgeometries. Novice et aZ.2 used standard k-c model topredict flow with re-circulation zones. Jones andMcGuirk3 have used standard k-e model to calculatethe dissipation of Reynolds stresses for the problem ofa round turbulent jet discharging into a confined crossflow and found only fair agreement in 3-D model.Habib and Whitelaw4 and Correa' have found thatstandard k-e model predicts flow well for non-swirling flows as compared to swirling flows. Singhet aZ.6 have also used k-e turbulence model to predictflow in dump confinement for contra swirling jets inco-axial mode. Kautmos and McGuire have doneprediction in a sector of an annular combustor usingstandard k-t: model in realistic geometries and foundreasonable agreement with measurements. Rizk andMongia" have simulated turbulence and combustionby two-step chemical reaction. Karki et aZ.9 have alsocarried out significant work in 3-D model combustorgeometries. Lee et aZ.ID have compared the predictionsby standard k-t: model with RSM turbulence modelsand found not much difference in predictions betweenthe two models. Predictions have also been done forstudies in simplified liner geometries with transversejets. McGuirk and Palma 11 and Zhou 12 have alsopredicted mixing parameters at the outlet of an
390 INDIAN J. ENG. MATER. SCI., OCTOBER 2005
annular combustor. Mohan et al" used standard k-s:model using finite volume discretization technique topredict flow in the annulus zone of a reverse flowcombustor model and calculated the flow splitsthrough different liner holes. They found reasonableagreement between measured and computed flowsplits for low dump-gaps whereas, for higher dumpgaps, significant deviations were seen. Analysis ofannulus flow has not been reported for straightthrough combustors, except for few diffuser studies,which report flow around straight-through liner domehead. Bharani 14 has experimentally investigated thevelocity distribution in the annuli of a plane reverse-flow combustor model. He has shown that percentageof flow-split through the outer liner surface holes,compared to that through liner dome and inner linersurface holes, is not affected significantly by increasein the inlet flow velocity. From the above discussion,it is clear that a number of numerical studies havebeen carried out in simplified and realistic linermodels by researchers all over the world but there ishardly any study, which focuses on the annulus flow.The flow pattern in the annulus has a substantialeffect on the liner flow pattern and influences thelevel and distribution of liner wall temperature. Theobjective of present analysis is to validate thecommercial CFD code 'FLUENT' againstexperimental data both in the annulus region and inthe liner and then analyse the flow inside the liner forthe can-type combustor
Experimental ProcedureThe experimental set up (Fig. la) used consists of
an air supply unit, a rectangular diffuser, a settlingchamber, a straight annular duct and the combustormodel. A single stage centrifugal blower capable ofdelivering 0.6 m3/s of air at a pressure of 0.57 m ofwater column supplies air to the set up. The blower iscoupled to a 3.7 kW dynodrive motor having a speedrange 240-2700 rpm. The air flow from the blower
750 100 600 1380 -500CcenbustormodelSc r eeo s
Fig. la- Schematic layout of the Experimental set-up
was controlled either by vanation of speed and/orthrottling the inlet to the blower. The rectangulardiffuser is connected to the blower outlet (0.11 m x0.145 m) by means of a flexible joint. Thisarrangement eliminated the transmission of blowervibrations to the test set up. The flow from therectangular diffuser was fed to a settling chamberhaving dimensions of 0.30 m x 0.345 m x 0.65 m.The settling chamber is fitted with honeycomb anddifferent screens to render uniform flow with reducedturbulence level, to the combustor model via a straightannular duct of length 0.5 m and diameter 54 mm.The outer casing of the combustor model was of152.4 mm diameter and 450 mm in length. The exitend of the casing is closed.
Inside the casing, a liner with 76.2 mm diameter(Fig. Ib) was placed symmetrically (axis of the linercoinciding with the axis of the casing). The liner ismade of aluminium. The hemispherical dome of theliner is made of wood. The tip of the liner dome wasplaced at a distance of 38.1 mm from the casingentrance, resulting in a dump gap ratio of 0.5. On thesurface of the liner, two rows of holes, namely theprimary holes and the dilution holes are provided. Thedesign of the holes was taken from Palma andMcGuirkl6
. There are 6 primary and 6 dilution holesof 10 mm and 20 mm diameter holes respectively.The primary holes are made 60 mm away from thedump inlet and dilution holes 80 mm furtherdownstream of the primary holes. There is an angulardifference of 30° between the primary and dilutionholes. An annular straight passage of inner diameter15 mm and outer diameter of 26 mm is cut on theliner dome tip. The liner is placed symmetrically inthe casing by three strips of plastic placed at 120°apart in the tangential direction between the liner andouter casing just beyond the hemispherical dome.
The flow enters from the straight annular duct tothe combustor model. Reynolds number (Reo) at inletis fixed as 1.17 x 105
JAIN et al: FLOW ANALYSIS IN A MODEL CAN-TYPE GAS TURBINE COMBUSTOR
symmetrically. As the annular exit of the combustormodel is blocked, the flow from the annulus passageenters the liner through the holes on the liner surface.
The objective of the present experimental study isto map the fluid flow in the annular region of thecombustor model and evaluate the mass flow splitsfor steady state conditions. The second objective wasto measure the flow at the exit of the liner. Thesemeasurements have been done by traversing the three-hole probe radially at pre-selected axial locations ofthe test section. The pressure probe is traversed fromthe liner wall to the casing wall in the annuluspassage. The readings have been taken at 4 mm stepsby giving ample time for every reading to getstabilized. The probe measurements have been takenusing the null technique. The total pressure has alsobeen noted at every measuring point. The axiallocations chosen for velocity measurement are 76.2mm and 137.5 mm from the dump inlet in the annulusregion and at the outlet of the liner.
Mathematical FormulationA commercial code 'FLUENT,15 which provides
comprehensive modeling capabilities for a wide rangeof incompressible/compressible flows have been usedin the present study. The numerical scheme employedbelongs to the finite volume group. The solutiondomain is subdivided into a finite number ofcontiguous control volumes and conservationequations are applied to each control volume. Surfaceand volume integrals are approximated using suitablequadrature formula. The mathematical formulationadopted is described briefly.
The equations for conservation of mass andmomentum in general co-ordinate system for steadyflow are written as
... (1)
... (2)
391
simulate directly in practical engineering calculations.Instead the instantaneous governing equations aretime averaged, ensemble averaged or otherwisemanipulated to remove the small scales resulting inmodified equations as
... (3)
... (4)
Turbulent flows are characterized by fluctuatingvelocity fluids. These fluctuations which are of smallscale and high frequency cause the transportedquantities such as momentum and energy also tofluctuate. These are computationally expensive to
These equations are of the same general form as theoriginal equations except for some additional terms.The additional terms are the Reynolds stresses andthese need to be modeled for closure solutions. TheRNG k-t. model has been used. The model improvesthe predictions for wall-bounded flows having curvedgeometries 17. The Boussinesq hypothesis is used torelate the Reynolds stresses to the mean velocitygradient as
... (5)
where III is the eddy viscosity, k is the turbulentkinetic energy and 8ij is the Kronecker delta.
Two additional transport equations, one for theturbulent kinetic energy (k) and the second for theturbulence dissipation rate (f) are solved to evaluateIll, which is computed as
where ell is a model constant.The additional equations for k and f for steady
incompressible flow in simplified form are
where Gk is the generation of turbulent kinetic energydue to the mean velocity gradient and is calculated as
... (9)
INDIAN J. ENG. MATER. SCI., OCTOBER 2005392
11.2and S is the mean rate of shear stress tensor defined as •• • • use=1
Iadd1mIbesrap
••... (10) •••0.8
>;2 0.6;j
0.4~dU dU.)where, S. = -_, +--}
I} 2 dXj
dXj
0.2CIE and C2E are constants. Uk and o, are the inverseeffective turbulent Prandtl numbers for k and Erespectively. The effective viscosity is modeled in theRNG theory using scale eliminations procedureresulting in a differential equation for turbulentviscosity as
O+-----+-----r-----r---~~--~~--~o me
Drill
0.2 0.4 0.6 0.8 1.2
Fig. 3-Velocity profile at the inlet of test combustor model
1.2
(p2 ) ~ A
d .JEi1 =1.72 ~dV11 \jv-1+cy
A )1where v=~ and cy =100
J1
---+--- simJlation
0.8
0.6-:53 0.4'
0.2
0
-0.2
1.2 •
0.8
> 0.6;j
3 0.4
0.2
O.
-0.2
1.2
r
0.8
;2. 0.6
:S 0.4
0.2
0
-0.2
• Experi",mtal (Rahim)
... (11)
In the high Reynolds number limit, the aboveequation gives
eu, = pC)1 -;
2 •
(a) Axial velocity at X = 45 mm
... (12)
with C~ = 0.0845, the effective viscosity is calculatedby using the above expression.
The additional source term R in the £ equation is
---+--- sirrulation..• &perirrental Rahim)
... (13) • •J • • .:# t
tlt, • 2 • •• 3
(b) Axial velocity at X = 138 mmwhere 1}=SkIE,1}o=4.38,,8=0.012
Fig. 2a-2-D Axi-symmetric geometry of the model can-typecombustor (flow in annulus)
Measuring Stations
_J H_~w:-_"Ilomoin ----1'"1_ (c) Axial velocity at X = 138 mm
Fig. 4-- Comparison of predicted and experimental results ofaxial velocity profile without liner: [(a) axial velocity at x = 45mm, (b) axial velocity at x = 138 mm, and (c) axial velocity at x=228 mm]
Fig. 2b- 2-D Axi-symmetric geometry of the model can-typecombustor (flow in liner)
JAIN et al: FLOW ANAL YSISIN A MODEL CAN-TYPE GAS TURBINE COMBUSTOR 393
Fig. 5-Comparison of axial veiocity-experimental versus prediction for liner flow without liner holes [(a) at x = 15 mm, (b) at x,:" 45mm, (c) at x = 91 mm, (d) at x = 138 mm, (e) at x = 228 mm, and (f) at x = 320 mm.
The values of constants in the turbulence modelused are the standard values reported in literature [C2e
= 1.42, C1e= 1.68, CI!= 0.0845, Uk = Ue= 0.72].In the RNG k-t: model, R has been used as the
additional term in the e equation and it is known toimprove the accuracy of the solution significantlybesides being more responsive to the effects of therapid strain and streamline curvature.
The pre-processor used for geometry creation andmesh generation for FLUENT solver is GAMBIT. 2-D axi-symmetric geometry has been created tominimize computation time. Fig. 2a shows the
1 • ••••
0.8
> 0.6;2:5 0.4
0.2
2 3
geometry with the liner but no flow entering in theliner and Fig. 2b shows the geometry with flow insidethe liner through liner holes.
A finite-volume based technique has been used tosolve the governing equations of mass and momentumand other turbulence quantities using quadrilateralmesh. The numerical method uses the segregatesolver in which the equations are solved sequentially.
The discretization of the non-linear equations hasbeen done using the first order upwind differencingscheme. The discrete equations are linearized usingthe point implicit (Gauss-Siedel) linear equationsolver. FLUENT uses. the continuity equation as an
equation for pressure. Since, pressure term does notexist in the continuity equation, the SIMPLEalgorithm is employed for introducing pressure intothe continuity equation. It uses a relationship betweenvelocity and pressure correction to enforce massconservation and to obtain the pressure field. Theunder-relaxation factor for all field variables was keptbetween 0.5 and 0.7 with pressure being theexception. For pressure, the under relaxation factorwas of the order of 0.2. The under relaxation factorfor pressure is linked to the under relaxation factor ofvelocities and is approximately equal to (1- underrelaxation factor for velocity). For lower values ofunder relaxation factor for velocity, wide range ofrelaxation factor for pressure can be used withoutaffecting the convergence. If the grid is highly non-orthogonal, reduced values of under relaxation factorfor pressure give faster convergence.
The inlet boundary conditions are given in the formof inlet velocity profile as measured duringexperimentation. Fig. 3 shows the inlet velocityprofile. The outlet boundary condition is given as zeropressure gauge for all computational cases.
·0.2
0.8 -+- SirnJlation
0.2
0.5 1 rtr, 1.5 3
(a) Axial velocity at 121 mm0.7
0.0 -+- SimJlation
0.5 . Experimental (Rahirr9
0.4
~ 0.3..•0.2:;:>
0.1
·0.10.5
-0.2
0.6'
1.5
(b) Axial velocity at 182 mm
• +-- •.0.5
0.4
Validation of CodeThe experimental data for the validation of code in
annulus passage was taken from Rahiml8. The
estimated uncertainties in the measured quantities asgiven by Rahim18 are given in Table 1. Figure 4(a-c)shows the comparison between the experimental andpredicted results at three axial locations across the
~ 0.3 • Experin"ental (Rahim)
:::l
--+- SntJlation
0.2
0.1
o 0.5 rtr, 1
(c) Axial velocity at the outlet1.5
Fig. 6-Comparison of experimental and predicted results forflow inside liner with liner holes.
5.259+01 .
4.4Oe+01
3.5.69+01
2.719+01
1.86e+01
1.01e+0' --'
1.62e+00 35m
-6.86e+0l
-1.53e+0·
-2.38e+0·
-3.23e+O·
Fig. 7-Vector plot of velocity in the combustor
s not[PLEinto
weenass
Thekept
thectorctor
or ofnders ofe ofhoutnon-actor
ormring
ocityzero
JAIN et al: FLOW ANALYSIS IN A MODEL CAN-TYPE GAS TURBINE COMBUSTOR 395
l.90e·O
l.07e+O
2.He+OO
-5.84e. Q
-1.41e+1l1
-2.24e·Ol
-3.07e·Ol
Fig. 8-Vector plot of velocity near the liner dome region (exploded view)
Fig. 9- Vector plot of velocity near the primary holes region (exploded view)
5.21 e+O I
4.38e+O I
3.56e+O I
2. 73e+O 1
-S.84e+OO
-1.4Ie+Ol
-2.24e+ 0 1
-3.07e+Ol
Fig. lO-Vector plot of velocity near the dilution holes region (exploded view)
396 INDIAN J. ENG. MATER. SCJ., OCTOBER 2005
Table 1- Estimated uncertainty in the measured quantities
Quantity Estimated uncertainty, WVelocity less than Velocity above5 rn/s IO rn/s
Veloc:PressureFlow angle
±5t08%± IO to 16 %+0.50
::::;±2%::::;±1%+ 0.50
test-combustor model. It is clearly seen that thepredicted results match with the experimental datareasonably well except in the region of high shear. Inthis zone, the experimental results may also be inerror due to placement of the probe. Therefore, it canbe concluded that CFO code 'FLUENT' with RNG k-£ turbulence model is capable of predicting the flowin the annulus region.
The second validation of FLUENT code was againcarried out against the experimental data of Rahiml8
in the can combustor model. The predicted resultshave been compared with the experimental values at 6axial locations across the combustor model [Fig. 5(a-D]' It is seen that the predicted results match theexperimental results with reasonable accuracy at thefirst 4 axial locations. At the remaining two axiallocations the predicted profile lies below theexperimental profile. This may be due to the flowacceleration close to the exit of the combustor model.
The third validation has been done against theexperimental results of the modified can combustormodel described under the experimental set-up. Theexit of the can combustor model was blocked and theflow only exhausted from the liner. The velocityprofiles measured in the annulus region are used toevaluate the mass flow split through the liner holes.
Parallel to the validation of CFO code, gridindependent check was also carried out for all thecases used for the validation. For the geometrywithout the liner, converged solution was obtained forthree-grid size and it was found that the grid with47,750 mesh element gave good results and there wasnot much improvement in results on refinement of thegrid. Similar study was carried out for another twogeometries to establish the right mesh density as45,250 mesh element for annulus flow and 70,000mesh elements for liner flow. For the present studies,triangular mesh has been used for the liner flow andquadrilateral mesh for the other geometries.
Results and DiscussionExperiments have been carried out in the test-
combustor model by fitting a liner with primary and
,.
Table 2-Comparison of mass flow split
Mass flow split Experimental FLUENT
Dome annulus 12.4% 14.64%Primary holes 21.77% 25.28%Dilution holes 65.83% 60.08%
dilution holes along with dome annular area in it. Theaim was to measure the mass flow splits as the flowenters into the liner through respective holes and tovalidate the FLUENT code based on the experimentaldata. The comparison between predicted velocitiesand experimental values is shown in Fig. 6a-c. Theresults show reasonable matching till the re-circulation zone is reached. Negative velocities in there-circulation zone could not be measured, as thesewere very small. The mass-flow splits calculated fromthe measured and predicted velocity profiles throughthe dump annulus, the primary and dilution holesrespectively are presented as the percentage of inletmass flow rate. Table 2 shows the comparisonbetween the experimental and predicted values.
The values are in % of the inlet flow rate goingthrough the respective holes. It is seen that the CFOcode over predicts the mass flow splits from the domeannulus and primary holes whereas under predicts forthe dilution holes. The over prediction is of the orderof 18% for dome annulus and 16% for primary holeswhereas under prediction for dilution holes is around9%.
Observation of velocity near the liner wall showsthat as the flow is about to enter the primary ordilution holes, there is increase in velocity as a resultof flow acceleration because of the downstream holesaffecting the mass flow splits.
It is known that flow inside the liner is dependentupon type of holes (e.g., plain or plunged), shape ofholes (e.g., circular or rectangular), liner pressuredrop, presence of swirl in the upstream flow, localannulus air velocity and pressure distribution
Fig. 7 depicts the velocity vector in a symmetricalplane in the combustor. From the results, it was clearthat the flow from the pre-diffuser distributes itselfsymmetrical in the annulus region and hence onlyresults are presented on the one side of the symmetricaxis. The flow enters the liner through the dome head.It is also seen that the flow from the annulus entersthrough the primary and dilution holes at an angle lessthan 90° towards the flow direction, the angle beingsmaller for the dilution holes. Observation of the flowin the liner shows the presence of reverse flow zonesat the dome, in between the dome head and the
primalbetweout tluthe vcdilutio
It i:wall,holesregionto theobserireduciregionthe coThe Ilhigh,The tlofswi
JAIN et al: FLOW ANALYSIS IN A MODEL CAN-TYPE GAS TURBINE COMBUSTOR 397
Nomenclatureprimary jet and a relatively large reverse flow zonebetween the primary jet and the dilution jet. To bringout these flow features clearly, the exploded views ofthe velocity vectors near the dome, primary anddilution holes are given in Figs 8-10.
It is seen from theses figures that near the linerwall, there are eddy formations just upstream of theholes resulting in enhanced turbulence near the wallregion and hence better mixing of flow. However, dueto the absence of the swirler, no recirculation zone isobserved near the center of the liner region leading toreduced mixing near the axis compared to the otherregions. This is not desirable in combustor design, asthe combustion should take place near the centerline.The penetration of the jet is also seen to be not veryhigh, so as to enhance mixing at the center region.The best mixing can be achieved by the combinationof swirler at the liner dome and opposing jets.
ConclusionsCFD code 'FLUENT' has been validated against the
experimental results of Rahiml8. After applying all theavailable turbulence models of FLUENT, it wasestablished that the RNG k- £ model gives the bestresults for such flow conditions. The code was furthervalidated for both liner and without liner cases in thetest-combustor model. The maximum deviationobserved was not more than 5%, which shows that theCFD code 'FLUENT' with RNG k- e turbulence modelcanbe used for carrying out parametric investigations inothergeometries for improving the combustor designs.
A liner fabricated based on the design of Palma andMcGuirkl6 to carry out further experimentation forflow inside the liner, shows that about 12% of theinlet mass flow goes through the holes in the linerdome, 22% through the primary holes and restthrough the dilution holes which is seen to be in closeagreement with the liner design conditions.
The predicted values of the mass flow splits werealso found to be close to experimental values. Thepredicted velocity profiles in the annulus region and atthe exit match reasonably well with the experimentalresults. The FLUENT code showed around 15% massflow splits through liner dome holes, 25% through theprimary holes and 60% through the dilution holes. Theresults are in close compliance with those suggested byPalma and McGuirkl6.
Comparison between predicted and measurementsshows that the CFD code can be effectively used to carryout parametric investigations improve the combustordesignwithout restoring to extensive experiments.
= model constants= diameter= external body force term= generation of turbulent kinetic energy due to mean
velocity= turbulent kinetic energy, m2/s2= static pressure= user defined source terms for k and E= mass added to continuous phase= velocity (m/s)= axial position
kPSio S.SmU
X
SymbolsClio Cl.
Oij
eJ-L
J-LejJJ-Ltpaloa.
= inverse effective Prandtl number for k and e= kronecker's delta= turbulent kinetic energy dissipation rate, m2/s3
= molecular viscosity= effective viscosity= turbulent or eddy viscosity= density of fluid= Prandtl number for k and (;
Subscriptsi, j, k, lx, r
= tensorial notations= axial and radial directions for 2D axi-symmetric
problems
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Company, New York), 1983.2 Novice A S, Miles G A & Lilley D G, J Energy, 3(2) (1979),
95-105.3 Jones W P & McGuirk J J, 2ltd Int Symp Turbulent Shear
Flows, Imperial College, London, (1979),233-245.4 Habib M A & Whitelaw J H, J Fluids Eng, 101 (1979) 521-529.5 Correa S M, AlAA J, 22 (11) (1984) 1602-1608.6 Singh S N, Agrawal D P, Malhotra R C & Raghava A K,
AIM J, 25 (1) (1987) 161-163.7 Koutrnos P & McGuirk J J, J Eng Gas Turbine Power, III
(1989) 113-122.8 Rizk N K & Mongia H C, J Propulsion, 7(3) (1991) 445-45l.9 Karki K C, Oechsle V L & Mongia H C, J Eng Gas Turbine
Power, 114 (1992) 1-7. •lO Lee D, Yeh C L, Tsuei Y M & Chou J, J Propulsion Power,
9 (2) (1993) 322-32811 McGuirk J J & Palma J M, AIM J, 30 (4) (1992) 963-972.12 Zhao J X, Computat Fluid Dynamics,S (1995) 231-243.13 Mohan R, Bharani S, Agarwal D P & Singh S N, Proc 24th Nat
Conf Fluid Mech Fluid Power, Howrah, Dec 26-28, 1997.14 Bharani S, Isothermal flow studies in a reverse flow gas
turbine combustor, Ph D Thesis, Dept. of Applied Mechanics,Indian Institute of Technology Delhi, NI'OWDelhi 1997.
15 User Manual, FLUENT Version 6.0 (2000).16 Palma J M & McGuirk J J, J Eng Gas Turbine Power, 115
(1993) 594-602.17 Pope S B, Turbulent Fluid Flows, (Cambridge University
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