1. Combustor modeling Webinar
GE Energy Efficient Engine
1/25/2016

2. Intro
Preliminary combustor design requires that an extensive number of geometrical and operational conditions be evaluated and compared
Coupling conjugate flow and heat transfer network with a combustion model enables the integrated solution of critical parameters
Mass flow rate distribution through air admission holes
Associated pressure drops
Liner wall temperatures
Flownex results were benchmarked against published test data from NASA funded the Energy Efficient Engine program
Preliminary design phase or when considering modifications to existing designs it’s essential to make realistic predictions of
Mass flow splits through the various air admission holes
Total pressure losses
Liner temperatures along the length of the combustor
Although powerful, CFD solutions of combustors are specialized, time consuming processes and therefore seldom used during initial sizing of a combustor
Network tools allow are capable of predicting, with reasonable accuracy, the same trends as more detailed numerical models.
Fast, accurate initial designs mean less time is spent on advanced 3D simulations and rig tests, thus reducing development time and cost

3. Empirical HT correlations
Radiation between participating gasses and an enclosed surface
Film effectiveness
Prediction of liner wall temperatures by conducting heat balance along liner wall
Typically inner wall is heated by convection & radiation from the hot combustion gases & cooled on the outside by the annulus air flow through convection and radiation from the outer liner surface to the casing wall
Specialized cooling mechanisms can also be employed in components
Convection
Film & jet impingement cooling
Fluid & surface to surface radiation
Conduction
Custom Correlations!!!
Forced convection
Radial and axial conduction

4. Combustion modeling
The combustion process has to be accounted for when a 1D analysis is conducted
Gas temperature effects fluid density, and therefore the flow distributions and pressure loss
Accurate gas temperature profile required for wall temperature predictions
NASA CEA program incorporated into networks allows prediction of adiabatic flame temperature as a function of local air/fuel ratio and the chemical equilibrium product concentrations from reactants

5. Conjugate flow and heat transfer network at a cooling slot exit

6. Combustor Exit Mass Flow [pps] Pilot/Total Fuel Mass Flow
Benchmark test cases
Operating conditions used as boundary condition in the network model were easy to parameterize in Flownex
Test Point
Inlet Pressure [psi]
Inlet Temperature [K]
Combustor Exit Mass Flow [pps]
Overall Fuel Air Ratio
Pilot/Total Fuel Mass Flow 1
174.9
637
57.1
0.0171
0.50 2
240.04
700
66.25
0.0173
0.40 3
745
68.65
0.0208
0.41 4
240.7
781
68.33
0.0229
0.35 5
241.3
788
67.78
0.0233 6
241.5
814
67.48
0.0246
Air flow distribution with 5.5% overall combustor pressure drop achieve with Flownex designer tool

7. Metal temperature results

8. Comparison to test data

9. Flownex Demo Model Why Flownex?
Commercial 1D thermal fluid network tool that employs the conservation of governing equations
Mass
Momentum
Energy
User friendly GUI
Integrated CEA program calculates chemical equilibrium product concentrations from any set of reactants – ideal combustion model
Library that employs industry standard correlations for gas turbine heat transfer
Scripting capabilities make tool flexible and user definable
Solve time
Simple Sensitivity analysis setup
Easy to link to 3rd party FEA, CFD or post processing software

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