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

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

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

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

Conjugate flow and heat transfer network at a cooling slot exit

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

Metal temperature results

Comparison to test data

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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