lecture_2011_10_20 - MSU ME444 Diesel Engine Combustion...

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Andrew Huisjen ME 444 Fall 2011 The Use of CAE Methods in the  Design of Engine Intake and Exhaust  Systems Adapted from a lecture previously given by James Novak, formerly of Ford Motor Company
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CAE Tools Overview n CAE: Computer Aided Engineering n Types: q CAD—3D solid modeling q FEA—structural/thermal analysis q CFD—3D fluid modeling n Flow losses in ducting n Port and in-cylinder flow q Engine cycle simulation q Rapid Prototyping
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CAE Tools Overview n Engine Cycle Simulation q PC based—simple analytical approach q 1D wave/thermodynamics approach—models intake and exhaust gasdynamics in a multi- cylinder engine q Thermodynamic “zero-dimensional” cylinder modeling approach—models combustion, emissions, fuel economy q For more detail or precision, linking with CAD, CFD, chemical kinetics, etc. is also possible
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1D Engine Modeling n Software: MANDY, WAVE, GT-POWER q All use essentially same fundamental principles q They model unsteady, compressible, “quasi-3D” gas flow through the intake and exhaust systems of multi-cylinder engines q Submodels: n In-cylinder combustion and heat transfer n Valve lift and port flow n Duct heat transfer and wall friction n Thermodynamic fluid properties n Flow losses: duct junctions, bends, area contractions and expansions, etc.
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GT-POWER models Simple 1-cylinder model Intake ducts Cylinder and crank train Exhaust ducts Exhaust valve Intake valve Fuel Injector
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GT-POWER models 16 valve Port Fuel Injection Throttle Plate Intake System Exhaust System Chrysler 2.4L I4 GT-POWER Model
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Modeling Parameters q Duct Geometry: n Intake and exhaust ports and manifolds n Secondary ducting—throttle body, MAF sensor, balance tubes, silencers, mufflers, etc. n Duct connectivity junctions q Valve lift profiles and phasing, and flow and pressure drop vs. lift q Engine specs: bore, stroke, compression ratio, valve sizes, etc. q Operating conditions: RPM, intake pressure and temperature, A/F ratio, combustion duration, etc.
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Simulation Methods n “Quasi-3D” form of Navier-Stokes Equations is applied from valve seats to atmosphere in all intake and exhaust passages n Equations are solved numerically with an explicit second-order finite-difference method
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Simulation Results n Results calculated from simulation come in two types: q Engine cycle resolved n Volumetric efficiency n Indicated torque, power, MEPs n Average temperatures; manifold and back pressures q Time resolved (CAD based) n Pressure, temperature, flow rates at any duct location n In-cylinder pressure, temperature, mass n SPL at tailpipe, inlet, or duct locations
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ENGINE SPEED VOLUMETRIC EFFICIENCY (%)
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lecture_2011_10_20 - MSU ME444 Diesel Engine Combustion...

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