Topic 4: Engine, Flow, & Combustion 1 April 5, 2014 EFC Topic 4.3 Benchmarking: comparisons, analysis, and validation Objectives Topic 4.3 Exposition of methods & metrics being used to assess simulation equivalency & efficacy of measured flow & combustion Define ECN 3.X Topics, Identify what is needed. - Identify action.

Topic 4: Engine, Flow, & Combustion 2 April 5, 2014 EFC Topic 4.3 Benchmarking: comparisons, analysis, and validation Presented by Dave Reuss Sources of contributions to EFC: Tech. Univ. Darmstadt; Brian Peterson, IFP Energie Nouvelles; Cecile Pera, Penn. State Univ; Dan Haworth, Univ. Michigan; David Reuss, Volker Sick, Politecnico di Milano; Tommaso Lucchini, Univ. Duisburg-Essen; Sebastian Kaiser, General Motors R&D; Xiaofeng Yang, Tang-Wei Kuo,

Topic 4: Engine, Flow, & Combustion 3 April 5, Global engine operating conditions In-cylinder flow characterization Simulated to measured combustion modeling validation 4.3. Benchmarking: comparisons, analysis, and validation ECN 3.X Efforts: Interdependency requires parallel efforts. Rational flow CCV metrics require knowledge of what flow parameters best correlate with fuel-mixing and combustion CCV Ultimately, all detailed (small time and space scale) simulation quantities must predict volume-average/global measure (work and engine-out emissions)

Topic 4: Engine, Flow, & Combustion 4 April 5, Global Engine Metrics

Topic 4: Engine, Flow, & Combustion 5 April 5, Global engine operating conditions In-cylinder 0-D & Global Metrics TCC-III P_cyl Pegging ECN 3.X Topic option: Document precision & accuracy for mechanical & pressure test-to-test & CCV. Location Peak Pressure

Topic 4: Engine, Flow, & Combustion 6 April 5, Global engine operating conditions In-cylinder 0-D & Global Metrics ECN 3.X Topic option: - Identify useful volume- & plane-averaged metrics. - Quantify flow metrics & values for simulation effectiveness. Field of View TCC Milano

Topic 4: Engine, Flow, & Combustion 7 April 5, Intake & Exhaust Systems 1-D quantities ECN 3.X Topic options: - Quantify effect of P_Intk_Port CCV on trapped mass & flow. - Quantify simulation noise precision and accuracy. TCC-III P IntakePort Discrepancy, (simulation – measurement) CoV, % Discrepancy, %   Measurement Noise LES CCV

Topic 4: Engine, Flow, & Combustion 8 April 5, 2014 ECN 3.X Topic options: - Quantify impact of intake-port 1-D pressure & 3-D velocity on in-cylinder CCV Global engine operating conditions Intake & Exhaust Systems 1-D quantities INTAKE Intake pipe velocity [m/s] SGEmac -200 CAD LES: 25 cycles PIV: 200 cycles Trapped Mass Mean P intake

Topic 4: Engine, Flow, & Combustion 9 April 5, In-cylinder flow characterization

Topic 4: Engine, Flow, & Combustion 10 April 5, 2014 SGEmac ECN 3.X Topic option: Identify methods and metrics to quantitatively assess equivalency of simulated & measured velocity and momentum dissipation Simulated-to-Measured Flow characterization Statistical Methods SIDI TUD PDF

Topic 4: Engine, Flow, & Combustion 11 April 5, Simulated-to-Measured Flow characterization Statistical Methods phase-average and standard deviation SIDI TUD Measured Ens. Ave LES Ens. Ave. Ens,. Std. Dev. Ensemble Average & Standard Deviation (CCV) of PIV & LES velocity are equivalent metrics. ECN 3.X Topic option: Identify rational measurements to characterize RANS “turbulence” TCC, RANS

Topic 4: Engine, Flow, & Combustion 12 April 5, 2014  Max velocity  Velocity noise Simulated-to-Measured Flow characterization Statistical Methods CCV vs. turbulence vs. noise ECN 3.X Topic option: - Standards exist to quantify measurement noise. - How are simulation noise & uncertainty quantified? PIV dynamic range PIV interrogation % first choices PIV interrogation quality Crankangle Simulation Noise ?

Topic 4: Engine, Flow, & Combustion 13 April 5, Simulated-to-Measured Flow characterization Proper Orthogonal Decomposition,  Snapshots one CA, all cycles  POD creates multi-dimensional “empirical” basis functions.  Modes created based on flow -high KE (V 2, or I 2 ) -and/or repeatable. Phase-dependent POD Mode 1 mid intake stroke - Eigen values capture KE. - Can be used for CCV of Modes cycle # KE, m 2 /s 2 TCC- I

Topic 4: Engine, Flow, & Combustion 14 April 5, 2014 TCC Proper Orthogonal Decomposition,  Velocity snapshots all CA, all cycles 2.mapped to single grid 3.normalized to KE of individual snapshot  POD creates single set of modes applicable to all CA, all cycles.  Normalized KE creates modes based on normalized velocity and intra-cycle persistence (cycle similarity) Phase-invariant POD Eigenvalue captures intra-cycle variability  flow similarity  CCV crank angle Coefficients Mode 2 Mode 1

Topic 4: Engine, Flow, & Combustion 15 April 5, Simulated-to-Measured Flow characterization ECN 3.X Topic option: POD is not universally or extensively used as a metric. Identify acceptable methods and standards of POD application. Combine Measured & LES snapshots + Phase-invariant POD  single set of POD Modes. crank angle Coefficients LES PIV Coefficients provide metric for direct comparison of measured vs simulated Intra-cycle and Inter-cycle equivalence.

Topic 4: Engine, Flow, & Combustion 16 April 5, Simulated-to-Measured Flow characterization Simulation efficacy of scalar mixing. ECN 3.X Topic option: Efficacy of simulations on one- & two-phase mixing, especially sub-grid. End of hydrogen injection ExperimentSimulation H2 mole fraction H 2 ICE

Topic 4: Engine, Flow, & Combustion 17 April 5, Combustion-Modeling validation

Topic 4: Engine, Flow, & Combustion 18 April 5, 2014 ECN 3.X Topic option: -Create defined methods for computing work (IMEP) and Apparent Heat Release, AHR. -Establish standard of accepted equivalence between measured and simulated AHR Combustion modeling validation Global heat release SGEmac I

Topic 4: Engine, Flow, & Combustion 19 April 5, Combustion modeling validation Ignition and early flame development.  PDF of burned gas 3-D projection OH PLIF, probability of flame Chemiluminescence, Single cycle SGEmac Single-cycle Mie-scattering PDF of burn-gas SIDI TUD  PDF of burned gas 2-D plane

Topic 4: Engine, Flow, & Combustion 20 April 5, Combustion modeling validation Ignition and early flame development. ECN 3.X Topic option: Identify optical metrics applicable to both measured & simulated data to define equivalency during early burning ( burned mass fraction <  20%) S T (m/s) PDF (S T ) SIDI TUD

Topic 4: Engine, Flow, & Combustion 21 April 5, 2014 ECN 3.X Topic option: What is needed? What experiments are possible ? Combustion modeling validation Fully Developed turbulent flame Turbulent-combustion of late-burned mass  Compressed scales  Dissipation  Near-wall  Poor optical access (esp. SC SIDI with a bowl)