1. 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, 2014-2015 - Identify what is needed. - Identify action.

2. 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, peterson@csi.tu-darmstadt.depeterson@csi.tu-darmstadt.de IFP Energie Nouvelles; Cecile Pera, cecile.pera@ifpen.frcecile.pera@ifpen.fr Penn. State Univ; Dan Haworth, dch12@engr.psu.edudch12@engr.psu.edu Univ. Michigan; David Reuss, dreuss@umich.edu, Volker Sick, vsick@umich.edudreuss@umich.eduvsick@umich.edu Politecnico di Milano; Tommaso Lucchini, tommaso.lucchini@polimi.ittommaso.lucchini@polimi.it Univ. Duisburg-Essen; Sebastian Kaiser, sebastian.kaiser@uni-due.desebastian.kaiser@uni-due.de General Motors R&D; Xiaofeng Yang, xiaofeng.yang@gm.com,xiaofeng.yang@gm.com Tang-Wei Kuo, tang-wei.kuo@gm.comtang-wei.kuo@gm.com

3. Topic 4: Engine, Flow, & Combustion 3 April 5, 2014 4.3.1.Global engine operating conditions 4.3.2.In-cylinder flow characterization 4.3.3.Simulated to measured combustion modeling validation 4.3. Benchmarking: comparisons, analysis, and validation ECN 3.X 2014-2015 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)

4. Topic 4: Engine, Flow, & Combustion 4 April 5, 2014 4.3.1. Global Engine Metrics

5. Topic 4: Engine, Flow, & Combustion 5 April 5, 2014 4.3.1.Global engine operating conditions 4.3.1.1.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

6. Topic 4: Engine, Flow, & Combustion 6 April 5, 2014 4.3.1.Global engine operating conditions 4.3.1.1.In-cylinder 0-D & Global Metrics ECN 3.X Topic option: - Identify useful volume- & plane-averaged metrics. - Quantify flow metrics & values for simulation effectiveness. KE @ Field of View TCC Milano

7. Topic 4: Engine, Flow, & Combustion 7 April 5, 2014 4.3.1.2.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

8. 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. 4.3.1.Global engine operating conditions 4.3.1.2.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

9. Topic 4: Engine, Flow, & Combustion 9 April 5, 2014 4.3.2. In-cylinder flow characterization

10. 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. 4.3.2. Simulated-to-Measured Flow characterization 4.3.2.1. Statistical Methods SIDI TUD PDF

11. Topic 4: Engine, Flow, & Combustion 11 April 5, 2014 4.3.2. Simulated-to-Measured Flow characterization 4.3.2.1. Statistical Methods 4.3.2.1.1.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

12. Topic 4: Engine, Flow, & Combustion 12 April 5, 2014  Max velocity  Velocity noise 4.3.2. Simulated-to-Measured Flow characterization 4.3.2.1. Statistical Methods 4.3.2.1.2.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 ?

13. Topic 4: Engine, Flow, & Combustion 13 April 5, 2014 4.3.2. Simulated-to-Measured Flow characterization 4.3.2.2.Proper Orthogonal Decomposition,  Snapshots sampled @ 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

14. Topic 4: Engine, Flow, & Combustion 14 April 5, 2014 TCC 4.3.2.2.Proper Orthogonal Decomposition,  Velocity snapshots 1.sampled @ 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

15. Topic 4: Engine, Flow, & Combustion 15 April 5, 2014 4.3.2. 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.

16. Topic 4: Engine, Flow, & Combustion 16 April 5, 2014 4.3.2. Simulated-to-Measured Flow characterization 4.3.2.8. 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

17. Topic 4: Engine, Flow, & Combustion 17 April 5, 2014 4.3.3.Combustion-Modeling validation

18. 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. 4.3.3.Combustion modeling validation 4.3.3.1. Global heat release SGEmac I

19. Topic 4: Engine, Flow, & Combustion 19 April 5, 2014 4.3.2. Combustion modeling validation 4.3.3.2. 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

20. Topic 4: Engine, Flow, & Combustion 20 April 5, 2014 4.3.2. Combustion modeling validation 4.3.3.2. 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%). 0.20 0.15 0.10 0.05 0.00 -5 0 5 10 15 S T (m/s) PDF (S T ) SIDI TUD

21. Topic 4: Engine, Flow, & Combustion 21 April 5, 2014 ECN 3.X Topic option: What is needed? What experiments are possible ? 4.3.2. Combustion modeling validation 4.3.3.2. Fully Developed turbulent flame Turbulent-combustion of late-burned mass  Compressed scales  Dissipation  Near-wall  Poor optical access (esp. SC SIDI with a bowl)