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EFC Topic 4.3 Benchmarking : comparisons, analysis, and validation

This document outlines the objectives, methods, and metrics employed in assessing simulation equivalency and efficacy in combustion and flow measurements, specifically in the context of global engine operating conditions and in-cylinder flow characterization. It emphasizes the importance of accurate and precise simulations, correlations with fuel mixing and combustion, and the validation of simulated-to-measured data. Additionally, it discusses parallel efforts and contributions from various universities and research institutions to enhance understanding through collaborative benchmarking in engineering research.

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EFC Topic 4.3 Benchmarking : comparisons, analysis, and validation

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  1. 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. 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.de • IFP EnergieNouvelles; Cecile Pera, cecile.pera@ifpen.fr • Penn. State Univ; Dan Haworth, dch12@engr.psu.edu • Univ. Michigan;David Reuss, dreuss@umich.edu, Volker Sick, vsick@umich.edu • Politecnicodi Milano; TommasoLucchini, tommaso.lucchini@polimi.it • Univ. Duisburg-Essen; Sebastian Kaiser, sebastian.kaiser@uni-due.de • General Motors R&D; Xiaofeng Yang, xiaofeng.yang@gm.com, • Tang-Wei Kuo, tang-wei.kuo@gm.com

  3. 4.3. Benchmarking: comparisons, analysis, and validation 4.3.1. Global engine operating conditions 4.3.2. In-cylinder flow characterization 4.3.3. Simulated to measured combustion modeling validation Ultimately, all detailed (small time and space scale) simulation quantities must predict volume-average/global measure (work and engine-out emissions) Rational flow CCV metrics require knowledge of what flow parameters best correlate with fuel-mixing and combustion CCV ECN 3.X 2014-2015 Efforts: Interdependency requires parallel efforts.

  4. 4.3.1. Global Engine Metrics

  5. 4.3.1. Global engine operating conditions 4.3.1.1.In-cylinder 0-D & Global Metrics ECN 3.X Topic option: Document precision & accuracy for mechanical & pressure test-to-test & CCV. Location Peak Pressure P_cyl Pegging TCC-III

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

  7. 4.3.1.2. Intake & Exhaust Systems 1-D quantities PIntakePort Discrepancy, (simulation – measurement) Discrepancy, % CoV, % Measurement Noise   LES CCV ECN 3.X Topic options: - Quantify effect of P_Intk_PortCCV on trapped mass & flow. - Quantify simulationnoise precision and accuracy. TCC-III

  8. 4.3.1. Global engine operating conditions 4.3.1.2. Intake & Exhaust Systems 1-D quantities -200 CAD PIV: 200 cycles INTAKE ECN 3.X Topic options: - Quantify impact of intake-port 1-D pressure & 3-D velocity on in-cylinder CCV. Trapped Mass • LES: 25 cycles Mean Pintake Intake pipe velocity [m/s] • SGEmac

  9. 4.3.2. In-cylinder flow characterization

  10. 4.3.2. Simulated-to-Measured Flow characterization • 4.3.2.1. Statistical Methods • SGEmac • next step • Resolution dependence • Model dependences • SIDI TUD PDF ECN 3.X Topic option: Identify methods and metrics to quantitatively assess equivalency of simulated & measured velocity and momentum dissipation.

  11. 4.3.2. Simulated-to-Measured Flow characterization 4.3.2.1.Statistical Methods 4.3.2.1.1. phase-average and standard deviation LES Ens. Ave. Measured Ens. Ave Ens,. Std. Dev. • SIDI TUD 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. 4.3.2. Simulated-to-Measured Flow characterization 4.3.2.1.Statistical Methods 4.3.2.1.2. CCV vs. turbulence vs. noise PIV dynamic range  Max velocity  Velocity noise Simulation Noise ? PIV interrogation % first choices PIV interrogation quality Crankangle ECN 3.X Topic option: - Standards exist to quantify measurement noise. - How are simulation noise & uncertainty quantified?

  13. 4.3.2. Simulated-to-Measured Flow characterization 4.3.2.2.Proper Orthogonal Decomposition, Phase-dependent POD • Snapshots sampled @ one CA, all cycles • POD creates multi-dimensional “empirical” basis functions. • Modes created based on flow • high KE (V2, or I2) • and/or repeatable. - Eigen values capture KE. - Can be used for CCV of Modes Mode 1 mid intake stroke KE, m2/s2 TCC- I cycle #

  14. 4.3.2.2.Proper Orthogonal Decomposition, Phase-invariant POD • Velocity snapshots • sampled @ all CA, all cycles • mapped to single grid • 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) Mode 1 Mode 2 Eigenvalue captures intra-cycle variability  flow similarity  CCV Coefficients TCC crank angle

  15. 4.3.2. Simulated-to-Measured Flow characterization Combine Measured & LES snapshots + Phase-invariant POD  single set of POD Modes. Coefficients provide metric for direct comparison of measured vs simulated Intra-cycle and Inter-cycle equivalence. LES PIV Coefficients crank angle ECN 3.X Topic option: POD is not universally or extensively used as a metric. Identify acceptable methods and standards of POD application.

  16. 4.3.2. Simulated-to-Measured Flow characterization 4.3.2.8. Simulation efficacy of scalar mixing. Experiment Simulation End of hydrogen injection ECN 3.X Topic option: Efficacy of simulations on one- & two-phase mixing, especially sub-grid. H2 mole fraction • H2ICE

  17. 4.3.3. Combustion-Modeling validation

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

  19. 4.3.2. Combustion modeling validation 4.3.3.2. Ignition and early flame development. Single-cycle Mie-scattering OH PLIF, probability of flame Chemiluminescence, Single cycle PDF of burn-gas  PDF of burned gas 2-D plane  PDF of burned gas 3-D projection • SIDI TUD • SGEmac

  20. 4.3.2. Combustion modeling validation 4.3.3.2. Ignition and early flame development. • SIDI TUD 0.20 0.15 0.10 0.05 0.00 PDF (ST) ECN 3.X Topic option: Identify optical metrics applicable to both measured & simulated data to define equivalency during early burning ( burned mass fraction < 20%). -5 0 5 10 15 ST (m/s)

  21. 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) ECN 3.X Topic option: What is needed? What experiments are possible ?

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