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Title: Capturing Cyclic Variability in EGR Dilute SI Combustion using Multi-Cycle RANS

Abstract

Dilute combustion is an effective approach to increase the thermal efficiency of spark-ignition (SI) internal combustion engines (ICEs). However, high dilution levels typically result in large cycle-to-cycle variations (CCV) and poor combustion stability, therefore limiting the efficiency improvement. In order to extend the dilution tolerance of SI engines, advanced ignition systems are the subject of extensive research. When simulating the effect of the ignition characteristics on CCV, providing a numerical result matching the measured average in-cylinder pressure trace does not deliver useful information regarding combustion stability. Typically Large Eddy Simulations (LES) are performed to simulate cyclic engine variations, since Reynold-Averaged Navier-Stokes (RANS) modeling is expected to deliver an ensemble-averaged result. In this paper it is shown that, when using RANS, the cyclic perturbations coming from different initial conditions at each cycle are not damped out even after many simulated cycles. As a result, multi-cycle RANS results feature cyclic variability. This allows evaluating the effect of advanced ignition sources on combustion stability but requires validation against the entire cycle-resolved experimental dataset. A single-cylinder GDI research engine is simulated using RANS and the numerical results for 20 consecutive engine cycles are evaluated for several operating conditions, including stoichiometric as well as EGRmore » dilute operation. The effect of the ignition characteristics on CCV is also evaluated. Results show not only that multi-cycle RANS simulations can capture cyclic variability and deliver similar trends as the experimental data, but more importantly that RANS might be an effective, lower-cost alternative to LES for the evaluation of ignition strategies for combustion systems that operate close to the stability limit.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE) - Office of Vehicle Technology
OSTI Identifier:
1391929
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Conference: 2015 ASME Internal Combustion Engine Division Fall Technical Conference, 11/08/15 - 11/11/15, Houston, TX, US
Country of Publication:
United States
Language:
English

Citation Formats

Scarcelli, Riccardo, Sevik, James, Wallner, Thomas, Richards, Keith, Pomraning, Eric, and Senecal, Peter K. Capturing Cyclic Variability in EGR Dilute SI Combustion using Multi-Cycle RANS. United States: N. p., 2015. Web. doi:10.1115/ICEF2015-1045.
Scarcelli, Riccardo, Sevik, James, Wallner, Thomas, Richards, Keith, Pomraning, Eric, & Senecal, Peter K. Capturing Cyclic Variability in EGR Dilute SI Combustion using Multi-Cycle RANS. United States. doi:10.1115/ICEF2015-1045.
Scarcelli, Riccardo, Sevik, James, Wallner, Thomas, Richards, Keith, Pomraning, Eric, and Senecal, Peter K. Sun . "Capturing Cyclic Variability in EGR Dilute SI Combustion using Multi-Cycle RANS". United States. doi:10.1115/ICEF2015-1045. https://www.osti.gov/servlets/purl/1391929.
@article{osti_1391929,
title = {Capturing Cyclic Variability in EGR Dilute SI Combustion using Multi-Cycle RANS},
author = {Scarcelli, Riccardo and Sevik, James and Wallner, Thomas and Richards, Keith and Pomraning, Eric and Senecal, Peter K.},
abstractNote = {Dilute combustion is an effective approach to increase the thermal efficiency of spark-ignition (SI) internal combustion engines (ICEs). However, high dilution levels typically result in large cycle-to-cycle variations (CCV) and poor combustion stability, therefore limiting the efficiency improvement. In order to extend the dilution tolerance of SI engines, advanced ignition systems are the subject of extensive research. When simulating the effect of the ignition characteristics on CCV, providing a numerical result matching the measured average in-cylinder pressure trace does not deliver useful information regarding combustion stability. Typically Large Eddy Simulations (LES) are performed to simulate cyclic engine variations, since Reynold-Averaged Navier-Stokes (RANS) modeling is expected to deliver an ensemble-averaged result. In this paper it is shown that, when using RANS, the cyclic perturbations coming from different initial conditions at each cycle are not damped out even after many simulated cycles. As a result, multi-cycle RANS results feature cyclic variability. This allows evaluating the effect of advanced ignition sources on combustion stability but requires validation against the entire cycle-resolved experimental dataset. A single-cylinder GDI research engine is simulated using RANS and the numerical results for 20 consecutive engine cycles are evaluated for several operating conditions, including stoichiometric as well as EGR dilute operation. The effect of the ignition characteristics on CCV is also evaluated. Results show not only that multi-cycle RANS simulations can capture cyclic variability and deliver similar trends as the experimental data, but more importantly that RANS might be an effective, lower-cost alternative to LES for the evaluation of ignition strategies for combustion systems that operate close to the stability limit.},
doi = {10.1115/ICEF2015-1045},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2015},
month = {11}
}

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