Characterization of temporal variations and feedback timescales of exhaust gas recirculation gas properties using high-speed diode laser absorption spectroscopy for next-cycle control of cyclic variability

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Abstract

Dilute combustion offers efficiency gains in boosted gasoline direct injection engines both through knock-limit extension and thermodynamic advantages (i.e. the effect of γ on cycle efficiency), but is limited by cyclic variability at high dilution levels. Past studies have shown that the cycle-to-cycle dynamics are a combination of deterministic and stochastic effects. The deterministic causes of cyclic variations, which arise from feedback due to exhaust gas recirculation, imply the possibility of using active control strategies for dilution limit extension. While internal exhaust gas recirculation will largely provide a next-cycle effect (short-timescale feedback), the feedback of external exhaust gas recirculation will have an effect after a delay of several cycles (long timescale). Therefore, control strategies aiming to improve engine stability at dilution limit may have to account for both short- and long-timescale feedback pathways. This study shows the results of a study examining the extent to which variations in exhaust gas recirculation composition are preserved along the exhaust gas recirculation flow path and thus the relative importance and information content of the long-timescale feedback pathway. To characterize the filtering or retention of cycle-resolved feedback information, high-speed (1–5 kHz) CO2 concentration measurements were performed simultaneously at three different locations along the low-pressure external exhaust gas recirculation loop of a four-cylinder General Motors gasoline direct injection engine using a multiplexed two-color diode laser absorption spectroscopy sensor system during steady-state and transient engine operation at various exhaust gas recirculation levels. It was determined that cycle-resolved feedback propagates through internal residual gases but is filtered out by the low-pressure exhaust gas recirculation flow system and do not reach the intake manifold. Intermediate variations driven by flow rate and compositional changes are also distinguished and identified.

Original languageEnglish
Pages (from-to)945-952
Number of pages8
JournalInternational Journal of Engine Research
Volume20
Issue number8-9
DOIs
StatePublished - Oct 1 2019

Funding

The authors would also like to thank Robert Bosch, LLC for providing the engine used in this study. The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was funded by the US Department of Energy’s Vehicle Technologies Office under the guidance of the Advanced Combustion Engine Research and Development program managed by Gurpreet Singh and Michael Weismiller.

FundersFunder number
LLC
U.S. Department of Energy
Robert Bosch

    Keywords

    • Dilute combustion
    • combustion stability
    • cyclic variability
    • exhaust gas recirculation
    • nonlinear dynamics

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