NDLI: Prediction of Cyclic Variability and Knock-Limited Spark Advance (KLSA) in Spark-Ignition (SI) Engine

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Yue, Zongyu Edwards, K. Dean Sluder, C. Scott Som, Sibendu
Copyright Year	2018
Abstract	Engine knock remains one of the major barriers to further improve thermal efficiency of Spark Ignition (SI) engines. Knock can be suppressed by lowering the compression ratio, or retarding the spark ignition timing, however, at an expense of efficiency penalty. SI engine is usually operated at knock-limited spark advance (KLSA) to achieve possibly maximum efficiency with given engine hardware and fuel properties, such as Research Octane Number (RON), Motor Octane Number (MON), and heat of vaporization, etc. Co-optimization of engine design and fuel properties is promising to improve the engine efficiency and predictive CFD models can be used to facilitate this optimization process. However, difficulties exist in predicting KLSA in CFD simulations. First, cyclic variability of SI engine demands that multi-cycle results are required to capture the extreme conditions. Secondly, Mach Courant-Friedrichs-Lewy (CFL) number of 1 is desired to accurately predict the knock intensity (KI), resulting in unaffordable computational cost, especially for multi-cycle simulations. In this study, a new approach to numerically predict KLSA using large Mach CFL number of 50 is proposed. This approach is validated against experimental data for a boosted Direct Injection Spark Ignition (DISI) engine at multiple loads and spark timings. G-equation combustion model coupled with well-mixed chemical kinetic model are used to predict the turbulent flame propagation and end-gas auto-ignition, respectively. Simulations run for 10 consecutive engine cycles at each condition. The results show good agreement between model predictions and experiments in terms of cylinder pressure, combustion phasing and cyclic variation. Engine knock is predicted with early spark ignition timing, indicated by significant pressure wave oscillation and end-gas heat release. Maximum Amplitude of Pressure Oscillation (MAPO) analysis is performed to quantify the KI, and the slope change point in KI extrema is used to indicate the KLSA accurately. Using a smaller Mach CFL number of 5 also results in the same conclusions thus demonstrating that this approach is insensitive to the Mach CFL number. The use of large Mach CFL number allows us to achieve fast turn-around time for multi-cycle engine CFD simulations.
Sponsorship	Internal Combustion Engine Division
File Format	PDF
ISBN	9780791851999
DOI	10.1115/ICEF2018-9605
Volume Number	Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development
Conference Proceedings	ASME 2018 Internal Combustion Engine Division Fall Technical Conference
Language	English
Publisher Date	2018-11-04
Publisher Place	San Diego, California, USA
Access Restriction	Subscribed
Subject Keyword	Cycles Compression Turbulence Computational fluid dynamics Engine design Spark-ignition engine Ignition Oscillations Combustion Fuels Pressure Waves Engines Optimization Stress Flames Heat Simulation Heat of vaporization Hardware Engineering simulation Thermal efficiency Cylinders
Content Type	Text
Resource Type	Article

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