Invited Review: A review of deterministic effects in cyclic variability of internal combustion engines

Abstract

We review developments in the understanding of cycle-to-cycle variability in internal combustion engines, with a focus on spark-ignited and premixed combustion conditions. Much of the research on cyclic variability has focused on stochastic aspects, that is, features that can be modeled as inherently random with no short-term predictability. In some cases, models of this type appear to work very well at describing experimental observations, but the lack of predictability limits control options. Also, even when the statistical properties of the stochastic variations are known, it can be very difficult to discern their underlying physical causes and thus mitigate them. Some recent studies have demonstrated that under some conditions, cyclic combustion variations can have a relatively high degree of low-dimensional deterministic structure, which implies some degree of predictability and potential for real-time control. These deterministic effects are typically more pronounced near critical stability limits (e.g. near tipping points associated with ignition or flame propagation) such during highly dilute fueling or near the onset of homogeneous charge compression ignition. We review recent progress in experimental and analytical characterization of cyclic variability where low-dimensional, deterministic effects have been observed. We describe some theories about the sources of these dynamical features and discuss prospects for interactive control and improved engine designs. Taken as a whole, the research summarized here implies that the deterministic component of cyclic variability will become a pivotal issue (and potential opportunity) as engine manufacturers strive to meet aggressive emissions and fuel economy regulations in the coming decades.

Cyclic dispersion in engine combustion—Introduction by the special issue editors

“…9 Larimore et al 15 focused on internal residual mass to control HCCI combustion. They developed a physics-based approach to estimate residual mass from cylinder-pressure and exhaust-temperature measurements.…”

“…14 The articles by Larimore et al 15 and Jungkunz et al 16 focus primarily on the simulation and control of deterministic processes which have been shown to dominate cyclic dispersion for advanced combustion modes which operate near the edge of stability, 9 whereas the article by Spelina et al 14 addresses aspects of knock from a purely stochastic perspective.…”

“…A common example is ''rebound'': a partial burn can be followed by a cycle with higher than average output due to fuel (unburned or partially burned) in the residual cylinder contents. The review by Finney et al 9 illustrates how the framework of dynamical systems theory provides concepts and analytical tools to characterize deterministic effects and dynamic structure in CCV, understand their physical origins, and exploit them for interactive control.…”

“…12,13 In this introductory overview, we place these articles (which include three invited review papers 4,9,10 ) in the larger context of engine research and offer brief but (we hope) tantalizing summaries.…”

“…Conventional spark-ignition (SI) 6,[9][10][11]14 and compression-ignition (CI) (diesel) engines; 7,12 Spray-guided stratified-charge engines; 4,5 Low-temperature combustion (LTC) engines, 8,9,12,13,15,16 including homogeneous charge compression ignition (HCCI) 8,9,15,16 and reactivitycontrolled compression ignition (RCCI). 12,13 In this introductory overview, we place these articles (which include three invited review papers 4,9,10 ) in the larger context of engine research and offer brief but (we hope) tantalizing summaries.…”