Characterization of lean combustion instability in premixed charge spark ignition engines

Abstract

The focus of this study was to identify and characterize the development of lean combustion instability in spark ignition engines. Statistical techniques from non-linear dynamics were used to process experimental combustion observations to reveal previously unrecognized patterns in cycle-to-cycle combustion variations. The presence of non-linear deterministic structure was confirmed in lean combustion variations from a single cylinder research engine and a four-cylinder production engine. The transition to non-linear deterministic behaviour appeared to occur via a period-doubling bifurcation sequence. Over the bifurcation region, engine dynamics appeared to pass through distinct dynamic stages including stochastic, periodic and possibly chaotic behaviour. The level of dynamic complexity and corresponding cycle-to-cycle communication were found to be a strong function of the residual gas fraction. Experimental observations were also compared with patterns predicted by a recently proposed low-order engine model. Further analysis of the time-series results indicated that the engine frequently exhibited complicated repeating combustion patterns 15 to 20 cycles in length under certain lean operating conditions. Similar dynamics were seen for the two very different engine designs. The work suggests that the underlying cyclic dynamics may not be dependent upon the details of such processes as mixing and combustion but are characteristic of all lean premixed spark ignition engines.

Analysis of pressure fluctuations in a natural gas engine under lean burn conditions

“…In order to develop effective control strategies for efficient combustion, it is important to understand the dynamics of cycle-to-cycle pressure variations [4][5][6]. Earlier studies on pressure fluctuations were carried out primarily in gasoline and diesel engines [7][8][9][10][11][12][13][14][15][16][17][18]. Using the methods of nonlinear dynamics and other techniques, researchers have investigated the complex dynamics of pressure fluctuations in these engines, including the possibility of chaotic oscillations [10][11][12][13][14][15][16].…”

Investigation of Deterministic and Random Cyclic Patterns in a Conventional Diesel Engine Using Symbol Sequence Analysis

“…Combustion processes in IC engines have cycle to cycle variations even though duration of engine cycle is same at constant speed. These cyclic variations are dependent on engine operating conditions and can be very large in some of the operating conditions [1,2]. Cyclic variations can be significant for even well controlled average ignition timings [3].…”

Characterizing dilute combustion instabilities in a multi-cylinder spark-ignited engine using symbolic analysis

“…Cyclic combustion variability associated with dilution with excess air (also known as lean fuelling) has been studied for many decades [1][2][3][4]. The most commonly observed instabilities with lean fuelling arise as the result of internal feedback processes within each cylinder.…”