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We describe a method for detecting and quantifying time irreversibility in experimental engine data. We apply this method to experimental heat-release measurements from four spark-ignited engines under leaning fueling conditions. We demonstrate that the observed behavior is inconsistent with a linear Gaussian random process and is more appropriately described as a noisy nonlinear dynamical process.

The goal of this work is to begin to understand and characterize the break-up of liquid fuel as it is torn from intake valve and port surfaces during the start-up period of a spark ignition engine. The lack of vaporization from warm engine surfaces causes the fuel to enter the combustion chamber as large droplets. Atomization results from the shearing effect of the intake air as it is pulled into the combustion chamber. Droplet sizes, air velocities, and break-up formations are studied using a high-resolution CCD camera and strobe. Indolene and iso-octane fuels are used to consider the effect of fuel properties on the break-up. The atomization processes that occur are characterized through the use of dimensionless groups. Results show that the fuel break-up follows the same processes seen for many other atomizing devices under the influence of co-flowing air. The role of valve gap, liquid fuel flowrate, air flowrate, and valve dimensions on the break-up process are discussed.

The goal of this investigation was to gain a better understanding of the effect of fuel/air charge composition on the dynamical structure of cyclic dispersion in lean-fueled spark ignition engines. Swirl and fuel injection timing were varied on a single-cylinder research engine to investigate the effects of charge motion and stratification on prior-cycle effects under lean operating conditions. Temporal patterns in the cycle-to-cycle combustion dynamics were analyzed using return maps, Shannon entropy, and symbol sequence statistics. Our results indicated a transition from stochastic behavior to noisy nonlinear determinism as equivalence ratio was decreased from near stoichiometric to very lean conditions. The equivalence ratio at which deterministic effects became important was strongly influenced by swirl and fuel injection timing. A comparison of our results and previous results from an eight-cylinder production engine showed similar trends.

A detailed investigation of the intake port mixing process was performed on a fired single cylinder port fuel injected research engine. The liquid fuel droplets were studied using several different methods of analysis ranging from spatially and temporally resolved to spatially and temporally averaged data. Comparisons of the port mixture preparation results were made to the combustion performance of the engine in order to develop correlations between the mixing process and resulting engine performance. It is suggested that while the nature of the fuel spray produced by the injector is important, there are several other factors that influence fuel delivery to the cylinder. Calculations are given that indicate drops must be very small to entrain in the flow and avoid wall wetting. Secondary drop formation mechanisms may ultimately determine the nature of the fuel delivery to the cylinder and have an impact on combustion performance.