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A system that allows collection and analysis of all of the exhaust from individual engine cycles has been built. Its development and performance are described. The system was used to study the cyclic variability of a 0.7 liter direct injection diesel cylinder operating at 1500 rpm and an equivalence of 0.6. Particulate emissions exhibited the greatest variability. The cyclic variability (standard deviation) of particulate emissions associated with in-cylinder processes was found to be about 40% of the mean. The variability of NOx emissions that could be associated with in-cylinder processes was much lower, only about 6% of the mean. The variability of pressure development in the combustion process itself, as indicated by IMEP, was very low, less than 2% of the mean.

A two-dimensional optimization process which simultaneously adjusts the spark timing and air-fuel ratio of a lean-burn natural gas fueled engine has been demonstrated. This has been done by first mapping the thermal efficiency against spark timing and equivalence ratio at a single speed and load combination to obtain the 3-D surface of efficiency versus the other two variables. Then the ability of the control system to find and hold the combination of timing and air-fuel ratio which gives the highest thermal efficiency was explored. The control system described in SAE Paper No. 940546 was used to map the thermal efficiency versus equivalence ratio and ignition timing. NOx, CO, and HC maps were also obtained to determine the tradeoffs between efficiency and emissions. A load corresponding to a brake mean effective pressure of 0.467 MPa was maintained by a water brake dynamometer. A speed of 2000 rpm was maintained by a fuel-controlled governor.

Soot formation and oxidation within the cylinder of a divided-chamber diesel engine have been studied experimentally and predicted analytically using a diesel combustion model. Experimental measurements of in-cylinder particle concentration were made using a unique sampling system which samples and quenches nearly the entire contents of the cylinder on a time scale of less than 1 ms. The experimental measurements are compared with predictions made using a stochastic combustion model coupled to an Arrhenius-type soot formation model, and 02 and OH soot oxidation models. Five engine conditions: low-load standard-timing (base case), high-load standard-timing, low-load advanced-timing, low-load standard-timing + EGR, and low-load standard-timing + 02, were examined experimentally, but only the first three were modeled.