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Particle formation, growth, coagulation and combustion in the cylinder of an indirect injection passenger car type diesel engine have been studied using a system which allows the cylinder contents to be rapidly expelled through a blowdown port, diluted, and collected in a sample bag for subsequent analysis. Characteristic blowdown times were about 0.5 ms. Samples were analyzed using a condensation nuclei counter to determine particle number concentrations and an electrical aerosol analyzer to determine particle volume concentrations in the 0.01 to 1.0 μm diameter range. Measurements were made with the engine operating at 1000 rpm and an equivalence ratio of 0.32. Peak particle number concentration in the cylinder 13 times the exhaust level, and peak particle volume (or mass) concentration in the cylinder 3 times the exhaust level were observed. These results suggest that significant particle coagulation and oxidation occur during the expansion stroke.

The formation of NO2 in the cylinder of a diesel engine has been investigated using a total cylinder sampling technique and a simple kinetic model. Exhaust measurements of NO2 as a function of equivalence ratio and as function of time after engine start were made. Samples obtained by total cylinder sampling from an operating direct injection diesel engine showed NO2/NO ratios of 25 to 50%. This is much higher than the 1 to 3% which was measured in the exhaust. Simulations of the sampling process indicate that conversion of NO to NO2 is at least partially responsible for the high NO2/NO measurements. However, the processes which produce the NO to NO2 conversion during the sampling also occur during normal combustion. This may lead to high NO2 concentrations during the combustion cycle which are then lowered during the expansion to the measured exhaust concentrations.

The performance of a closed-loop electronic fuel injection timing control system for diesel engines has been investigated, both experimentally and analytically. The Electronic Control System (ECS) studied is a version of the “Optimizer,” a peak seeking control which can find the maximum of one variable with respect to another. In this case, it was used to find the timing for maximum brake torque (MBT). The ECS can also be operated in a “biased” mode in which it will hold the timing either advanced or retarded of MBT, but in a fixed relationship to it. Performance and emissions of a medium duty engine equipped with the ECS were measured on an engine dynamometer. The results clearly demonstrate that, for a variety of operating conditions and for two fuels, the ECS can find and hold the timing at MBT or in fixed relationship to it.