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Fundamental regeneration rate data of cellular ceramic particulate traps are presented. The data were obtained from systematic bench experiments using scaled traps and simulated engine conditions. The study was conducted over a wide range of parameters, covering scaled regeneration flow rates from subidle engine flow to full flow at rated engine conditions, trap inlet temperatures from 500 to 650°C, oxygen concentrations from 5 to 21%, and particulate accumulation levels in the trap from a pressure drop ratio (relative to the clean unit) of 2 to 60. The effect of each parameter on the maximum trap temperature and regeneration time is independently studied and described. Favorable regeneration conditions in terms of minimizing the energy requirements for regeneration and avoiding trap destruction are identified. Finally, it is illustrated that regeneration maps of this type can be applied to develop a control logic for an automatic regeneration system.

Particulate and sulfate emission characteristics of two catalyzed radial- flow wire-mesh particulate traps are presented. The traps were found to be ineffective for particulate reduction. The first trap was dynamometer tested for 25 consecutive EPA Heavy Duty Diesel Transient Cycles and 40 hours of steady state operation. During steady state testing, particulates were sampled from both the raw and diluted engine exhaust. The total particulate matter was chemically analyzed for sulfate, organic, moisture, and nonextractable fractions. The data indicate significant conversion of fuel sulfur to hygroscopic sulfuric acid. Although solid carbon fraction was reduced, total particulate mass increased. Sulfuric acid condensation presented operational and particulate sampling difficulties. Sampling from the raw exhaust with heated lines showed good sulfur balance between fuel and exhaust contents, but sulfate emission also exceeded the baseline for total particulate matter.

Some results of a systematic analysis of important sources of hydrocarbon emissions from a direct injection diesel engine are presented. The following sources are considered and investigated: (1) local over-mixing, (2) poor end of injection, (3) fuel emptying from sac volume. The analysis uses systematic engine experiments and an existing two-dimensional thick evaporating spray model to determine the contribution of various hydrocarbon sources to the total hydrocarbon emissions in the exhaust. The results show that at idle and light load conditions, local overmixing is the major source of hydrocarbon emissions. The amount of fuel over-mixed is directly controlled by mixing rate, ignition delay, and the lean limit of combustion. Mixing rate calculations show that the injection rate shape and nozzle geometry are more important than the physical properties of the fuel in determining the amount of fuel overmixed.