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Two catalyst formulations were tested on a diesel engine. A Fourier Transform Infrared (FTIR) analyzer was used to measure concentrations of nitric oxide (NO) and nitrogen dioxide (NO2). Other exhaust gas components were measured by conventional analyzers. The results indicate that nitrogen oxides (NOx) undergo complex chemical reactions in the diesel oxidation catalyst (DOC). The increase of NO2 occurring at a certain temperature range is accompanied by a decrease of the total NOx emission. NO2 is probably an important itermediate product in the lean NOx catalyst reaction chain.

In underground noncoal mines the emission of nitrogen dioxide (NO2) in the exhaust of a diesel engine is more important than the emission of nitrogen oxide (NO) because of the much lower permissible exposure limit for NO2. Consequently, the tendency of aftertreatment devices such as oxidation catalytic converters (OCCs) to oxidize NO to NO2 is counterproductive. The U.S. Bureau of Mines (USBM) is investigating the effects of OCCs upon NO2 emission by using a Fourier Transform Infrared (FTIR) exhaust gas analyzer to compare the concentration of NO2 in diesel exhaust upstream and downstream of the OCC. We find that some OCCs increase the concentration of NO2 much more than others, and that over some temperature ranges the aftertreatment results in an apparent decrease in NO2 concentration.

There is a growing body of evidence that in-cylinder surfaces play an important role in determining the nature and quantity of soot emitted by diesel engines. This paper describes recent experimental results which demonstrate the importance of both the deposition of soot on walls during the combustion process and its subsequent reentrainment during exhaust blowdown. Soot deposition was demonstrated both experimentally and theoretically. The principal mechanism of soot deposition during combustion is thermophoresis. Our results suggest that the gross rate of in-cylinder deposition in the indirect injection diesel engine is between 20 and 45 percent of the net soot emission rate. Thus, a significant fraction of the soot emitted may have been stored on combustion chamber surfaces and protected from oxidation. Further evidence of wall deposition and subsequent reentrainment has been obtained by making time-resolved measurements of soot concentrations in the exhaust.

Time resolved primary and agglomerate particle size distribution measurements have been made on samples obtained from within the cylinder and from the exhaust of a single-cylinder modification of a 2.8 liter displacement, four-cylinder, naturally-aspirated, high swirl, direct-injection diesel engine. The total cylinder sampling method has been used to sample, quench, and dilute the entire contents of the cylinder in about 1 ms. Experiments have been performed at an equivalence ratio of 0.7 and a speed of 1000 RPM. An electrostatic aerosol sampler and a transmission electron microscope have been used to determine primary and agglomerate particle size distributions for both in-cylinder and exhaust samples. An electrical aerosol analyzer and a diffusion battery followed by a condensation nucleus counter were used to further characterize the agglomerate size distributions of exhaust samples.

In-cylinder and exhaust soot mass measurements have been made on a single-cylinder conversion of a 4-cylinder, 2.8 1, high-swirl, direct-injection diesel engine using a sampling system which allows dumping, diluting, quenching, and collecting the entire contents of the cylinder on a time scale o£ about 1 ms. Experiments have been performed at engine speeds of 1,000 and 1,500, and equivalence ratios, ϕ, of 0.4 and 0.7. Soot mass first appears shortly after top dead center and reaches a peak between 15 and 30 crankangle degrees after top dead center (CAD ATDC). After reaching its peak value, soot concentration decreases with increasing crankangle and approaches exhaust levels by 40-60 CAD ATDC. The time lag between the start of combustion and the first appearance of soot increases with ϕ and ranges from 0.2 to 1 ms. The initial rate of soot formation ranges from 0.26 to 0.30 mg ms−1 and varies little with speed or ϕ.

Measurements of particle concentrations in one cylinder of a 1982 5.7 liter GM V-8 diesel engine have been made using a unique total cylinder sampling system. The first part of the paper is devoted to an examination of the performance of the sampling system. The role of blowoff and nucleation in the formation of sample artifacts is discussed. The remainder of the paper is devoted to the results of a study of the formation and removal of carbon particles during diesel engine combustion. Several operating conditions have been examined. The influence of injection timing, load, EGR, and oxygen addition on particle formation and removal has been investigated. The concentrations of volatile and nonvolatile particulate matter have been measured as a function of crankangle position. Particle formation begins 1-5 crankangle degrees (CAD) after the start of combustion.