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This report describes tests of a fuel additive in a medium-duty, high-swirl, direct-injection diesel engine. The additive was found to have little influence on general combustion performance or on NOx emissions. On the other hand, it had a profound effect on particulate emissions. This was most clear under high load where particle emissions are highest. Here, when the engine was switched from running on the base fuel to the additive treated fuel, particle emissions at first increased and then fell to levels about 40% lower (by particle volume) than those initially produced by the base fuel. The additive had a long lasting effect. After running with the additive for about 25 hours, emission levels with the base fuel were only slightly higher than those with the additive treated fuel. We believe that the additive action is associated with a combination of cleaning and surface conditioning. More work should be done to understand the relative importance of these two mechanisms.

Experiments were performed to measure the number-weighted particle size distributions emitted from a gasoline direct injection (GDI) engine. Measurements were made on a late model vehicle equipped with a direct injection spark ignition engine. The vehicle was placed on a chassis dynamometer, which was used to load the engine to road load at five different vehicle speeds ranging from 15 - 100 km/hr. Dilution of the exhaust aerosol was carried out using a two-stage dilution system in which the first stage dilution occurs as a free jet. Particle size distributions were measured using a TSI 3934 scanning mobility particle sizer. Generally speaking, the presence of the additives did not have a strong, consistent influence on the particle emissions from this engine. The polyether amine demonstrated a reduction in particle number concentration as compared to unadditized base fuel.

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.

This study examines the effect of a ceramic particle trap and a manganese fuel additive on the mutagenic activity and chemical composition of diesel exhaust particulate matter from a heavy-duty mining engine. Particles were collected by dilution tunnel sampling from a 4-cylinder, Caterpillar 3304, naturally-aspirated, indirect-injection engine operated at six steady-state conditions. Depending on engine load and speed the ceramic particle trap reduced the following emissions: particulate matter, 80 – 94%; soluble organic fraction (SOF), 83 – 95%; 1-nitropyrene, 94 – 96%; and SOF mutagencity, 72% (cycle-weighted average). When the Mn fuel additive was used without a ceramic particle trap the total cycle mutagenic activity emitted increased 7-fold, in part, due to elevated emissions of 1-nitropyrene.

Low emission heavy-duty diesel engines are increasingly utilizing four-valve designs with vertical central injectors. However, two-valve DI diesel engines with inclined injectors offset from the centerline of the piston bowl are likely to continue to be used in medium and light duty applications for some time. In such situations, designing of the hole-type nozzle is very difficult and may cause unavoidable back-drilling problems. The purpose of this paper is to solve back-drilling problems connected with hole-type nozzles and improve fuel-air mixing which leads to more efficient combustion. Based on geometric considerations, this paper introduces single-cone hole-type nozzles, double-cone hole-type nozzles, and the critical principal angles for hole-type nozzles. The single-cone hole-type nozzles and double-cone hole-type nozzles can meet requirements for height of the spray impingement points and spray orifice distribution angle at the same time.

Diesel particles carry charges ranging from 1-5 units of elementary charge per particle. The charge is bipolar, i.e., there are approximately equal numbers of positively and negatively charged particles. The charge distribution with respect to size follows a high temperature, Boltzmann equilibrium relationship. The first part of this paper describes charge measurements made on diesel particles emitted by three different diesel engines, and postulates a charging mechanism. The second part of the paper is an examination of how this natural charge may be used to collect particles from the exhaust. The charge level produced by combustion is only slightly lower than the charge level produced by the corona discharge in a conventional electrostatic precipitator. Thus, a simple electrostatic precipitator without a corona section will collect diesel particles affectively.

Particle concentrations and size distributions were measured in the exhaust of a turbocharged, aftercooled, direct-injection, Diesel engine equipped with a ceramic filter (trap). Measurements were performed both upstream and downstream of the filter using a two-stage, variable residence time, micro-dilution system, a condensation particle counter and a scanning mobility particle sizer set up to count and size particles in the 7-320 nm diameter range. Engine operating conditions of the ISO 11 Mode test were used. The engine out (upstream of filter) size distribution has a bimodal, log normal structure, consisting of a nuclei mode with a geometric number mean diameter, DGN, in the 10-30 nm range and an accumulation mode with DGN in the 50-80 nm range. The modal structure of the size distribution is less distinct downstream of the filter. Nearly all the particle number emissions come from the nuclei mode, are nanoparticles (Dp < 50nm), and are volatile.

Particle mass and size distribution measurements have been made on the exhaust of an Onan prechamber diesel engine. Seven fuels were examined: no. 1 and no. 2 diesel fuel, 40 and 50 cetane number secondary reference fuels, and no. 2 diesel fuel doped with three different concentrations of Lubrizol 565, a barium-based smoke suppressant. The no. 1 and no. 2 diesel fuels and the 50 cetane number reference fuels produced very similar emissions with emission indices in the range 0.3-1.3 mg (gm-fuel)-1 and volume mean diameters between .09 and 0.15 μm. The 40 cetane number reference fuel produced both smaller emission indices, 0.2 to 0.8 mg (gm-fuel)-1, and particle diameters, 0.03 to 0.09 μm. These reductions were apparently related to the longer ignition delay period of the 40 cetane number fuel, which allowed better mixing of the fuel and air prior to combustion.

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.

Combustion characteristics of an L-head engine combustion chamber have been examined using ionization probes and piezioelectric pressure transducers. The method describes how pressure rise rates, peak pressures, mean effective pressures, and flame arrival times were recorded. The flame arrival times were then used to find the position and shape of the flame front as a function of time. The influence of spark plug location on the above parameters was then examined for two different combustion chamber shapes.

Because of the more hostile environment in the compression ignition engine compared to the spark ignition engine, development and application of CI engine in-cylinder diagnostic methods have lagged those for SI engines. However, with more stringent federally mandated particulate and NOx standards which will go into effect in 1991 and 1994, the need for detailed information on the combustion processes in the cylinder is vital to controlling tailpipe emissions. The present paper contains a summary of the state-of-the-art techniques for determining in-situ species concentrations and profiles; particle concentrations, profiles, and size distributions; and temperature fields. Optical and physical probing methods, total cylinder dumping methods, and optical diagnostics applied for use in CI engine combustion chambers are discussed.