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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.

An adaptive control system which determines the optimum system parameters based on the engine response to changes in those parameters, has been tested as an ignition timing control system on several gaseous fueled engines. The changes in the MBT timing for speed, load, air-fuel ratio, and fuel type were explored. The ability of the control system to correct the timing for these parameters was demonstrated. An air-fuel ratio control based on the same technique is also discussed.

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.

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.

The formation of particles in the combustion chamber of a direct injection diesel engine has been studied with the use of the Total Cylinder Sampling Method. With this method, nearly the entire contents of the cylinder of an operating diesel engine can be quickly removed at various times during the combustion process. The particle mass and size distributions present in the sample can then be analyzed. If quenching of the combustion process is quick and complete, the resulting samples are representative of the particle mass and size distributions present in the cylinder near the time sampling begins. This paper discusses the effect of injection timing and piston bowl shape on the particle formation and oxidation. Example size distribution measurements are also shown. The particle concentrations in the cylinder were measured for three different injection timings with the standard piston installed in the engine.

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.