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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.

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.

Flame arrival data, determined by ionization gaps and a radiation detector, are presented for a multi-hole CFR engine equipped with six spark plugs spaced around the periphery of the combustion chamber, using a shrouded intake valve to produce swirl and with a standard valve to eliminate it. For results with the shrouded valve, path equations for the burnt gases are derived for several velocity distributions that satisfy the Navier-Stokes equations of motion for the unburned gas. Previous velocity distribution and observed flame movement data are presented in support of the derived model for the path of the burnt gases.

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.

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.

A unique system which allows sampling of the entire contents of one of the cylinders of a 5.7-liter V-8 indirect-injection diesel engine has been developed. An explosively actuated cutter ruptures a diaphragm in the combustion chamber and allows the contents of the cylinder to rush out and be subsequently diluted and quenched with cool nitrogen. Particles are collected with a high-volume impactor/filter system. This system has been used to collect a series of particle samples at crankangles ranging from 5 to 40 degrees after top dead center. Particle samples from the exhaust were also obtained. The samples have been extracted to determine the soluble organic fraction. These extracts have been analyzed for five polycyclic aromatic compounds: pyrene, fluoranthene, benz(a)pyrene, benz(k)fluoranthene, and 1-nitropyrene. The results indicate significant removal of the first four between the combustion chamber and the exhaust manifold.

Carbon black particles, which morphologically and chemically simulate a diesel exhaust soot, were mixed with the intake air of a single-cylinder direct injection diesel engine to investigate the efficiency of their removal by oxidation in the combustion chamber. An aerosol generation system, which is capable of generating carbon black aerosol of a size distribution and mass flow rate comparable to those of the soot agglomerates, was developed first. The aerosol was then introduced into the engine which was operating on conventional fuel. Four methods were used to characterize the exhaust particles: an electrical aerosol analyzer, a condensation nuclei counter, a low volume filter, and a micro-orifice cascade impactor. The size distribution and concentration of the diesel soot particles in the lubricants were investigated by methods of photosedimentation and quantitative spectrophotometry, respectively.

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.

Two types of in-cylinder optical probes were applied to a single cylinder CFR engine to detect knocking combustion. The first probe was integrated directly into the engine spark plug to monitor the radiation from burned gas in the combustion process. The second was built into a steel body and installed near the end gas region of the combustion chamber. It measured the radiant emission from the end gas in which knock originates. The measurements were centered in the near infrared region because thermal radiation from the combustion products was believed to be the main source of radiation from a spark ignition engine. As a result, ordinary photo detectors can be applied to the system to reduce its cost and complexity. It was found that the measured luminous intensity was strongly dependent upon the location of the optical sensor.