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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.

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.

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.

A miniature homogenous charge compression ignition (HCCI) free-piston engine compressor aimed at an ankle-foot orthosis application is described. Analysis of the human ankle shows that a fluid power source in the neighborhood of 10 W is needed. To account for compressor and actuator inefficiencies, the power output at the engine cylinder is designed to be 30 W. A compact engine compressor package has been designed and mathematically modeled. Experiments using existing engine components characterized the leakage model. Through the dynamic simulation of the engine, major parameters of the engine have been specified. Simulations indicate that the HCCI free-piston engine compressor, designed in a prototype package scale of about 80×40×20 mm is a viable compact and efficient fluid power supply. Simulation results demonstrate that the overall efficiency of the engine compressor is expected to be 5.9% and that the package should have a higher energy density than batteries.

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.

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.

A test reactor was designed for a 6.7 kW, 303 cc, single cylinder, air cooled, gasoline fueled engine. The reactor was very efficient at hydrocarbon (HC) and carbon monoxide (CO) reductions - with up to 99.9 and 98.6% removed, respectively. It had no effect on oxides of nitrogen (NOx) emissions. With the reactor, the engine met the California Air Resources Board (ARB) proposed Tier II emission standards. A factorial test was used to determine that A/F ratio and air injection rate significantly affected CO reduction efficiency whereas air injection location, ignition timing, and engine load did not. Relationships were established between CO reduction, air injection rate, and reactor core temperature.

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.

Particle formation, growth, coagulation and combustion in the cylinder of an indirect injection passenger car type diesel engine have been studied using a system which allows the cylinder contents to be rapidly expelled through a blowdown port, diluted, and collected in a sample bag for subsequent analysis. Characteristic blowdown times were about 0.5 ms. Samples were analyzed using a condensation nuclei counter to determine particle number concentrations and an electrical aerosol analyzer to determine particle volume concentrations in the 0.01 to 1.0 μm diameter range. Measurements were made with the engine operating at 1000 rpm and an equivalence ratio of 0.32. Peak particle number concentration in the cylinder 13 times the exhaust level, and peak particle volume (or mass) concentration in the cylinder 3 times the exhaust level were observed. These results suggest that significant particle coagulation and oxidation occur during the expansion stroke.