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A sheet of laser light from a frequency-doubled Nd-YAG laser (λ = 532 nm) approximately 150 μm thick is shone through the cylinder of a single cylinder internal combustion engine. The light scattered by the fuel spray is collected through a quartz window in the cylinder and is imaged on a 100 × 100 diode array camera. The signal from the diode array is then sent to a microcomputer for background subtraction and image enhancement. The laser pulse is synchronized with the crank shaft of the engine so that a picture of the spray distribution within the engine at different times during injection and the penetration and development of the spray may be observed. The extent of the spray at different positions within the chamber is determined by varying the position and angle of the laser sheet with respect to the piston and the injector.

Flame fronts were examined in a premixed-charge, spark-ignition, ported engine using a two-dimensional visualization technique with 10 nanoseconds time resolution and 200 microns best spatial resolution. The engine had a pancake chamber, a compression ratio of 8, a TDC swirl number of 4 and was operated at 300 to 3000 rpm with stoichiometric and lean propane/air mixtures. The measurements were made far from, and near to, the cylinder wall. A pulsed laser sheet was passed through the engine and the light scattered by sub-micron TiO2 or ZrO2 seeding particles was collected by a 100 x 100 diode array with fields of view of 1 cm x 1 cm, 2 cm x 2 cm, and 9 cm x 9 cm. The thickness of the flame front is as small as, or smaller than, the 200 micron best resolution of the measurements thus confirming that premixed-charge engine turbulent flames generally appear to be wrinkled laminar flames.

Laser Doppler velocimetry was used to make cycle-resolved velocity and turbulence measurements under motoring and firing conditions in a ported homogeneous charge S.I. engine. The engine had a flat pancake chamber with a compression ratio of 7.5. In one study, the effect of the intake velocity on TDC turbulence intensity was measured at 600, 1200, and 1800 rpm with three different intake flow rates at each speed. The TDC swirl ratio ranged from 2 to 6. The TDC turbulence intensities were found to be relatively insensitive to the intake velocity, and tended to scale more strongly with engine speed. For the combustion measurements, the engine was operated at 600, 1200, and 2400 rpm on stoichiometric and lean propane-air mixtures. Velocity measurements were made in swirling and non-swirling flows at several spatial locations on the midplane of the clearance height. The TDC swirl ratio was about 4. The measurements were made ahead, through, and behind the flame.

Laser Doppler velocimetry has been used to make cycle-resolved velocity and turbulence measurements in a homogeneous-charge, spark-ignition engine. The engine had a ported intake and disc-shaped chamber with a compression ratio of 7.5 to 1. It was operated at a speed of 1200 rpm and with a TDC swirl number of 4. A stoichiometric propane-air mixture was used, and ignition was near the wall. Measurements of the tangential velocity component were made in both firing and non-firing cycles at nine spatial locations along a radius 180 degrees downstream of the spark. The radial velocity component was also measured at four of the locations. All measurements were made in the center of the clearance height. Tangential component measurements were made as close as 0.5mm from the cylinder wall, and the radial component was measured as close as 1.5mm from the wall.

Atomization and full-cone sprays from single cylindrical orifices are considered. The following subjects are reviewed: the structure of the breakup region; the structure of the far field; modern models that, given the outcome of the breakup process, compute the steady and transient of sprays; some comparisons with detailed measurements; and some practical applications. The following conclusions are reached: the spray breakup and the development regions are the most relevant in engine applications; the inner structure of the breakup region is still largely unknown; two- and three-dimensional spray models are available but remain mostly untested, particularly in their vaporization and combustion components, in part because of a lack of accurate measurements in controlled engine-type environments; engine applications of such models are, nonetheless, recommended for very valuable learning, interpretative, and exploratory studies, but not for predictions.

A closed-circuit television technique has been developed for the real time viewing and recording of combustion and related processes in internal combustion engines. The technique has been applied to a transparent piston, transparent head engine, and shadowgraphs of combustion chamber events have been observed and recorded. The technique is particularly suited for the study of changes in the combustion process due to variations of engine parameters such as mixture ratio, load, speed, spark timing, injection initiation, etc., since the changes can be observed and recorded at the same time that they occur. A brief and qualitative study of flame and pressure cyclic variations is reported and discussed as an example of an application for which the television technique is particularly suited.

Combustion in a divided-chamber, stratified-charge engine is considered and flame and pressure results obtained with a two-dimensional, unsteady model are compared with corresponding engine data. The model is applied to eight engine conditions differing in speed, load and size of the prechamber orifice. The model employs one overall chemical reaction rate, the k-ε representation of turbulence, and a wall heat loss proportional to the heat release. The computed results are shown to be in good agreement with the experimental ones in spite of the complexity of the problem and the early stages of detailed model validation studies. They are also shown to compare somewhat better than earlier ones obtained with an ad-hoc jet turbulence model. Both studies prove the importance of the prechamber jet to the overall combustion process for the particular engine investigated.

The goal of this theoretical-experimental work is to model two-dimensional, unsteady (and steady) two phase flow combustion in internal combustion engines (and steady reactors) and to test and improve the model with parallel experimental programs. The purpose of this research is to make more detailed current understanding of this important family of combustion problems and to aid the development of cleaner and more efficient engines. In this paper, preliminary theoretical-experimental results of our efforts toward the stated goal are presented. The theoretical results are preliminary but prove the feasibility of detailed computations of combustion in internal combustion engines and show how informative such computations can be. In a section of this paper, preliminary results are reported of detailed computations of two-dimensional, unsteady sprays penetrating and vaporizing into an inert gas in a closed volume (without combustion).