Phenomenological Analysis of Injection, Auto-Ignition and Combustion in a Small DI Diesel Engine

A new phenomenological analysis of injection and combustion is established in an 4-cylinders DI Diesel engine of the production size class equipped with an inclined 5 holes injector. Measurements are performed at representative engine conditions for partial load.

In a first part, the penetration of the liquid diesel fuel phase is visualized in the whole combustion chamber by simultaneous Laser Induced Fluorescence (LIF) and Mie scattering techniques. The experiments have revealed the influence of the injection timing on the spray penetration and dynamic. The interactions “spray/air motion” and “spray/combustion chamber” are analyzed along with the injection technology influence.

In a second part, the auto-ignition and combustion are analyzed by a time resolved direct imaging of the chemiluminescence process. Experiments based on the correlation of two separated images of the combustion phenomena in a single cycle have allowed a detailed comprehension of spatial and temporal description of the auto-ignition and reaction zones development. Several auto-ignition sites are revealed in the vicinity of the injector nozzle. The reaction zones are shown to develop independently and then to merge to a unique one in the whole combustion chamber. Finally the flame is convected by air motion in the cylinder.