Stereoscopic Observation on an Ignition Position of Diesel Spray

In a direct injection diesel engine, fuel spray was auto-ignited by an elevated temperature and pressure atmosphere in a combustion chamber. Since an ignition might appear in which a suitable mixture for exothermic reaction was prepared and flame might be developing to a combustible mixture, a settlement of ignition in time and space could control the entire combustion. The ignition position was usually investigated with photometric observations such as high-speed video systems. However plane observations could not inform the exact position of the ignition because spray had the 3D structure. In this paper, a new trial for the measurement of the ignition position was reported. A single shot diesel spray injected into a test chamber was ignited by elevated temperature and pressure atmosphere in the chamber. The chamber had an impingement plate so as to measure an ignition delay of a wall impingement diesel spray. Stereoscopic observation was realized using the two-way fiber optical system that was specially designed. Front and side views of ignition phenomena were captured. Using these images, the ignition position was settled in the 3D space on the impingement wall. As the result, it was confirmed that the ignitions took place at a side periphery of the spray and some times they appeared on the impingement wall. The ignition position of a wall impingement spray was greatly affected by the distance form nozzle to impingement wall. Further, difference of the onset positions of luminous and non-luminous flame kernels was discussed in this report.