STUDY OF DIESEL SPRAY COMBUSTION IN AIR CONTAINING BURNT GAS USING A SHOCK TUBE

ABSTRACT

Diesel spray combustion was observed in an “overtailored” shock tube. A constant-temperature gas phase was established for a sufficient length of time for spray combustion studies for Mach numbers less than 2.3. It was confirmed that this shock-tube technique is a useful tool for studying diesel spray combustion. First, using the overtailored shock tube, diesel spray combustion was studied in burnt hot gas, which was produced by combustion of an air-rich propane/air mixture. The results were as follows: (1) above [Air]/[C₃H₈] = 100, the ignition delay, the combustion time, and the total thermal radiation per injection were almost of the same order as those of shock-heated air. The heat of radiation corresponded to 5–9% of the combustion heat of light oil. (2) Below [Air]/[C₃H₈] = 100, the ignition delay decreased from around 5 ms to less than 1 ms with decreasing [Air]/[C₃H₈], whereas the combustion duration increased from around 10 to 30 ms with decreasing [Air]/[C₃H₈]. With [Air]/[C₃H₈] = 20, the flame remained throughout the measuring time (= 25 ms), because the spray did not burn out in the oxygen-lean mixture. Second, the processes of ignition and combustion were also observed in oxygen-enriched air at constant temperature. The 50% oxygen mixture gave the strongest thermal radiation from the soot at the same initial temperature.

Keywords:

• burnt gas
• diesel combustion
• overtailored
• shock tube
• spectral intensity
• thermal radiation

Acknowledgments

An abridged version of this article was presented at the 19th International Colloquium on the Dynamics of Explosions and Reactive Systems at Hakone, Japan, July 27 to August 1, 2003.