Spontaneous ignition of single fuel spray was investigated at hot and high pressure air. Ignition lags were studied in relation to air temperature, air pressure, cetane number of fuel and injection pressure. The experimental results are summarized as follows:
(i) Ignition lag can be divided into physical lag and chemical lag by a statistical treatment of a great deal of ignition lag times at same condition.
(ii) Ignition lag decreases according to increasing of air pressure, and the almost part of all ignition lag is physical lag.
(iii) According to increasing of air temperature and cetane number, Ignition lag decreases respectively. In these cases, physical lag and chemical lag decrease together.
(iv) The effect of fuel injection pressure to ignition lag is little.
(v) Ignition lag expressed as follows:
τ= 0.12
p-0.49 exp. 3750/
TThese experimental results suggest that, in hot and high pressure air, physical lag accounts for almost part of all ignition lag. Therefore, control and improvement of combustion in diesel engines must be done in physical process of the spray.
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