空気の不活性成分のピストン圧縮自着火への寄与

抄録

The effect of inert species on low-temperature piston-compression ignition is examined. Pseudo-air is prepared, replacing inert species in the air with pure argon. Lean mixtures are composed of leaded or unleaded gasoline as a fuel and the pseudo-air or real air as an oxidizer. Cool-flame ignition delay τ₁ shows no differences. A distinction between the two oxidizers can be found in blue flame ignition delay τ₂ under considerably lean conditions at equivalence ratios of 0.7. An anti-knock additive, tetramethyl lead, does not seem to be responsible for this distinction. When the pseudo-air is used as an oxidizer, onset of cool and blue flames in a pancake chamber shows a sliced-pineapple-like structure having a central core and a ring portion near the cylinder wall. Only when air is used as an oxidizer, does a blue flame appear in the ring portion in the vicinity of the cylinder wall earlier than in the central core. Inert species, nitrogen or argon, would participate as the third body in elementary chemical reactions appearing in preflame periods. Argon may be quite inert chemically, but nitrogen or nitrogen compounds probably act as a chemical species on the preflame reactions in low-temperature ignitions.