Effects of Lubricant Additives on Auto-Ignition under a Hot Co-Flow Atomosphere

Paper #:
  • 2017-01-2231

Published:
  • 2017-10-08
Abstract:
Low speed pre-ignition (LSPI) may lead to extreme knock (superknock or megaknock) which has a severe influence on engine performance and service life thus limits the development of downsized GDI engine. One reason for LSPI is auto-ignition occurs in the region where the contaminants, such as lubricants or heavy ends of gasoline, are rich. In this paper, 8 groups of lubricants are injected into a hot co-flow by a single-hole nozzle with a diameter of 0.2 mm under 20 MPa injection pressure. The ignition delays and lifted flames of lubricants with additives of calcium, magnesium and ZDDP (Zinc Dialkyl Dithiophosphates) under the hot coflow are recorded with a high-speed camera. The experiments are carried out at one atmospheric pressure and the co-flow temperature varies from 1123 K to 1223 K. The study shows that the ignition delays of lubricants decline sharply with the increase of co-flow temperature in the whole temperature range. The lubricant with higher contents of calcium at low temperature from 1123 K to 1173 K shows a shorter ignition delay while the difference is almost negligible at high temperature from 1173 K to 1223 K. The lubricant with higher contents of ZDDP presents a longer ignition delay over the entire temperature range. And the experimental results also indicate that the ignition delay is not sensitive to the magnesium contents. The results of this study have some guiding significance for the explanation of LSPI in the engine. And the negative effect of ZDDP additives on combustion and emissions needs to be tested in the future.
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