Numerical Investigations for Mechanism of Pre-Ignition Induced by Lubricant Oil Droplets in Supercharged DISI Engines[J]. 2016, 50(7): 51-57.
DOI:
Numerical Investigations for Mechanism of Pre-Ignition Induced by Lubricant Oil Droplets in Supercharged DISI Engines[J]. 2016, 50(7): 51-57.DOI: 10.7652/xjtuxb201607009.
Numerical Investigations for Mechanism of Pre-Ignition Induced by Lubricant Oil Droplets in Supercharged DISI Engines
Multidimensional computational fluid dynamics coupled with a skeletal chemical kinetic model of gasoline substitute is used to investigate the mechanism of pre-ignition induced by lubricant oil droplets in a supercharged direct-injection spark-ignition(DISI)engine under high load and at low speed. The influence of lubricant oil droplet on the auto-ignition of gasoline and air mixture is evaluated in a constant volume combustion bomb with the thermodynamic conditions similar to those in the DISI engine cylinder at the compression top dead center. The results show that the ignition delay time of gasoline and air mixture is shortened by the presence o
f lubricant oil droplet when n-heptane and hydrogen peroxide ketone(C
8
KET)are used as lubricant oil evaporation substitutes respectively
and this behavior is more obvious when C
8
KET is used as lubricant oil evaporation substitute. The ignition delay time of gasoline and air mixture first decreases then increases with the increasing lubricant oil droplet diameter. In addition
the ignition delay time of fuel-air mixture is further shortened with the increasing lubricant oil droplet temperature and the temperature and pressure of the fuel-air mixture. A numerical investigation for auto-ignition of gasoline and air mixture with the presence of lubricant oil droplets in the supercharged DISI engine is carried out by using C
8
KET as lubricant oil evaporation substitute. The results show that the ignition delay time of the fuel-air mixture around the lubricant oil droplets is shortened by the constituents with good ignition performance evaporating from lubricating oil droplets
which causes auto-ignition of fuel-air mixture in this area before the spark ignition and leads to the occurrence of pre-ignition. A mechanism of pre-ignition induced by lubricant oil droplets is finally proposed following the conclusions above.
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references
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