Study On The Oil-gas Separator Matching And Design Of The Four Cylinder Diesel Engine

The gas phase flow field and the discrete phase flow field of the original cyclone oil-gas separator in the four cylinder 2.8L diesel engine are simulated and analyzed in this paper.The results indicate that the advantage of this cyclone oil-gas separator is the low pressure drop and obvious separating effect with small droplets.But the structure of the cyclone oil-gas separator limits the movement of whirlwind vortex,leading to the great reduction of the flow path of oil droplets and the low separating efficiency.And the flow rate of the blow-by greatly affects the separating efficiency of the cyclone separator.The best separating effect only exists in a certain flow rate.For the purpose of improving the separating performance of separator,a new labyrinth oil-gas separator is designed and selected to match with the diesel engine with the consideration of space layout of the diesel engine.The new labyrinth oil-gas separator is analyzed computationally through gas phase flow field and discrete phase flow field,the results indicated that the import and export pressure difference is 457Pa,the separation efficiency is 87%under the condition of 70L/min of the flow rate of the blow-by.Compared to the great loss of the original cyclone oil-gas separator,pressure loss was maintained in the reasonable range.The separating efficiency increased by 11%.Therefore,the separating performance of new labyrinth oil-gas separator is better than cyclone oil-gas separator.The main separation region of the labyrinth oil-gas separator is composed of the cylindrical orifice plate and baffle.This separation region has obvious separating effect on large oil droplets,however there is high pressure loss.The combined layout of rectangular baffle not only extends the flow path of oil droplets but also leads to formation of vortex by the blow-by in the process of accelerating.Therefore,the probability of separating is increased.The structure of labyrinth oil-gas separator is improved based on its characteristics;two designed improving scenarios are simulated.Based on the analysis of the results,the scenario of M20 is determined the final scheme.The separating efficiency is 90.65%,which increased by 4.2%.The pressure loss is 387Pa,reducing by 15.3%.The flow area of orifice plate in labyrinth oil-gas separator influences the pressure loss and the flow rate of blow-by directly,which is the design point of the labyrinth oil-gas separator.This study carried out the comparison and analysis of the character of flow field and separating performance of cyclone and labyrinth oil-gas separator,providing reference and gist for the improvement of the separating performance of cyclone and labyrinth oil-gas separator.