Development Of Air-oil Sparator For Diesel Engine

More and more stringent exhaust emission legislative restriction and ever-increasingrequirement of low engine oil consumption make the crankcase ventilation system developcontinuously, which need to effectively separate the engine oil in the crankcase blowby. Oiland gas separator is the chief component of the crankcase ventilation system, and itsseparation performance heavily influences the reliability and emission of the engine.However, most of existing oil and gas separator have a shortage that is it cannot adapt thechange of crankcase blowby with the working condition. We employ a composite oil and gasseparator that is composed of active passive series separator, the active centrifugal part isdriven by external electric motor, the rotating speed of impeller can be adjusted according tothe working condition, it not only play a role of pre-separation but also provide anappropriate inlet speed for passive whirlwind part. Thus, it can realize highly efficientseparation of the oil and gas. The numerical simulation method has the advantage of shortcapital investment, fast calculated speed, complete information of flow filed and strongsimulated power, which is used more and more widely in the practical application. Thus,using numerical simulation to research the internal flow and separation performance,optimize the structure of the separator can shorten the development period, which has greatutilization value. This paper finds out the rules of crankcase blowby by bench test,researches on the gas phase field and two-phase flow field using numerical simulation, andoptimizes the structure of the separator. Finally, this paper calibrates the composite oil andgas separator with the data of blowby test, provides the theoretical basis and reference for thesubsequent test calibration.There are two main aspects in the contents of this article and the first one is finishingthe simulation and size optimizaton on the active centrifugal part. According to the crankcaseblowby test result preliminary identify the size of the active part and established the3D solidmodel based on the ProE software,then put in the ANSA software for meshing.Completedthe simulation calculation with the FLUENT software and obtained the active centrifugal part’s pressure field, velocity field and the distribution of the turbulence characteristics aswell as mastered the gas internal flow in the active centrifugal part.Also obtained theseparation efficiency of the different dimensions by calculating, and determine the size of theactive centrifugal part based on the above-mentioned datas.The second one is making the simulation calculation and calibration of the air-oilseparator and puting forward two kind of blades as retrofit scheme.Meanwhile have theprocess of establishing model,meshing and simulation calculation on the air-oil separator;study of the effect of operating conditions on the separation performance.Then receive aconclusion that the increasing of the inlet pressure, inlet velocity and the the impeller rotatespeed will improve the separation efficiency of the separator while the total pressure drop ofthe separator will rise.According to the crankcase blowby test results obtained the impellerrotate speed with high separation performance on various conditions. Finally put forwardtwo kinds of blades for improving the getter capacity to better meet the requirement of thebigger crankcase blowby and the simulation results indicate that the axial-flow fan-shapedleaves have a better getter capacity.