PIV Appling Study And Numerical Simulation Of The Flow In Diesel Engine

Internal combustion engine,which has been born one hundred years,becomes to the representation of dynamical machinery due to its high thermal efficiency.Nowadays,how to optimize its combustion and emission is very important for its development.During the internal combustion engine processing,it concludes combustion and emission, which are the based on the flow in the cylinder,thus the research of the flow in the cylinder is the basis for a comprehensive study of the internal combustion engine.Experiment and numerical simulation are two common researching methods for researching internal combustion engine.In this thesis,there is a lot of work in both fields.In testing the flow in the cylinder of ICE,the advantage of PIV experiment overcomes many disadvantages showing up in other test equipments,such as one point,non-transient and interference test.So it has been become a long-awaited research mean for the researchers in the related area.Because of the instantaneous,full and non-interference results,nowadays PIV experiment becomes the standards in testing fluid inside cylinder.Researching and applying this technology are the major tasks in this thesis.First,in this thesis we study the principle of PIV and set up dragged-down experiment equipment in order to research the flow in the cylinder of the 2135 diesel engine.Secondly,in order to take the photo of the PIV test,we undermined the emission valve and designing a new emission system,which can keep old motion law.Thirdly,it fully described the two-phase theory related tracer particles,which is the key technology of PIV test.At the same time,it has set up a numerical model for the tagging of tracer particles and put up standard for judging the tagging of tracer particles in the basis of BBO equation related to tracer particles motion.Fourthly,in this thesis,it creatively applies diesel-aired tracer particles to displace other tracer particles,which is experimentally proved reliable,cheap and easily acquired. Fifthly,in order to use film optical to shine the fluid field during PIV test,we designed lens optical set which can create film optical and finished film and application with the assist of geometrical optical principle,and the theory is related to the white light diffraction.Sixthly, for the need of close-range technology to photo the fluid field within the cylinder,we designed a fixed then the camera ring according to the knowledge related to photo and has acquired some high-quality photos of cylinder fluid field.Finally,we designed electronic synchronization control system and selects post technology related to PIV photos according to CCD manual.There is detailed information in the second chapter.Though researching and applying PIV technology,we got the satisfied results from the test of the flow in cylinder.At the same time,this paper also includes the numerical simulation with the same photo condition of cylinder and contrast of the result got from PIV test and numerical simulation..For the numerical simulation,since the computer has been invented,the research about the complex flows including the Diesel in-cylinder process has developed very rapidly.Most of the research organizations apply CFD to research internal combustion engine and combine it with the advanced technology,such as the PIV technology.In the thesis,it takes the 2135 diesel as the representation and carries it out plenty of calculations with real structural data, practical boundaries and scientific hypothesis.There are some important conclusions resulting from the abundant flow-field information,such as:firstly,the inlet stroke in the miniature high-speed Diesel is carried under high whirlpool ratio and the inlet angle is over 2.5 times as it in the compress stroke.The long-time inlet process,the inlet channel for producing high whirlpool ratio and dissymmetrical inlet valve make the in-cylinder flow under the influence of inlet whirlpool inertia at all times,and even there is a strong whirlpool flow at the end of combustion.Secondly,with the influence of inlet whirlpool and compress stroke,the oil beam and the fire mass rotate around the cylinder center line accompany with vortex of inertia. Thirdly,the change of flow-field and velocity in different configuration combustion chamber are very similar at same rotate speed.That shows the speed makes the main effect.However, the change of flow-field and velocity is obvious at same rotate speed even if the same configuration combustion chamber.There is detailed information in the third chapter.In addition,this paper also supplies many PIV pictures and other evidence pictures for the fuel spray in the third chapter.This information got from PIV experiment and CFD numerical simulation(k-εmodel) shows as follow:firstly,the results acquired from the PIV test and CFD are similar at qualitative aspect.Radial flow field in the cylinder all show up a big symmetrical whirlpool in cylinder center at the post time of compress stroke.Secondly,the PIV experiment shows that the flow analysis photos of radial flow field at compress stroke keeping many small whirl alive with the big swirling vortex flow of macro-graphics,but numerical simulation without this character.There is detailed information in the fourth chapter.