Study On The Influence Of Different Impact Conditions On The Distribution Characteristics Of Near-Wall Mixture

In recent years,with the increasing attention to environmental protection worldwide,the emission regulations of internal combustion engine are increasingly stricter.As an inevitable product of combustion in a confined space,the spray wet wall phenomenon of internal combustion engine is inevitable,and the spray wet wall is one of the important sources of HC and CO problems.Although existing theories believe that wet wall can be reduced and controlled and utilized by improving the shape of combustion chamber and organizing the flow direction,there are few research achievements on the development of micro-physical processes such as fluid-structure interaction between fuel and combustion chamber wall after wet wall phenomenon.In this paper,spray wet wall phenomenon is taken as the research object,and the influence of different boundary conditions on fuel spray morphology development and near wall mixture concentration is studied.The metal wall processing platform,fuel spray wall bumping test platform and 3D simulation model were mainly built.MATLAB software was used to process the test images and extract the characteristic parameters,and then quantitative analysis was carried out on the fuel spray spreading radius,enrolling height,near the wall area mixture concentration and other parameters.Based on the preliminary work,the following three aspects are carried out.In terms of fuel spray wall impact test,this paper studies the morphology development process of n-decane fuel spray after wall impact under different wall temperature and wall wettability conditions,and summarizes and analyzes the effects of different wall impact conditions on the characteristics of mixture parameters in the near wall region and liquid spray concentration.The test results show that the spread radius and entrainment height of the n-decane fuel spray after hitting the metal wall first increase and then decrease with the passage of time under different wall temperature conditions.The spreading radius and entrainment height of the spray after hitting the wall gradually increased,while the spray concentration near the wall showed a decreasing trend.Under different wall wettability conditions,the overall spreading radius and entrainment height of the fuel spray hitting the wall increases with the increase of the oleophobicity of the metal wall,and the spray concentration in the near-wall area decreases with the increase of the oleophobicity of the metal wall.The concentration is the largest,and the spray concentration in the near-wall area after hitting the chemically treated metal wall is the smallest.In the numerical simulation calculation of the mixture concentration in the near-wall region,the effects of wall temperature,wall wettability and ambient pressure on the mixture concentration in the near-wall region after the n-decane fuel spray hits the wall are studied.The simulation results show that: under the conditions of different wall surface temperatures and different wall wettability conditions,with the increase of wall surface temperature and wall surface roughness,the mixture concentration in the near-wall area after the n-decane fuel spray hits the metal wall surface increases,and at the same time,the uniformity of the regional mixture concentration decreases,the mass fraction of the high-concentration region increases,and the mass fraction of the low-concentration region decreases;Under different ambient pressure conditions,with the increase of the ambient pressure,the mixture concentration in the near-wall area after the n-decane fuel spray hits the metal wall surface decreases.At the same time,the uniformity of the mixture concentration in the near-wall region increases,the mass fraction of the low-concentration region increases,and the mass fraction of the high-concentration region gradually decreases.