Rsearch On Processing Surface Topography Of Plain Orifice And Influence On Liquid Injection

The machining surface topography of the nozzle inner wall is one of the most important influences on the quality of fuel injection, which largely decides the combustion and emissions characteristics. In order to precisely control the precision of the combustion organization, it usually requires that the nozzle diameter should be about a few hundred microns. In this case, the relative size of the topography on machined surface is big enough that the nozzle processed by hydrostatic extrusion or other conventional methods may result in problems such as dimension error and nozzle damage. In this thesis, we studied the influence of the nozzle surface topography on the nozzle performance quantitatively at the stage of fuel injection and atomization which is caused by collision, and we mainly discussed the influence from the following aspects, including the split length of the single jet, the mass flow rate, the spay angle and the fineness of the atomization caused by the collision of two jets.First of all, we studied the nozzle surface topography and get the most distinctive feature of the machined surface measured by scanning electron microscopes. Given the limitation of the traditional two dimensional surface roughness parameters Ra, we used the three dimensional surface parameters to assess the nozzle. We carried out analysis on the surface topography by using spectral analysis and fast Fourier transform. Using these methods, we get the amplitude figure and power spectral density figure, and established the three-dimensional modeling of the fuel nozzle.Secondly, the FLUENT was used to complete the simulation about the influence of the nozzle surface topography on the internal flow. Based on above mentioned works, we can study the outlet jet of the nozzle. The inlet pressure of the nozzle determines the internal flow pattern. And according to the trend of pressure increasing, we can divide the flow patterns. And we can get the turning point of the internal flow pattern changing through numerical simulation. We made a detailed discussion about the influence of the nozzle surface topography on the streamline distribution, the velocity distribution and static pressure distribution. Besides, we discussed the relationship between the surface topography, nozzle exit velocity and mass flow rate for different length-diameter ratio of nozzle.Finally, particular simulations and analysis about the influence of the nozzle surface topography on jets were carried out, and jet experimental system was built to verify the simulation results. Through the simulation,the relationship between the inlet pressure of the single jet, roughness and the angle of spray cone, breakup Length, fluid loss was discussed. Besides,we discussed the influence of the nozzle burr on jet and the relationship between the nozzle inner surface topography and saunter mean diameter. In confirmatory experiments, we summarized the possible causes of the difference by the comparison between the experimental and the simulation results.