Experiments Research On Spray Characteristics Of Diesel Fuel Injection System For High-pressure Common Rail

With the development and more and more requirement of modern society on dynamic performance, economic performance and emission characteristics of engines, more attention is paid to fuel atomization characteristics because atomization quality of fuel is the most important factor in diesel combustion process. However, the theories of fuel atomization are far from mature. Especially in recent years, for the sake of reduce nitric oxide emissions of diesel, diesel injection pressure are developing towards high-pressure direction, which makes research on the affection of eject pressure getting more and more important.By tracking the latest progress on the research, the spray characteristics with high-pressure common rail were studied in this dissertation. A test bench for fuel spray with high pressure common rail was built by using spray visualization pressure cylinder, GS-1000 high-pressure common rail fuel injection system and high-speed camera. The experiments were designed and made, which the observation of internal structure of spray field detailed was realized under different conditions. Based on the image obtained from the experiment test and that were handled by C# programming, a lot of valuable spray characteristics data were obtained, then the spray structure was studied according to these handled spray data. After data analysised, the calculation formula of spray characteristics under high-pressure environment was fitted.Main research results are as following:(1) A test bench for spray characteristics with high pressure common rail was built,and a lot of original valuable experiments were obtained.(2) Using C# programming language, image analysis software was developed, which realize observation and analysis for the spray images from tests, and achieve the quantitative analysis for spray penetration and spray cone angle, and improve the efficiency and accuracy on the contrast of the previous image analyses.(3) The internal structure of spray field was observed in detail and the main parameters of atomization characteristics,i.e. spray penetration and spray cone angle, under various working injection conditions were obtained, and the spray principles under were analyzed.Main conclusions include:under the high pressure condition, with acceleration of the injection pressure and the atmosphere density increasing, fuel spray penetration reduces, and spray cone angle gets larger. With the increasing injection pressure, spray penentration gets longer, and spray cone angle becomes smaller, however, the change is tiny and can be omitted.(4) Through analyzing the related parameters that influenced the spray characteristics and using the conservation principle of mass and momentum, the formula about spray penetration and spray cone angle that fit for the environment in high pressure fuel injection were improved and mended, which make up for the lack of the previous work. The formula can reflect the main influential parameters of spray characteristics and is good practical value to some extent.