Experimental Study Of The Influence Of The GDI Gasoline Injector Deposit On The Spray Characteristics

Gasoline engine using the technology of GDI can effectively improve economy and emission performance of the engine. However, the injector exposure to the combustion chamber, where the environment is bad, will produce and accumulate deposit as the growth of the working time, and affect the performance of the GDI engine. In the background of the increasing crisis of the energy and environment situation, carrying out the research into the GDI engine injector deposit has important significance to control the produce and accumulate of the deposit and then improve the performance of GDI engine.According to the requirements of the test which research the spray characteristics of the gasoline engine injector, designed a set of gasoline engine injector control system which including control interface, control circuit and the control program. Control circuit includes a DC/DC booster circuit, ECU communication circuit and injector Control circuit. This injector control system can meet the requirements of different types of fuel injector high-speed opening and closing by adjusting the control parameters, to achieve the purpose of precise control various gasoline engine fuel injector. MATLAB software had used to write the program which is used to process the spray image of the test. The process mainly includes:import the image, remove the background of the image, display image, image segmentation, image edge and corrosion, the refining of image edge, extract the image edge, calculate the spray cone angle and through distance, analyzed and summarized the influence of the injector deposit on the spray characteristics.This study adopts the method of shadow in the test, using four kinds of different deposit levels of gasoline injectors which are new injector and mileage of20000km,50000km and80000km respectively, and five different injection pressure which are4MPa,6MPa,8MPa,10MPa,12MPa respectively, researched the influence of the injector deposit on the spray characteristics.From the research we can draw the following conclusion:1. From the overall trend analysis, in the different injection pressure, the spray through distance and the spray cone angle of the injector mileage of20000km and50000km larger than the new injector and the injector mileage of80000km at the same time; This gap of spray through distance increasing as the injection pressure increasing but this gap of spray cone angle decreasing as the injection pressure increasing.The spray through distance of the injector mileage of80000km much smaller than the new injector.2. In the different injection pressure, the four kinds of injector all display the trend that the spray cone angle decreasing as the time growth and tend to be stable at the last; The speed of the spray cone Angle decreases rapidly after the injection began to inject and presents the tendency of the wave; spray through distance of four kinds of injector growing at a rapid rate at the early time of the injection, as the spray of slowing growth, and then the rate decrease as the time growth.3. Degree of atomization of the injector mileage of20000km and50000km significantly worse than that the new injector and the injector mileage of80000km; Especially the spray of the injector mileage of50000km, in the progress of development of the spray, the oil concentration gradient of each orifice is very large, and oil beam of each orifice sharper than other injector, and the trend of spray develop in the mode of independent from each orifice is larger, the uniformity of spray concentration is poor.4. From the overall trend analysis, when the injection pressure is4MPa, the spray cone angle of the new injector and the injector mileage of20000km and50000km are larger, the spray cone angle decrease a little as the injection pressure increase; Spray cone angle increases when the injection pressure increases to12MPa. The spray cone angle of the injector mileage of80000km increasing as the injection pressure increased from4MPa to6MPa and decreasing as the injection pressure increased from6MPa to10MPa, but increasing again as the injection pressure increased from10MPa to12MPa.5. From the overall trend analysis, the spray through distance of the new injector decreased a little when the injection pressure increased from4MPa to6MPa; the spray through distance increasing as the injection pressure increased from6MPa to10MPa; the spray through distance decreasing as the injection pressure increased from lOMPa to12MPa. The spray through distance of the injector mileage of20000km increasing as the injection pressure increased from4MPa to6MPa but decreasing as the injection pressure increased from6MPa to8MPa; and increasing as the injection pressure increased from8MPa to12MPa.The spray through distance of the injector mileage of50000km increasing as the injection pressure increased from4MPa to12MPa. The spray through distance of the injector mileage of80000km decreasing as the injection pressure increased from4MPa to10MPa and increasing as the injection pressure increased from10MPa to12MPa.