Research On The Key Matching Technology Of Electronic-Controlled Injector Of Diesel Engine

Fuel injection system is very crucial to the driving, fuel economy, emission and NVH performance of diesel engine. Structure and performance of electronic-controlled injector which is one of the key component of fuel injection system have a huge influence on injection process and spray quality and mixture formation. This thesis conducted researches according to the matching technology demand of high pressure common rail system injector during design and manufacture process, aimed to making the evaluation of injector more comprehensive and detailed and the matching of injector more efficient and accurate.Two groups of injectors with the same structure and dimensions manufactured by two different manufacturers were tested. These two groups differs greatly in difference of fuel mass injected by different injectors in the same group. Full power engine test results show that fuel mass characteristics difference results in difference of engine performance. It is shown by part load engine test results that fuel consumption of the engine using the first group of injector is lower than fuel consumption of the engine using the second group of injector, this trend is more obvious in low load region. Soot emission of the engine using the first group of injector is lower than that of the engine using the second group of injector at most full power points.Injection time of four different kinds of injectors were tested under different rail pressure and different energizing time. The difference between energizing time and injection time was analyzed, and it is concluded that the differences between energizing time and injection time of different kinds of injectors are almost the same under the same conditions. Injection time of these four different kinds of injectors were averaged also. The averaged injection time were fitted by using curved surface fitting based on the least square method. Formulation of injection time expressed in rail pressure and energizing time was acquired, and it is showed that the difference between injection time and energizing time of 93.9% tested points are within ±120?s.Injection power consumption which is divided into spray power consumption and pressure loss power consumption were evaluated through theoretical calculation. Flow coefficient of nozzle hole which affects accuracy of calculation results were analyzed in detail. Static leakage power consumption was analyzed through both theoretical and experimental method. It is certified that theoretical result and experimental result show a good agreement with each other. Hydraulic control and electrical drive power consumption were estimated through a method using both theoretical calculation and experimental results. Injector power consumption of a diesel engine were evaluated under rated point and the maximum torque point. Spray power consumption is about 40% of the total injector power consumption. The fuel consumption which can be lowered by injector structure optimization is less than 1.0g/(k Wh).Multi-injection fuel mass characteristics were studied experimentally. The fuel mass changing of the second injection with the time interval between these two injections is caused by pressure fluctuation. The maximum multi-injection fuel mass deviation approaching ±50% exists under each rail pressure. The absolute fuel mass deviation amplitude increases with the increasing of either the standard fuel mass of the second injection or rail pressure. The relative fuel mass deviation range decreases with the increasing of the standard fuel mass of the second injection. Periods of fuel pressure fluctuation at injector inlet and the second injection fuel mass changing with the time interval are the same. Two kinds of injectors with different structure and different dimensions results in different fuel mass deviation amplitude of the second injection.