Research On Measuring The Intermittent And High Frequency Injection Quantity Provided By A High Pressure Common Rail Fuel Injection System Based On The Displacement Method

With the wide use of diesel and the fast development of modern techniques in diesel, theelectro-control high pressure common rail injection system has become an acknowledged andoptimal fuel injection system in engine industry. This system can realize precise control forthe fuel injection process and has multiple controlled spurts in the work engine cycle. Becausethe average periodic steady flow rate is low, as well as the injection duration and the intervalof time between two spurts is more and more small, the injection process has the property ofhigh frequency and intermittent.In the course of research, analysis, produce, test, usage and maintenance for high pressurecommon rail injection system, professional test systems are needed. The level of examinationand measurement has a direct impact on the working ability and total cost of the injectionsystem. The intermittent and high frequency fuel injection rate is one of the most importantparameters of the test. So the determination of the injection flow rate is the key to studyingthe injection law, establishing the corresponding accutate relation between the pulse-widthand fuel rate of injection. The flow rate of periodic or each spurt in the multiple injections andthe number of injection can be precisely achieved by this measuring system for the highfrequency and intermittent injected fuel. An injected fuel rate measuring system for theelectro-control high pressure common rail injection system, with high dynamic character, highmeasurement accuracy and high efficient, is of vital importance to promote the developmentand application of high pressure common rail injection techniques, reduce the emission andfuel consumption, and improve diesel performances.Firstly, this paper reviews the measuring method, operation principle and mainperformance parameters of the typical measuring instrument for fuel injection quantity both athome and abroad, and then introduces the basic composition and main character of a highpressure common rail injection system as the research object. The functional requirement isanalyzed and a scheme for the high frequency and intermittent fuel injection quantitymeasurement by use of the displacement method is proposed. The measuring system isconstructed and an improved design is proposed basing the mechanical construction of theexisting fuel injection quantity measuring device on the market, such as the design of injectorsupport, fuel damper, cooling fuel groove, piston and the measuring cylinder, etc. This paperclearly raised the improving methods for the measuring device, i.e, adopting a ball griddisplacement sensor which can be used in water or oil to measure the displacement of thepiston, adding a top cover and a bottom cover to the piston substrate, compensating thetemperature and pressure in the upper measuring cylinder, setting thire cooling loops. Byanalyzing the principle and character of this measuring system, we establish simulation mathematic models. Finally, other component parts in this measuring system are presented.The control system was consisted by a PC as a host computer and a PLC as slave computer,and Labview is used to base the software environment on a PC.The high frequency and intermittent fuel injection quantity measuring system can be usedto measure the periodic flow rate of several kinds of high pressure common rail injector.