Study Of A New Short Needle Injector

Since the speeding up of Chinese railway system, the malfunction rate of diesel engine made in our country has increase dramatically. Among them, the malfunction rate of the fuel injection system is definite. They mainly are: the poor reliability of the fuel injector, the short periods of the maintenance, the not good enough performance. In order to adapt the high-speed development of Chinese railway system, meet the more and more high reliability and performance requirement of the fuel injection system; it is necessary to study the structure of injector in locomotive diesel engine.This paper adopted the advance impact stress theory and fluid theory. According to theoretical analysis and calculates, the paper put forward the improving measures. By adopting needle of smaller mass to a new short needle injector, the impact stress of needle valve on sealing surface of valve seat was decreased. By combing with other measures such as use of double cone sealing, small pressure stress volume and injection orifice of small diameter, the performance of the injector was improved. By adopting high quality spring raw material and manufactured technology, the reliability and performance of the injector was improved further.Through the flow test of steady-state high-pressure liquid, it is good to improve the flow coefficient by adopting the use of double cone sealing in needle. The present situation of the flow coefficient and the flow dispersity of the injection nozzle matching parts is known well. The factors influencing the flow of the injection nozzle matching parts are analyzed.The fuel spray particle measure analyzing test shows that the fuel spray subdivision with the injector with short needle valve can reach 50%～60%Through fuel pump test, the injection performance of these two fuel injection system have been analyzed and compared. The results show that the injector with short needle valve can raise injection pressure while insuring the fuel injection system mechanical load unchanged.In this study, not only the injector with short needle valve can improve the reliability of the fuel injection system, but also improve the performance about spray and flow obviously. The optimization structure is benefit to improving reliability and decreasing fuel consumption and emission. It is welcomed by the department of locomotive and also brings the considerable economic and social return.