Abstract: Oil pressure fluctuation caused by last injection can lead to oil mass deviation of this injection during multi-injection of high pressure common-rail system. Influence of rail pressure on the oil mass deviation amplitude of the second injection under two different injection pulse width of the first injection is researched. The results show that the changing of oil mass deviation amplitude with rail pressure shows different law under different injection pulse width of the first injection. The influence of rail pressure on the amplitude of pressure fluctuation caused by a single injection is also studied under two different injection pulse width. The results show that the influences of rail pressure on the oil mass deviation amplitude and pressure fluctuation amplitude are almost the same when the injection pulse width is small, but there is a difference when the injection pulse width is large. Mechanism of the influences of rail pressure on oil mass deviation amplitude is discussed in detail. A coefficient named injection time deviation coefficient which demonstrates the mechanism of the influence of rail pressure on oil mass deviation is put forward . The influence law of rail pressure on oil mass deviation amplitude is acquired.

Key words: high pressure common-rail system;multi-injection;oil mass deviation;pressure fluctuation;rail pressure;injection time deviation coefficient