Abstract: An internal flow model is established based on the size and distribution characteristics of diesel injector nozzle deposit. The effect of nozzle deposit on internal flow is calculated by the way of VOF (volume of fluid) method. A constant volume spray model is established based on KH-ACT breakup model and the calculated result of coupled internal flow. The effect of nozzle deposit on spray characteristics is calculated. The internal flow model and spray model are verified through the injection flow-rate and spray tests on the fuel injection pump test bench. The research results show that the internal deposit could result in reducing the internal flow velocity, weakening the cavitation effect, and decreasing the penetration distance and the Sauter mean diameter (SMD). The outlet deposit leads to an increase in the internal flow velocity and the enhanced cavitation effect, whereas its effect on penetration distance is small. The SMD increases in the early stage of injection, and the change of the late stage is small. Key

Key words: dieselengine, nozzledeposit, internalflow, spraycharacteristic, numericalsimulation