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A three-dimensional model of a diesel engine exhaust port was established. The reliability of modeling method and the exhaust port model were verified by the steady-flow test, PIV test and pressure field test. Based on the exhaust port model, the influence of the key section parameters such as inlet area S1, throat area S2, and outlet area S3 on the flow capacity of the exhaust port was studied. The results show that, under different pressure difference and exhaust back pressure conditions, the mass flow rate increases first and then converges with the increase of the area ratio of outlet and inlet or the area ratio of throat and inlet. With the increase of the relative pressure difference, the optimal area ratio of outlet and inlet decreases and converges to 1.02, but the optimal area ratio of throat and inlet increases and converges to 1.13.

A three-dimensional model of a diesel engine intake port was established and was verified by steady-flow test. Based on this model, the influence of intake valve lift on the flow capacity of intake port was studied and a design method of maximum valve lift was put forward. The results show that, under different intake pressure and relative pressure difference conditions, the discharge coefficient increases first and then converges with the increase of valve lift. Under the same valve lift condition, with the increase of relative pressure difference, the discharge coefficient decreases slightly in subsonic state and decreases sharply from subsonic state to supersonic state, but the mass flow rate increases slightly. The optimum ratio of valve lift and valve seat diameter is related to relative pressure difference, it increases first and then keeps constant with the increase of relative pressure difference.

Accurate injection timing is necessary for the coordination of fuel injection system, intake system and combustion chamber. However, the electric unit pump has obvious delay characteristic, so the delay characteristics of electric unit pump were studied in this paper. Five main parameters of the delay characteristics were defined, which were namely electronic delay, electromagnetic delay, electro hydraulic delay, hydraulic delay and mechanical delay. Then six delay points were determined such as current generation delay, solenoid valve closing delay, injector opening delay, injection delay, solenoid valve opening delay and fuel pressure relief delay by analyzing the working process of the system. Based on the method of experiment, the change rules of the delay time were obtained at different input conditions by changing the parameters of cam speed, injection pulse width, injection timing, peak current and holding current finally.