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Corresponding Author

El-Kady, M.

Subject Area

Mechanical Power Engineering

Article Type

Original Study

Abstract

The two major problems of automotive diesel engines, namely the combustion noise and high NO emissions can be reduced and become less serious by reducing the fuel mass injected during the delay period. The injector of the diesel fuel injection system is provided with a suitable viscous damping unit to increase the viscous fri9ction force which resist the needle lift. In this paper, a general outline of the viscous damping unit is introduced and the considered fuel injection system is simulated numerically. The pressure in the different parts of the injection system is predicted using the theory of wave action where the finite difference principle has been incorporated. The needle valve motion is represented by the equation of motion and the rate of fuel injected is predicted using the theory OE the two Orifices in series. The influence of the viscous dancing on the injection process has been theoretically examined and the reduction percentage of the fuel mass injected during the delay period has been estimated for different values of damping coefficient. An experimental study for the verification of the predicted results has been carried out. A satisfactory agreement between the predicted and the experimentally recorded results of pressure in the Injection system has been observed. It is found that, providing an extra viscous damping to the injector of the injection system, keeps the rate of the fuel Injected low at the start of the injection Process, then the injection rate rises fast subsequently. As a result, a good reduction of the amount of the fuel injected during the expected delay period is obtained.

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