Simulation of automotive fuel injection equipment

Abstract

The ever increasing demands on Diesel engines for increased efficiency and reduced smoke emissions and noise have given rise to more stringent requirements for the associated fuel injection equipment and greater emphasis on the understanding of the factors affecting its performance and the optimisation of its design. This work describes how the simulation of the complex phenomena arising in transient high pressure wave flows in diesel fuel injection equipment has been carried out, using a digital computer. Previous published research in producing fuel injection equipment models relied on producing simplified subsets of generalised differential equations, but in this work an alternative approach, which makes use of the increased powers of modern computers has been adopted. The model is built up of a series of small elements, and the equations derived by considering the significant forces acting on each element. The emphasis in the work was to write a usable and useful suite of programs which can be, and have been, used in design and development work on a variety of systems, large and small, inline and rotary. The model has been verified by comparison with about a hundred experiments using different systems and conditions, and agrees within the limits of experimental error. Examples of the use of the program show how design criteria may be established, how transient phenomena during the pumping cycle may be examined in detail, and how factors such as fuel spray drop size and velocity may be evaluated. They also show how, as a result of a deeper understanding of fuel injection phenomena, a recurrent problem, the occurrence of secondary injections, was attacked and a novel and effective solution found.

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