Design and Optimisation of an Intake System for an Off Shore Race Engine.

In this paper the fluid dynamic behaviour of a highperformance airbox for a naturally aspirated off shore race engine is analysed by varying its geometrical configuration. In fact, since the introduction by the Union International Motonautique of more restricting rules and boat shape constraints, the design of off-shore engines airboxes has become particularly challenging especially for the introduction of an air restrictor near the inlet to limit the maximum engine power. Accordingly, to optimize the time-to-race, the work has been developed using a numerical approach with the following objectives: − the maximum as possible reduction of the fluid dynamic losses; − an uniform distribution of the mass flow rate among the 12 cylinders (a typical off-shore engine subdivision). To this aim, a design procedure has been proposed: it consists of a preliminary 3D steady state analysis of different airbox geometries to identify the best configuration in terms of the previously defined targets, and a subsequent unsteady 3D-1D-coupled approach whose results are representative of the actual airboxengine behaviour. The defined procedure allowed the choice of an optimal airbox geometry and, finally, the improved performance has been experimentally verified.