The use of CFD codes is well established in the development of reciprocating engines, owing to the time and money saving that can be achieved. The analysis of an engine behavior is usually a quasi-steady type. In fact, with the use of 1D and 3D codes, it is possible to predict the torque and power output of the engine before it is tested on a bench [1]. However, such an analysis may result to be not sufficient to predict the effective improvements that could be obtained on the transient behavior when modifying the intake and exhaust system of the engine. The aim of this paper is to find a methodology that is able to quickly optimize the really important parameters of the engine-transmission matching.
In this study, several predictions of acceleration tests of a commercial scooter were carried out through the use of a 1D CFD code. In a close cooperation with Ricardo Software, we implemented a model that simulates the CVT transmission, that is usually employed in scooters, taking in consideration the behavior of both the CVT itself and the centrifugal clutch.
The results of the simulations were compared with the experimental measures in order to validate the CFD model, showing a very good agreement. Then, some modifications were introduced on the intake system of the engine to improve the response on the acceleration tests in terms of elapsed time and final speed.