INTEGRATED NUMERICAL-EXPERIMENTAL METHOD IN HIGH SPEED 2T GASOLINE ENGINE DESIGN REFINEMENT 2001-01-1855
A complete two stroke engine predictive tool has been developed in order to evaluate how geometric parameters affect both performances and exhaust emissions.
The method is based on a two-step procedure. In the former one, the coupling between 0D and 1D simulation schemes, used to model engine volumes and ducts respectively, provides the boundary conditions necessary for the latter procedure, in which a 3D approach is applied to a variable geometry in order to obtain detailed information of cylinder flow and concentration fields during the scavenging period.
The first step retains the advantages of being a simple and rapid facility as it doesn't demand carefulness in the preliminary activity devoted to define the calculation geometry; moreover it is able to compute global parameters (torque, fuel and air consumption). For these reasons it can be considered a suitable tool to be extensively adopted together with the experimental process.
The second step is devoted to the comprehension of the phenomena and to the evaluation of the different pathways, which the subsequent optimisation process should be directed to.
The overall procedure has been tested on a high speed small two stroke engine by comparing the numerical results with experimental data. Then, the validated method has been used to evaluate the effect of transfer port geometric variations on performances and loss of fresh mixture.