Browse Publications Technical Papers 2001-01-1814
2001-12-01

OPTIMISATION OF THE SCAVENGING AND INJECTION PROCESSES OF AN AIR-ASSISTED DIRECT FUEL INJECTION 50 CC. 2-STROKE S.I. ENGINE BY MEANS OF MODELLING 2001-01-1814

This paper summarizes the optimisation work of the air-assisted direct fuel injection 50 cc. 2-stroke spark ignition DERBI TSI engine. The methodology employed is based on the use of mathematical models to assist to the design procedure. The models used are a 1D wave action model and a 3D CFD model. In the paper is described the modelling procedure for some of the engine systems: exhaust, injection, scavenging and mixture processes. The existing 1D model has been improved to simulate 2-stroke engines. Some studies have been devoted to the calculation of tapered pipes, exhaust system, reed valves and injection system.
The study of the exhaust shows that only the exhaust parts closest to the cylinder have influence on the exhaust response in terms of performance. The study of the injection system shows that the injection pressure and duration will depend on the discharge duct diameter and compressor clearance. The phase angle between engine and compressor crankshaft will not affect injection pressure or duration. A procedure for drawing new ports geometry by parametric design has been used. This allowed testing new ports geometry by CFD. Two different combustion chambers are compared in terms of mixture enhancement. Finally, the injection and mixture process for different injection strategies is assessed.

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