Dynamic Thermal Behavior of a GDI Spray Impacting on a Heated Thin Foil by Phase- Averaged Infrared Thermography

The regulations about pollutant emissions imposed by Community's laws encourage the investigation on the combustion optimization in modern engines and in particular in those adopting the gasoline direct injection (GDI) or direct injection spark-ignited (DISI) configuration. It is known that the piston head and cylinder surface temperatures, coupled with the fuel injection pressure, strongly influence the interaction between droplets of injected fluid and the impinged wall. In the present study, the Infrared (IR) thermography is applied to investigate the thermal footprint of an iso-octane spray generated by a multi-hole GDI injector impinging on a heated thin foil. The experimental apparatus includes an Invar foil (50 ?m in thickness) heated by Joule effect, clamped within a rigid frame, and the GDI injector located 11 mm above the surface. Thermal images of the impinging spray are acquired from the dry side of the foil at several time delays after the impact instant at two different injection pressures (10 and 20 MPa). The temperature difference distributions are employed to describe the unsteady dynamics of the impingement.