Experimental and Numerical Analysis of Spray Evolution, Hydraulics and Atomization for a 60 MPa Injection Pressure GDI System

Paper #:
  • 2018-01-0271

Published:
  • 2018-04-03
Abstract:
In recent years, the GDI technology has significantly spread over the automotive market following the continuous push toward the adoption of combustion systems featuring high thermodynamic conversion efficiency and moderate pollutant emission levels. Following this path, the injection pressure level has been progressively increased from the initial 5-15 MPa level nowadays approaching 35 MPa. The main reason behind the progressive injection pressure increase in GDI (Gasoline Direct Injection) engines is the improved spay atomization, ensuring a better combustion process control and lower soot emissions. On the other hand, increasing the injection pressure implies more power absorbed from the powertrain. Therefore, the right trade-off has to be found between soot formation tendency reduction thanks to improved atomization and the energetic cost of the high pressure fuel injection system. In this paper, a GDI 5-hole, side-mounted injector was tested in a wide range of injection pressure conditions - from 5 up 60 MPa - in terms of terms injection rate and spray development. The spray global shape was investigated by high speed imaging, while the atomization level and droplet velocity were measured by means of a PDA (Phase Doppler Anemometry) system over several measuring points from 20 to 50 mm downstream the nozzle. A numerical model of the spray was developed and validated against the experimental data in order to simulate the spray penetration, cone angle, and atomization over a wide range of injection pressure. The results show that the decreasing trend for the drops SMD (Sauter Mean Diameter) from 5 up to 60 MPa, approaching its asymptote and suggesting an adequate cost/benefits analysis in terms of soot reduction for further pressure increases
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