Abstract
The effects of fuel blend properties on spray and injector performance has been investigated for several operating conditions in a side-mount injector for Gasoline Direct Injection (GDI) using two certification fuel blends, Euro 5 and Euro 6. Several X-ray diagnostic techniques were conducted to characterize the injector and spray morphology. Detailed internal geometry of the GDI injector was measured with a feature-resolution of 1.8 micrometers, through the use of hard X-ray tomography. The geometry characterization of this six-hole GDI, side mount injector, quantifies relevant hole and counterbore dimensions and reveals the intricate details within the flow passages, including surface roughness and micron-sized features. Internal valve motion was measured with a temporal resolution of 20 microseconds and a spatial resolution of 2.0 micrometers, for three injection pressures and several injector energizing strategies. The needle motion for both fuels exhibit similar lift profiles for common energizing commands. A combination of X-ray radiography and Ultra-Small-Angle X-ray Scattering (USAXS) was used to characterize the fuel mass distribution and the droplet sizing, respectively. Tomographic spray radiography revealed the near-nozzle distribution of fuel mass for each of the fuels, and the asymmetry produced by the angled nozzles. Under evaporative conditions, the two fuels show minor differences in peak fuel mass distribution during steady injection, though both exhibit fluctuations in injection during the early, transient phase. US-AXS measurements of the path-specific surface area of the spray indicated lower peak values for the more evaporative conditions in the near nozzle region. These spray measurements portray the specific behavior of real fuel blends under a variety of conditions, illustrating the need to examine multi-component fuels to better understand relevant cases. Furthermore, this work furnishes the realistic boundary values for simulations to appropriately predict the sprays which were experimentally measured, and influenced by those realistic conditions.
