Spray Structure From Double Fuel Injection in Multihole Injectors for Gasoline Direct-Injection Engines

Abstract

Citation: Mitroglou, N., Nouri, J. M. & Arcoumanis, C. (2009). Spray structure from double fuel injection in multihole injectors for gasoline direct-injection engines. Atomization and Sprays, 19(6), pp. 529-545. doi: 10.1615/AtomizSpr.v19.i6.30 This is the unspecified version of the paper.This version of the publication may differ from the final published version. Permanent ABSTRACTThe spray characteristics of double fuel injection in multi-hole injectors for direct-injection gasoline engines have been evaluated in a constant-volume chamber using Iso-Octane as fuel. Measurements of droplets mean and rms velocity and their diameter were obtained using a 2-D phase Doppler anemometer (PDA) at injection pressures up to 120bar, atmospheric chamber pressures and ambient temperatures up to 115°C. Complementary spray visualisation made use of a pulsed light, a CCD camera and a high-speed video camera synchronised with the injection process. Spray images with double injection revealed that there are delay times in needle opening and closing of the order of 0.6ms and 0.3ms, respectively, and that dwell times less than 0.5ms introduced a pre-spray prior to the second injection event while, for dwell times more than 0.5ms, the images showed that the overall jet-spray structure in the cases of the first and second injection event remained the same as those of single injection.PDA results near the injector exit quantified the relatively strong pre-spray at 0.3ms dwell time and revealed that its strength reduced with increasing dwell time so that at 1ms there was no sign of the prespray. The effect of ambient chamber temperature on the spray velocity for double injection was found to be significant at temperatures above 90°C; results at higher temperatures, 115°C, showed a consistent reduction in the mean droplets velocity up to 10% within the core of the first and second sprays, with a corresponding increase in the RMS velocity fluctuations due to the increased vaporisation rates and the droplets momentum loss. The droplet size distribution of the double injection spray was, in general, similar to that of single injection except during the dwell time when the droplets arithmetic mean diameter (AMD) with pre-spray was found to be smaller than those without the pre-spray because of the different type of droplets and the much higher data rates in the case of the pre-spray.

Multi-hole gasoline direct injection:In-nozzle flow and primary breakup investigated in transparent nozzlesand with X-ray

“…Goddwin et al 5 showed axial droplet velocities of around 80 m/s for a 5 MPa gasoline spray from a swirl injector in the near-nozzle region. For higher injection pressures and multi-hole injectors, Mitroglou 6 shows mean velocities of around 110 m/s for 8 MPa injection pressure and 150 m/s for 12 MPa injection pressure at 2.5 mm nozzle distance.…”

Spray measurement technology: a review

“…Knowledge of the internal nozzle geometry for real spray equipment is therefore necessary to relate these features to external spray characteristics and to facilitate predictive simulation. Furthermore, for transient sprays-particularly for the multi-pulse injection strategies [24, [195][196][197] that are increasingly common in automotive applications-the geometry changes rapidly as the needle moves within the injector. Indeed, small quantity injections can be composed entirely of the transients associated with opening and closing of the injector.…”

Large-eddy spray simulation under direct-injection spark-ignition engine-like conditions with an integrated atomization/breakup model

“…It also has the flexibility to direct spray plumes at desired locations to help meet the combustion system requirements. 2…”