Fuel concentration in isothermal Diesel sprays through structured planar laser imaging measurements

Abstract

ELSEVIER SCIENCE INCPayri, R.; Gimeno, J.; Marti-Aldaravi, P.; Manin, J. (2012). Fuel concentration in isothermal Diesel sprays through structured planar laser imaging measurements. International Journal of Heat and Fluid Flow. 34:98-106. doi:10.1016/j.ijheatfluidflow.2011.12.007 Fuel concentration in isothermal Diesel sprays through structured planar laser imaging measurements AbstractThe mixing of isothermal liquid sprays in engine-like conditions has been investigated by applying the Structured Planar laser Imaging technique to remove multiple light scattering. The intensity of the illumination plane has been recovered by removing multiply scattered light and mapping the spray three-dimensionally via discrete tomography. Based on the extinction of light within the illumination plane, the number density has been extracted. Coupled with 2-D maps of droplet diameters obtained through LIF/Mie ratio, the number density allowed to calculate the fuel concentration in the sprays. The mixture fraction of DI Diesel sprays injected into an inert environment held at room temperature has been evaluated and compared to a validated model based on gas-jet theory. The experimental results showed good agreement with the predictions when assuming a Gaussian radial distribution and tuning the Schmidt number. A Schmidt number below the unity demonstrated to be the best fit to the results. In addition, the Gaussian distribution showed to be a good assumption based on the closeness to the experiments, although some differences in shape have been noticed. For different testing conditions, whilst the influence of ambient density on mixing was expected, the effect of injection pressure brought up additional information concerning the global mixing of liquid sprays.

LIF/Mie Droplet Sizing of Water Sprays from SCR System Injector using Structured Illumination

“…In the setup used here the instantaneous LIF/Mie ratio is available only for conventional illumination since SLIPI used here requires three images obtained for different modulation phases of the structured light sheet. Interesting option for instantaneous imaging is two-pulse SLIPI based only on two phases as discussed by Payri et al [21] and Kristensson et al [22]. This approach however requires a dual cavity laser.…”

An Analytical Model of a Two-Phase Jet with Application to Fuel Sprays in Internal Combustion Engines

“…The governing equations (18), (20) were solved by Schlichting [24] for the single phase axisymmetric jet. A solution for the fuel volumetric fraction can then be obtained by using the equation of conservation of mass for the fuel phase (equation (19)).…”

“…Equations (18), (20) can be solved by defining a stream function Ψ similarly to the case of the single-phase laminar jet [24], where: Similarly to the single phase jet, the stream function will be assumed to have the following functional form: (26) where η =r / x and F is a function to be determined. Substituting the velocity components into equation 20with expressions derived from equations (25), (26), an ordinary differential equation for F is obtained: (27) The general solution of equation 27which satisfies the necessary boundary conditions is [24]: (28) where ξ = γη and γ is a constant to be determined below.…”

“…Experimental correlations also exist for the radial distributions of mixture velocity and fuel concentration. Commonly [14], [18] a Gaussian profile is assumed for both the velocity and fuel concentration: Where x, r are the axial and radial coordinates within the jet, Sc is the droplets' Schmidt number (see definition below) and a constant λ was determined experimentally.…”

Verification of a new CFD compressible segregated and multi-phase solver with different flux updates-equations sequences

“…Internal flow studies deal with the influence of the injector geometry on the flow pattern [1], the cavitation phenomena [2], the needle lift [3] and eccentricity and other manufacturing issues relevance, etc. ; and external flow studies deal with fuel break-up [4,5], atomization and fuel-air mixing processes [6]. This division is made because of the different flow nature: in the internal part the flow is continuous, mono-phase liquid (or multi-phase if cavitation is considered); and in the external part far from the injector exit the flow is dispersed multi-phase.…”