Planar droplet sizing for studying the influence of ethanol admixture on the spray structure of gasoline sprays

Abstract

A novel planar droplet sizing (PDS) technique based on laser-induced fluorescence (LIF) and Mie-scattering is utilized for the characterization of the spray structure under gasoline direct-injection spark-ignition (DISI) conditions. Fuel effects on the spray structure and cyclic variations are studied for a gasoline surrogate fuel (Toliso, consisting of 65 vol.% isooctane and 35 vol.% toluene) and the gasoline-ethanol blend E20 (20 vol.% ethanol admixture). Sauter mean diameter (SMD) results are compared with those from phase-Doppler anemometry (PDA) measurements showing good agreement especially at early points in time (up to 1.2 ms after start of injection). The liquid spray propagation and SMD are very similar for both fuels indicating similar atomization behavior. Both investigated fuels show comparable cyclic variations of the spray shape. A larger width and slightly larger droplet sizes are observed for the E20 spray when stronger evaporation occurs (at 2 ms). At these later points in time, the PDS-measured droplet sizes differ from the PDA-results. Here the limitation of the PDS-technique becomes obvious as a partial evaporation of the droplets may lead to large systematic errors. A numerical simulation of single droplets is provided for clarification of issues of droplet evaporation in PDS. Graphic abstract

Droplet thermometry based on an optimized two dye two-color laser-induced fluorescence concept

“…Additionally, a temperature reduction due to evaporation of at least 10 K is reasonable for ethanol droplets. In a numerical simulation, a droplet temperature reduction of about 17 K for isolated ethanol droplets was observed for initial droplet diameters of 5 μm-40 µm within the first 1.2 ms [38] (the initial droplet temperature was 293 K). This corresponds to a droplet size reduction of 3.4% for an initially 10 μm large droplet.…”

Experimental analysis of Lagrangian paths of drops generated by liquid/liquid sprays

“…However, for sprays Deskmukh and Ravikrishna [10] and Desentes et.al [11] have presented methods to account for attenuation effects due to absorption, non-homogenization, and Mie scattering of the laser sheet for volume fraction measurement. Kannaiyan et.al [12], Koegl et.al [13] and Zimmer et.al [14] have demonstrated accurate measurement of the Sauter mean diameter (SMD) by separating detection of LIF and Mie scattering signals with optical filters. Kristensson et.…”

Characterization of Fluorescence Tracers for Thermometry and Film Thickness Measurements in Liquid Coolants Relevant for Thermal Management of Electric and Electronic Components

“…Here, besides the usual sCMOS cameras, the use of high-speed cameras was also achievable. A similar setup based on two sCMOS cameras was used in earlier investigations [20,25,26,88].…”

“…The LIF/Mie technique is based on the d 3 dependence of the LIF signal and the d 2 dependence of the Mie signal [13][14][15][16][17][18][22][23][24]. A quantitative characterization of the spray in terms of absolute SMD is only possible with adequate calibration such as phase doppler interferometry (PDI) or micrometric droplet measurements with a droplet generator [14,25,26]. In addition to the LIF/Mie approach, other techniques such as the Raman/Mie ratio [27], the polarization ratio [28][29][30][31][32], and MDR (morphologydependent resonances) images of micro droplets [33] enable a determination of a 2D droplet size distribution.…”