Planar droplet sizing for studying the influence of ethanol admixture on the spray structure of gasoline sprays
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RESEARCH ARTICLE
Planar droplet sizing for studying the influence of ethanol admixture on the spray structure of gasoline sprays Matthias Koegl1,2 · Yogeshwar Nath Mishra1,3 · Kevin Baderschneider1 · Chris Conrad1,2 · Bastian Lehnert1,2 · Stefan Will1,2 · Lars Zigan1,2 Received: 19 May 2020 / Revised: 23 July 2020 / Accepted: 20 August 2020 © The Author(s) 2020
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.
* Matthias Koegl [email protected] 1
Lehrstuhl für Technische Thermodynamik (LTT), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany
2
Erlangen Graduate School in Advanced Optical Technologies, FAU, 91052 Erlangen, Germany
3
Present Address: NASA-Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
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Vol.:(0123456789)
209
Page 2 of 20
Experiments in Fluids
(2020) 61:209
Graphic abstract
1 Introduction The spray formation controls the combustion process of IC engines in terms of pollutant emissions, efficiency and consequently CO2-emissions. The atomization and mixture formation processes of gasoline direct injection spark ignition (DISI) engines are very complex. Atomization and mixture formation are mainly governed by the thermo-physical properties of the fuel and they affect subsequent processes like the soot formation essentially (Chen and Stone 2011; Shirazi et al. 2019; Storch et al. 2015; Koegl et al. 2019a). The usage of alternative biofuels like ethanol and butanol may contribute to an effective reduction of the CO2-emissions, but their utilization could rise the complexity of the mixture formation and combustion processes. Previous studies showed that an ethanol admixture to gasoline
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could lead to a soot reduction of DIS
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