Temperature Effects on Droplet Oscillation Decay with Application to Fuel Property Measurement

Journal Article · Fri May 07 00:00:00 EDT 2021 · Atomization and Sprays

DOI:https://doi.org/10.1615/atomizspr.2021039068· OSTI ID:2331209

Dang, Wanjun ^[1]; Gurunadhan, M. ^[2]; Schoegl, I. ^[2]; Menon, S. ^[2]

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1. Louisiana State Univ., Baton Rouge, LA (United States); Louisiana State University and A&M College
2. Louisiana State Univ., Baton Rouge, LA (United States)

Observation of oscillation decay in droplets has been shown to be an effective approach in determining physical properties such as viscosity and surface tension for emerging biofuels using μl quantities. Herein this work extends the approach to higher temperatures relevant to fuel injection conditions for internal combustion engines. Experiments are conducted that use high-resolution strobed imaging of moving, heated, μm-sized, fuel droplets to capture shape oscillation decay through image processing and analysis. Two fuels are investigated, iso-butanol and a primary reference fuel (PRF 84), which is a mixture of iso-octane and n-heptane. A piezoelectric droplet generator is used to generate a continuous train of single droplets, which are given an initial perturbation and subsequently undergo damped oscillations, captured using strobed imaging. Surface tension and viscosity calculated at four different temperatures ranging from 30°C-55°C using the frequency and decay time associated with the fundamental mode are found to be within ~ 10% of reference values obtained from the literature. Complementary numerical simulations are performed that utilize a volume-of-fluid approach to track transient droplet oscillation phenomena along with heat and mass transfer in a 2D axisymmetric domain. Simulations, where droplet size and temperature can be independently varied, capture an expected decrease in oscillation frequency and increase in decay time, with increase in fuel temperature. The simulations are further used to study the relative contribution to deviations in surface tension and viscosity predictions due to heat and mass transfer from the droplet, as well as viscous effects violating the inviscid flow assumption in the droplet oscillation theory. Mass loss effects are found to be negligible. Temperature change due to heat transfer is found to have the next highest sensitivity, particularly for the more volatile PRF 84, which has a lower viscosity and associated Ohnesorge number. For isobutanol, which has a higher viscosity and Ohnesorge number, viscous effects contribute the most to deviation in fuel property predictions.

• Research Organization: Louisiana State Univ., Baton Rouge, LA (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: EE0007981
• OSTI ID: 2331209
• Journal Information: Atomization and Sprays, Journal Name: Atomization and Sprays Journal Issue: 10 Vol. 31; ISSN 1044-5110
• Publisher: Begell House
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
droplet heat and mass transfer
droplet oscillation
surface tension and viscosity measurement