Physical property measurement of primary reference fuels and blends using a droplet generator and high-speed imaging*

A liquid fuel delivery system for a fuel screening device has been developed using a piezoelectric droplet generator. Besides fuel delivery, it is desired to use the setup to characterize fuel physical properties relevant to spray atomization, evaporation, and mixing in internal combustion engines. This has motivated the development of a technique for real-time measurement of fuel viscosity and surface tension using shape oscillation dynamics. Shape oscillation theory relates the frequency of drop oscillation to fluid surface tension and its decay to fluid viscosity. This technique is applied to measure viscosity and surface tension of droplets in real-time by imaging the droplets and determining the amplitude and frequency of the droplet shape oscillation as a function of time. Measurements are compared with literature data and predictions of physical properties based on mixing rules.