Date of Award

Spring 2023

Document Type

Open Access Thesis


Mechanical Engineering

First Advisor

Sang Hee Won


Spherically symmetric isolated single droplet combustion has been observed mainly in microgravity conditions. This study sought to determine if spherically symmetric combustion can be produced in a lab-scale experiment using flow acceleration to counteract the effects of buoyancy. The experiment was conducted in a converging channel that decreased in width along its length to accelerate the flow and limit the formation of a boundary layer. The rate at which the area decreased was governed by the initial velocity condition set at the channel inlet.

The droplets were generated using a piezoelectric actuator which forced fuel out of an injector with a very narrow inner diameter. A thin metal disk at the top of the main fuel reservoir allowed the piezoelectric to directly influence the pressure of the fluid in the system. The flowrate of fuel through the system was held constant by a syringe pump. The diameter of droplets produced was approximately 0.5 – 0.6 mm and the fuels used were n-Heptane and ethanol.

It was found that the initial velocity at the inlet of the converging channel was 1 m/s. This velocity was used to define the curvature needed to observe sphere symmetric flames. A transition from laminar flow to turbulent flow within the converging channel due to the boundary layer growth was found. The droplet diameter and flame diameter were observed at various points along the length of the channel. The droplet diameter was determined using backlight imaging and a Photron Fastcam SA-Z highspeed camera. To observe the flame diameter, an Andor iStar intensified complementary metal oxide semiconductor (ICMOS) camera was used.

From this study, it was concluded that spherically symmetric flames can be created and observed under normal gravitational conditions utilizing accelerated fluid flow through a converging channel. The nature of this apparatus allows for further investigation into spherically symmetric isolated droplet combustion utilizing laser diagnostic techniques and nuclear magnetic resonance (NMR) imaging to analyze the composition of partially combusted samples. This will allow further study into the effects of preferential vaporization on multi-component mixtures.


© 2023, Mason Carrington Williams