Ignition in low temperature combustion engines is governed by a coupling between lowtemperature oxidation kinetics and diffusive transport. Therefore, a detailed understanding of the coupled effects of heat release, low-temperature oxidation chemistry, and molecular transport in cool flames is imperative to the advancement of new combustion concepts. This study provides an understanding of the low temperature cool flame behavior of butane isomers in the counterflow configuration through the addition of ozone. The initiation and extinction limits of butane isomers' cool flames have been investigated under a variety of strain rates. Results revealed that, with ozone addition, establishment of butane cool diffusion flames was successful at low and moderate strain rates. Iso-butane has lower reactivity than n-butane, as shown by higher fuel mole fractions needed for cool flame initiation and lower extinction strain rate limits. Ozone addition showed a significant influence on the initiation and sustenance of cool diffusion flames; as ozone-less cool diffusion flame of butane isomers could not be established even at high fuel mole fractions. The structure of a stable n-butane cool diffusion flame was qualitatively examined using a time of flight mass spectrometer. Numerical simulations were performed using a detailed chemical kinetic model and molecular transport to simulate the extinction limits of the cool diffusion flames of the tested fuels. The model qualitatively captured experimental trends for both fuels and ozone levels, but over-predicted extinction limits of the flames. Reactions involving low-temperature species predominantly govern extinction limits of cool flames. The simulations were used to understand the effects of methyl branching on the behavior of n-butane and iso-butane cool diffusion flames.

Microfluidics is an emerging technology that has gained attention by the industry for its capabilities to investigate and visualize fundamental recovery mechanisms at the pore scale in a microdevice, mimicking, to some extent, the actual rock pore-network. While current technologies are capable of building micromodels that are either water-wet or oil-wet, a technique to achieve a representative mixed-wet property is still unreached. In this work, we introduce a novel surface coating capability using thin film deposition to fabricate surfaces with selective wettability, oil-wet and water-wet, an effort to mimic actual mixed-wet rock. This unique approach enables the generation of hydrophobic surfaces in selected regions by altering the hydrophilic surface property of silicon substrate at the microscale. A selective wettability control mask and Perfluorodecyltrichlorosilane (FDTS) hydrophobic coating using molecular vapor deposition (MVD) were used for surface wetting properties alteration. Surface measurements, including contact angle measurements, X-ray photoelectron spectroscopy (XPS), and Transmission Electron Spectroscopy (TEM) imagining, were performed to evaluate the thin-film composition and morphology. By altering the wetting state of the substrate by the coated film, a selective mixed wettability surface was achieved. This technique has the potential to be utilized in microfluidic device developments. Tuning the wetting state of the substrate to mimic the mixed-wet characteristics of reservoir rocks, such as carbonates and shales, can enhance our understanding of complex fluid behaviors in porous media and provide a crucial contribution to many subsurface petroleum engineering applications such as enhanced oil recovery (EOR) and CO2 storage.