P. A. Bui

Bio: P. A. Bui is an academic researcher from University of Massachusetts Amherst. The author has contributed to research in topics: Heat flux & Quenching. The author has an hindex of 1, co-authored 1 publications receiving 87 citations.

The role of radical wall quenching in flame stability and wall heat flux: hydrogen-air mixtures

Abstract: The role of wall quenching of radicals in ignition, extinction and autothermal behaviour of premixed H2–air flames impinging on a flat surface was studied using numerical bifurcation techniques, with detailed gas-phase chemistry and surface radical recombination reactions. Quenching out of radicals was found to retard the system at ignition due solely to the kinetics of the surface reactions. While kinetically extinction is also retarded, the thermal feedback from the wall recombination of radicals can render the flame more stable and lead to a higher wall heat flux as a function of wall temperature compared to an inert surface under some conditions. It is also shown that the combined kinetic and thermal effects of wall radical quenching can expand the autothermal regime. Implications for estimating flammability limits near reactive surfaces of tubes are finally discussed. M This article features multimedia enhancements available from the abstract page in the online journal; see http://www.iop.org.

Micro and mesoscale combustion

Abstract: A review of research and development on micro and mesoscale combustion is presented, with an emphasis on fundamental understandings achieved in the field during the last decade. Due to its small scale nature, increasing effects of flame–wall interaction and molecular diffusion are the characteristic features of micro and mesoscale combustion. After brief review of device developments, overview of fundamentals in micro and mesoscale combustion as well as possible future directions is presented.

High-Temperature Kinetics of the Homogeneous Reverse Water-Gas Shift Reaction

Abstract: The high-temperature rate of reaction of the homogeneous, reverse water–gas shift reaction (rWGSR) has been evaluated in quartz reactors with rapid feed preheating under both low- and high-pressure conditions. The form of the power-law rate expression was consistent with the Bradford mechanism. The Arrhenius expressions for the reaction rate constant, corresponding to the empty reactor, were in very good agreement with the low-pressure results of Graven and Long, but yielded rate constants roughly four times greater than those obtained in our packed reactor and those reported by Kochubei and Moin and by Tingey. Reactor geometry was not responsible for these differences because computational fluid dynamics simulations revealed similar residence time distributions and comparable conversions when the same kinetic expression was used to model the rWGSR in each reactor. Most likely, the empty NETL reactor and the Graven and Long reactor did not attain an invariant value of the concentration of the chain carrier (H) at low reaction times, which led to an overestimation of the rate constant. Conversions attained in an Inconel® 600 reactor operating at comparable conditions were approximately two orders of magnitude greater than those realized in the quartz reactor. This dramatic increase in conversion suggests that the Inconel® 600 surfaces, which were depleted of nickel during the reaction, catalyzed the rWGSR. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1028–1041, 2004

Submillimeter‐scale combustion

Abstract: Until recently, the concept of combustion within a confined space defined by a microburner was thought to be impossible. Extensive literature dating back to Davy's seminal work in 1817 has discussed how thermal and chemical quenching set a minimum size below which no flame can exist. In this report, though, it is shown that microcombustion is possible if the wall composition and structure are carefully controlled. It is suggested that there are three keys to obtaining microcombustion: (1) the walls of the microburner need to be fabricated from materials that do not quench radicals so that the gas-phase combustion reactions can occur unimpeded; (2) the device needs to be insulated well enough that the net heat generation is sufficient to keep the reacting mixture hot enough to sustain significant combustion; and (3) the flow pattern in the burner needs to be such that the temperature is low enough not to melt the walls, yet the flame fills the entire space. Using this design strategy, devices burning methane–air and propane–air mixtures in a 750-μm slot were designed and optimized to achieve high conversion. These results show that microcombustion is possible with consideration of microscale engineering challenges and fitting combustor design. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3206–3214, 2004