A. C. Fernandez-Pello

Bio: A. C. Fernandez-Pello is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Ignition system & Flame spread. The author has an hindex of 36, co-authored 112 publications receiving 4274 citations. Previous affiliations of A. C. Fernandez-Pello include Northwestern University & Harvard University.

Sooting behavior dynamics of a non-buoyant laminar diffusion flame

Abstract: Local soot concentrations in non-buoyant laminar diffusion flames have been demonstrated to be the outcome of two competitive processes, soot formation and soot oxidation. It was first believed that soot formation was the controlling mechanism and thus soot volume fractions could be scaled with a global residence time. Later studies showed that this is not necessarily the case and the local ratio of the soot formation and oxidation residence times is the prime variable controlling the ultimate local soot volume fractions. This ratio is a strong function of geometry and flow field, thus a very difficult variable to properly quantify. This study presents a series of microgravity, low oxidizer flow velocity, experiments where soot volume fraction measurements have been conducted on a laminar, flat plate boundary layer type diffusion flame. The objective of the study is to determine if the above observations apply to this type of diffusion flames. The fuel is ethylene and is injected through a flat plate poro...

Controlling Mechanisms of Flame Spread

Abstract: Recent advances in the experimental study of the mechanisms controlling the spread of flames over the surface of combustible solids are summarized in this work. The heat transfer and gas phase chemical kinetic aspects of the flame spread process are addressed separately for the spread of flames in oxidizing flows that oppose or concur with the direction of propagation. The realization that, in most practical situations, the spread of fire in opposed gas flows occurs at near extinction or non-propagating conditions is particularly significant. Under these circumstances, gas phase chemical kinetics plays a critical role and it must be considered if realistic descriptions of the flame spread process are attempted. In the concurrent mode of flame spread, heat transfer from the flame to the unburnt fuel appears to be the primary controlling mechanism. Although gas phase chemcial kinetics is unimportant in the flame spreading process, it is important in the establishment and extension of the diffusion ...

Flame spread in an opposed forced flow: the effect of ambient oxygen concentration

Abstract: The velocity of flame propagation over the surface of thick PMMA and thin paper sheets has been measured as a function of the velocity and oxygen concentration of a forced gas flow opposing the direction of flame propagation. It is shown that although for thin fuels the flame spread rate always decreases as the opposed flow velocity increases, for thick fuels the dependence of the spread rate on the gas velocity is also a function of the ambient oxygen concentration. For low oxygen concentrations the flame spread rate decreases as the velocity of the gas flow increases. For high oxygen concentrations, however, the spread rate increases with the flow velocity, reaches a maximum and then decreases as the gas velocity increases. The velocity of the opposed flow at which the maximum occurs is a function of the oxygen concentration, decreasing as the concentration decreases. Following phenomenological considerations and simplified descriptions of the primary mechanisms occurring during the flame spread process, the experimental results are correlated by two non-dimensional parameters, one describing the gas phase kinetic effects and the other describing the process of heat transfer from the flame to the fuel. Such a correlation provides a powerful means of predicting the flame spread prcess as well as physical insight into the mechanisms controlling the propagation of the flame.

Forward smolder of polyurethane foam in a forced air flow

Abstract: An experimental study is conducted of forward smolder of polyurethane foam. Air is used as oxidizer, and is forced in the direction of smolder propagation under conditions that produce approximately one-dimensional forward smolder propagation. The objective of the study is to provide further understanding of the mechanisms controlling forward smolder and verification of theoretical models of the problem. Upward and downward forward smolder are compared to also observe the effect of buoyancy on the process. Measurements of the temperature histories at several locations throughout the foam sample are used to infer the characteristics of the smolder process, and to calculate the smolder propagation velocity along the sample length as a function of the air flow velocity and gravitational orientation. It is found that as the flow velocity is increased, there is a transition in the smolder characteristics from a smolder process that is characterized by the propagation of a single exothermic oxidation (smolder) reaction to one characterized by the propagation of two reactions, an oxidative smolder reaction preceded by an endothermic pyrolysis reaction. Buoyancy is observed to affect this mode of smolder at very low air velocities, or when the smolder front approaches the sample end. The smolder velocity data are correlated well in terms of a nondimensional smolder velocity derived from previously developed theoretical models of forward smolder. The good agreement between theory and experiments verifies that the smolder controlling mechanisms and simplifying assumptions implicit in the models are appropriate at least for the present experimental conditions.

Heat and Mass Transfer

Abstract: Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

Recent advances in droplet vaporization and combustion

Abstract: Recent progress on understanding the fundamental mechanisms governing droplet vaporization and combustion are reviewed. Topics include the classical d2-Law and its limitations; the major transient processes of droplet heating and fuel vapor accumulation; effects due to variable transport property assumptions; combustion of multicomponent fuels including the miscible fuel blends, immiscible emulsions, and coal-oil mixtures, finite-rate kinetics leading to ignition and extinction; and droplet interaction. Potentially promising research topics are also suggested.

Evaporation and combustion of sprays

Abstract: A description is provided of recent spray evaporation and combustion models, taking into account turbulent two- and three-dimensional spray processes found in furnaces, gas turbine combustors, and internal combustion engines. Within the class of spray models of interest, two major categories are distinguished, including locally homogeneous flow (LHF) models and separated flow (SF) models. SF models are of the greatest practical importance, but LHF models have distinct advantages in some cases. Attention is also given to recent progress on modeling interactions between drops and the flow in both dilute and dense sprays, involving sprays having low and high liquid volume fractions, respectively.