Andy Rodriguez

Bio: Andy Rodriguez is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Flame spread & Internal heating. The author has an hindex of 2, co-authored 2 publications receiving 22 citations.

Transition from opposed flame spread to fuel regression and blow off: Effect of flow, atmosphere, and microgravity

Abstract: The spread of flames over the surface of solid combustible material in an opposed flow is different from the mass burning (or fuel regression) in a pool fire. However, the progress of a flame front over a solid fuel includes both flame spread and fuel regression, but the difference between these two processes has not been well clarified. In this work, experiments using cylindrical PMMA samples were conducted in normal gravity and in microgravity. We aim to identify the transition from opposed flame spread to fuel regression under varying conditions, including sample size, opposed flow velocity, pressure, oxygen concentration, external radiation, and gravity level. For a thick rod in normal gravity, as the opposed flow increases to 50–100 cm/s, the flame can no longer spread over the fuel surface but stay in the recirculation zone downstream of the cylinder end surface, like a pool fire flame. The flame spread first transitions to fuel regression at a critical leading-edge regression angle of α ≈ 45°, and then, flame blow-off occurs. Under large opposed flow velocity, a stable flat blue flame is formed floating above the rod end surface, because of vortex shedding. In microgravity at a low opposed flow (

Effect of external and internal heating on the flame spread and phase change of thin polyethylene tubes

Abstract: The flame spread over combustible materials is often affected by the fire thermal radiation and convection and the heat exchange with adjacent objects, which are especially complex on melting thermoplastics. This work chooses polyethylene (PE) tubes with a 2-mm thin wall to study the flame-spread behaviors under three heating conditions, (a) hot inner boundary, (b) hot ambient, and (c) external radiation. The tubes could simulate the insulation of electrical wires, and the inner boundary was controlled by flowing oil through at a constant temperature. Results show that just above the fuel molten point, the flame-spread rate unexpectedly decreases with the increasing environmental temperature, because the conductive cooling changed to convective cooling of molten PE. A thin layer of fuel can remain after the flame spread, and as the boundary temperature increases, the remaining PE decreases while the dripping mass increases. Under intense heating, burning behaviors eventually become similar regardless of the heating scenario. This work helps understand the flame spread and phase change of thermoplastic fires, particularly wires and cables, under various heating scenarios of realistic fire events.

A Review of Fundamental Combustion Phenomena in Wire Fires

Abstract: Electrical wires and cables have been identified as a potential source of fire in residential buildings, nuclear power plants, aircraft, and spacecraft. This work reviews the recent understandings of the fundamental combustion processes in wire fire over the last three decades. Based on experimental studies using ideal laboratory wires, physical-based theories are proposed to describe the unique wire fire phenomena. The review emphasizes the complex role of the metallic core in the ignition, flame spread, burning, and extinction of wire fire. Moreover, the influence of wire configurations and environmental conditions, such as pressure, oxygen level, and gravity, on wire-fire behaviors are discussed in detail. Finally, the challenges and problems in both the fundamental research, using laboratory wires and numerical simulations, and the applied research, using commercial cables and empirical function approaches, are thoroughly discussed to guide future wire fire research and the design of fire-safe wire and cables.

A review of near-limit opposed fire spread

Abstract: Creeping fire spread under opposed airflow is a classic fundamental fire research problem involving heat transfer, fluid dynamics, chemical kinetics, and is strongly dependent on environmental factors. Persistent research over the last 50 years has established a solid framework for different fire-spread processes, but new fire phenomena and recent developments continue to challenge our current understanding and inspire future research areas. In this review, we revisit the problem of opposed fire spread under limited and excessive oxygen supply. Various near-limit fire phenomena, as recently observed in flaming, smoldering, and glowing spread under various environment and fuel configurations, are reviewed in detail. Particularly, aspects of apparent importance, such as transition phenomena and heterogenous chemistry, in near-limit fire spread are highlighted, and valuable problems for future research are suggested.

Critical Drip Size and Blue Flame Shedding of Dripping Ignition in Fire

Abstract: Dripping of molten fuels is a widely observed fire phenomenon, and, by igniting other fuels, it can promote fire spread and increase fire hazards. In this work, dripping phenomena from fires of horizontally oriented wires, coated with polyethylene (PE), are investigated in the laboratory. It is found that as long as a flame is attached to the drip, thin tissue paper can be ignited by a single drip. Below a minimum diameter (Dmin = 0.63 mm), the drip floats up. Above a critical diameter (Dcrt = 2.3 mm), a flame can remain attached to the drip and ignite tissue paper as it falls through a distance of at least 2.6 m, thereby posing a significant fire hazard. A falling burning drip appears to the eye to be a blue chain of flame as a result of persistence of vision. Photographic evidence identifies a flame-shedding process, most likely associated with continual sequential ignition of fuel vapor within a von Karman vortex street generated behind the falling burning drip. The frequency of flame shedding agrees with both the frequency of modeled vortex shedding and the frequency of the unexpected sound that is heard during the process. This is the first time that combustion characteristics of dripping fire phenomena have been studied in detail, and this helps to better evaluate the risk and hazards of wire and facade fires.

A bibliometric study of pool fire related publications

Abstract: Pool fire is a common form of fire, which is constantly investigated along with the development of fire science and is also comprehensively employed as stable fire sources in examining other fire scenarios such as building and tunnel fires. According to the records in Science Citation Index Expanded database in the Web of Science Core Collection, a total of 1073 articles or reviews related to pool fires have been published from 1966 to 2019. In order to have a better understanding of knowledge structure of this topic and further identify its development history and currently popular concerns, a bibliometric analysis of pool fire research is conducted by means of visualization software VOSviewer and CiteSpace. This work visually provides a comprehensive overview of pool fire research in terms of annual publication output, source journals, productive countries/regions, authors and their cooperation network, subject terms, and reference co-citation analysis. The analysis provides networks of co-cited references, authors, countries, subject terms, and their respective clusters, indicating their ranking in contributions to the pool fire related publications. The results can be applied to enhance the understanding of pool fire research and support further work in this area.

Transitional flame-spread and fuel-regression behaviors under the change of concurrent wind

Abstract: On the occurrence of an environmental wind, the steady-state flame spread will go through a transitional process to a new steady state of the concurrent flame spread. However, such a transition between two steady states was rarely studied, despite that it often happens to many fire events. This paper presents an experimental study on the transitional flame-spread behavior over the horizontal PMMA plate by applying different concurrent airflows from the still air. The flame spread rate at the pyrolysis leading edge and the regression rate in the fuel rear end were studied during this transition. Such a transition could be divided into three stages based on both the length of pyrolysis and the fuel regression rate, (1) increasing to maximum, (2) dropping from peak, and (3) reaching a new steady-state. The concurrent wind velocity showed different influences on the flame spread rate and the fuel-rear regression rate during the transition. This work provides novel experimental data on the transitional behavior of wind-assisted flame spread, which helps evaluate the fire hazard under the sudden change of environmental conditions.