John Easton

Bio: John Easton is an academic researcher from Case Western Reserve University. The author has contributed to research in topics: Flame spread & Combustion. The author has an hindex of 6, co-authored 22 publications receiving 136 citations. Previous affiliations of John Easton include Glenn Research Center.

Flame spread: Effects of microgravity and scale

Abstract: For the first time, a large-scale flame spread experiment was conducted inside an orbiting spacecraft to study the effects of microgravity and scale and to address the uncertainty regarding how flames spread when there is no gravity and if the sample size and the experimental duration are, respectively, large enough and long enough to allow for unrestricted growth. Differences between flame spread in purely buoyant and purely forced flows are presented. Prior to these experiments, only samples of small size in small confined volumes had been tested in space. Therefore the first and third flights in the experimental series, called “Saffire,” studied large-scale flame spread over a 94 cm long by 40.6 cm wide cotton-fiberglass fabric. The second flight examined an array of nine smaller samples of various materials each measuring 29 cm long by 5 cm wide. Among them were two of the same cotton-fiberglass fabric used in the large-scale tests and a thick, flat PMMA sample (1-cm thick). The forced airflow was 20–25 cm/s, which is typical of air circulation speeds in a spacecraft. The experiments took place aboard the Cygnus vehicle, a large unmanned resupply spacecraft to the International Space Station (ISS). The experiments were carried out in orbit before the Cygnus vehicle, reloaded with ISS trash, re-entered the Earth's atmosphere and perished. The downloaded test data show that a concurrent (downstream) spreading flame over thin fabrics in microgravity reaches a steady spread rate and a limiting length. The flame over the thick PMMA sample approaches a non-growing, steady state in the 15 min burning duration and has a limiting pyrolysis length. In contrast, upward (concurrent) flame spread at normal gravity on Earth is usually found to be accelerating so that the flame size grows with time. The existence of a flame size limit has important considerations for spacecraft fire safety as it can be used to establish the heat release rate in the vehicle. The findings and the scientific explanations of this series of innovative, novel and unique experiments are presented, analyzed and discussed.

Gravitational effects on flame spread through non-homogeneous gas layers

Abstract: Flame propagation through non-uniformly premixed gases occurs in several common combustion situations. Compared with the more usual limiting cases of diffusion or uniformly premixed flames, the practical concern of non-uniform premixed gas flame spread has received scant attention, especially regarding the potential role of gravity. This research examines a system in which a fuel concentration gradient exists normal to the direction of flame propagation and parallel with the gravitational vector. This paper presents experimental and numerical results for flame spread through alcohol/air layers formed by diffusive evaporation of liquid fuel at temperatures between the flash-point temperature and the stoichiometric temperature. A gallery, which had either the top and/or one end open to maintain constant pressure, surrounded the test section. The numerical simulations and experiments conducted include normal and microgravity cases. An interferometer was used, in normal gravity only, to determine the initial fuel layer thickness and fuel concentration distribution before and during flame spread. Both the model and experimental results show that the absence of gravity results in a faster spreading flame, by as much as 80% depending on conditions. This is the opposite effect to that predicted by an independent model reported earlier in this symposium series. Determination of the flame height showed that the flame was taller in microgravity, an effect also seen in the results of the numerical model reported here. Having a gallery lid results in faster flame spread, an effect more pronounced at normal gravity, demonstrating the importance of enclosure geometry. The interferometry and numerical model both indicated a redistribution of fuel vapor ahead of the flame. Numerical simulations show that, despite the rapid flame spread in these systems, the presence of gravity strongly affects the overall flow field in the gallery.

Transient flame growth and spread processes over a large solid fabric in concurrent low-speed flows in microgravity – Model versus experiment

Abstract: Concurrent-flow flame spread over a thin charring material was studied in an unmanned spacecraft. Two sample sizes were used: 5 cm by 29 cm and 41 cm by 94 cm, the largest ever samples burned in controlled experiments in microgravity. A low-speed ambient airflow of 20 cm/s was used. The samples were ignited from their upstream ends and were allowed to burn for several minutes. Video recorded during the burning process and readings from thermocouples on the sample surfaces were examined. The results showed that flames reached a quasi-steady state with nearly constant flame length for both sample sizes. However, the pyrolysis length exhibited an initial overshoot before reaching steady state for the large sample. This phenomenon has not been reported or observed until now. While steady state pyrolysis lengths were similar, the 5 cm wide sample had a slightly larger spread rate (by ∼13%) and a shorter burnout time (pyrolysis length over spread rate) compared to the 41 cm wide sample. A previously developed three-dimensional transient model was used to conduct the numerical study. Detailed profiles of the gas and solid phases, including flow patterns, species concentrations, temperature, solid burning rate, and heat flux distributions are examined. The modeling results reveal that flow reduction in a growing boundary layer along the sample surface accounts for the overshoot of the flame length observed for the large sample. Compared to a wide sample, a narrow sample has more effective oxygen transport across the width of the sample. This results in a stronger flame, a shorter flame standoff distance from the sample surface, and larger heat feedback to the sample. This accounts for the shorter burnout time for the narrow sample compared to the large sample.

In-Flight Manual Electronics Repair for Deep-Space Missions

Abstract: Severe limitations on mass and volume available for spares on long-duration spaceflight missions will require electronics repair to be conducted at the component level, rather than at the sub-assembly level (referred to as Orbital Replacement Unit, or 'ORU'), as is currently the case aboard the International Space Station. Performing reliable component-level repairs in a reduced gravity environment by crew members will require careful planning, and some specialty tools and systems. Additionally, spacecraft systems must be designed to enable such repairs. This paper is an overview of a NASA project which examines all of these aspects of component level electronic repair. Results of case studies that detail how NASA, the U.S. Navy, and a commercial company currently approach electronics repair are presented, along with results of a trade study examining commercial technologies and solutions which may be used in future applications. Initial design recommendations resulting from these studies are also presented.

Repair of Electronics for Long Duration Spaceflight

Abstract: To reduce mission risk, long duration spaceflight and exploration activities will require greater degrees of self-sufficiency with regards to repair capability than have ever been employed before in space exploration. The current repair paradigm of replacing Orbital Replacement Units (ORUs) of malfunctioning avionics and electronic hardware will be impractical, since carrying all of the spares that could possibly be needed for a long duration mission would require upmass and volume at unprecedented and unacceptable levels. A strategy of component-level repair for electronics, however, could significantly reduce the mass and volume necessary for spares and enhance mission safety via a generic contingency capability. This approach is already used to varying degrees by the U.S. Navy, where vessels at sea experience some similar constraints such as the need for self sufficiency for moderately long time periods, and restrictions on volume of repair spares and infrastructure. The concept of conducting component-level repairs of electronics in spacecraft requires the development of design guidelines for future avionics (to enable repair), development of diagnostic techniques to allow an astronaut to pinpoint the faulty component aboard a vastly complex vehicle, and development of tools and methodologies for dealing with the physical processes of replacing the component. This physical process includes tasks such as conformal coating removal and replacement, component removal, replacement, and alignment--all in the difficulty of a reduced gravity environment. Further, the gravitational effects on the soldering process must be characterized and accounted for to ensure reliability of the newly repaired components. The Component-Level Electronics-Assembly Repair (CLEAR) project under the NASA Supportability program was established to develop and demonstrate the practicality of this repair approach. CLEAR involves collaborative efforts between NASA s Glenn Research Center, Langley Research Center, Johnson Space Center, the National Center for Space Exploration Research, and the U.S. Navy. The project goals are 1) develop and demonstrate a manually-operated electronics repair capability to be conducted in a spacecraft environment; and 2) develop guidelines for designs of electronics that facilitates component-level repair for future space exploration efforts. This multi-faceted program utilizes a cross-disciplinary approach to examine pre- and post-repair diagnostics, conformal coating removal and replacement, component soldering, and electronics design for supportability. These areas are investigated by a combination of trade studies, ground based testing, reduced gravity aircraft testing, and actual spaceflight testing on the International Space Station (ISS) in multiple experiments. This paper details the efforts of this program, with emphasis on early trade study results, ground-based efforts, and two upcoming ISS experiments.

Numerical methods for engineers

Abstract: The fifth edition of "Numerical Methods for Engineers" continues its tradition of excellence. Instructors love this text because it is a comprehensive text that is easy to teach from. Students love it because it is written for them--with great pedagogy and clear explanations and examples throughout. The text features a broad array of applications, including all engineering disciplines. The revision retains the successful pedagogy of the prior editions. Chapra and Canale's unique approach opens each part of the text with sections called Motivation, Mathematical Background, and Orientation, preparing the student for what is to come in a motivating and engaging manner. Each part closes with an Epilogue containing sections called Trade-Offs, Important Relationships and Formulas, and Advanced Methods and Additional References. Much more than a summary, the Epilogue deepens understanding of what has been learned and provides a peek into more advanced methods. Approximately 80% of the end-of-chapter problems are revised or new to this edition. The expanded breadth of engineering disciplines covered is especially evident in the problems, which now cover such areas as biotechnology and biomedical engineering. Users will find use of software packages, specifically MATLAB and Excel with VBA. This includes material on developing MATLAB m-files and VBA macros.

Stabilization, propagation and instability of tribrachial triple flames

Abstract: A tribrachial (or triple) flame is one kind of edge flame that can be encountered in nonpremixed mixing layers, consisting of a lean and a rich premixed flame wing together with a trailing diffusion flame all extending from a single point. The flame could play an important role on the characteristics of various flame behaviors including lifted flames in jets, flame propagation in two-dimensional mixing layers, and autoignition fronts. The structure of tribrachial flame suggests that the edge is located along the stoichiometric contour in a mixing layer due to the coexistence of all three different types of flames. Since the edge has a premixed nature, it has unique propagation characteristics. In this review, the propagation speed of tribrachial flames will be discussed for flames propagating in mixing layers, including the effects of concentration gradient, velocity gradient, and burnt gas expansion. Based on the tribrachial edge structure observed experimentally in laminar lifted flames in jets, the flame stabilization characteristics including liftoff height, reattachment, and blowout behaviors and their buoyancy-induced instability will be explained. Various effects on liftoff heights in both free and coflow jets including jet velocity, the Schmidt number of fuel, nozzle diameter, partial premixing of air to fuel, and inert dilution to fuel are discussed. Implications of edge flames in the modeling of turbulent nonpremixed flames and the stabilization of turbulent lifted flames in jets are covered.

Extinction of laminar partially premixed flames

Abstract: Flame extinction represents one of the classical phenomena in combustion science. It is important to a variety of combustion systems in transportation and power generation applications. Flame extinguishment studies are also motivated from the consideration of fire safety and suppression. Such studies have generally considered non-premixed and premixed flames, although fires can often originate in a partially premixed mode, i.e., fuel and oxidizer are partially premixed as they are transported to the reaction zone. Several recent investigations have considered this scenario and focused on the extinction of partially premixed flames (PPFs). Such flames have been described as hybrid flames possessing characteristics of both premixed and non-premixed flames. This paper provides a review of studies dealing with the extinction of PPFs, which represent a broad family of flames, including double, triple (tribrachial), and edge flames. Theoretical, numerical and experimental studies dealing with the extinction of such flames in coflow and counterflow configurations are discussed. Since these flames contain both premixed and non-premixed burning zones, a brief review of the dilution-induced extinction of premixed and non-premixed flames is also provided. For the coflow configuration, processes associated with flame liftoff and blowout are described. Since lifted non-premixed jet flames often contain a partially premixed or an edge-flame structure prior to blowout, the review also considers such flames. While the perspective of this review is broad focusing on the fundamental aspects of flame extinction and blowout, results mostly consider flame extinction caused by the addition of a flame suppressant, with relevance to fire suppression on earth and in space environment. With respect to the latter, the effect of gravity on the extinction of PPFs is discussed. Future research needs are identified.

Flame spread: Effects of microgravity and scale

Abstract: For the first time, a large-scale flame spread experiment was conducted inside an orbiting spacecraft to study the effects of microgravity and scale and to address the uncertainty regarding how flames spread when there is no gravity and if the sample size and the experimental duration are, respectively, large enough and long enough to allow for unrestricted growth. Differences between flame spread in purely buoyant and purely forced flows are presented. Prior to these experiments, only samples of small size in small confined volumes had been tested in space. Therefore the first and third flights in the experimental series, called “Saffire,” studied large-scale flame spread over a 94 cm long by 40.6 cm wide cotton-fiberglass fabric. The second flight examined an array of nine smaller samples of various materials each measuring 29 cm long by 5 cm wide. Among them were two of the same cotton-fiberglass fabric used in the large-scale tests and a thick, flat PMMA sample (1-cm thick). The forced airflow was 20–25 cm/s, which is typical of air circulation speeds in a spacecraft. The experiments took place aboard the Cygnus vehicle, a large unmanned resupply spacecraft to the International Space Station (ISS). The experiments were carried out in orbit before the Cygnus vehicle, reloaded with ISS trash, re-entered the Earth's atmosphere and perished. The downloaded test data show that a concurrent (downstream) spreading flame over thin fabrics in microgravity reaches a steady spread rate and a limiting length. The flame over the thick PMMA sample approaches a non-growing, steady state in the 15 min burning duration and has a limiting pyrolysis length. In contrast, upward (concurrent) flame spread at normal gravity on Earth is usually found to be accelerating so that the flame size grows with time. The existence of a flame size limit has important considerations for spacecraft fire safety as it can be used to establish the heat release rate in the vehicle. The findings and the scientific explanations of this series of innovative, novel and unique experiments are presented, analyzed and discussed.

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.