Genichiro Kushida

• Aichi Institute of Technology

Near-limit characteristics of flame spread are of importance from the fire-safety point of view. This paper presents results of opposed-flow flame-spread experiments in a narrow channel. With an increase in the opposed-flow velocity, the spread velocity first increases and then slightly decreases. Flame spread was not possible when the opposed-flow...

This paper reports experimentally observed characteristics of smoldering and flaming spread along a cellulosic combustible solid. A thin cylindrical sample was burned in a forced oxidizer flow, and quasi-steady, downward opposed-flow spread was observed. The oxidizer velocity and the oxygen concentration were varied, and the spread velocity and the...

This paper presents an experimental and theoretical study on limit conditions for smoldering combustion of biomass fuel. A fuel rod was burned in an oxidizer flow in a Tsuji-Yamaoka type, counterflow configuration, and the spread rate and temperature distribution were measured. The spread rate and maximum temperature increased with an increase in o...

Smoldering spread along a horizontally-oriented thin cellulosic solid in a narrow channel is a representative near-limit fire phenomenon. Because of the narrowness of the domain, the phenomenon allows reduced-dimensional modeling. This paper presents a one-dimensional model, which considers two reactions, i.e., cellulose pyrolysis that produces cha...

Fire whirl, which is generated by swirling flow and buoyant flow, is sometimes observed in a big fire. It is a tornado-like vortex of flame and terrible disaster. In particular, the movement of fire whirl expands the damage of fires. However, there are many unclear points about the fire whirl movement. Most of previous studies on fire whirl movemen...

This paper presents results of experimental and numerical investigations of flame spread along a thin solid in an opposed oxygen flow in a narrow channel. Experiments are conducted at various oxygen flow speeds and gas-phase heights. For a low gas-phase height or a low oxygen flow speed, a large portion of solid is left unburned, and the burned reg...

This paper presents experimental observations and a theory of near-floor flame spread along a thin solid. Experiments were conducted by igniting at the center of a thin circular paper sheet that was held at a given height h from the bottom floor. It was observed that the flame front was corrugated and often broke into separated structures when h wa...

It is important for the generation of fire whirl to know how a swirling flow around a flame affects the flame behavior, and therefore it is very useful to investigate the flame behavior and the transient local distributions of physical property such as velocity, pressure, temperature, etc. around the flame by using a numerical analysis. In the pres...

Oxygen tends to be deficient in a narrow space or in a microgravity environment where natural convection is suppressed. When a combustible solid is burned in such an environment, smoldering combustion without flame occurs. Since smoldering combustion is often observed in the initial stage of a fire, insights into smoldering combustion help understa...

Smoldering combustion occurs when a solid is burned in a narrow channel between two parallel plates. A fingering pattern is then formed owing to the instability of smoldering front. The objective of this paper is to modify the theory proposed by Kagan and Sivashinsky and assess its validity by comparing its predictions with experimental data. A hea...

This paper presents results of theoretical and experimental studies on smoldering combustion of thin solid with a particular focus on its stability. In a recent study, an effective Lewis number was proposed to be the governing parameter of the phenomena; it was shown that combustion characteristics such as the fraction burned and the finger width c...

This paper presents numerical and experimental results of the smoldering propagation along a thin solid in a narrow space. This study particularly focuses on the formation of a fingering pattern caused by an instability mechanism—an important phenomenon from a fire safety point of view because the formation of such a pattern increases the smolderin...

This paper presents a simplest model that describes the smoldering propagation over a thin solid in a narrow space. A two-equation model is derived based on phenomenological arguments. The Lewis number, defined as the ratio of the solid thermal diffusivity to the oxygen diffusion coefficient, is identified as an important parameter. Numerical solut...

Dynamic behaviors of gas/plasma mixture generated by microwave discharge jet at atmospheric pressure have been investigated in terms of the effects of working gas dynamics on the discharge characteristics, focusing on the following four points: formation of discharge jet at the ignition phase, growing speed of plasma plume in relation to gas flow r...

The authors experimentally investigated the dynamic behavior of buoyancy-induced flame oscillation under a swirling flow produced by rotating a cylindrical burner tube, focusing on the characterization of the complex dynamics in flame front by a use of nonlinear time series analysis. A Wayland method (R. Wayland et al., 199340. Wayland , R. , Bro...

Fluid mechanical properties of microwave discharge jet for argon and helium plasmas at atmospheric gas pressure is investigated. Kelvin-Helmholtz (K-H) instability due to shear flow of working gas with surrounding air is seen to reflect on the plasma structure. Pulsation phenomenon for helium plasma jet is found not to have a counterpart in gas flu...

From the viewpoint of nonlinear dynamics, the dynamic behavior of buoyancy-induced flame oscillation has been experimentally investigated under a swirling flow produced by rotating a cylindrical burner tube. As the rotational Reynolds number increases, the dynamic behavior undergoes a significant transition from periodic oscillation to low-dimensio...

Numerical simulations have been conducted to study methane diffusion flame with burner rotation. The burner rotational speed is from 300 rpm to 1200 rpm; the burner diameter is 1 cm and 2 cm; the injection velocity is 10 cm/s and 15 cm/s. Quantitative data obtained includes the velocity profile, the temperature profile, and the frequencies of fluct...

This paper adds vortex flows around Burke–Schumann diffusion flames to predict the flame heights and the flame shapes of small fire whirls. The resulting model matches the measurements of methanol flames in a previous laboratory experiment and the results of numerical calculations in this paper. Burgers Vortex is assumed inside the vortex core radi...

The buoyancy-induced oscillation is referred to as the so-called flame flickering and its dynamics are important when revealing mechanism of flame oscillations encountered in some combustion systems. Many aspects of flame oscillation / buoyancy coupling have been extensively explored, but the effect of swirling flow on buoyancy-induced flame flicke...

Decomposition of Methane Hydrate is studied numerically. Global one-step irreversible reaction model is applied for melting Methane Hydrate and its Arrhenius type of temperature dependency. Two-dimensional, time-dependant phenomena in the cold Methane Hydrate block are simulated. As the time goes by, local temperature increases due to thermal condu...

Unsteady behavior of buoyant diffusion flames which were observed at various gravity fields was studiednumerically by a finite volume method using the low-Mach number approximation and the temperaturedependent physical properties such as viscosity and diffusivity. The numerical model was a time-dependent and axisymmetric flow including a single-ste...

A numerical study was made on the time-dependent ignition process of a horizontally placed solid fuel heated by external radiation. As soon as the solid starts to be heated, a hot plume with combustible fuel is ejected into the oxygen-containing atmosphere to be mixed and to react leading to a spontaneous ignition. The effects of gravity and ambien...

The effects of natural convection on self-ignition of solid fuel heated by external radiation were studied numerically. The numerical model includes thermal heating and subsequent degradation reactions in the solid phase with heat and mass transport of evolved degradation products into an atmosphere containing oxygen. The combustible fuel component...

An axisymmetric, time-dependent model is developed describing auto-ignition and subsequent transition to flame spread over a thermally-thin cellulosic sheet heated by external radiation in a quiescent microgravity environment. Due to the unique combination of a microgravity environment and low Reynolds number associated with the slow, thermally ind...

A mathematical model of the transient three-dimensional heat transfer between a slowly moving ambient gas stream and a thermally thick or thin flat surface heated by external radiation in a microgravity environment is presented. The problem is motivated in part by fire safety issues in spacecraft. The gas phase is represented by variable property c...

A numerical study on the characteristics of turbulent fluctuations in two-dimensional fuel jet diffusion flames developed in a co-flowing air stream is made by adopting the flame surface model of infinite chemical reaction rate and unit Lewis number. The time dependent Navier-Stokes equation with variable density is solved numerically by using a fi...

Attention is given to a theoretical model describing the behavior of a thermally thin cellulosic sheet heated by external thermal radiation in a quiescent microgravity environment. This model describes thermal and oxidative degradation of the sheet and the heat and mass transfer of evolved degradation products from the heated cellulosic surface int...

The present study examines the time-dependent behavior of a 2D diffusion flame developed in the shear layer of a fuel jet into a coflowing airstream in terms of the flame surface model of the infinite chemical reaction rate with a unity Lewis number. The time-dependent compressive Navier-Stokes equation with the equation for the coupling function i...

A numerical study on the transition from laminar to turbulent of two-dimensional fuel jet flames developed in a co-flowing air stream was made by adopting the flame surface model of infinite chemical reaction rate and unit Lewis number. The time dependent compressible Navier-Stokes equation was solved numerically with the equation for coupling func...

Fluid flow and heat transfer in a plate-fin and tube heat exchanger were studied, using a fundamental model consisting of a pair of parallel plates and a square cylinder passing perpendicularly through the plates, which simulated plate-fins and a tube, respectively. The analytical results are reported about the unsteady flow and heat transfer at th...

Fluid flow and heat transfer in a two-dimensional miter-bend were examined in connection with a corrugated wall channel as a means of augmenting a forced-convective heat transfer with a single-phase flow in a heat exchanger. In a previous paper, experimental results were not in perfect agreement with those of theoretical analysis because of the eff...

Fluid flow and heat transfer in a two-dimensional miter-bend have been examined in connection with a corrugated wall channel as a means of augmenting a forced-convection heat transfer with a single-phase flow in a heat exchanger. Pressure losses, distributions of mean velocity fluctuation, streaklines, power spectra of velocity fluctuation and loca...

Fluid flow and heat transfer in a two-dimensional miter-bend have been examined in connection with a corrugated wall channel as a means of augmenting a forced-convection heat transfer with a single-phase flow in a heat exchanger. In the previous paper, experimental results were not in perfect agreement with those of theoretical analysis, because of...

Fluid flow and heat transfer in a plate-fin and tube heat exchange were studied, using a fundamental model consisting of a pair of parallel plates and a square cylinder passing perpendicularly through the plates, which simulated plate-fins and a tube, respectively. The analytical results were reported for a laminar flow at Reynolds number Re=200 in...

Three-dimensional flow and heat transfer in a rectangular miter-bend, with a 90°C turn, were studied for the purpose of examining the effect of centrifugal force due to bending, in connection with a corrugated wall channel as a means of augmenting the forced-convection heat transfer with a single-phase flow in a heat exchanger. Analysis of the resu...

Three-dimensional flow and heat transfer in a rectangular miter-vend, with a 90° turn, were studied for the purpose of examining the effect of centrifugal force due to bending, in connection with a corrugated wall channel as a means of augmenting a forced-convection heat transfer with a single-phase flow in a heat exchanger. Analysis of the results...

Axisymmetric forced oscillations of a shallow spherical shell subjected to harmonic excitation are investigated. Based on modal equations derived from the von Karman dynamic equations, a theoretical analysis is conducted of the harmonic oscillation as well as the subharmonic oscillation of order 1/2. The theoretical analysis reveals that in certain...

名古屋大学博士学位論文 学位の種類 : 工学博士(論文) 学位授与年月日 : 昭和63年12月1日