Tsuneyoshi Matsuoka

Symmetric and Nonsymmetric Flame Spread between Parallel Plates of Thick Combustible Solid

To identify the occurrence conditions of a symmetry-breaking phenomenon, numerical simulations of flame spread along parallel, combustible plates are performed. Two-dimensional, time-dependent cons...

Geometrical Effects of a Narrow Channel on Flame Spread in an Opposed Flow

ABSTRACT Geometrical effects on the flame spread over thermally thick combustibles in a narrow channel were experimentally investigated. Two series of experiments were conducted with two kinds of fuel geometry to form a narrow channel: parallel plates and cylinder. Both channels were made of polymethyl methacrylate, which also served as a combustible specimen, and the channel height varied from 1 mm to 10 mm. An oxidizer flow was supplied at specified velocities of 30 cm/s or 90 cm/s. The flame spread through the channels in the direction opposite to the oxidizer flow was observed. Although the spread rates had similar trends, there was a slight difference between their values at the same conditions. The effective velocity and the excess-volume ratio were evaluated to explain the geometrical effects. Accordingly, it is suggested that the variation of the velocity profile due to the channel geometry is the main factor affecting the spread rate.

High-speed imaging of temporal thermal field in thermoplastic material during flame spread

We have developed a real-time holographic interferometry system with high-speed camera in order to visualize two dimensional, time-dependent temperature distributions in gas and solid phases simultaneously during the combustion of transparent thermoplastic material. The ultimate goal of this study is to contribute to upgrade the flame spread modeling at which the complex physical processes (e.g., fuel regression, bubble formation, motion inside the molten layer) have been mostly ignored, although those effect are not so well-known and not well-studied. As first step, thermal response of thermoplastic material subjected to the disturbance in gas phase was investigated. Thick transparent PMMA slab was used as sample specimen and the thermal status in gas, molten and solid phases over spreading flame downwardly was examined. Whole optical set was carefully arranged and tuned to obtain satisfactory clear interference fringes appeared in gas and solid phases during the combustion event. Following the disturbance introduced in the system, the time change of refractive index in gas, molten and solid phases and the corresponding temperature distributions was recorded via a high-speed camera. Response delay time was carefully analyzed to discuss the potential role of the liquid phase on the burning character.

Modified Regression Rate Formula of PMMA Combustion by a Single Plane Impinging Jet

A modified regression rate formula for the uppermost stage of CAMUI-type hybrid rocket motor is proposed in this study. Assuming a quasi-steady, one-dimensional, an energy balance against a control volume near the fuel surface is considered. Accordingly, the regression rate formula which can calculate the local regression rate by the quenching distance between the flame and the regression surface is derived. An experimental setup which simulates the combustion phenomenon involved in the uppermost stage of a CAMUI-type hybrid rocket motor was constructed and the burning tests with various flow velocities and impinging distances were performed. A PMMA slab of 20 mm height, 60 mm width, and 20 mm thickness was chosen as a sample specimen and pure oxygen and O2/N2 mixture (50/50 vol.%) were employed as the oxidizers. The time-averaged regression rate along the fuel surface was measured by a laser displacement sensor. The quenching distance during the combustion event was also identified from the observation. The comparison between the purely experimental and calculated values showed good agreement, although a large systematic error was expected due to the difficulty in accurately identifying the quenching distance.