Atsushi Saima

A study of the influence of intermediate combustion products on knocking

Abstract This study investigated the behavior of the OH (characteristic spectrum of 306.4 nm), CH (431.5 nm) and C 2 (516.5 nm) radicals that are intermediate products of combustion and preflame reactions. Spectroscopic measurements were made of the absorption behavior of the radicals in the end and center zones of the combustion chamber of a spark-ignition engine. Two types of test fuels were used, iso-octane (100 RON) and n-heptane (0 RON). The results showed that the behavior of the OH, CH and C 2 radicals in preflame reactions differed depending on the octane number of the fuels and between normal and abnormal combustion.

Simultaneous measurement of light absorption and emission of end gas during the knocking operation

Abstract Simultaneous measurements were made in the same cycle of the light absorption and emission behavior of the OH (characteristic spectrum of 306.4 nm), CH (431.5 nm) and C 2 (516.5 nm) radicals in the end-gas region using spectroscopic methods. The data obtained with absorption spectroscopy in particular made the following clear. First, the changes observed in the absorbance behavior of the radicals during combustion in an actual engine corresponded to the phenomena associated with the degeneracy of a cool flame. Secondly, prior to the occurrence of auto-ignition under abnormal combustion characterized by knocking, the absorbance waveforms showed distinct evidence of a behavior corresponding to that of a blue flame.

Separation of Condensation Jet Image Using Filter Effect of Wavelets Transform

The present paper describes the application of discrete wavelet transform to the analysis of condensation jets in order to clarify the fluid and heat transfer phenomenon. The condensation jets in the nozzle vicinity are experimentally visualized via the laser light sheet method to obtain condensation particle density images of the jets. The image of the condensation particle density in the jet is decomposed to mean and fluctuation images via wavelet multiresolution. The dominant temperature boundary and the mean component outside the boundary were obtained from wavelet separation images. The boundary was compared to the experimentally obtained temperature distribution.

Stabilizing Effect and Diffusion Control on Diffusion Flames by Magnetic Field

Diffusion control and stabilizing effect on diffusion flame of propane gas were found in a magnetic field. Magnetic field strength was changed at 0.11.38xl05A/m at the center of the field. Experiment of diffusion control was carried out with a nozzle of 8-mm diam. Experiments of stabilizing effect were carried out with a nozzle of 2-mm diam. These nozzles were set at the center position of the uniform magnetic field and propane gas was run through with these nozzles at a constant flow rate. Property of propane gas and flame are diamagnetism, on the other hand air and oxygen gas are paramagnetism. Particularly volumetric susceptibility of oxygen gas is very large value. The magnetic pressure on flames was attributed to paramagnetic (air) and diamagnetic (flame) properties. As magnetic field was applied, the flame changed from an oscillating flame to a stable flame with a low frequency and small oscillating amplitude. The stabilizing effect was examined by temperature and luminosity measurement by observation with the schlieren method and high-speed photographs. The width of the outer swelled combustion gas region became narrower and keeps a constant width when the magnetic field was applied. In the condition that magnetic field was not applied, when oxygen gas was injected coaxially in the outer nozzle as secondary flow of gas, the length of the diffusion flame changed extremely short. Under this condition when magnetic field was applied, the flame length increased with increasing in magnetic field. This means that the diffusivity of oxygen gas can be controlled by magnetic field. In this study, flow control of fuel and stabilizing effect to oscillating flame are proved by using magnetic field. These effects were expressed by pressure acting on the flame by magnetic force.

Plasma Jet Igniter Properties. Analysis by Electron Temperature Measurement.

A temporal change of local electron temperature on the central axis of the plasma jet was measured in an enivironment of hydrogen. The electron temperature was measured by applying the two-line radiance ratio method. The diffusion of plasma jet was clarified for various plasma jet igniter configurations and supplied electrical energies. The relationship between the characteristic length of the igniter and the plasma jet was elucidated. The progression of the plasma jet was influenced by the waveform of the discharged voltage in the vicinity of the igniter. The electron temperature and the length of the plasma jet increased as cavity volume decreased and as orifice diameter increased. It appears that an igniter which has a small characteristic length is favorable with regard to penetration of the plasma jet and to generation of a high electron temperature. Therefore, it is considered that the plasma jet igniter configurations exert different influences on plasma jet penetration and combustion enhancement.

Eddy Diffusions of a Fuel Gas from a Cylindrical Fuel Burner

It is easy to determine the mechanism of time average eddy diffusion of fuel gas in a flame. But it is very difficult to determine the instantaneous movements of fuel gas in the flame. In the experiment described in this paper the fuel jet was ignited at various positions in the fuel jet by electric sparks, and the spreading of the flame was observed. Ignition probability was measured at various positions of the fuel jet, being determined by the mixture ratio and mean velocity of fuel jet and the velocity of secondary air. It seems that the ignition probability chiefly depends upon the fluctuation of the fuel concentration. It was found that, for an ignition for obtaining a steady flame, a spark must be provided immediately behind the burner tube wall.