Search Results

With the aim of elucidating the mechanism causing abnormal combustion, a study was made of light emission and absorption characteristics at wavelengths corresponding to the spectra of the OH (characteristic spectrum of 306.4 nm), CH (431.5 nm), C2 (516.5 nm) radicals. Spectral properties were measured in the end-gas region of the cylinder for various types of fuel having different octane numbers. During combustion in an actual engine, the behavior of the CH and C2 radicals prior to the occurrence of abnormal combustion characterized by knock is indicative of behavior in the negative temperature coefficient (NTC) region. The experimental results revealed that the behavior of the OH, CH, C2 radicals differs between normal and abnormal combustion.

With the aim of elucidating the mechanism generating knock, an examination was made of the preflame reaction behavior of end gas in the combustion chamber in the transition from normal combustion to abnormal combustion characterized by the occurrence of knocking. 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 C2 (516.5 nm) radicals in the end-gas region using spectroscopic methods. The absorbance behavior of a blue flame prior to autoignition is believed to be an important factor in the mechanism causing knock.

The investigation regarding the plasma jet ignition was explored by using a combustion vessel. The first purpose is to elucidate the issuing duration and the penetration of hydrogen plasma jet. A temporal change of local electron temperature was measured along the central axis of plasma jet. A small characteristic length of igniter seems favorable with regard to the plasma jet penetration and the generation of high temperature, as compared with the case of the igniter that has the excessive cavity volume. The second purpose is to elucidate relationship between the characteristic length and the combustion enhancement effect, when the excessive volume of cavity and the excessive supplied electrical energy were used. The influence of the characteristic length on the plasma jet penetration and the combustion enhancement differs with the supplied energy. The combustion enhancement seems to be caused by the plasma jet in case of excessive supplied energy.

The investigation regarding performance of plasma jet igniters was explored by using a constant volume vessel. This study focused on investigating the relationship between the jet effect, the hot gas jet issued from the igniter, and combustion enhancement. The hot gas penetration was visualized by the schlieren system with CCD camera and image intensifier. In the cases of small energies, 0.63 and 0.90 J, the combustion enhancement effect is similar to that of combustion jet igniter. In cases of supplied energies, 2.45 and 5.00 J, the jet effect influences on the combustion enhancement effect for small characteristic length of the igniter.

Using absorption spectroscopy, simultaneous measurements were made of the behavior of the OH (characteristic spectrum of 306.4 nm), CH (431.5 nm) and C2(516.5 nm) radicals in the end-gas region and center of the combustion chamber of a spark-ignition engine during preflame reactions with four types of fuel having different octane numbers. The results of this research show that the behavior of the OH, CH and C2 radicals in preflame reactions differed significantly in both the center and end-gas region of the combustion chamber depending on the octane number of the fuel and also between normal and knocking combustion conditions.