In the preceeding papers, "the resonance factor", which predicts the degree of combustion oscillation, was proposed, and applied to both the furnace with a single burner and that with multiple burners. It was found that the combustion oscillation occurred in the region of low primary and secondary air flow rates in both furnaces and that the region of combustion oscillation was affected by the openness of secondary air vane and the burner arrangement in a furnace under a fixed flame holder condition. If the operational conditions of the practical burners are not within this region, the furnace will not oscillate at all. This study's objective is to clarify the effects of the position of the secondary air guide sleeve and the openness of the secondary air guide vane on the combustion oscillation region in a multiburner furnace, since the combustion oscillation condition varies with position and strength of the heat release zone is a furnace and thus is governed by the configurations of flame holder which is composed of an impeller, air guide sleeves and air guide vanes. Futhermore, a procedure of burner operation while avoiding combustion oscillation is demonstrated.

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This paper deals with numerical simulations of a laminar reactive two-dimensional mixing layer. We have especially focussed on the early stage of flame growth. The effects of fuel dilution and coherent vortices on their flame structures are discussed. The simulations are based on a modified HSMAC method. Fast and slow fluids are the fuel and oxidizer, respectively. The velocity ratio is 4 : 1. The fuel is diluted by nitrogen. An oxygen mass fraction of the oxidizer is fixed at 0.27. The simulations have been applied to three cases of methane mass fractions of 1, 0.3, and 0.2. As a result, it is revealed that three flows occur at the leading edge of the undiluted flame, which are attributed to two separated approach flows and one accelerated flow in the flame. The dilution causes blow-off. Blow-off may well be determined by the first Damkohler number based on the hydrodynamic characteristic time of coherent vortices and the chemical characteristic time of the propagation of the partial premixed flame at the leading edge.

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The excess air ratio of the burned zone, Ad, which was estimated by two-zone model analysis, was compared with the excess air ratio of the modeled steady-state fuel spray and diffusion flame. There was little correlation between λ_d and the averaged excess air ratio in the cylinder λ_m, and λ_d was mainly dominated by the characteristics of fuel spray and ignition delay. The excess air ratio during the premixed combustion period minimally influenced upon the NO formation fraction if the premixed combustion fraction was less than 50%. The major factors of NO_x reduction were investigated using the two-zone model. As a result, it was made clear that a large NO_x reduction due to timing retard was mainly caused by both a decrease of combustion temperature and a large decrease in combustion pressure on the expansion stroke, and a small NO_x reduction with the decreased nozzle hole diameter was caused by a decrease of combustion pressure based on the decrease of the heat release rate in the premixed combustion.

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We investigated the effects of a high-temperature environment on diesel spray combustion and formation and oxidation of soot in the flame by eliminating the effects of wall temperature and boundary layer as much as possible using a rapid compression machine which has large combustion chamber. When gas temperature increased, short ignition delay and elongation of combustion was observed by analyzing the cylinder pressure diagram. However disappearance time of luminous flame did not change. Recombination of thermal dissociation must be considered as apparent heat release. Higher surrounding gas temperature results in increased soot formation time and extended low-density soot region in the flame, in spite of almost the same time histories of total amount of soot.

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It is reported that SO₂ and NO_x in a flue gas can be removed by corona discharge and that pulse corona discharge is as energy-efficient as the electron-beam treatment. However a large amount of data are required to assess the industrial application of the corona discharge method to remove SO₂ and NO_x from combustion flue gas. In this study parametric experiments of SO₂ and NO_x removal from actual and simulated combustion gas have been performed on a laboratory scale, where combustion gas composition, temperature, residence time in a discharge duct and the polarity of high voltage electrode are changed for DC and pulsed corona discharge. The following experimental results are obtained : (1) the increase in H₂O and O₂ concentration improves the SO₂ and NO_x removal performance, (2) dendritic powders of (NH₄)₂SO₄ are apt to deposit on a high-voltage electrode, and (3) the electrode polarity has a nominal effect on the removal performance under our experimental conditions.

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This paper deals with a pellet-packed bed for trapping diesel particulates. This trap has the labyrinths of the flow passage which favors inertial impaction to ceramic pellets, ensuring the required trap efficiency with a longer lifetime prior to clogging as long as the appropriate pellet diameter and trap size are selected. Experiments were made on a single-cylinder test engine to investigate the trap efficiency, pressure loss and effects on engine performance. From the comparison of the test results with those of the ceramic monolith filter, it is shown that the pellet-packed bed has smaller pressure loss during engine operation than the monolith. This enables us to maintain a higher trap efficiency with less sacrifice of engine performance for a longer time. It is noted that the soluble organic fraction in particulate matter can also be trapped because of its greater specific surface area. Trap regeneration and pellet material are discussed from the practical point of view.

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