The purpose of this study is to develop the compact auxiliary heater using tubular flame for home CHP (combined heat and power). The tubular flame is formed in a rotating flow field by injecting the air-fuel mixture tangentially into the cylindrical chamber. Combustion gas of the tubular flame has a high heat transfer coefficient due to the swirl flow. In this study, the effect of the swirl intensity on heat transfer characteristics on the coiled-tube heat exchanger are investigated. Nusselt number on the coiled tube heat exchanger is estimated for the combustion and non-combustion conditions. The Nusselt number is agreed with the Dhir's correlation equation for the swirling flow.

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In previous works, 3D-CT reconstruction of instantaneous light emission distributions of turbulent premixed flames, and time-series 3D-CT distributions have been successfully obtained. However, for high speed detection of flames, the images were blurry due to low quantity of light. In present study, for 3D observation of high speed turbulent flames, non-scanning 3D-CT technique using a multi-directional quantitative schlieren system with flash light source is proposed for instantaneous density distribution of unsteady premixed flames. In this paper, with a 20 directional schlieren camera, instantaneous density distributions of a high speed turbulent flame, which can be used as an industrial furnace burner flame, have been CT-reconstructed.

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OH-PLIF measurements and numerical simulations were conducted for co-axial laminar jet flame of CH_4/N_2 in high-temperature air (relevant to High-Temperature Air Combustion Technology: HiCOT) flow and that of CH_4/CO_2 in high-temperature O_2/CO_2 (High-Temperature Oxygen Combustion: HiTOx) flow. In both HiCOT and HiTOx conditions, two types of lifted flames were observed: one (Lifted Flame A) showed strong OH signal near the flame base at high CH_4 mole fraction of the fuel stream (X_<CH4>) and another (Lifted flame B) showed strong OH signal near the flame tip at low X_<CH4>. The present computations successfully reproduced these two types of lifted flames. In the computations, Lifted Flame A was formed near stoichiometric line while Lifted Flame B was formed in the far downstream region of stoichiometric line. Based on the classification using the flame temperature, Lifted Flame A was classified to a tnbranchial lifted flame and Lifted Flame B was classified to mild combustion.

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Variations of the flame structures and the Fuel-NOx formation characteristics under the high CO_2 diluted conditions have been experimentally investigated using a tubular flame burner. The OH radical distribution in the CH_4/O_2/CO_2 flame has been measured using LIF for various O_2 concentrations and preheating temperature conditions. The results showed that, preheating under the low O_2 concentration condition led to an increase of the OH peak value. On the other hand, under the high O_2 concentration conditions, OH peak value took almost the constant for various preheating conditions.

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We have adopted the concept of dynamical system theory to detect thermoacoustic combustion oscillations in a staging fuel combustor. Permutation entropy, which represents the degree of randomness estimated for a sequence in rank order patterns in the values of time series data, can capture the notable change in combustion dynamics by the onset of thermoacoustic combustion oscillations under high temperature and pressure conditions.

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The influence of density and water content of wooden biomass briquette on the thermal diffusivity is investigated. The temperatures of three position inside the cylindrical briquette are measured by using sheath K-type thermocouple and the difference equation derived from one-dimensional heat equation is used to estimate the thermal diffusivity. In low water content briquette, the thermal diffusivity with high density (1300kg/m^3) is slightly greater than that with low density (800 kg/m^3). In high density briquette (1300kg/m^3), there is a tendency that the thermal diffusivity with high water content (10.8%) is greater than that with low water content (2.3%) after drying.

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To investigate the combustion characteristics of Jatropha oil as an alternative fuel for boiler, combustion experiments were conducted using a liquid fuel test apparatus in CRIEPI. As well as the NOx concentrations in the exhaust gas, the flame radiation intensity was measured using two-color method. The heat absorption balance of the burner and furnace sections was also measured. The results show that the flame radiation intensity of C heavy oil / Jatropha oil (50%/50%) mixture is lower than that of 100% C heavy oil. Because of this, the heat absorption of the burner and the furnace section that is nearest to the burner for C heavy oil / Jatropha oil mixture is lower than that for 100% C heavy oil. It was also found that NOx emission of C heavy oil / Jatropha oil mixture is lower than that of 100% C heavy oil because of the lower fuel NOx formation due to the lower nitrogen content in Jatropha oil.

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This study examined the optimization of the combustion in the bark boiler. In the bark boiler system the improvement on the total system efficiency with drying of the bark is very important because the bark contains much water. The numerical simulation was conducted in this study. It was replaced by a methane gas fuel the bark of solid fuel and the chemical reaction rate has been adjusted.

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Liquid fuel films attached on wall surfaces are presumed to cause soot emissions during the cold startup period of gasoline direct injection spark ignition engines. In this study, soot formation originated in combustion of liquid fuel films was investigated by using a 3D simulation. Calculations were performed for a Rapid Compression and Expansion Machine model. Effects of physical properties and the composition of the fuel were examined. Results showed that a portion of liquid fuel films remained until the end of the expansion stroke without evaporating even with the passage of the flame under the cold startup condition. Emission factors of liquid fuel films and soot were lager for PRF095 (i-C_8H_<18> 83%, n-C_7H_<16> 4%, C_6H_5CH_3 13%) than those of PRF100 (i-C_8H_<18> 100%). PRF100-ND having evaporation properties same as n-C_<10>H_<22> and chemical kinetics same as i-C_8H_<18> was prepared numerically. Emission factors of PRF100-ND were larger for liquid fuel films and smaller for soot than other fuels under the cold startup condition.

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The numerical analysis has been carried on to elucidate nanoparticle formation mechanism in vapor-phase flame synthesis. The governing equations expressing the particle formation were integrated to two dimensional axis symmetry diffusion flame calculation code. The effect of chemical reaction, particle diffusion, Brownian motion, and sintering kinetic were considered. Inlet fuel velocity and fuel dilution ratio were set as numerical parameters. The particle formation mechanism was described from the demeanor of particle number density, total particle volume, and total particle surface area. Inlet fuel velocity gives little affect to particle formation to change, on the other hand fuel dilution would be the important factor to determine the particle size.

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The purpose of this study is to develop of a direct injection Diesel nozzle, which is obtained high-dispersion spray inside a cylinder with suitable for lean combustion. In this study, it was researched that effects of existence of hole length of nozzle hole and inclination of nozzle hole of the atomization enhancement nozzle, which was designed at previous study, on spray characteristics. As a result, it was clarified that in case the multi-hole nozzle with the bypass, one of atomization enhancement mechanics, which inclination of 45 degrees was installed toward clockwise direction, spread of the spray becomes wide considerably, breakup length becomes short about 25 % and spray angle becomes large about 30 % compared with the nozzle without inclination of the bypass. Moreover, Sauter mean diameter was obtained about 15μm and spray characteristics were improved considerably.

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Secondary atomization of emulsified fuel in spray flame was visualized by magnified shadow imaging. An emulsified fuel spray was injected into a flame stabilized in a laminar counterflow field. Direct photography of the flame using a color high-speed video camera and magnified shadow imaging of spray droplets using a monochrome high-speed video camera were used. As a result, "blight spots" were observed in spray flame of the emulsified fuel, whereas it was rarely observed in spray flame of n-dodecane. Observations indicated that the droplet flame rapidly expanded. This expansion was linked to secondary atomization such as puffing and micro-explosion, which were visualized by magnified shadow imaging.

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The influence of chevron nozzle on jet engine performance has been investigated in this paper. The experiments have been conducted for three different chevron nozzles using a small turbojet engine and the results have been compared with one for the standard propelling nozzle. According to the test results, the penalties of thrust loss have been observed for all chevron nozzles tested under different rotational speeds, although they have been proven to be effective to suppress the jet noise. It has also been observed that the running lines on the compressor map have moved away from the surge line, resulting in lowering the pressure ratio and increasing the air mass flow.

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We theoretically and numerically investigate the nonlinear dynamics of a pulse combustor using low-dimensional random dynamical system. Noise-induced transition to chaos is clearly observed in a specific range of bifurcation parameters. This is clearly demonstrated by nonlinear time series analysis involving the phase space and permutation entropy.

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In this study, the four types of the heat media for the power generation system with the thermo-electro device have been examined. The media were heated up to 350℃ by a small vortex combustors embedded in them. The effects of the preheating of the unburned mixture as well as the heat transfer from the burned gas to the combustor wall were investigated. Results showed that, the media was heated up rapidly in the cases of the burned gas channel was long enough. On the other hand, the gas preheating contributed to the enhanced heat transfer to the wall due to the decrease of the flame length, and thus, increase of the heat transfer area.

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Behaviors of the pressure wave and flame front in deflagration-to-detonation transition (DDT) in a vortex flow were observed to clarify DDT process in a vortex flow. Two types of DDT were observed. The flame, which is located at the back of the pressure wave, catches up the pressure wave. After that, the velocity of the pressure wave reaches the value of the C-J detonation. This is one of the DDT processes. Another process is that the local explosion occurs near the wall of the detonation tube and expands concentrically and the velocity of the pressure wave reaches eventually the value of C-J detonation.

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