The great feature of the Vuilleumier cryocooler is that little work is required to operate displacers, i.e., pressure drop generated in the working space and mechanical losses at seals and bearings are quite small. A small Vuilleumier cryocooler was fabricated to study its cold production, and it was tsested over 2500 hours in an atmospheric environment. The cooling performance was mapped not only at the design point, but also at off-design points. The charge pressure, hot wall temperature and cycle speed were selected as major operating parameters. The results of the machine showed that the nominal cooling capacity was 1.75 watts under the input power of 154 watts, and that 2.3 watts was the maximum cooling capacity. This paper describes the comparison between the experimental resluts and calculation which depended on the thermodynamic characteristics for obtaining of a simple model.

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Formation mechanisms of N₂O and NO have been experimentally investigated using a temperature-controlled one-dimensional laminar-flow pulverized coal combustion furnace. The temperature range is 800-1100°C including that of usual fluidized bed combustion. The effect of temperature and the separated contribution of Volatile-N and Char-N are clarified using raw coals and their chars carbonized in an actual bubbling fluidized bed combustor. N₂O formation and destruction reactions strongly depend on temperature, and N₂O almost disappears with the inclease of temperature above 1100°C. The conversion ratios of Volatile-N to N₂O and NO are higher than those of Char-N. While the Fast Volatile-N released at the early stage of combustion process is mainly converted to NO, the Slow Valatile-N released at the char combustion stage is selectively converted to N₂O.

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The effect of gravity on fuel droplets burning interactively has been studied experimentally. Experiments on two droplets aligned horizontally were conducted both in normal gravity and in microgravity. Results show that in normal gravity, oxygen starvation between the flames is not as severe as in microgravity. Natural convection, which supplies oxygen to the flame, is stronger at a smaller initial separation distance when two flames exist separately. The instantaneous burning rate for the same normalized droplet diameter has a maximum in normal gravity when the initial separation distance is changed and decreases monotonically in microgravity with decreasing initial separation distance, except for the initial period of burning. Thus, the effect of gravity, which decreases the burning lifetime, is greatest at a certain initial separation distance.

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The temperature histories for single droplets of water-in-'A' heavy oil emulsions were measured simultaneously by taking pictures of combustion behavior with a high-speed camera, in order to elucidate the growth mechanism of microexplosions. The occurrence of microexplosions is mainly dominated by the relative ratio of the sizes of water droplets dispersed in the emulsified fuels to the size of the oil droplet, and it is also related to the heat capacity of the oil droplet. The apparent activation energies from the experiments for the ignition time lag reveal that the emulsified fuels have the effects of both retarding the ignition by absorption of the latent heat and conversely, promoting the ignition by flashing the boiling water droplets accompanied by a small amount of oil. Surfactants may be the factor retarding the ignition and suppression of the occurrence of microexplosions for the resultant effect of stabilizing the emulsified fuels.

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The interaction between reaction and turbulent mixing strongly affects for the structures of a turbulent diffusion flame, the characteristics of which are greatly affected by the combination of working conditions such as burner exit configurations, burner size, fuel and oxidant. This study discusses in detail the turbulent diffusion flame structure and its similarity using a laboratory-scale turbulent diffusion flame measured by laser Rayleigh scattering. It also discusses the factors affecting the similarity in flame structure and the turbulent diffusion flame length determined using its turbulent power spectral density. The -5/3 power law holds in the fuel jet and combusion regions. In the air entrainment regions, however, the -5/3 and -1 power laws coexist, and this shows that both turbulent and molecular thermal diffusions become important. The constancy of turbulent diffusion flame length at high Reynolds number is discussed with respects the characteristics of flame structure.

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A droplet cloud of liquid fuel produced by an ultrasonic atomizer was ignited by a spark, and the ball of flame propagating outwards was observed in detail in order to elucidate the mechanism of flame propagation and the complicated group combustion behavior of spray flames. For this purpose, the instantaneous images of droplet clusters, OH-radical chemiluminescence and C₂-band flame luminosity were taken simultaneously, and the light emission signals in OH- and CH-bands, Mie-scattering signal from droplets, and the size and velocity of droplets were monitored simultaneously in time series. It was found that a nonluminous flame propagated ahead of the luminous flame, that droplets disappeared in the luminous flame zone due to their rapid evaporation, and that a number of small droplet clusters burned in the diffusion combustion mode associated with solid-body emissions inside a ball of flame.

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This paper reports on an experimental study of the dispersion process of an injected spray with the objective of optimizing its characteristics. A phase Dopplcr anemometer was used to measure the injected spray from a fuel precharging type injector, under an open air condition. Average mean diameters and velocities of the fuel droplets were calculated for repetitive injections. The average mean velocity showed reasonable agreement with the velocity obtained by visualization. At higher load conditions, atomization was achieved with high speed air flow such that the mean diameter was reduced. From medium to full load conditions, the fuel droplets were distributed in a tube like profile due to the shape of the nozzle. The first group of droplets had high velocity and small mean diameter in contrant to the second group. Relative velocity was not very small even in the fine droplets within the air flow from the injector, as expected.

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A chemical gas-phase process capable of reducing nitric oxide from diesel engine exhaust is studied. In this process, the reductant consists of water-solved methylamine (CH₃NH₂). The reactions were carried out in an electrically heated quartz flow reactor at temperatures in the range of 300 K to 900 K with molar ratio [CH₃NH₂]/[NO] from 1 to 5. Results show that an addition of methylamine into exhaust at relatively low temperatures is effective in breaking down nitric oxide into N₂ and H₂O, and a NO reduction ratio of more than 70% is obtained in the reactor temperature range of 673 K to 800 K with molar ratio of 1.3.

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The efficiency of TiO₂-V₂O₅ catalyst for selective catalytic reduction (SCR) of NO_x was investigated using a single-cylinder direct-injection diesel engine. Ammonium carbonate solution and urea solution were mixed with exhaust gas as deoxidizer instead of NH₃ gas injection. The catalyst provided a substantial reduction in NO_x emissions for a catalyst bed temperature of about 190-430°C. NO_x removal rate was about 70-95% for a space velocity of 6300-12500 h^-1, catalyst temperature of : 350-400°C and NH3 molar ratio of 1-2. Reaction at temperatures above 400°C induced combustion of NH₃ and catalyst sintering. It was recommended that the urea solution be used as deoxidizer in practical application to achieve high denitration efficiency and low leakage of NH₃. However, injection of urea solution caused an increase of Bosch smoke pollution and a reduction of SO₂ concentration due to the emission of sulfate dust produced by reaction of leakage NH₃ with SO₂ and particulate matter (PM). The PM contained a relatively large amount of Na⁺, K⁺ and SO₄^--, which contribute to deterioration of catalyst efficiency, and therefore the PM had a significant effect on the catalyst activity.

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This paper deals with exhaust gas emission characteristics in a glow-assisted DI engine fueled with methanol. The engine used was a 3.64-litter, four-cylinder, water-cooled, four-stroke-cycle, diesel engine manufactured for medium duty trucks. The experiments were carried out to investigate the influence of the condition of intake air on exhaust emission characteristics. The results indicate that intake throttling can favorably reduce NO_x, formaldehyde and unburned methanol emission and improve thermal efficiency. Intake heating can reduced formaldehyde and unburned methanol emission and improved thermal efficiency but increase NO_x emission. EGR can reduce NO_x and unburned methanol emission and improve thermal efficiency but increase formaldehyde emisison.

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