The author assumed that the major physical equations relating to the heat transfer phenomena in a boiler furnace were those of mass balance, heat balance, radiation heat transfer, and material properties, and solved the system of these equations without dimensions. In this result it was found that the heat transfer performance in the boiler furnace could be described by five dimensionless numbers including the excess air ratio.

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The capacity of hot water relief valves has been determined with an empirical correlation describing a critical flow. To clarify the correlation, critical flow experiments were conducted by using an industrial relief valve. The experimental data approximately agreed with the correlation. On the other hand, a nonequilibrium homogeneous model based on the isentropic equation of state was proposed and the nonequilibrium factor in the valve was determined. The nonequilibrium effects appeared on the critical flow rate only at relatively low inlet subcooling conditions. At high subcooling conditions, the critical flow rate could be described by the Bernoulli equation where the saturated pressure corresponding to the inlet water temperature was used at the valve throat.

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To establish an advanced control system for a multi solid circulating fluidized bed boiler (MSFB), a simplified dynamic model of the 70 t/h MSFB unit was developed. Equations of material balance and enthalpy balance were obtained for six regions in the unit : dense bed zone, reducing zone and oxidizing zone in the combustor, cyclone, hot solid reservoir and external heat exchanger. The solid circulating rate inside the combustor was determined to predict the observed temperature profile in the combustor of the 70 t/h unit. It was shown that calculated results of gas components, char conversion and temperature profile were able to describe steady-state operation data considerably well. The solid circulating rate strongly affected the temperature profile in the combustor. It was also found from calculated results for unsteady-state operations that slower responses followed after the sharp responses accompanied with load change and that the char reactivity and the external solid circulating rate affected the peak temperature and the settling time of the responses.

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An experimental study has been conducted on the effect of fuel volume and water content on the onset probability of microexplosion of emulsified fuels. Water in fuel and fuel in water emulsions were consisted of n-dodecane, silicone oil and water doped with small amount of surfactants. Test emulsions contained in Pyrex glass capillaries after degasification were immersed in an oil bath. The waiting time for the onset of microexplosion was measured at 433 K under atmospheric pressure for fuel volume ranging from 1×10^-8 m³ to 10×10^-8 m³ and water content from l0% to 60%. The weakest link destruction model was adopted for predicting the distributions of the waiting time. It was confirmed that the waiting time at constant temperature was correlated with the Weibull distribution and that the shape parameter was unity. The results showed that the mean waiting time for microexplosion was inversely related to the fuel volume and the water content. A new empirical equation was proposed for the mean waiting time of the onset of microexplosion including the effect of fuel volume and water content.

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It is important for high-power kerosene stoves to have a wide TDR (turn-down ratio), because this kind of stove can be used in cold areas where the heating load is greatly changed. In order to develop high-power kerosene stoves, we prepared the matrix burner of counterflow premixed flames (twin-flame matrix burner), and investigated the performance of kerosene combustion. In this study, we clarified that the characteristics of blowoff and quenching in this burner are arranged between the calorific capacity of the combustion chamber and the premixed air ratio. Furthermore, in introducing the secondary air from slits and ports separately, we can improve the exhaust emission in this burner. Consequently, we have developed the twin-flame matrix burner for high-power kerosene stoves which has a wide TDR (5 : 1).

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CWM droplets produced from a rotary atomizer were intermittently introduced into an electrically heated furnace, and the ignition and initial combustion processes were investigated under various experimental conditions. The shapes of flying droplets and their changes are similar to those of large droplets suspended on thin fused silica. The ignition position changes with ambient air temperature. Volatile and char combustion are observed to coexist together, so there are almost no changes in size distribution or mean diameter along the furnace axis because of the swelling and shrinking of droplets, and the mass reduction loss of droplets are obtained by approximate calculation.

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Combustion-driven oscillation is excited in the burning zone of a furnace, and its magnitude is determined by the position and heat release strength of the heat sources. In previous papers, it was shown that "the resonance factor" is useful in detecting the degree of combustion oscillation in a furnace. In this paper, by applying this method to multiburner furnaces, the effects of burner arrangements, two-stage combustion rate, excess air ratio and gas mixing ratio on the occurence of oscillation are examined. Consequently, the following results are obtained. (1) The oscillation condition is characterized by the fuel flow rate and primary and secondary air flow rates in the burner throat. (2) The low-positioned burner has stronger ability to excite the depth mode oscillation of the gas column in a furnace than the middle and high-positioned ones. (3) The effects of the two-stage combustion rate and excess air ratio on combustion oscillation are found to be represented only by the primary and secondary air flow rates. (4) The exhaust gas mixing combustion method suppresses the combustion oscillation.

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A premixed catalytic combustion of propane was studied at a temperature below 650°C and without gas phase reaction, using a platinum-impregnated foam catalyst. profiles of the compositions and the temperatures measured in the catalyst plate show features of low temperature and lean-burn catalytic reaction as follows : (1) The catalytic reaction was so fast that more than 97% of the fuel was burnt in the narrow region near the front of the catalyst plate. (2) Only several ppm of propane were detected in the central region of the outlet surface of the catalyst plate, so that the local combustion efficiency was estimated to be almost l00%. (3) However, more unburnt propane was detected at the edge of the catalyst plate where the temperature was low owing to heat loss. (4) Since a small quantity of CO was found near the inlet surface of the catalyst plate, there existed an intermediate oxidation reaction. (5) Catalyst saving was achieved with the use of a porous insulating layer on the outlet surface of the catalyst plate.

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The effects of aromatic hydrocarbons in fuel oils on autoignition of fuel sprays in hot surrounding air were studied using a rapid compression machine and a total gas sampling device. Ignition delays and concentrations of gaseous hydrocarbons produced by fuel decomposition were measured for test fuels which have various contents of aromatics. The results show that the paraffinic contents in the fuels were the main source initiating ignition reactions and that the accumulation of lower hydrocarbons due to pyrolysis or weak oxidation before significant heat release occurs is suppressed in fuels containing large quantities of aromatic hydrocarbons. Consumption of much oxygen by aromatic compounds early in the ignition delay periods may obstruct the oxidation process of paraffinic hydrocarbons.

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Chemiluminescence emission from opposed jet burner flames was measured by a CCD (Charge Coupled Device) camera with an image intensifier. Radial profiles of the emission intensity were obtaine by the Abel transform of results of the side-on observation. The profiles of emission intensity of these radicals are similar and each peak is located at the center of the flame zone. The emission of C₂ and CH radicals produced in the early stage of the combustion reaction was observed on the burned gas side of the flame zone where the mean temperature is significantly high, suggesting that unburned mixture exists even on the burned gas side of the flame zone. From the emission profiles of OH radical which can be used as a measure of the reaction zone, it can be seen that the outer diameter of the flame zone increases with the mixture supply velocity, while the inner diameter remains constant. It was found that the profiles of OH emission intensity and NO concentration are similar. This fact suggests that NO originating from prompt NO is predominant in the distributed reaction zone.

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To elucidate deformation and breakup processes of a liquid jet across an airstream, tomograms of the liquid jet were taken by means of the laser light sheet method. In this method, fluorescent dye, Eosine-Y, was contained in the injected water, and the liquid jet was illuminated by the Nd : YAG laser light sheet. There are two types of atomization mechanisms. In the first mechanism, a horizontal section of the liquid column is distorted into a bow shape, and there exists a cavity without drops behind the liquid column. Small drops are produced at both tips of the bow. The continuous length and the width of the liquid column were measured from the tomograms. In the second mechanism, in which velocities of both the airstream and the injecting liquid are low, the liquid column is distorted in a snakelike shape and drops are produced near the tip of the liquid column.

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In both spark ignition engines and diesel engines, the exhaust gas recirculation (EGR) system is well know as an effective technique to reduce nitric oxide emission. However, it has not been applied practically to heavy-duty diesel engines because wear of piston rings and cylinder liner is increased by EGR. It is widely considered that sulfur oxide in exhaust gas strongly relates to the wear. This paper presents a numerical model to reveal the mechanism of wear which estimates the amount of sulfur oxide diffused into lubricating oil film. The calculated results show that the sulfur oxide concentration in the oil layer is related strongly to the EGR rate, inversely with engine speed, and decreases under light load conditions. There is a good agreement between the results and the experimental facts.

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Because scavenging and exhaust flows strongly relate with the combustion process in two-stroke cycle engines, it is necessary to develop a total-system simulation model as a design tool of these engines. The model proposed in this paper consists of four essential elemental models which are non-steady flow in both the transfer and exhaust pipes, change of state in the gas of the crank case, the reed valve characteristic and change of state in the engine cylinder. The calculated results show that the model is useful in understanding the history of pressure, temperature and flow rate in the engine with changing specifications and operating conditions of the engine. It is confirmed that the computing time is reasonably short and this model is useful as a design tool for two-stroke engines.

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