This report describes the development of a small-sized mechanical pump. The pump can be used in thermal control systems, such as mechanical pumped loops (MPL) of spacecrafts. This pump has following three features. 1) Ammonia used as working fluid. 2) Small sized design for spacecrafts. 3) Axial type motor used for driving gear. The trochoid gear miniaturized the pump with the external diameter of 48[mm], the thickness of 19[mm] and weight of 150[g]. As a result of the performance test, 0.5[L/min] flow rate, 45[kPa] of total pressure and 2[MPa] withstand pressure were achieved.

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A gradual flow exists inside in the continuous sintering kiln that is the mass production plant of ceramic product. This gradual flow is generated by the preset-temperature difference of the kiln. Understanding this internal flow pattern of kiln becomes important information not only for aiming at the performance improvement of the kiln, but also for preventing various troubles. However, internal atmosphere of kiln exists reduction atmosphere and ultra high temperature, and atmospheric temperature of kiln exceeds 1000 degree, a conventional flow sensor cannot be applied. In this research, the flow sensor for the high temperature space using the thermo-couple was designed. Flow sensor was made experimentally, and the effect was confirmed.

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When rapid melting and solidification like are welding happen, the flow behavior is very complex. The flow is determined by the effect of surface tension, viscosity, and gravity. Two-dimensional change of geometry was analyzed by using a particle method for a melted upper plate on a base plate with a hole. Relation between initial geometry and upper surface unevenness was calculated. The calculation results show that the upper plate with a triangular notch at the center reduces upper surface unevenness.

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Now, reduction of flow rate by increasing available temperature difference of heat medium is the main way to decrease power consumption for the cool water transporting system. In order to decrease power consumption of the cool water transporting system more, the possibility of ice-water transporting system has been under examination. In this study, the method to extract ice/water mixture from dynamic ice storage tank was proposed and experiments were conducted. It was obtained that extracting IPF were 2 to 4%. Extracting mechanism of ice/water mixture and knowledge for higher extracting IPF were shown.

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The present study investigates a thermoacoustic Stirling cycle cooler that uses pressure fluctuation caused by thermoacoustic self-excited vibration for compression. Unlike a mechanical compressor, the thermoacoustic compressor which uses pressure fluctuation does not have a crank mechanism or a piston cylinder, and therefore requires no sealing. This is expected to remarkably improve the reliability and service life of coolers. In this system, the stack plays an important role in the thermoacoustic phenomenon. In this paper, the influence of density of the stack material on the thermoacoustic phenomenon was reported.

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Heat-driven oscillations of liquid-vapor column with phase change were experimentally and analytically investigated by using a horizontal glass tube. The horizontal part of glass tube which made 4mm inner diameter is 620mm in length and heating part located center of horizontal tube is 35mm in length. The heating was used Nichrome wire heater covered glass fiber mesh tube. The supply rate of heat is from 0W to 21.4W. The behavior of the top of vapor plug is observed by a high-speed video camera. In order to clarify the effect of thermal energy on oscillation, the vapor plug behavior is also calculated and compared to experimental value.

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A time series analysis was performed to calculate decay ratio and resonance frequency from a dominant pole of a transfer function by applying AR methods to time-series of the core inlet flow rate. Experiments were conducted with the SIRIUS-F facility, which simulates ABWR with MOX fuel installed. The variations in the decay ratio and resonance frequency among five common AR methods are within 0.03 and 0.01Hz respectively. In this system, the appropriate decay ratio and resonance frequency can be estimated on the basis of Yule-Walker Method with the model order of 30.

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A liquid droplet on a plate slides down at a critical inclination angle of the plate. Applying the theoretical results about the sliding angle of droplets obtained in the preceding report, the surface properties of SAMs were evaluated. The advancing and receding contact angles of SAMs plates made by immersion method were measured for BCA and ethylene glycol. From the results of 4 kinds of test plates with different immersion time, the contact angle hysteresis becomes minimum (about 3°) for the reference plate (immersion time 5min) with most homogeneous monolayers among others. The experimental sliding angles agreed well with theoretical ones. The sliding angle φ of the reference plate is minimum and the difference of φ from the other plates with some defects on the surfaces is more than 6° for BCA and 4° for ethylene glycol. Hence the surface defects on SAMs plates could be detected from the simple measurements of sliding angles of droplets

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This paper is concerned with propagation behavior of detonation in a channel with a right-angled corner. In the present numerical analysis from quenching to reestablishment of detonation, the semi-implicit second order MacCormack-TVD scheme is used with Navier-Stokes equations including chemical reactions. It was found that the diffraction of detonation front at the right-angled corner is due to the strong unsteady Prandtl-Meyer expansion, and reestablishment of detonation can be attained downstream the corner in the stoichiometirc gas mixture of H_2 and O_2. The reflected shock wave resulting from collision between the channel wall and the incident detonation plays an important role for the reestablishment process of detonation.

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The release of NO_x, SO_x, HC and CO_2 from internal combustion engines is still a major issue in the development of modern engines. Especially new concepts like EGR(Exhaust gas recirculation) is developed, detailed information about the pollutant formation is required. However, the experiments of actual standard engines are generally very complicated processes including the residual gas of last cycle and the flow in an engine cylinder. Thus, experimental data measured using actual engines become unreliable. To obtain the essential data on combustion of hydrocarbon-N_2-O_2-mixtures, the experiments have been carried out to examine the influence of oxygen concentration on combustion characteristics under conditions of high temperature and pressure, which are achieved by a spark ignited opposed rapid compression machine. The main conclusions are follows: (1) The maximum burning pressure decreases with decreasing oxygen concentration at same EGR ratio. (2) The reduction ratio of the flame speed decreases with increasing the compression ratio. (3) The reduction ratio of flame speed depends on a fuel property.

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A major source of air pollution is internal combustion engines. Especially, compression ignition engines in today's automobiles contribute the most to particulate emission and soot, and it is recognized that these emissions have a detrimental effect on human and earth environment. So improvement of spray combustion for diesel engines is of urgent necessity. Experiments have been conducted to obtain essential data on spray combustion are influenced by impinging injection in a closed vessel. The effect of the impinging injection on maximum burning pressure, total burning time and flame speed is investigated at condition of 300K of initial temperature and 0.1MPa of initial pressure. The travel time of flame front is measured by ionization probes located at two different positions from the center of combustion chamber.

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This paper describes low temperature flammable limits of kerosene vapor-air mixture. Based on Burgess-Wheeler law, the adiabatic flame temperature for the mixture was calculated to be ca 1700K and the flammable conditions of (stoichiometric ratio λ, mixture temperature t_u℃) were estimated as follows ; t_u>-3400λ+1820 for fuel rich limits, t_u>795λ-1308 for fuel lean limits, and t_u>69.7λ^<-0.3756> for condensation of kerosene vapor in the mixture. The experimental results showed good agreement with the lowest mixture temperature of 60℃ in flammable condition. It was also shown that the lowest value depended on the saturated vapor pressure of the liquid fuel.

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In present study, an advanced CT reconstruction technique for measuring an instantaneous three-dimensional distribution of chemiluminescence light emission of a primixed flame is accomplished for a spherically expanding spark-ignited flame of a propane-air rich premixture. The 3DCT reconstructed data of the spherically expanding flame shows a spherical shell-like structure of flame front, however, more detail structure of flame front couldn't be observed because of the low S/N ratio of the 3D image data.

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Numerical analysis of ultra-micro combustor was carried out by comparing with experimental results. First of all, we aimed at agreement of temperature distribution in the combustion chamber to the experimental result, which was basic data provided from a combustion phenomenon. We succeeded in simulating influence of porous material as inflow entrance and were able to confirm reliability of the present analytical model. Furthermore, we examined flame stability limits and influences of mixture preheating and wall surface temperature by using detailed chemical kinetics. The obtained results are as follows: Main combustion reaction occurs intensely near the outward wall of a combustion chamber. An increase of wall surface temperature brings high-intensity combustion of the whole combustion chamber.

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The reaction mechanism on flame synthesis of carbon nanomaterials has been investigated using a gas chromatograph ; the flame synthesis of carbon nanomaterials has been carried out in methane/air laminar, fuel-rich premixed flame under atmospheric pressure. By placing a pair of porous media in the upstream and downstream sides of the combustion space, excess enthalpy burning was applied for the methane/air mixture. The results show that the concentrations of methane, carbon monoxide and hydrogen are large.

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Experiments have been conducted to examine on how the combustion behavior of co-axial diffusion flame and boilers are influenced by the discharge of electro-magnetic energy at a given wave number. The fuel used for the study is town gas. The combustion characteristics for co-axial diffusion flame in electro-magnetic field are observed by taking the direct photographs with high-speed digital video camera and the rate of temperature rise in water container is examined as a function of air-fuel ratio. The average flame temperature is measured by two-color pyrometer. The main results obtained for the study are as follows: that (1) the discharge of the electro-magnetic energy into hydrocarbon fuel combustion is very effective to increase the flame temperature, (2) the rate of temperature rise is about 3〜6% at 1.68 of excess air-ratio, though these values decrease with decreasing excess-air ratio due to much soot generation and (3) for demonstration test of boiler the values of energy saving rate is more than 3%

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Experiments have been carried out to examine on how the fuel spray combustion is influenced by electro-magnetic wave around 1200cm^<-1> of wave number and 0.90 of spectral emissivity, which belongs to the regime of infrared ray. Particularly, the study will be focused on the combustion of single fuel droplets as being characteristics of spray combustion. The fuels used for the study are n-heptane, benzene and ethanol. The experimental date indicates that such electro-magnetic wave has an ability to accelerate the combustion rate of fuel droplets. This means that such electro-magnetic wave may be very effective to accelerate the burning rate of spray combustion.

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Experiments have been performed to examine the flame temperature rising rate of spray combustion by the utilization of the electro-magnetic wave around 1200cm^<-1> of wave number and 0.90 of spectral emissivity. The main acquisitions obtained for the study are as follows: (1) The average flame temperature rise due to the discharge of electro-magnetic wave to spray combustion is approximately 3% and (2) In order to promote the burning rate of hydrocarbon fuel spray it is very significant to utilize the electro-magnetic wave having the absorption band of methane and its precursor.

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The experiments have been conducted to improve the combustion characteristic on DME-air mixtures by adding propane and these combustion characteristics are analyzed by utilization of the spherical flame propagation under microgravity environments achieved in a freely falling bomb. The range of equivalence ratio is 0.65 to 1.0. The main results are as follows: (1) the microgravity environment is very suitable method to determine the combustion characteristics even at very lean side of mixtures and (2) the addition of propane to DME causes to increase the burning velocity monotonically due to the increase of heat of combustion.

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This study tried to impress supersonic wave in processing emulsified fuel. Supersonic wave has an effect of producing minute cluster of water particles in the fuel and also an effect of restraining separation of oil and water for emulsified fuel. Combustion analysis using diffusion burner shows that emulsified fuel with impression of supersonic wave improves combustion due to atomization of water particles. Analysis of radical intensities in the flame reveals that emulsified fuel impressed by supersonic wave produces a lot of OH radicals in the flame, which may improve chemical reaction and result in low smoke emissions.

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It is important to stabilize the flame for the combustion technology, and lifting/blow-off and stability limits of the diffusion flame have already been researched. As for the methane and hydrogen diffusion flame, there are a lot of uncertain elements of the combustion characteristic at the flame-base with increasing the fuel velocity. In this study, the transition behavior from the stable flame to lifting and blow-off is observed experimentally with and without the co-flowing air. The parameters are co-flow velocity, oxygen concentration, flow rates and so on. The results obtained are as follows. The flame lifting occurs easily when the co-flowing velocity is higher or oxygen concentration decrease. The phenomenon of the flame squeezing at the upstream of the fuel is concerned with the fuel velocity.

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Homogeneous Charge Compression Ignition (HCCI) combustion has attracted considerable interest in recent years as a new combustion concept for internal combustion engines. The HCCI combustion process has four issues to be resolved: ignition timing control, slower combustion reaction rate (maximum heat release rate), difficulty expanding stable operation to the high load region and avoidance of knocking. In this study, an attempt was made to overcome these issues by applying internal exhaust gas recirculation (EGR). Internal EGR rates and octane numbers were varied and examined their respective influence on HCCI combustion.

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In recent years the study of Homogeneous Charge Compression Ignition (HCCI) combustion is carried out actively because of environmental concerns and drain of fossil fuels. Theoretically, HCCI combustion is highly effective ; accordingly it enable to decrease Nitrogen Oxide (NO_x) and Particulate Matters (PM) simultaneously. However, HCCI combustion has the problem that the ignition timing control is difficult and operating range is narrow. In this study, Dimethyl Ether (DME) was supplied to a test diesel engine to operate HCCI combustion. The results of these analyses showed that the CO_2 influenced combustion reactions and ignition timing in the DME-HCCI combustion. This paper discusses the influence of CO_2 in the HCCI combustion.

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The compression ignition of Dimethyl Ether has two stages of combustion, which were known as cool and hot flame respectively. Since the temperature and pressure of mixture was increased by the heat release during cool flame, the amount of heat release during cool flame has strong effects on ignition of hot flame. In this paper, the effects of CO_2/H_2O addition on heat release of cool flame were investigated from chemical kinetic computations. From the systematic computations, it was confirmed that the amount of heat release at cool flame depends strongly on the concentration of O_2 at cool flame onset.

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In order to clarify misfire and knock limits of HCCI combustion in a multi-cylinder engine fueled with DME/Natural-gas, exhaust gas temperatures and cylinder liner temperatures at the top ring position were measured in each cylinder of a four-cylindered engine, comparing with a single cylinder engine. It is found that the liner temperature and the exhaust gas temperature become lower at the cylinders of No.1 and 4 than No.2 and 3 near the misfire limit condition due to intermittent occurrence of misfire in the end cylinders of No.1 and 4, which seems to be caused by the cooling system of a multi-cylinder engine. The minimum DME amount for obtaining stable ignition is larger in the multi-cylinder engine than the single cylinder one.

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Detecting intermediate species existing between ignition stages is crucial to validate the detailed chemical mechanism for compression ignition depending on fuels. We have developed a pulse sampling method using direct species detection in a differential pumping system, by which HCHO, H_2O_2 etc. are detected in the crank-angle resolved manner. In this study, the effect of additives such as CH_3OH and O_3 is evaluated with this method. It was confirmed that heat release and extent of low temperature oxidation decrease with increasing addition of CH_3OH as predicted by Curran et al. DME 2000 mechanism. O_3 addition is confirmed to increase fuel consumption and heat release in the cool ignition stage, which accelerates the final hot ignition timing. The large coefficient of O_3 addition effect in the range under 100ppm addition was not observed in the experiments. The effect of residual gas is discussed as the reason of this discrepancy.

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In order to improve NO_x, smoke emissions and the brake thermal efficiency, we pursued the multi-stage injection under the common rail fuel injection system in a DI diesel engine, and investigated the effect of the fuel injection characteristics on engine performance, exhaust gas emissions and combustion characteristics. As a result, the following conclusions were obtained ; (1) The multi-stage fuel injection, which consists of the pilot injection with a small fuel quantity and the after injection with a injection timing near the main injection one and a small fuel quantity, is effective on the point of smoke emissions (2) The after injection with a small fuel quantity increases NO_x emissions, but reduces the smoke emission.

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The effects of CO_2 and N_2 addition on intermittent spray combustion were examined experimentally. Under the same condition of ambient temperature and pressure, and the same injection pressure, the rates of CO_2 and/or N_2 addition were changed from 0 to 20%. The ignition delay and combustion period became longer with the increase of CO_2 and N_2 addition, especially in the case of CO_2 addition. The flame temperature became lower with the CO_2 addition, and, especially, the region with higher temperature became smaller. Though the combustion delayed with the CO_2 addition, the amount of soot in flame did not change so much.

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Unregulated harmful emissions of single cylinder DI diesel engines with large rates of cooled EGR were investigated by FTIR (Fourier transform infrared spectroscopy). The unregulated harmful emissions increase remarkably with intake oxygen content below 14% due to EGR. These trends correlate very well with those of THC emission. catalysts are effective on greatly reducing CO and THC emissions as well as some unregulated harmful emissions such as aldehydes and some unsaturated hydrocarbons. However, the effect of the catalysts is very small on aromatics and methane.

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This paper presents results of two different trials to reduce NO_x from diesel engines: one is pre-shock injection method and the other is the method with pre-shock jet created by using premixed charge combustion. The both concepts are based on the fact that dominant part of NO_x formation is the area close to the spray tip, where mixing intensity is weak. The mixing intensity of this area is to be maintained high by the two methods. The result shows reasonable effect for the reduction of NO_x, but the extent was not as significant as expected. It was found that the pre-shock jet was not realized in the present setup, and further attempt was necessary to evaluate the concept.

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It has been received much attention that nano-PM is bad for health. Therefore, PM characteristics in exhaust gas from diesel engine with fuel additives were investigated. The blend ratio of benzene in test fuel was changed from 0% to 30% and ferrocene was mixed. The excess air ratio of a DI diesel engine was changed from 0.7 to 3.0. The engine speed was set to 1080rpm and the fuel injection timing was set to 22deg. BTDC. The components of PM such as Dry soot, SOF and Sulfate were measured by a PM analyzer. The size of primary particles and aggregate were measured. In addition, the size distributions of agglomerate were analyzed by SMPS and ELPI. In case of ferrocene mixed fuel, the primary, particles were smaller and the aggregate were larger than in the case of the other fuels. Further, nano-particles below 50nm increased. From the comparison of PM component between λ=1.0 and 2.2, it was clear that PM components of two conditions were different even if the size distributions were similar.

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In this study, the emission characteristics of aldehydes and VOCs from off-road engine have been evaluated. Major aldehydes from off-road engine were formaldehyde and acetaldehyde. The emission characteristics of aldehydes are similar to that of CO. Aldehydes emission is highest in high engine and low load condition. As compares with formaldehyde and acetaldehyde, VOCs emission level is low. The emission characteristics of VOCs is similar to CO and aldehydes in high engine speed. But in middle engine, VOCs emission level is almost same regardless of load.

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Energy accumulated type variable valve timing (EAVVT) system ; a new type of hydraulic variable valve timing system has been developed. In our study, expansion of HCCI operating range was attempted by a single cylinder diesel engine combined with EAVVT system and supercharging. Numerical calculations with an elementary chemical reaction model were conducted to analyze HCCI ignition timing control by changing intake valve close timing with supercharging. As a result, maximum IMEP in HCCI operation was increased to 0.51MPa.

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In this study, the influence of knock phenomenon in HCCI combustion was evaluated by combustion information which was extracted by wavelet transform. It was found that high rate of heat release and knock were caused by early ignition timing due to engine load increase, and the knock brought about noise, friction and cooling loss increase. It was also indicated that the increase in cooling loss estimated by cooling water caused by knock was predictable by wavelet transform which could detect ignition process, frequency and occurrence timing of knock.

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A new combustion method of high compression ratio SI engine was studied and proposed in order to achieve higher thermal efficiency of SI engine. A variable speed piston-crank mechanism was adopted which allowed the piston to move rapidly near TDC. As a result, this concept can be operated at the compression ratio of 14 using regular gasoline. A new single cylinder engine was designed and built for proving its performance. The experimental results show that a knocking limit has improved and better indicated thermal efficiency has been obtained under engine speed upto 3000r/min using an eccentric cam mechanism.

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This paper describes one of new concepts on application of detonation waves to the engine systems. The detonation wave is a combustion wave which propagates with a supersonic speed and a steep pressure rise. In normal engine systems, such as the spark ignition engine and the gas turbine, the detonation phenomena should not occurred because their steep pressure rise. But, in principle, the detonation can short a combustion time to a minimum. The decrease of the combustion time increases a thermal efficiency. Examples which are developed as detonation engines are a Scram-Jet engine, a Ram Accelerator and a Pulse Detonation Engine (PDE). The present article describes the PDE which are developed recently, and which utilizes the propagating detonation wave through a chamber.

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This paper presents the results of experiments conducted with a 2-cycle engine that was the world's first such engine to comply with the emissions regulations applied to small off-road engines by the U.S. state of California in 2000. The reed valve was attached in the engine head surface of a wall taking advantage of two scavenging ports which are the features of the engine. Therefore, both exhaust gas and air flow into a combustion chamber directly. The combustion state and emission of this stratified scavenging (EGR and Air) engine are investigated. Moreover, the result analyzed using ion current as the detection method of an engine combustion state is reported.

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This paper describes a newly developed one-dimensional knocking prediction program. Combustion is forcibly advanced from one side of the cells to trace the input heat release. Unburned cells are compressed by combustion and the Livengood-Wu integral equation is used to judge whether autoignition occurs or not. A higher indicated mean effective pressure was predicted for a stratified air-fuel mixture than for a homogeneous air-fuel mixture in a high-compression-ratio engine because the spark timing for trace knock was advanced. A suitable mixture stratification was found to be a combination of a slightly rich center and a slightly lean periphery. The calculated results corresponded to the experimental data obtained with a single-cylinder engine, especially with regard to the effect of advancing the spark timing for trace knock.

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A knocking is the big factor which prevents improvement in an internal combustion engine's thermal efficiency. With the aim of understanding knocking better, light emission spectroscopy was applied in this study to examine preflame reactions that can be observed prior to autoignition. Light emission intensity was measured at wavelengths of 306.4nm (characteristic spectrum of OH), 395.2nm (HCHO). In this research, it measured about the generating phenomenon of the preflame reactions in different engine speed and octane number.

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A Rapid Compression/Expansion Machine (RCEM) was established to investigate knock characteristics in spark-ignition (SI) combustion. The effects of SI timing and compression ratio were experimentally investigated using the RCEM. High compression ratio and advanced SI timing lead to strong knock. The knock intensity was drastically decreased with a hydrogen injection into near the end of combustion chamber. The scale of knock intensity reduction was higher when the hydrogen injection timing was adjusted close in SI timing. And the knock intensity was lower with larger hydrogen injection quantity under the condition of the SI timing near TDC ; however, it oppositely increased with increase in hydrogen quantity under the SI timing relatively earlier due to excessive flame propagation of the hydrogen included unburned mixture.

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Gasket ion sensor had been developed as a sensor for combustion diagnosis. It is necessary to evaluate gasket ion sensor for measuring the combustion quality The fundamental characteristics of this sensor were investigated using a constant volume vessel. When the material and the thickness of insulation were varied, the waveforms of ion current were also varied. As the maximum pressure increased, the effects of insulation material and thickness on the ion current were occurred independently of combustion phenomena. When the insulating sheet was inserted into the gasket, the waveforms of ion current corresponded to the combustion quality independently of insulation material and thickness.

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Experiments have been carried out to examine the influence of oxygen concentration in intake air and fuel concentration on flame speed for small gasoline engine by using carburetor and EFI system. The travel time of flame speed front is measured using ionization probes located at different point of cylinder head. The main conclusions are as follows: 1) the flame speed monotonically increases with increasing the engine rotation at any concentration in intake air. 2) Mean increasing rate of pressure is not affected by oxygen concentration in intake air and fuel concentration under without load. 3) It is possible to improve the combustion behavior with using EFI system for small gasoline engine.

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Indicated thermal efficiency of internal combustion engines was studied by using the engine cycle simulation with exhaust energy recovery model. The simulation could represent the thermal efficiency of experimental results. In this paper, NA type Miller cycle engine system, lean burn system, non-throttling system with VVT, super charging system by turbo charger and energy recovery system by turbo compound were evaluated at the point of indicated thermal efficiency. It is suggested that lean bum and turbo compound is ideal system on thermal efficiency improvement for light load and full load operation respectively. In addition, turbo charger is effective technology on both light and full load conditions.

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Recently, the environmental issues on an earth scale and the depletion of energy resources are requiring internal combustion engines to improve fuel economy and to reduce NO_x emissions and particles urgently, which cause mainly atmospheric pollution. For this purpose, an alternative fuel and new combustion techniques have been studied so far. In this context, the interest in using alcohols as an engine fuel has increased. Among the various alcohols, Ethanol is known as the most suited fuel for spark-ignition engine. The most attractive features of Ethanol as an SI engine fuel are that Ethanol can be produced from renewable energy sources such as agricultural products and it has high octane number. Ethanol can be used in SI engines as pure or blending with gasoline. For pure Ethanol some modifications on engine design, where it can be used in SI engines by blending with gasoline at low concentrations without any modification. As the combustion properties of Ethanol, however, differ from those of gasoline fuel, it is necessary to investigate the combustion characteristics of Ethanol and the effects of Ethanol addition to gasoline in detail for the proper application of Ethanol to a new internal combustion engine. The main purpose of this work is to measure the laminar burning velocity of Ethanol and clarify the effects of Ethanol addition on octane combustion properties.

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The object of this research was developing the method of measuring and calculating the internal exhaust gas recirculation (EGR) rate under the internal EGR by means of the intake valve timing control in a direct injection (DI) diesel engine. The obtained results were as follows ; (1) The Internal EGR rate was more exactly calculated by the measuring of the oxygen concentration change during a cycle in the intake port using the oxygen concentration sensor. (2) Considering EGR by the valve overlap under this measuring method, the larger the internal EGR rate becomes, the larger NO_x reduction rate.

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Evaporative diesel spray simulations using Large Eddy Simulation (LES) are developed to predict the heterogeneous structure in the diesel spray. KIVALES, which is LES version of KIVA3V res.2 code, is used as the base code. The SGS stress model is k-Δ model and gradient diffusion model is applied for the scalar transportation. To advective terms, interpolated donor cell differencing scheme is used and break up is taken into account for modified Tab model. The computational grid used is a finer computational grid of 720,000 cells. As a result, LES can capture the instantaneous 3-D flow field with coherent vortices, and good agreement between LES and experimental results is observed in the intermittency at the spray periphery, liquid length and vapor length.

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Laser induced fluorescence measurement of formaldehyde has been conducted in a homogeneous charge compression ignition engine cylinder operated with dimethyl ether. It is crucial to quantitatively trace the intermediate, which controls the low temperature oxidation as a chain reaction suppressor. For this purpose, the fluorescence signal intensity depending on pressure, temperature and composition was corrected using "Two-Step Decay Model", which successfully predicts the non-linear pressure dependence of the fluorescence decay rate. In this study, the model parameters depending on H_2O partial pressure were separately determined using an optical cell. The crank angle resolved profile of HCHO concentration obtained by this correction corresponds with the result of detailed chemical kinetic mechanism calculation.

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This study tried to investigate the evaporation and ignition of a diesel spray using a rapid compression machine focusing on mixture formation of fuel and air. Swirl velocity and nozzle hole-number were changed in this report. Photography of spray development using high-speed digital video camera and measurement of pressure history showed relationship between air motion and spray evaporation during ignition delay period. In the case of low swirl, wall impingement of spray and rich mixture formation near injector outlet restrain spray evaporation. In the case of high swirl, spray interference for a large hole-number injector strongly affects spray evaporation.

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Simultaneous measurements of velocity and scalar distribution in a turbulent jet were carried out by means of particle image velocimetry (PIV) and laser induced fluorescence(LIF). In order to clarify the turbulent transport-process of momentum and scalar, the turbulence characteristics are calculated based on the temporal-averaged data. Furthermore, the local instantaneous flux of scalar by a fine scale structure of the turbulence is discussed and compared with a couple of the subgrid scale models for the large eddy simulation.

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Relationship between the burning velocity of laminar flames and flame stretch can be evaluated using unstretched laminar burning velocity U_1, and Markstein length L. In this study, numerical simulation of spherical laminar flame propagation are examined on the basis of this relationship. The simulation was carried out for the propane-air mixtures of the equivalence ratio of 0.8 and 1.3, at the mixture pressure of 0.10 and 0.50MPa. The results were compared with corresponding experimental measurements. This method was found to reliably simulate the flame propagation of laminar flame in the case of positive Markstein length. The increase in the burning velocity of unstable flames due to the flame instability, in the case of negative Markstein length, may be estimated from observed differences between experiment and simulation.

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