In this study, effects of aspect ratio on mixed convective heat transfer in horizontal rectangular duct were examined numerically and experimentally. The working fluid was water. As thermal boundary conditions, the upper and the bottom walls were insulated thermally and the side walls were heated and cooled walls respectively in the heat transfer section. In the numerical analysis, the fluid flow and the temperature distributions for Ri=1.61, Pr=6.99, Re=100, and aspect ratio Ar=0.2 10, were obtained by solving non-dimensional governing equations using SIMPLE procedure. The QUICK scheme was applied to convection term of these equations. In the experimental analysis, the flow behavior for Ar=0.5 2 was visualized by dye-injection method. Results show that the swirl flow was generated along the main flow direction. The vertical and horizontal velocities at the cross section were increased with A,. The prediction equations of the pitch length and the average Nusselt number were derived.

View full abstract

In order to know the heat transfer and fluid flow characteristics of a vertical channel having grooved pattern in one side, we have carried out a numerical analysis using the commercial CFD code. This system may be used as a wall of house to reduce the electricity consumption of an air conditioner. The side wall is heated by radiation of solar energy and is cooled by natural convection of air. This paper describes fluid flow characteristics of inside channel having grooved pattern which are exposed to radiation heat and are cooled by air. We have analyzed the steady state of natural convection in the vertical channel by using Phoenics code (CHAM Limited). From the results obtained in the numerical analysis, it is found that air inside the channel heated by solar energy. This system have a potential to warm the air in a room, however, it is difficult to establish the flow of warmed air from the vertical channel to the room.

View full abstract

Heat transfer enhancing method is more and more needed to decrease power consumption. This study was carried out to develop a high performance vortex generator, and find out the relationship between vortex structure and heat transfer. Double delta winglet pair was developed to reduce pressure drop with keeping up vortex strength. It was clarified that double delta winglet pair had higher performance than deltawinglet pair by 11% at flow velocity of 1.0m/s by measuring average heat transfer coefficient and pressure drop. It was found out that double delta winglet pair had the position of vortex core at short distance from heat transfer surface than delta winglet pair. Therefore, the heat transfer coefficient was larger than delta winglet pair's one, even though it's vortex strength was smaller than that.

View full abstract

The purpose of this study is to improve atomization characteristics of a direct injection Diesel nozzle, which spray with large spray angle, short liquid core length and small droplet diameter are obtained. In the previous study, the single hole atomization enhancement nozzle, which excellent spray characteristics are obtained at relatively low injection pressure, was developed. In this study, it was investigated about atomization of spray of the multi-hole atomization enhancement nozzle, and aimed to improve atomization characteristics and to obtain excellent spray characteristics. Effects of dimensions of the atomization enhancement nozzle, such as hole diameter and geometric shapes of nozzle hole, on atomization characteristics were investigated. As a result, it was cleared that in case of the multi-hole nozzle with hole number of N = 4, breakup length becomes short and spray angle becomes large about two times compared with the actual single hole nozzle. Atomization characteristics of continuous injection and intermittent injection were improved considerably by using the multi-hole nozzle with round inlet shape of nozzle hole and the multi-hole nozzle of hole number of N= 4 at high-ambient pi essure conditions for actual Diesel engine.

View full abstract

An experimental study was made of the characteristics of ambient gas entrainment into a non-evaporating fuel spray injected by a Diesel common rail injection system into a high-pressure constant volume vessel. The gas flow field around the spray was measured using a particle image velocitmetry coupled with a laser induced fluorescence (LIF-PIV) technique. The mass flow rate of the ambinet gas into the spray through the spray boundary was calculated by using the ambient gas velocity data. The spray-ambient gas interactions along the spray boundary were categorized into three sections, that is, (1) the entraiment section from nozzle exit to the middle of the spray, (2) the capturing section at the spray tip, and (3) the recirculation section between (1) and (2) where relatively large-scale vortexes appear along the spray boundary. The ambient gas flow rate into the spray through the section (2) is more dominant rether than that through the section (1). The total flow rate of the ambient gas into the spray increases as the ambient gas density increases.

View full abstract

Effect of CO_2 addition on combustion and emission characteristics of diesel spray in a high temperature and high pressure vessel was experimentally examined under low O_2 concentration ambient. The rate of O_2 concentration was changed from 8 to 21% and the rate of CO_2 concentration was changed from 0 to 15%. It is confirmed that O_2 concentration is a dominant parameter for the combustion characteristics. The flame temperature decreases with the decrease of O2 concentration and with the increase of CO_2 addition. Furthermore the soot production was suppressed under the very low O_2 concentration condition.

View full abstract

The heat release rate analysis was conducted to quantify the spray combustion characteristics of diesel fuel under the very low O_2 concentration condition. It is confirmed that, as the decrease of O_2 concentration, the shape of heat release rate has changed from the normal diesel combustion like one to the smooth heat release rate curve with only one peak. The period which has the negative heat release rate becomes longer with the decrease of O_2 concentration and the existence of fuel decomposition reaction around this period is inferred. The emissions of CO and NO cannot be found in the O_2 concentration region from 8% to 12% .

View full abstract

Temperature distribution of the mixture inside engine cylinder at intake-valve closing of a HCCI engine has been estimated, using the two pressure histories (cited from reference literature) of the same engine but with intentionally different intake temperatures. Our method of the estimation utilizes the two phenomena that are appreciably dependent on the mixture temperature, i.e., NO emission and autoignition-delay. Our analysis indicates that the temperature history of each local volume of the mixture asymptotically settles down to each certain history when the number of local volumes in our multi-zone model is increased, and that the number of local volumes necessary for the correct temperature estimation is about 15.

View full abstract

Homogeneous Charge Compression Ignition (HCCI) combustion has attracted considerable interest as a new combustion concept for internal combustion engines in recent years because of their potential for high efficiency and clean combustion. However the HCCI combustion process has two issues to be resolved: ignition timing control, slower combustion. Authors focused attention on exhaust gas recirculation (EGR) and using a fuel having two components with different ignition characteristics to resolve these issues. In this study, the influence of EGR and a fuel having two components with different ignition characteristics were investigated by using spectroscopic measurements and chemical kinetic simulations. And two stroke engine was used for the test engine. Currently, HCCI combustion is being widely researched using four-stroke test engines. However, the cylinder head of a four-stroke engine has a complex valve train system, making it difficult to obtain optical measurements inside the combustion chamber. Compared with a four-stroke engine, a two-stroke engine has a simpler cylinder head construction that allows greater freedom for making optical measurements in the combustion chamber and it is easier to apply EGR continuously. Since the purpose of the present study was to investigate HCCI combustion mechanisms on the basis of optical measurements, it was decided to use a two-stroke test engine. And, in this study, it has been understood a lot of OH radicals are generated if EGR and a fuel having two components with different ignition characteristics are used at the same time.

View full abstract

Intermediate species formed in the cool ignition stage of autoignition were evaluated by exhaust gas analysis with FT-IR in a test engine at hot ignition suppressed conditions. PRF (iso-octane/n-heptane) and NTF (toluene/n-heptane) were used as the fuels. The fuel consumption rate decreases with increasing iso-octane content in PRF and toluene content in NTF. HCHO generation rate increases with increasing iso-octane content in PRF but the opposide trend was found in NTF. These tendencies correspond to the difference in the detail reaction mechanism for PRF and NTF oxidation. Finally the essential mechanism affecting the ignition property of n-heptane is discussed by developing a simplified model reproducing the experimental results.

View full abstract

As fuel volatility and ignitability have strong influences on mixture formation and combustion, expansion of operation limit of premixed diesel combustion can be expected with optimizing fuel properties. In this study, JIS #2 diesel fuel and three primary reference fuels (PRF) with octane number from 0 to 40 were used to investigate the effects of volatility and ignitability on premixed diesel combustion. With the similar ignitability but different volatility, diesel fuel and normal heptane show the similar operation limit, indicating little effect of fuel volatility. With increasing in octane number from 0 to 40, the combustion phasing is retarded, higher intake oxygen concentration can be used within the tolerance of combustion noise, and the operational load of premixed diesel combustion is expanded by about 0.13 MPa in indicated mean effective pressure (IMEP).

View full abstract

This paper investigates the performance, exhaust emissions, and combustion characteristics of a dual fuel diesel engine fueled by compressed natural gas (CNG) supplied in an intake-pipe as the main fuel. The experiments used standard ignition fuels prepared by n-hexadecane and heptamethylnonane which are used to define the ignitability of diesel combustion, and focused on the influence of fuels with similar or poorer ignitability than ordinary gas oil such as fuels with cetane numbers (C.N.), 55, 50, 45, 40, 35, and 30. Compared with gas oil ignition, standard ignition fuels with C.N. below 40 showed significantly delayed ignition timings, higher exhaust gas temperatures, and extremely lower brake thermal efficiencies with increasing CNG supply ratios. Therefore, it is concluded that the lower practical C.N. limit for this engine is about 45 for dual fuel operation.

View full abstract

This paper investigates the performance, exhaust emissions, and combustion characteristics of a dual fuel diesel engine fueled by small amounts of hydrogen added to compressed natural gas (CNG) supplied into an intake-pipe as the main fuel. The experiments used ordinary gas oil for the ignition, and the equivalence ratios of the premixed mixtures with CNG and hydrogen were varied in the ranges 0-0.41 and 0-0.075, respectively. The brake thermal efficiency with the dual fuel operation showed similar values compared with normal diesel operation at high loads. With increasing CNG supply ratio, the CO concentration increases but this increase is suppressed significantly by the hydrogen addition. Regardless of the gas fuel, the smoke emissions decreased monotonously and sharply with increasing gas fuel (CNG + hydrogen) supply ratio. The hydrogen addition causes increases in the NOx emissions, and further study is necessary to determine ways to reduce these.

View full abstract

A combustion process of the natural-gas dual-fuel engine is simulated using CFD with a combustion model taking account of a mixing process. Here, the special attention is focused on the effects of double-pilot injection condition on the combustion process. The result shows that the tendencies of incylinder pressure histories agree with that measured by the experiments. Furthermore, details of the combustion process of a double-injection condition are discussed.

View full abstract

An experimental study was conducted to investigate the effect of LPL-EGR on combustion and exhaust emissions characteristics of a four cylinder DI diesel engine during steady state and transient operation. The engine is equipped with high-pressure loop (HPL) and low-pressure loop (LPL) EGR systems. The results show that the LPL-EGR system is more effective than the HPL-EGR system in terms of NOx and Soot reductions over a wide range of steady state lower load. However, fuel consumption tends to increase by using the HPL-EGR system at low load. It was found that although the boost change is stable, the EGR ratio response is slower at LPL-EGR.

View full abstract

This paper describes with numerical studies on predicting for combustion and exhaust gas emissions in the cylinder of a diesel engine manufactured for medium duty trucks. The EGR rate is changed from 1 to 37% under the low load, engine speed 1500 rpm condition. The predicted pressure, rate of heat release and NOx have good agreements with measured ones. NO2 is formed by the conversions from NO formed by post flame reactions by oxidation in the cylinder. Soot is also tried to simulate under the same condition. However, it is difficult to predict both qualitative and quantitative soot emission values.

View full abstract

This study clarified the influence of high temperature gas jet on combustion enhancement effect for lean mixture in the plasma jet ignition by the use of combustion bomb. The hot gas jet was generated by the plasma and was ejected after the plasma jet finished injecting. The combustion chamber had a cylindrical shape with 80 mm of diameter and 40 mm of thickness and its volume was about 201 cm3, and the igniter was attached to the bottom of combustion chamber. The igniter was composed by central electrode, orifice and cavity. Tests were carried out with propane-air mixture at equivalence ratio of 0.6 and cavity depth, orifice diameter and discharge energy were varied. The hot gas jet was visualized by schlieren method in the absence of combustion, and combustion development processes were also visualized and the combustion pressure was measured. The voltage throughout electrical discharge and the plasma luminescence was also measured. The electrical discharge began early and the intense luminescence was emitted from plasma jet as the supplied energy increased. The electrical discharge and light emission durations were not so influenced by igniter configuration. The initial flame kernel and hot gas jet were similarly developed. For small diameter orifice and large volume cavity, flame propagation was enhanced and combustion duration was shortened, because the hot gas jet velocity increased. Because the discharging duration was very short as compared with combustion period, the hot gas jet was more effective against the combustion enhancement than the plasma generated by electrical discharge.

View full abstract

Six-stroke diesel engine proposed here has two combustion processes in one cycle, i.e. intake, 1st compression, 1st combustion, 2nd compression, 2nd combustion and exhaust. However, soot emission increased due to weak swirl in combustion chamber at 2nd combustion process. In the previous study, in order to improve 2nd combustion, cam profile was changed to introduce the fresh air between 1st and 2nd combustion process. However, fresh air wasn't introduced into the cylinder at 2nd combustion process because of high cylinder pressure that was generated by 1st combustion. In this study, in order to introduce fresh air between two combustion processes, supercharging system was applied. And fuel injection ratio of 1st and 2nd combustion process was changed from original fuel injection ratio 8:8[mg/cycle] to 10:6[mg/cycle] or 6:10[mg/cycle]. As results, at 6:10[mg/cycle] with supercharging, soot, CO and NO emissions decreased due to introduction of fresh air into cylinder at 2nd combustion and low heat release rate of 1st combustion as compared with original fuel injection ratio.

View full abstract

The objective of this research is to investigate the effect of the EGR guide employed to generate a strong in-cylinder thermal stratification on the recharged EGR gas flow into the cylinder in the gasoline HCCI engine equipped with the blowdown supercharging (BDSC) system. The recharged EGR gas flow was visualized using an optical access engine. A steady gas flow from the exhaust port into the cylinder was visualized via PIV method. The effect of the pressure difference between the exhaust port and the cylinder and the geometry of the EGR guide on the recharged gas flow were investigated. The results indicate that the flow field pattern is largely affected by the EGR guide height, and that an increase in the EGR guide height is effective to generate a strong in-cylinder thermal stratification.

View full abstract

The reduced elementary reaction model of DME oxidation was made based on detailed elementary reaction model DME 2006. In developing the model, major oxidation reaction mechanisms were considered; 1) The low temperature oxidation mechanism caused by OH radical production through 02 addition and isomerization, 2) Accumulation process of CH2O and H202 before high temperature oxidation, 3) The high temperature oxidation mechanism initiated by H202 dissociation. The new reduced model consists of 41 reactions for 26 species. The validation was made by comparing with the analysis results of the detailed elementary reaction model. The reduced model shows good agreement with the detailed model on ignition delay and mole concentration history of major intermediate species over a wide range of both equivalence ratio and initial temperature.

View full abstract

Burner low-temperature flames were established on a Powling burner with a diethyl-ether/toluene/air (toluene content in fuel by liquid volume: 0.5 vol% and 1.0 vol%) at an equivalence ratio of 2.0, under the atmospheric pressure, in order to understand the low-temperature ignition inhibition mechanism by toluene. Aromatic hydrocarbons and unsaturated aliphatic hydrocarbons measurement are preformed by a liquid and gas-chromatograph. The temperature in the low-temperature flames were measured using a fine thermocouple. The formation of aromatic hydrocarbons in the yellow column is promoted by toluene addition. Toluene addition retarded the cool-flame appearance and reduced the distance between cool and blue flames. The similarity to burner low-temperature flames and a compression ignition low-temperature flames can be confirmed also here.

View full abstract

It was explored that the flame propagation behavior of hydrogen-air mixture under the application of positive and negative non-uniform electric field by using a constant volume vessel. For applying a non-uniform electric field, a needle-shaped electrode was attached to the center of the combustion chamber ceiling and a plate electrode was attached to the bottom of the chamber. A Nd:YAG laser was used to apply laser-induced breakdown for igniting the mixture at the center of combustion chamber. A homogeneous hydrogen-air mixture was supplied at three equivalence ratios of 0.4, 1.0 and 3.5 and ignited under atmospheric pressure and room temperature. The flame propagation process was visualized with a conventional Z-shaped schlieren system. In case of lean mixture and applying positive polarity non-uniform electric field, the wrinided flame appeared by the effect of preferential diffusion and the wrinkle was enhanced when the input voltage was larger than 12 kV because a brush corona discharge occurred and turbulence was generated at the flame front. However, for the stoichiometric mixture, the pre-mixed combustion process was not influenced by the positive polarity non-uniform electric field and, for rich mixture, the flame front was merely moved toward downward by corona wind. When a negative polarity non-uniform electric field was applied, for any cases, the combustion was not affected because the corona wind was not generated. Therefore, the electric field hardly affects the flame propagation of hydrogen-air mixture and the corona wind which is generated by the positive brash corona only influences the combustion process.

View full abstract

This research aims to study the characteristics of hydrogen jets in argon atmosphere, which provides the fundamental condition of hydrogen jet in the argon circulated hydrogen engine. The experiments were carried out using a constant-volume vessel under various conditions of ambient gas and hydrogen injection. The results show that the development of the hydrogen jet in argon is slower than that in nitrogen due to its high density and faster at a higher injection pressure, at a lower ambient pressure and with a larger nozzle-orifice diameter.

View full abstract

This study aims to explore the effects of fuel composition on spray ignition using a constant volume vessel. Ignition delays of two-component fuels (n-alkane + HMN) with a wide range of n-alkane volume percentages were measured under two ambient conditions. Based on the results, estimated cetane numbers (CNe) of n-alkane were calculated by the equation, CNe = CNllmN + 100(CN,,佑NHmN)/r. The results showed that the dependency of ignition delays on n-alkane volume percentages changed at a certain percentage for all fuels. The dependency of CNe on n-alkane percentages was considerably affected by ambient pressure.

View full abstract

A new pretreatment technique for cellulosic ethanol production from rice straw and wood chip with supercritical dimethyl ether (DME) was performed. Finely-milled rice straw and wood chip were reacted with supercritical DME, to break down the lignin and to hydrolyze the cellulose and hemicellulose. Componential analysis by HPLC was made to determine the saccharification. The result shows that monosaccharide such as glucose and fructose was produced from rice straw. The saccharification was estimated to be about 12wt%, which suggests the possibility of cellulose decomposition with supercritical DME. However, the saccharide yield was low as compared with that of pretreatment with supercritical water. Few monosaccharides were produced from wood chip which contains much lignin.

View full abstract

In Engine, four types of journal sliding bearings of piston pin bearings(consist of one connecting rod small end bearing and two piston pin boss bearings), connection rod big end bearing and main bearing are used and these bearings are influenced each other. By comparing a simultaneous analysis and approximate analyses proposed by authors for engine bearings, practical approximate analyses are established and the considerations of balance weight are clarified. To save computation time for engine bearing analysis by finite width bearing theory, variable step's Runge-Kutta methods with inherent algorithm of engine bearings are examined. In this paper, as an another method to save computation times, easy methods with iteration are introduced. As the iteration methods, evaluation method at edge step and evaluation method at middle step are proposed. By comparing computation time, it is clarified that the time by evaluation method at middle step become less.

View full abstract

By comparing a simultaneous analysis and approximate analyses proposed by author for four types of engine bearings of piston pin bearings(consist of one connecting rod small end bearing and two piston pin boss bearings), connection rod big end bearing and main bearing ,these analyses are clarified. It is nessecary for finite width bearing theory for paractial bearing design and practiocal phenomena analysis to save computation time, variable step's Runge-Kutta methods and iteration easy method with inherent algorithm of engine bearings are examined.

View full abstract

The flow visualization inside the oil film was tried using the method of photochromism. One of the photochromic dyes is dissolved in the PAO and used as a test solution for flow visualization and velocity measurement. The light source used is a 3rd harmonic of Nd-YAG laser. This ultra-violet light is shaped to a thin light sheet and irradiated to the oil film of test solution. The test oil of irradiated position is marked by a blue color and the movement of the mark was photographed by a high speed color video camera. The flow velocity was quantified from the obtained images and confirmed the validity of this technique by comparing to the velocity analyzed from the flow rate measurement. The usefulness for flow visualization was confirmed by demonstrating this technique to 3 different flow fields.

View full abstract

The human race depended on the fossil fuel, and gave rise to the international problem such as the exhaustion of fossil fuels and global warming. We will have to change its focus from nonrenewable fossil fuel technology to renewable power source. The authors focused on solar energy and have developed a collector unit. There is variously use of the solar heat. The authors especially paid attention to the solar still and made its prototype. The reason is the shortage of water raised as one of the international problems. It is forecast that the world population exceeds 9 billion in 2050, and is requested securing a further drinking water (1). This device utilizes solar heat and it warms seawater. The generated steam is condensed and the fresh water is obtained. It thinks about an ideal solar still in this study, as part of effective use of the solar heat.

View full abstract

A waste heat recovery system is effective technology for ship energy saving. However, it is not practical used for a small-size ship, because it has too large scale and low efficient performance for the ship. We study a marine waste heat recovery system used a reciprocating steam expander of Rankine Cycle. An axial flow turbine expander is widely used for a general marine waste heat recovery system. However, the efficiency of the axial flow turbine expander is not so high, when steam flow rate is low or has different design condition. A volumetric expander like the reciprocating steam expander has a possibility to get a high efficiency in every condition. Firstly, we design a small-size expander for experiments, which uses compressed air for power source. And we make a simulation model of expander. As a result, we estimate fundamental performance of the expander.

View full abstract

Since a thermoacoustic engine is an external combustion engine triggered by the Stirling cycle, it has the potential to draw work out of multiple heat sources such as industrial exhaust heat, automobile exhaust heat and solar energy. Also, as it has a simple structure and uses sound waves for heat exchange, and requires no moving parts such as pistons and turbines, it offers advantages of being a low-cost, long-use, and maintenance-free system. On the other hand, there are issues to be solved for its practical use. Although a thermoacoustic engine has an advantage of requiring no moving parts, it has a disadvantage of possessing no system to adjust the acoustic field that is suitable for heat exchange. This research on a thermoacoustic engine operating by self-excited oscillation is an attempt to determine the device configuration that treats all the acoustic fields following a certain point as traveling-wave phases by the use of a numerical calculation.

View full abstract

In this paper, a method of rationally determining an optimal renewal plan is proposed for energy supply systems based on the optimization approach. In the planning of this proposed method, it becomes necessary to consider many factors such as the deterioration of each pieces of existing equipment, candidate pieces of equipment with upgraded efficiency reflecting technology improvement in the proper renewal year, the structure of renewal system, and so on. It is also necessary to determine the system's operational policy to match energy demands, which change daily and hourly through the year. A numerical study is carried out for a hospital with the total floor area of 25 000m2, where electrical (e.g., heat pump) and gas (e.g., gas engine cogeneration) systems are compared together with theircombination of gas and electricity driven equipment (hybrid) system. Through this numerical study, the following results are obtained: a) Theoretically, the hybrid system is, of course, the best renewal system. However, the economic difference between the hybrid and the electrical systems is very small. b) The gas system is worse economically than the electrical one relatively due to the low energy efficiency of the related equipment, the high price of energy, and so on.

View full abstract

Recently, a small and high output power sources are required with advancement of portable equipments. In addition, environment-friendly properties are needed in the power sources. At present, lithium-ion batteries and fuel cells are used widely as the output power sources. But there are some problems in these sources, such as low energy density and low output power density. On the other hand, internal-combustion engines have high energy and high power density. In particular, the rotary engine is simple in the structure, so it is suitable for small and high output power source. Furthermore, hydrogen, one of environment-friendly fuel, can be treated stably in the rotary engine. In this paper, output power characterization of the 20cc hydrogen rotary engine was carried out as a first step for developing the small and high output power source with environment-friendly characteristics. The obtained results of the output power and the torque were compared with those of the gasoline rotary engine.

View full abstract

It is known that HCCI operating range extends to higher loads by use of mixed fuel with different ignitability, because main heat release is delayed into the expansion stroke where reactant density is lower. In this study, effect of ignition mechanism of the main fuel on heat release phasing in dual-fuel HCCI combustion was investigated based on elementary reaction-kinetic mechanisms. Two kinds of dual-fuel, methane/DME and toluene/DME, were used for analysis. As the results, it was found that the induction period from low temperature reaction to the early stage of high temperature reaction is strongly influenced by the OH reactivity of the main fuel, as well as heat release during the induction period. The analysis suggested that toluene/DME mixed fuel has an advantage in the knock limit since heat release is largely retarded compared with methane/DME mixed fuel.

View full abstract

In this study, effects of fuel composition of biomass gas on the ion current of burner flame were researched to clarify feasibility of ion current probe method for biomass gas flame. A mock biomass gases consisting of H2, CH4, CO, CO_2 and N2 were used in this study. As a result, it was showed that the ion current are not detected when CH4 are not included in the fuel. It was also showed that the increase of the ratio of CH4 or H2 content makes the ion current value increase, the increase of the ratio of CO_2 makes the ion current value decrease and the increase of the ratio of CO doesn't change the ion current value. This suggests that the change of the composition of biomass gas can be detected by the ion current probe method when CH4 is included in the fuel. Meanwhile, effects on ion current value of each gas flow per unit flame surface were similar to the effects of the ratio of each gas contents.

View full abstract

This paper presents a controller design approach to provide the precise force control considering interference suppression in load devices. In the control system, a pneumatic actuator and a voice coil motor are combined as a dual-stage actuator to expand the servo bandwidth. However, the interference between the actuators deteriorates the performance of disturbance suppression, especially at around the cross-over frequency. In this paper, therefore, PQ method is adopted to suppress the interference. The proposed approach has been verified by experiments using an actual load device.

View full abstract

This paper studies a control of vortex-induced vibrations of a circular cylinder supported by a cantilever beam. A servo motor is installed as an actuator to suppress the vibration of the system, and the beam is clamped at the axis of the motor. The beam-cylinder system is hanged in front of an air tunnel and allowed to tilt statically. When the wake frequency coincides with the natural frequency of the structure in the uniform flow, resonant vibration may occur and this is known as the rock-in phenomena. In this research, feedback control by the linear quadratic regulator and a disturbance cancellation control by the minimum order observer are applied to the system for vibration reduction. Performance of each control law is investigated by the numerical simulation.

View full abstract

A tower crane is widely used in a dam construction site. As the crane gyrates, a cargo swings in the circumferential and radial direction. In order to carry cargos to a required position in short time, the swinging motion should be suppressed. Since the crane operation is strongly relied on the operator's empirical technique simple automatic crane operating procedure by which swinging motion is suppressed enough to complete conveyance in a short time is strongly required. In this study, two-stage velocity pattern was adopted for simple automatic operation to minimize residual swinging motion. The applicability of the proposed method was investigated by means of numerical simulations.

View full abstract

In previous research, we did a modeling of 2-axis arm mechanism by using Functional modeling method. This Functional modeling method has characteristics that this method is based on energy flow. In this presentation, the control method of this mechanism is proposed. The nonlinearity in the modeled block diagram is dealt as the system errors.

View full abstract

In recent years, electric vehicles (EV) are becoming increasingly important because of the environmental problem, such as global warming and less oil reserves. However, almost small EV has only a seat-belt for safety device. To improve the safety, we decided to install an Anti-lock brake system (ABS) device in the small EV. To study the influence of the ABS device upon the vehicle's motion, the presenter researched the numerical simulation of this vehicle. We introduced 2-wheel model and ABS model that considered oil transience condition, for numerical simulation. This paper presented effect of cooperative control of hydraulic brake, mechanical brake and regenerative brake for vehicle motion on icy road.

View full abstract

In recent years, electric vehicles have come to be widely used. The braking force of electric vehicle is the sum of mechanical brake force and regenerative brake force. The mechanical brake force is proportional to the treadless force on the brake pedal. On the other hand, the regenerative brake force produced by the driving motor. The regenerative brake force with the braking conditions, for example, the degree of deceleration, rotation speed of tires, body speed and charging level of the battery. Then it is important for the stability of the electric vehicle in braking motion that the actual brake force distribution decided by the mechanical brake force and the regenerative brake force are maintained in the front tire lock region. In this report, the effect of ABS is researched when the road surface condition is different in a right and left tires. The further more effects of ABS and regenerative brake force on a stability of a small electric vehicle in braking motion are clarified.

View full abstract

The studies of safety and stability systems of small electric vehicles can be divided broadly into two areas of interest, namely skid control by motor sensors and safety improvement by Anti-Lock Braking System (ABS). However, for a small electric vehicle, there is no space to install a brake unit for ABS in driving tire because an in-wheel motor system is used as the driving unit, and there have been no simulations of an ABS that combines a mechanical brake system and a hydraulic brake system. The purpose of the present study is to improve the safety and stability systems of the small electric vehicle. The effect of a regenerative brake on a turning motion and the influences of the weight movement with the suspension were investigated. In this report, the hydraulic-mechanical hybrid brake system was combined with the ABS as a braking system for a small electric vehicle. A hybrid simulation model comprising velocity and the pressure of the brake fluid in the brake piping by the characteristic curve method was constructed for the hydraulic and mechanical brake system. The braking pressure of the braking unit, which included the antilock braking unit modeled by the lumped constant model, was controlled to compensate for the small stiffness value of the mechanical braking system.

View full abstract

In this paper, an active safety devise for skid control of a small in-wheel electric vehicle that uses a hybrid hydraulic-mechanical brake system is proposed. During past research, it is known that by using a hybrid hydraulic-mechanical brake system a small electric vehicle can accommodate an anti-lock brake system (ABS). When skid occurs, especially on icy road, ABS will maximize the slip ratio and cornering force during braking, thus, assuring the stability control of the vehicle and eliminating the possibility of accident. Before we can acknowledge the control method of ABS, we have to investigate the effectiveness on hybrid hydraulic-mechanical brake system. We had to consider that the rear brake system has a regenerative brake produce from the in-wheel motor system. The experimental result of the effectiveness of an ABS of a small electric vehicle utilizing a hybrid hydraulic-mechanical brake system during braking on an icy road is calculated in a simulation.

View full abstract

Sound is produced due to vibration of air and humans will recognize it by their ears. Sound pressure is amplified in the external auditory meatus (E.A.M.) and make the tympanic membrane (T.M.) vibrate. Finally, it is transmitted into the inner ear through the ossicle. Therefore, it is considered that human perception of sound is influenced by the vibration behavior of T.M. and ossicle. The purposes of this study are to establish the middle ear analytical model and to reveal the vibration characteristics of middle ear by numerical computing. In this study, we construct the simple middle ear analytical model on the assumption that the malleus and incus are rigid bodies and the stapes is one-degree-of-freedom mass. Also, above-mentioned assumption on the malleus and incus makes its rotation movement and expresses the motion of pry of the ossicle. And we entertained the vibration characteristics of middle ear for various sounds. Through this study, we evaluated the natural frequency of the middle ear. Also we estimated the frequency of sound that human can hear most easily. As a result, it is found that the present middle ear analytical model can simulate the hearing system of human.

View full abstract

A low for the safety of bicycles that are able to be ridden with two children is established in 2009.Consequently, development of such bicycles has been attracting a lot of attention. To improve for the operability, we proposed a power steering system for such bicycles. But, in this case, weight and inertia of the handle is increased, and the handling is worse. In this paper, we consider the safe manual control for the bicycle. The limitation of the stability of the bicycle system is shown by the normalized dynamics.

View full abstract

A bifilar suspension pendulum, a uniform density bar suspended at its two points by two strings of same length, may swing in two vertical planes (Mode 1 and 2) or make torsional oscillation about a vertical axis (Mode 3). The period and pattern of the modes depend upon the ratios of the string length and of the distance of the supporting points to the distance between two end points of the strings attached to an upper wall. The three modes make linearly independent oscillation, but may give rise to nonlinear coupling. Typical couplings obtained so far in numerical computations are reported.

View full abstract

It is important for structure and machine maintenance to detect the damage location and to evaluate the level of damage at that point. To understand the relation between natural frequency, in this paper, damping ratio and steel structural component with damage, dynamic characteristics of structure component was investigated by vibration test. Comparing between specimen with damage and without damage, natural frequency and damping ratio indicates change clearly. Damping ratio depends on the damage location, it becomes large value as the damage location approaches a lower position. And damping ratio of specimen with heavily damage indicates smaller to slight one.

View full abstract

In this study, we estimate structural dynamic reliability of piping systems supported by elasto-plastic damper subjected to nonstationary random input excitation. Analytical model of elasto-plastic damper has a bilinear hysteretic characteristics. Analytical model of piping systems is constructed by using finite element method. At first, we make nonstationaty random inputs by combining of stationary random processes and envelop functions. At second, we investigate the stresses of the piping and the absorbed energy of damper for nonstationary random input excitations. At third, we evaluate structural dynamic reliability based on probabilistic vibration theory. This structural dynamic reliability takes into account of the integrity of both the piping systems and elasto-plastic dampers. At last, we examine the effects of the supporting conditions such as supporting locations and capacities of damper on structural dynamic reliability, and also study the impronement of structural dynamic reliability reliability.

View full abstract

We investigate running stability of the high-speed-moving vehicle subjected to the seismic excitation considering the passengers' dynamic characteristics. The analytical model of the vehicle consists of the body, the trucks and the wheelsets. The passengers are modeled as the 2-DOF system in horizontal and vertical directions. The behaviors of the vehicle and the passengers are simulated with the actual seismic input to the system. Then the possibility of the rollover of the vehicle is evaluated. We focus on the effect of the dynamic characteristics of the human and the number of the passengers when the vehicle is subjected to the seismic excitation.

View full abstract

A waveform of a water surface caused by water sloshing in a rectangle tank often changes because of nonlinear effect of fluid. In the case of a small water depth, shallow water wave theory can be applied to this phenomenon. Then we propose a sloshing prevention control method using concentrated mass model and moving plate. This model consists of masses, connecting linear springs and connecting dampers. In this control method, the liquid of the container is formulated by the concentrated mass model and a displacement of the moving plate is obtained by optimal regulator. The effectiveness of the proposed method is confirmed by a numerical simulation.

View full abstract