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Published: September 04, 2010
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Article type: Index
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A1-A4
Published: September 04, 2010
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Yasunari KAMADA, Takao MAEDA, Junsuke MURATA, Isao OBIKA, Masaya YADA
Article type: Article
Session ID: G0800-1-1
Published: September 04, 2010
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In these years, the biomass resource has attracted attention as a renewable energy. This report describes the experimental results of a small scale updraft fixed-bed reactor. The wood chips and the pellets were used as a raw material of the gasification. Real-time monitoring of the temperatures and fluid permeation resistance on inside of the reactor, CO concentration were recorded. The experiment using only wood chip compared with the experiment using the fuel that pellet mixed.
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Shuichi UMEZAWA, Haruo AMARI, Jin YASUDA, Hitoshi KAWAMURA, Shuzo KATO ...
Article type: Article
Session ID: G0800-1-2
Published: September 04, 2010
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Reduction of CO_2 emissions and energy saving are the urgent issues for many fields of industries at present. Steam, occupying considerable energy consumption rate in the whole industry, is generally generated at boilers. The boiler efficiency was generally thought to be approximately ninety percent. However, rate of heat loss from steam pipes can not be neglected on occasions. Accordingly, we executed measurement of total boiler efficiency considering heat loss from steam pipes in an operating factory. Two methods were employed for the measurement of heat loss from steam pipes. One is how deference is calculated between steam flow rate at boiler exit and that at machinery using steam. The other is how each drain flow rate from drain-trap is measured. Both results are compared and discussed.
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Naoki SHIKAZONO, Hiroshi KANNO, Kazuma KOMATSU, Hiroshi IWATA
Article type: Article
Session ID: G0800-1-3
Published: September 04, 2010
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Oblique wavy surface can achieve very high heat transfer enhancement with small pressure loss penalty because it can produce effective secondary flow without separation. In the present study, applicability of oblique wavy surface to gas-liquid separation in mist flows is investigated. Plate, oblique wavy and sine wavy surfaces are tested by air-water experiment. It is confirmed that oblique wavy surface can completely separate liquid droplets whose sizes are larger than approximately 10 microns.
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Hitoshi HAYASHIBARA, Koichi HIRATA, Yoichi NIKI, Takahiko ITOH, Sumiko ...
Article type: Article
Session ID: G0800-1-5
Published: September 04, 2010
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Azimuth thruster is divided into two versions generally. Motors for thrust are installed on ship's hull, and propellers are driven by mechanical transmission gears in case of one version of azimuth thruster. This type of thruster has a perpendicular middle driving shat, the reaction torque acts on the pod because of the driving torque of the perpendicular middle driving shat. When the single perpendicular middle shat is modified to contra-rotating system and the driving torque of outer perpendicular middle shat is equal to that of inner perpendicular middle shat, it is possible to cancel the reaction torque acting on the pod and to prevent the interference between rotation of motor and gyration of pod in principle. We made experimental model of azimuth thruster, and measured reaction force in steering. The difference between modified model and conventional model was evaluated.
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Yoichi NIKI, Koichi HIRATA
Article type: Article
Session ID: G0800-2-1
Published: September 04, 2010
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In this paper, to develop a method of reducing specific fuel consumption of a marine Diesel engine by the marine hybrid system, the specific fuel consumption of the marine Diesel engine was measured in fluctuating load. We used the rack displacement of the fuel injected pump for the measurement. From results, The relation of the fuel consumption and the rack displacement can be linearly-approximated. It is confirmed that the specific fuel consumption is increased 0.7% at the maximum in load fluctuating without torque rich and the specific fuel consumption can be reduced with the marine hybrid system.
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Chiaki NAKAJIMA, Yoichi TAKEDA, Akio OHJI
Article type: Article
Session ID: G0800-2-2
Published: September 04, 2010
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Dimethyl ether (DME), which is attracting fuel as a clean and manageable fuel, is considered to apply to Chemically Recuperated Gas Turbine (CRGT) system. CRGT system is improved by reforming the fuel mixed with steam for the hydrogen-rich gas by recovering the exhaust heat of gas turbine. In this study, to construct the optimum CRGT system, a thermal performance analysis of the CRGT system fueled by DME was performed. And then dependence of the several parameters on the reformed gas LHV and the generator output was obtained.
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Yasunori TSUJI, Seiji SHIBA, Koji SUEOKA, Tsuguhiko NAKAGAWA
Article type: Article
Session ID: G0800-2-3
Published: September 04, 2010
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The reduction of the CO_2 exhaust is now important problem all over the world. Improving the thermal efficiency of the internal combustion engine becomes one of the solutions for that. Separating CO_2 and N_2 in the low-calorie fuel will improve the thermal efficiency of the engine. In this study the numerical simulation model of the gas turbine combined cycle is constructed with the Brayton cycle, the Rankine cycle and the heat exchange steam boiler and the thermal efficiency was quantitatively evaluated in the various fuel cases. Both thermal efficiencies have improved 2.0% and 3.4% by separating N_2 and CO_2. It is concluded that separating CO_2 whose specific heat ratio is smaller than N_2, improves the thermal efficiency better because it makes combustion temperature higher and compression load lower.
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Yosuke TSUSHIMA, Yoichi TAKEDA, Akio OHJI
Article type: Article
Session ID: G0800-2-4
Published: September 04, 2010
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Combined cycle (CC) operated is known as a highly effective power generation system and operated widely in the world. However, decrease of power output of Gas turbine (GT) at high ambient temperature is the problem to be solved. It is desirable to understand the characteristics of the system for effective operation. We installed a small scale CC system with a micro gas turbine (μGT) to improve the system design. Optimum start up condition is adjusted by changing of fuel/air ratio. Low fuel ratio is more preferable compared with high fuel ratio.
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Tamotsu INOUE, Hiroyuki IYOTA, Shogo ISSHIKI
Article type: Article
Session ID: G0600-1-1
Published: September 04, 2010
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A simple method is required for measuring humidity in a wide range of conditions from room air to superheated steam for several hours. In this study, we applied the theory of a psychrometer to develop a humidity monitoring system by using cylindrical porous ceramic media as a sensing element. This system contains a section for supplying/discharging water. We tested the performance of this system in terms of its measurement accuracy and response time. At a gas flow rate of 1 m/s and a gas temperature less than 310℃, the error of the steam mole fraction was observed to be less than 10%. In addition, a response time was reduced as a sensing element diameter was smaller. The system had a 90% response time of less than 60 s at a gas temperature of 200℃, a gas flow rate of 1 m/s, a flow rate of supplied water of 0.01 g/s and a water temperature of 25℃ when a sensing element diameter was 9mm.
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Takashi KITAHARA, Hiroyuki IYOTA, Tamotsu INOUE, Nobuya NISHIMURA
Article type: Article
Session ID: G0600-1-2
Published: September 04, 2010
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We have developed a humidity sensor by applying the principle of the Assman psychrometer. Cylindrical porous ceramic material was used in this sensor for sensing humidity. Some water flowing in the center of the sensing element is supplied to the surface by means of capillary flow, and the temperature of the wetted surface is used as a wet-bulb temperature. In this study, the relationship between the water evaporation rate and the surface temperature of the humidity sensing element were experimentally and theoretically investigated under various gas temperature (100-300℃) and flow velocity (1-10 m/s) conditions. Three types of porous materials with different pore size distributions were used as the sensing element. The difference between the surface temperature and the calculated value of wet-bulb temperature was observed to be large when the evaporation rate was high and the porosity and the median diameter of the sensing element was low.
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Soe Minn Khine, Kazuhide Kaifuku, Tomoya Houra, Masato Tagawa
Article type: Article
Session ID: G0600-1-3
Published: September 04, 2010
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Hot-wire anemometers (HWAs) for measuring a fluctuating velocity field can be operated in two modes, i.e., the constant current (CC) and the constant temperature (CT) modes. The CC mode suffers from a response lag due to the thermal inertia of the hot wire, whereas the CT mode can avoid this problem by virtually eliminating the inertia with a negative feedback amplifier. Thus, the HWA is almost always operated in the CT mode. The CC mode, however, is promising for many applications because of the simplicity of the electronic circuitry to heat the wire. In the present study, the response of the CC anemometer is theoretically analyzed, and a compensation scheme for the response lag is proposed. The scheme is experimentally tested in a turbulent wake flow behind a cylinder. As a result, the compensated CC mode provides results almost identical to those obtained in the CT mode, and the CC anemometer can be used as a reliable measurement technique for turbulent velocity fluctuations.
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Kazuya KOIKE, Shigeki HIRASAWA, Tsuyoshi KAWANAMI
Article type: Article
Session ID: G0600-1-4
Published: September 04, 2010
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We experimentally studied the effect of dynamic predictive models on the model prediction control to minimize temperature change at an object position in a vertical plate with varying noise-heat-generation. When the dynamic predictive model is made with experimental results of step response change of the noise-heater and the control-heater, temperature change at the object position is 2.2℃. When the dynamic predictive model is made with averaging 21 data of the experimental results, temperature change at the object position is 0.08℃. When the dynamic predictive model is made by combination with experimental results and network model calculations, temperature change at the object position is 0.06℃.
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Nobuhiro HIMENO, Akihiro TASHITA, Satoshi IGARASHI
Article type: Article
Session ID: G0600-1-5
Published: September 04, 2010
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The present study proposes a high-performance thermal insulator using a functional fibrous material of high reflectivity for thermal radiation, and the performance of thermal insulation was experimentally investigated for the glass fiber having aluminum powder on its surface as one of such functional fibrous materials. The heat transfer coefficient was measured in a rectangular cavity for vacancy, glass wool, glass wool with aluminum powder and glass wool with multilayer of aluminum foil. The experimental results showed that radiation heat transfer has serious effects on the performance of thermal insulator and that glass wool with aluminum powder is effective in thermal insulation.
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Fumiyoshi KIMURA, Tatsuo NOGUCHI, Kenzo KITAMURA
Article type: Article
Session ID: G0600-2-1
Published: September 04, 2010
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Fluid flow and heat transfer characteristics of the natural convection induced over a V-shaped open cavity were investigated experimentally. The main concerns were directed to the influence of the open angles of the cavity θ. The angle was varied systematically from 90° to 180°. The flows in the cavity and the surface temperatures were visualized with fine particles and liquid crystal thermometry, respectively. The results showed that the ambient fluid descends to the center of the cavity, and then generates a pair of vortices in the cavity when θ<130°. The local heat transfer coefficients from the cavity were also measured. The results showed that the heat transfer is enhanced markedly when θ=120°, and the overall heat transfer coefficient from the cavity θ=120° became 17% higher than that from the horizontal plate.
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Hirotaka ISOMI, Hiroki HANAZAWA, Tetsuaki TAKEDA
Article type: Article
Session ID: G0600-2-2
Published: September 04, 2010
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This study is to investigate an effect of natural convection on the mixing process by molecular diffusion in a vertical stratified fluid layer. There are many experimental and analytical studies on natural convection in the vertical slot. However, there are few studies on natural convection with molecular diffusion of the two component gases in the vertical stratified fluid layer. Experimental study has been performed on the combined phenomena of molecular diffusion and natural convection of the two component gases to investigate the mixing process in the vertical slot consisting of one side heated and the other side cooled. The density change of the gas mixture and the temperature distribution in the slot was obtained and the mixing process when the heavier gas ingress into the vertical slot filled with the lighter gas from the bottom side of the slot was discussed.
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Takao KOSHIMIZU, Daisaku KASAO, Hiromi KUBOTA, Yasuyuki TAKATA
Article type: Article
Session ID: G0600-2-3
Published: September 04, 2010
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Numerical simulation of heat and fluid flow has been performed to estimate the value of heat transfer coefficient between the working gas and walls in oscillatory flows. Transient two-dimensional equations of continuity, momentum and energy were solved utilizing a TVD scheme. A physical model of a simple circular tube in which the wall temperature is constant was used for the numerical simulation. In this study, the value of local heat transfer coefficient in oscillatory flows was clarified by analyzing the numerical result of the two dimensional simulation and compared with the value calculated by the correlating equation reported up to now.
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Yusuke Shiroma, Shoichi Matsuda, Izuru Senaha, Sumio Kato
Article type: Article
Session ID: G0600-2-4
Published: September 04, 2010
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This paper shows the influence of flow behavior of multiple impingement jets on characteristics of heat transfer of narrow spaces. The jets were set a 5×5 nozzles of sharp edged orifice type with D=5 mm in diameter. The jet-to-jet space is 10 mm. The experiments were performed for the separation distance, H, between jet exit and impingement plate ranging from H/D=1 to 3, at Reynolds number 1600〜3300. The time and spatial temperature profiles over the impingement plate were measured using at infrared camera (TVS-8500, Avio) with a two-dimensional array of Indeum-Antimony (In Sb) sensors. To clarify the influence of the flow behavior on heat transfer fields, we visualized a smoke flow field by means of a laser light sheet method (LLS). Based on these experimental data, the relationships between the fluid flow and the heat transfer characteristics were clarified.
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Koji TORIYAMA
Article type: Article
Session ID: G0600-2-5
Published: September 04, 2010
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This paper describes the effect of axial angle on mixed convection in horizontal square duct with uniform wall temperature by the three-dimensional numerical analysis. The velocity fields and the pressure and temperature distributions obtained by SIMPLE method using non-dimensional governing equations. The QUICK scheme was applied to the convection term of momentum and energy equations. Numerical results show that the three-dimensional flow behavior was influenced by axial angles. The heat transfer behavior was discussed corresponding to the flow, and the heat transfer enhancement was different about 10% by axial angles.
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Eiji SAKAI, Toshihiko TAKAHASHI, Terutaka FUJIOKA
Article type: Article
Session ID: G0600-3-1
Published: September 04, 2010
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First stage nozzle vane of gas turbine are exposed to severe high temperature combustion gas environment, which causes fatigue cracking on the nozzle surfaces. Since welding repair is one of the impacting factors to costly maintenance strategy of gas turbine, an appropriate method to predict crack propagation is desired to develop. This study describes an attempt to estimate temperature distribution by steady-state conjugate heat transfer analysis. Temperature distribution was compared with the results of previous heat conduction analysis, which was performed under thermal conditions determined by micro-structural observation and hardness distribution of a disposed nozzle vane. The temperature distribution estimated here qualitatively agreed with the previous one and was found to be useful for understanding of crack propagation mechanism.
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Ryota TOYOHARA, Kiyoshi KAWAGUCHI, Daisuke WATANABE, Tomoya KURAISHI
Article type: Article
Session ID: G0600-3-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In a car under summer solar radiation, it is well known that the temperature in a car cabin becomes very high and is found to be over 90 degree C on the top of the front dashboard and also air temperature around the driver's seat were over 65 degree C. Thus, ventilation system is one of the effective methods for keeping comfortable thermal environment of a car cabin. In this paper, we conducted numerical simulations under the conditions that ventilation cold air came into the cabin forcibly from face mode vents and hot air in the cabin was exhausted freely from a rear duct located on rear dashboard, and examined the ventilation effects on the number of inlet ducts, exhaust duct position, and exhaust duct diameter. It was clarified that central side inflow, rear center exhaust, and exhaust duct diameter of D=100[mm] were the effective ventilation methods for temperature mitigation around driver's seat.
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Yuta SUGAI, Tetsuaki TAKEDA
Article type: Article
Session ID: G0600-3-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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From the view point of the safety characteristic, the passive cooling system should be designed for the Very High Temperature Reactor (VHTR) as the best way of the reactor and vessel cooling systems (VCS). So, the gas cooling system by natural convection is the one of candidate system for the VCS of the VHTR. This study is to develop the passive cooling system for the VHTR using the vertical rectangular channel inserting porous materials. From the results obtained in this analysis, it was found that the amount of transferred heat from the heated wall will be increased even if the heat removed by natural convection. It will be important to consider the thermal radiation from the vessel wall to the concrete vessel.
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Yoshiki KINOMOTO, Toru SAWAI, Tomoyuki MINENO, Takeshi KAJIMOTO, Tadas ...
Article type: Article
Session ID: G0600-3-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Woody biomass has come to attract attention as renewable resources because of the issue of global warming and air pollution. Plastics substitution is one of the most promising utility form of woody biomass, and many studies have been made on the molding method of wood. But that has been no study on the injection molding of thermal fluid wood powder. To clarity viscous property of thermal fluid wood powder, experimental studies on the flow characteristics of thermal fluid wood powder are conducted. It is confirmed that thermal fluid wood powder has non-Newtonian flow property, and the empirical equation to predict the viscosity is developed.
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Hisanobu KAWASHIMA, Masatoshi FUKUSHIMA, Tsuneaki ISHIMA
Article type: Article
Session ID: G0600-3-5
Published: September 04, 2010
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The aim of this study is to evaluate the characteristics of the force heat transfer along a perpendicular heating board with multi-holses. The wall temperature and distribution of it near the wall were measured by using the multi-thermocouple. The local heat transfer coefficient along the multi holes board became larger than that of the flat board under the conditions both laminaer flow and turbulent flow. The temperature was recorded in the high resolution of the time. The responsibility at the time of the thermocouple was confirmed by performing the heat collision experiment. By analyzing FFT to the obtained temperature results, the characteristics of the frequency along the heating multi-holse board was confirmed.
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Kohei KASAI, Tomohiro YAMAGUCHI, Hiroshi YAMAZAKI, Hiroshi NOMURA, Yas ...
Article type: Article
Session ID: G0600-4-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The regenerative heat exchanger is important function for deciding an efficiency of Stirling engines. The pressure loss and the heat transfer process have considerable effects on performance of regenerative heat exchanger. In this paper, we studied on effects of suppressing a side leak on performance of regenerator. The side leak means a working fluid flow passing through an clearance gap between the periphery of the thermal storage matrix and the inside wall of the regenerator. Two types of regenerative heat exchanger were designed. One is a type suppressing the side leak and other is conventional type allowing side leak. Using stainless steel wire sheets with different mesh size, several types thermal storage matrix were made to change porosity. The result shows that the side leak suppressed type has a lower pressure loss and higher thermal regeneration rate, compared with conventional type.
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Satoshi OKAJIMA, Norihisa MATSUNAGA
Article type: Article
Session ID: G0600-4-2
Published: September 04, 2010
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Experiments have been carried out to develop the high efficiency equipment of dryer using resonance phenomena by the far infrared rays of specific band. The super crystal radiant materials developed to realize the resonance with dryness substance are made up tourmalines, transition metals and so on and its spectral emissivity is approximately 0.95 ranging from 4 μm to 20 μm. in wave length. The incandescent lamp as the supply energy of far infrared rays is employed and radiant energy obtained from incandescent lamp of 270W may be approximately 1250W through the super crystal radiant materials. The test samples used for the study are shiitake mushroom, scallop, apple, carrot, pineapple and so on. The acquisitions obtained from the study are as follows that such dryness method using resonance frequency by super crystal radiant materials is very useful for realization of high efficiency dryness so as not to lose the effectiveness of umami and flavor and it means that the realization of high energy saving on dryness may be possible.
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Suetaka EBINA, Takao NAGASAKI, Yutaka ITO
Article type: Article
Session ID: G0600-4-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The effect of solid particles on the performance of pulsating heat pipe (PHP) has been investigated by using looped PHP with water as working fluid. The PHP is made of copper tubes with 3 mm OD and 2mm ID, and the number of turns is 12. Lengths of heating, adiabatic and cooling sections are 50mm, 100mm and 50mm, respectively. In order to improve performance, particles of various size and material, that is, alumina particles (10μm, 0.6μm), copper particles (10μm, 3μm) and silver particle (0.1μm), were added. In case of alumina particles, it was found that the larger particle was more effective than the smaller one. On the other hand, in case of copper particles, there was no great difference between the two sizes. Silver particle was similar to copper particles in performance. Every particle in this experiment has an optimum concentration in the heat transport performance of PHP. Liquid plug oscillation was enhanced significantly by adding particle in proper concentration.
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Niro NAGAI, Shinya YAMAHATA, Shigenobu MIYAMOTO
Article type: Article
Session ID: G0600-4-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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As to the snow melting system where geothermal energy is transported from underground to road surface by circulating water in winter, while solar heat is collected on road surface and stored into underground in summer, the experimental demonstrations have been conducted for several years in Fukui city at three places such as parking lot and bridges. This system showed enough heat storage and snow melting power for road surface area of several thousand m^2 order, and also demonstrated good long-term reliability. Through numerical simulations of this system, the non-dimensional correlation for many system parameters was derived, which shows possibility of simplification of evaluation process for system performance.
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Shinichi Nagaie, Hiroshi Katanoda, Minoru Fukuhara
Article type: Article
Session ID: G0600-4-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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A micrmini Kagoshima satellite called KSAT has been developed by the Kagoshima satellite development group. This satellite was piggybacked on Akatsuki, which was developed by JAXA. Since the thermal environment in space is very harsh, the thermal design of the satellite is necessary in order to previously confirm that the electric devices installed in the satellite work within an allowable ranges of temperature. The main purpose of this study is to decide how to finish the outer surface of the satellite panel from the view point of thermal design. After deciding the surface-finishing method, the nodal analysis of the satellite was performed in order to calculate the variations of temperatures of the components of the satellite going around the earth. The results of the present nodal analysis show that the electric components of the KSAT remain within the allowable ranges of temperature.
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Keisuke HASHIMOTO, Tomohiro TAKEDA, Kiyoshi KAWAGUCHI, Daisuke WATANAB ...
Article type: Article
Session ID: G0600-4-6
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In recent years the fan heater used for industry and residence has become smaller, lighter, and more silent as the result of improvement. However there are problems that the fan heater size is very large, and the noise is very high due to air pressure loss of heat exchangers. Therefore we have been developing the centrifugal type fan with the function of heat exchanger. The features of this new type fan heater are that the fan heater size is very small and silent because the fan and the heat exchanger are in one body. This paper described the effects of the flow between fan blades on the distribution of local heat transfer coefficient on the blade surface of fans with different diameter. The heat transfer characteristics and the flow patterns in the fans with different diameter were clarified by calculating the flow in the fan, and measuring the local heat transfer coefficient on the blade surface.
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Motohiro OSHIMA, Daichi FUKUSHIMA, Jiro SENDA, Kozo ISHIDA
Article type: Article
Session ID: G0600-5-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Atsushi HAMAOKA, Yuki EDA, Minoru OHTSUKA, Kotaro UNO, Naoki ONO
Article type: Article
Session ID: G0600-5-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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As heat generation increases in CPUs and other small electronic devices, more miniaturized and efficient cooling technology has been required. In this study the authors investigated combination of impinging flow and high-carbon alcohol aqueous solutions in mini tube. The authors performed experiments and compared heat-transfer characteristics about cooling methods and working fluids. T-junction tube made of quartz glass realized the impinging flow. The flow tube has a circle cross section, and a diameter was 2.0 mm. They adopted pure water and butanol aqueous solutions for working fluids. Concentration level of butanol aqueous solutions was 1.50wt%, 3.00wt%, 4.50wt%, and 7.15wt%. It was found from the experimental results that liquid film of the butanol aqueous solutions extend in a direction toward high-temperature region and the butanol aqueous solutions gave higher cooling ability.
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Shotaro Nishiguchi, Masahiro Shoji
Article type: Article
Session ID: G0600-5-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Some alcohol solutions such as butanol show non-linear surface tension dependence. It is known that dryout of the heat surface is inhibited by Thermal Marangoni Effect of non-linear surface tension. These solutions are called Self-rewetting Liquids. Boiling heat transfer of butanol aqueous solution is studied in experimental systems of forced convection boiling. This test is also performed inside a mini channel. Mass flux is 1286kg/m^2s or 2374kg/m^2s, subcooling was changed from 0K to 50K. Bulk liquid concentration changed from 0.00wt% to 7.15wt%. Wall temperature was measured by using thermocouple and radiation thermometer. At high mass flux (G=2374kg/m^2s), CHF of butanol aqueous solution is from 20% to 50% higher than that of pure water in subcooled region. Burnout of butanol aqueous solution was Fast Burnout (Upper stream CHF).
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Mohammad Nasim Hasan, Masanori Monde, Yuichi Mitsutake
Article type: Article
Session ID: G0600-5-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The lower limit for homogeneous nucleation boiling during liquid contact with hot surfaces has been determined by a new model proposed by the authors. In this model a characteristic liquid cluster is considered at the boundary in which bubble is generated due to external heating. A particular stage of bubble generation has been identified as the boiling explosion that corresponds to large scale vaporization when the energy consumption due to bubble generation in the cluster exceeds the external energy deposition to it. To calculate the rate of external energy deposition and boiling heat consumption in the liquid cluster, the ideas of 1-D heat conduction and molecular theory of homogeneous nucleation have been used. For water (20 ℃) contact with hot steel surfaces at atmospheric pressure, the model shows that immediate boiling explosion occurs for surface temperature above 335 ℃ while stable solid-liquid contact prevails during contact with surfaces at or below this temperature limit. The interface boundary temperature for stable solid-liquid contact as obtained in the present model corresponds to a value of 303℃ which is close to the thermodynamic limit of liquid superheat for water at atmospheric pressure. From the definition of interface boundary temperature of two constant temperature 1-D semi-infinite solids contact, this limit for homogeneous nucleation boiling explosion on brass and copper surfaces is also found to be an identical one.
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Jongdock PARK, Katsuya FUKUDA, Qiusheng LIU
Article type: Article
Session ID: G0600-5-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The knowledge for saturated and subcooled pool boiling CHF mechanisms is becoming increasingly important as the fundamental database for the design such as the high heat flux cooling systems using subcooled liquid pool boiling, the thermal control system of microelectronic assemblies and so on. Steady-state and transient boiling heat transfer characteristics for highly wetting liquid due to an exponentially increasing heat input with time have been investigated. Steady-state and transient critical heat fluxes (CHFs) were measured by using a 1.0 mm-diameter horizontal cylinder in a pool of highly wetting liquid such as ethanol with periods ranging from about 10 ms to 20s for wide ranges of subcooling and pressure. The transient CHFs depending on the periods were divided into two principal groups: the first one was in long period and the CHF occurred with fully developed nucleate boiling heat transfer processes, and the second one was in short period with explosive boiling heat transfer processes from non-boiling and the direct transition to film boiling occurred. The CHFs increase with an increase in subcooling at test pressures and they are independent of pressures at high subcoolings.
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RAMLI BIN AZIZAN, Shinichi MORITA, Masahiro SAITO, Tomohiko FURUHATA, ...
Article type: Article
Session ID: G0700-1-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Six-stroke diesel engine proposed here has six processes in one cycle and by the direct EGR in the 2nd combustion process, NO emission is expected to decrease. However, weak mixing in 2nd combustion process produced much soot. To improve 2nd combustion process, changing valve timing and supercharging is introduced. The result showed that supercharging was effective in soot reduction. In CASE1 (exhaust valve was opened and shut after 1st combustion process) and CASE2 (the exhaust and intake valves were opened and shut after 1st combustion process) the improvement was not accomplished because the decrease of combustion gas containing oxygen in the 2nd combustion. In CASE3 (the timing of exhaust valve opening was advanced), a fresh air could be introduced into the 2nd combustion due to the pressure drop in the cylinder after the 1st combustion. As the result, NO and Soot in the 2nd combustion process decreased.
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Yuya OZAWA, Koji YOSHIDA, Hideo SHOJI, Akira IIJIMA
Article type: Article
Session ID: G0700-1-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The purpose of this study is to clarify the influence of water contents and fuel injection timing of emulsified fuel on diesel engine performance. The ignitability of emulsified fuel was inferior to diesel fuel and the ignition timing of emulsified fuel which contained large amount of water delayed. Especially, the ignition timing was much delayed and the maximum combustion pressure of emulsified fuel was lower than that of diesel fuel in low load condition, however the ignition timing approached to diesel fuel and the pressure increased with an increase in brake mean effective pressure. The thermal efficiency of emulsified fuel was slightly lower than that of diesel fuel, however thermal efficiency was improved when the fuel injection timing was advanced. Therefore there is optimum fuel injection timing according to water contents. The smoke emission of emulsified fuel was lower than that of diesel fuel and decreased with increasing in water content.
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Yuji Yamazaki, Nobuhide Tachibana, Masanori Wakikawa, Zhili Chen
Article type: Article
Session ID: G0700-1-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Since the expansion ratio of Miller cycle is longer than the compression ratio, energy in the working gas can be converted into more work, and sequentially benefits improving the thermal efficiency of the engines. In this study, we applied the Miller cycle to a diesel engine by delaying the timing of IVC (Intake Valve Close), and investigated effects and factors of the improvement of thermal efficiency by thermodynamic calculations and experiments.
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Ryuichi YAMAGUCHI, Satoshi MASADA, Noritaka YOSHIKAWA, Koji YOSHIDA
Article type: Article
Session ID: G0700-1-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The In-Direct Injection (IDI) 2-Stroke CI engine with DME was proposed. The electrical controlled low-pressure injection system for gasoline engine was applied to prevent the leakage of DME. The engine performance was investigated to clarify the influence of cross-sectional area ratio of connecting passage of divided-chamber, the ignition timing and the engine speed on combustion process. The ignition could be accurately controlled by the injection timing with IDI combustion chamber and the early injection timing gave high maximum rate of heat release. The ignition timing of sub-chamber was earlier than that of main-chamber when the injection timing was advanced. When the small cross-sectional area of connecting passage of divided-chamber was applied, on high load condition, high brake thermal efficiency could be achieved because the strong swirl in sub-chamber was generated. At the high load and the engine speed 2000rpm, high brake thermal efficiency was obtained because the charging efficiency improved.
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Ding Ding, Shuntaro Komori, Zhili Chen
Article type: Article
Session ID: G0700-1-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In this study, premixed compressed ignition and high temperature diffusion combustion were combined to reduce the emissions of soot and NOx simultaneously in a diesel engine.To establish the combustion methods, we applied two-stage injection. The premixed combustion was ignited in the lststage of the injection without emissions of soot and NOx and then a high temperature field was created.This achieved the high temperature diffusion combustion in the 2nd stage of the injection with very low emission of soot and NOx. As a result, PM and NOx were much more reduced simultaneously compared to conventional combustions.
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Masatoshi IWAI, Yuya OZAWA, Koji YOSHIDA, Hideo SHOJI, Akira IIJIMA
Article type: Article
Session ID: G0700-1-6
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The cellulosic liquefaction fuel (CLF) is made from woods by direct liquefaction process. CLF was divided two fractions by distillation: these were 200 to 250℃ (CLF1) and 250 to 300℃ (CLF2). Coconuts-oil methyl ester (CME) was used to mix CLF and diesel fuel. The purpose of this study is to analyze the ignition characteristics and performance of CLF-CME-diesel fuel blends and to clarify the most desirable CME mixing ratio for practical use. Tested weight mixing ratios of CME and CLF to diesel fuel were 0, 5, 10, 15 and 20 wt.%. When CLF1 and CLF2 were mixed, the crank angle at ignition delayed, however the ignitability was improved in high load operating condition. The engine performance and exhaust gas emission were hardly influence by mixing ratio of CME. Therefore, the CLFl-CME-diesel fuel blends which included CME 5 wt.% was the most suitable fuel for practical use to the diesel engine.
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Tatsuo AKIMOTO, Takayuki SUZUKI, Masao KOHZAKI
Article type: Article
Session ID: G0700-2-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Because of air pollution and dry up of fossil fuel, Hydrogen Fuel is focused on as the alternative fuel of fossil fuel. So we research about Rotary Engine, which has good compatibility with Hydrogen Fuel because of its particular mechanics. In this work, we applied hydrogen to rotary engine with compact size, and several kinds of engine oil were used to improve the driving stability. In addition, we measured the output power and torque of 20cc rotary engine to compare with performance of 20cc hydrogen rotary engine. As a result, the highest torque of 0.27 [N-m] in the 20cc rotary engine was obtained at 4000rpm.
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Asako SATO, Koji YOSHIDA, Hideo SHOJI, Akira IIJIMA
Article type: Article
Session ID: G0700-2-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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An air motor with regenerating system which was designed for a bicycle was developed, and the air motor was driven by compressed air without gas emission. The purpose of this study is to elucidate characteristics and regeneration performance of air motor, and the effect of supply air pressure and rotational frequency on output power were experimentally investigated. The maximum cylinder pressure increased as the supply air pressure increased, although the maximum cylinder pressure was less than the supply air pressure. The maximum cylinder pressure reduced as the revolution frequency increased because the inlet valve opening duration was decreased. Therefore, the output power can be improved by the optimization of valve timing. The output power and flow rate increased with an increase of supply air pressure, however both were decreased as the revolution frequency increased due to friction loss. The regeneration pressure was decreased in case of high revolution frequency.
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Mitsuhiro Soejima, Yoshiaki Ushijima
Article type: Article
Session ID: G0700-2-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Some studies to reduce the friction of valve train mechanism have been conducted in order to prevent the global warming by improving the fuel economy for internal combustion engines. In the case of the contact between the cam and the shim offset on the valve lifter for the direct-type valve train, the characteristics of friction diagrams measured with the cam / slipper follower friction tester were examined and also the oil film thickness between the valve lifter and the shim was predicted by the hydrodynamic lubrication theory so that the followings have been summarized, (1) The friction of rolling contact between cam and follower becomes considerably small because the shim offset on the valve lifter rotates under the contact of cam. (2) The thickness of oil film with the round side face or the flat bottom face of the shim is enough to make the shim to rotate on the vale lifter.
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Akihiro HAYAKAWA, Yukihide NAGANO, Toshiaki KITAGAWA
Article type: Article
Session ID: G0700-2-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Turbulent burning velocity of spherically propagating flame kept increasing with flame propagation. The turbulence which effectively wrinkles the flame front may be increasing with flame progress. Such turbulence intensity is called effective turbulence intensity and it is estimated from energy spectrum of turbulence. The relationship between burning velocity of spherically propagating turbulent flame and effective turbulence intensity was estimated. As a result, it is found that turbulent burning velocity is well correlated with turbulence Reynolds number based on Taylor micro scale and effective turbulence intensity regardless of turbulence intensity.
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Takeru SATOH, Satohshi SUDOH, Hiroshi YAMASAKI, Hiroshi NOMURA, Yasush ...
Article type: Article
Session ID: G0700-2-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In order to make a successful lean burn, it has been an important subject for certain ignition with small spark energy. Experimental and numerical researches have been performed to obtain the detailed information about the ignition and combustion characteristics of flanged spark plugs in flow fields using propane-air mixture. It was mainly investigated that the attached flanges had effects on reduction of ignition energy and acceleration of flame propagation in a swirling flow field modeled an actual engine. We obtained results that the minimum ignition energy decreases in a wide range of swirling flow velocity, and that the flame propagation velocity accelerates. The degrees of these useful effects depend on the flange shape.
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