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Gen SHIBATA, Tomonori URUSHIHARA
Article type: Article
Session ID: 2322
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In this paper, 18 kinds of binary blended fuels were used to investigate the operational differences, and NTL series fuels which was composed from n-heptane and toluene showed the possibility of high torque engine operation because of the dual phase high temperature combustion. The effects of fuel composition on high temperature combustion and engine performance are argued.
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Yusuke SOMA, Sinichi MORIYA, Koji YOSHIDA, Akira IIJIMA, Hideo SHOJI
Article type: Article
Session ID: 2323
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The purpose of this study is to elucidate flame propagation behavior under the application of uniform and non-uniform electric fields by using a constant volume vessel. Electric fields are applied in the direction of the chamber's vertical axis. A Nd:YAG laser is used to apply laser-induced breakdown for igniting the mixture at the center of the combustion chamber. A homogeneous propane-air mixture is supplied at three equivalence ratios of 0.7, 1.0 and 1.5. Under a uniform electric field, the flame is vertically oblong, resulting in a cylindrically shaped flame, however flame front is merely deformed and the combustion duration is not so influenced by the electric field. In a non-uniform electric field, turbulence occurs at flame front and the whole flame front moves downward, and the combustion is markedly enhanced when the input voltage is larger than 12 [kV] because both the electrical potential and corona wind affect combustion.
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Keisuke KIMURA, Hideyuki OGAWA
Article type: Article
Session ID: 2324
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Expansion of stroke/bore ratio has a great potential to improve thermal efficiency in co-generation engines. The factors related on thermal efficiency in gas engines with three stroke/bore ratios were analyzed with CFD engine code. Improvement in indicated thermal efficiency with larger stroke/bore ratios was obtained due to improvement in the degree of constant volume heat release and decrease in cooling loss in wide ranges of excess air ratio and engine speed. The degree of improvement with expansion of stroke/bore ratio from 1.0 to 1.5 is more significant than from 1.5 to 2.0. The degree of constant volume heat release improves with longer strokes due to shorter flame propagation distance and increase in combustion speed with increasing turbulence of charge gas in cylinder.
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Takafumi KOJIMA, Kazuie NISHIWAKI
Article type: Article
Session ID: 2325
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The purpose of this study is to find the statistical characteristics of the mixture heterogeneity in turbulent flow field for moderating the premixed charge compression ignition (PCCI) combustion and for increasing an output limit, which is restricted by an intense knock. We analyzed the interrelationship between mixture heterogeneity and reaction in a diesel PCCI combustion, using the large eddy simulation (LES) in conjunction with a reaction kinetics model. The quasi-steady gas jet model has been employed for fuel sprays. The auto-ignition and combustion behaviors were analyzed for a variety of injection conditions, including nozzle geometry, injection timing and injection pressure, in direct-injection PCCI operations. As a result, the start of the combustion event was advanced with advancing injection timing. The peak values of heat release rate increase with increasing amount of stoichiometric mixture in a hot flame reaction phase.
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Ryoh INOSHIRI, Kohsuke WATANABE, Hiroyuki KATAYAMA
Article type: Article
Session ID: 2401
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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A compact-sized and high performance free-piston Stirling cooler, whose piston is directly driven by a linear motor, has been developed: the plastic displacer, stuffer, and regenerator enhance thermal insulation and the copper heat exchangers improve heat exchange performance. We studied a jet effect on the FPSC cooling efficiency by using the original displacer equipped with a jet mechanism: there is an inlet valve at the compression space side of the displacer and are jet orifices at the expansion space side, thereby a working gas is injected into the displacer at a compression process and jetted out from it at an expansion one. This new mechanism improved the COP and its dependence on a jet orifice location and/or the number of jet orifices were investigated. Their optimization is also discussed in this paper.
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Toshio OTAKA, Masahiro OTA
Article type: Article
Session ID: 2402
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper proposes the small-size Stirling refrigerator with an active-type regenerator. When a n-type Stirling refrigerator with the regenerator in a displacer use light weight and flexible matrixes, those matrixes reciprocate in a regenerator housing. This phenomenon changes the flow loss and the residual gas volume in the regenerator matrixes. Moreover, the variation of the matrix volume influences the cooling capacity and COP. Then, we propose the active-type regenerator that actually transforms the matrix according to the reciprocation of the displacer. The active-type regenerator uses a urethane matrix that the swelling and compression are done by a matrix piston. The indicated cooling capacity of the Stirling refrigerator with the active-type regenerator is greater than the refrigerator with the conventional-type regenerator by about 1.3 times. Moreover, the indicated COP of the Stirling refrigerator with the active-type refrigerator is greater than the Stirling refrigerator with the conventional-type regenerator by about 1.5 times. The active-type regenerator has those advantage, we strongly recommend the small-size Stirling refrigerator with the active-type regenerator is put to practical applications.
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Hiroshi SEINO, Kazuya IKEDA, Kazuhiro HAMAGUCHI
Article type: Article
Session ID: 2403
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Feasibility study of the pulse tube refrigerator to apply onboard air conditioner for railway vehicles is begun from the viewpoint of energy conservation. In this study, capacity of air conditioning is generated by integrating a small size atmospheric pulse tube refrigerator using dry-air and compressor will be operated by driving force of wheels of vehicles without additional power supply. In experiment, cooling capacity of the basic pulse tube refrigerator is 2W. It is possible that capacity of air conditioning is achieved by accumulating necessary number of basic pulse tube refrigerator under car body.
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Yoshihiko HARAMURA, Kazuhiro KUBOTA
Article type: Article
Session ID: 2404
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper deals with heat transfer due to a periodical annular jet induced by displacer motion. The heaters are sheets of small foil, one of which was heated as its temperature was kept constant using a CTA system. The distribution of heat transfer coefficient was estimated considering heat flow in the substrate by solving steady heat conduction. It was revealed that the number of nodes where heat transfer coefficients are assumed affects the peak value but does not space averaged value. The space averaged heat transfer coefficient was compared with a correlation for steady impinging jet. The experimental values were about twice higher than that from the correlation.
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Koichi HIRATA, Mitsutoshi IIDA, Teruyuki AKAZAWA
Article type: Article
Session ID: 2405
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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When a freight ship is in a harbor, a Diesel engine generator is operated to supply electric energy in the ship. Exhaust gas from the Diesel engine causes air pollution in the harbor area. In order to solve the air pollution, we have tried to develop a heat recovery system with Stirling engine generators since 2005. In this paper, we report results of our research project related the heat recovery system and the Stirling engine generators. Also we discuss about technical subjects for practical use.
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Masataka OHMAE, Junichi ONO, Nobushige TAMAKI
Article type: Article
Session ID: 2406
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The atomization enhancement nozzle, which large spray angle and small Sauter mean diameter are obtained under low injection pressure, was invented in the previous study. The purpose of this study is to apply this nozzle to a D.I. Diesel injector. In this paper, the effects of geometric shapes on atomization characteristics under high-ambient pressure correspond to T.D.C. were investigated. As a resalt, although high-penetration spray was not obtained, the spray, which the spread of the spray is large, was obtaind compared with the single hole nozzle.
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Keiya NISHIDA, Yuhei MATSUMOTO, Jian GAO, Seoksu MOON
Article type: Article
Session ID: 2407
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Laser absorption scattering (LAS) measurement was made of the D.I. Diesel spray injected by a common rail injection system into a high-pressure and high-temperature constant volume vessel. Effects of nozzle-hole diameter and flat wall impingement on spray and mixture properties, such as spray tip penetration, mass of ambient gas entrained into the spray and mass of vapor phase fuel in the spray were investigated. The mass of ambient gas entrained and the mass of vapor phase fuel, both of which are normalized by the total (vapor and liquid) fuel in the spray, are increased as the nozzle hole diameter is small-sized. The flat wall impingement of the spray suppresses the ambient gas entrainment and fuel evaporation.
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Keiichi KATSUTA, Shuji KAMATA, Tsukasa HORI, Jiro SENDA, Hajime FUJIMO ...
Article type: Article
Session ID: 2408
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper reports the application of high spatial resolution photography method to pilot diesel spray. This method enables to measure the whole spray shape and fuel droplets characteristics at an instant. The photographic system is composed of a specialized lens system and a large sized film. In this paper, this photographic method applied to measure the pilot spray injected through a single hole nozzle into a quiescent high pressure atmosphere at room temperature. The light source is the second harmonic of Nd:YAG laser. The result shows there are a number of large size droplets in the downstream of spray, and this method has applicability for the measurement of low number density spray like a pilot spray.
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Hirokazu NISHIJIMA, Atsushi UENO, Akihiko AZETSU
Article type: Article
Session ID: 2409
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The effects of injection rate modulation, i.e., periodical fluctuation of injection rate, on the spatial dispersion of fuel droplets and inner structure of fuel spray were investigated by using an electronically controllable fuel injection system. The major experimental parameters were the modulation frequency and the modulation amplitude. It was confirmed there are two mechanisms of wider spray, i.e., the effect of larger maximum injection rate and the effect of high frequency modulation itself. From the temporal movement of fuel droplets obtained by high-speed photographs, the reason of this phenomenon was discussed.
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Masato AOKI, Satoshi KATAOKA, Hiroomi HAGIO, Akihiko AZETSU
Article type: Article
Session ID: 2410
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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To understand the effect of Palm Methyl Ester (PME) mixing on spray combustion characteristics of diesel oil, the intermittent spray flame formed in a high temperature and high pressure combustion vessel was visualized by ICCD camera and analyzed by two color method. The mixing rate of PME to diesel oil was changed up to 60%. It was confirmed that the ignition delay and combustion period were almost equal level. On the other hand, flame temperature and soot production decreased slightly with the PME mixing.
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Yoshimitsu WADA, Jiro SENDA, Tsukawa HORI, Masashi MATSUMOTO
Article type: Article
Session ID: 2411
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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It is well-known that flow condition inside injection nozzles has much effect on spray characteristics. Despite its importance, the two-phase gas-liquid flow is difficult to be simulated by using computational fluid dynamics due to the existence of cavitation which involves small-scale and high-speed phase-change phenomena. To resolve this problem and to link between flow condition including the effect of cavitation and spray characteristics, the authors have developed a phenomenological modeling scheme. This paper proposes novel modeling schemes which make it possible to realize high-accuracy computations of growth and shrinkage processes of cavitation bubbles.
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Chiemi YAMAMOTO, Toshikazu UCHINO, Masahiro SAITO, Tomohiko FURUHATA, ...
Article type: Article
Session ID: 2412
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Nanometer size particulate matter (Nano-PM) emitted from a flame of fossil fuel has been received attention due to their harmful potential for health. However, detailed knowledge about Nano-PM formation mechanism has not been clarified yet. The objective of this study is to investigate the relation between the PM characteristics and sulfur in fuel using standard Nano-PM generator. A pool flame was used for production of Nano-PM. Kerosene and Thiophen added Kerosene were used as fuels. It was clear that the flame form changed from closed flame to open flame, when fuel flow rate M_f was over 0.4mg/s in the both fuels. The flame tip of open flame was opened and visible soot was emitted from the tip. As for the size distribution of PM, the peak diameter was gradually increased with an increase of fuel flow rate in Kerosene flame, but it was suddenly increased when the fuel flow rate exceeded 0.4mg/s, in Thiophene added Kerosene flame.
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Masaru Ogura, Takahide Kawamura
Article type: Article
Session ID: 2413
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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An engine shows the highest heat efficiency around the maximum and the torque. In this research, interval combustion operation is proposed. The new electromagnetic drive valve system which the principle of linear actuator was applied to was proposed, and it tried that operation experiment. And, it was described about the predominance point in case of electromagnetic drive valve adoption, the engine layout when it was applied to 4 cylinder.
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Hideaki MIZUNO, Koichi ASHIDA, Atsushi TERAJI, Kenshi USHIJIMA, Shinic ...
Article type: Article
Session ID: 2414
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In this study, we investigated a method of estimating the piston temperature in reciprocating engines. The piston temperature is strongly affected by the cylinder temperature distribution and in-cylinder turbulence. For that reason, it is necessary to take into account the effects of cooling by the intake air flow, the process of the temperature rise due to combustion, in-cylinder flow, and the shape of the combustion chamber on flame propagation. We conducted a 3D combustion simulation that, took into account various phenomena such spark ignition, flame propagation, and cooling loss. The values of the gas temperature and heat, transfer coefficient on the piston surface found from this 3D combustion simulation were input as the boundary conditions of a non-steady-state heat conduction analysis. The piston surface temperature, internal temperature and heat, flow were then calculated. It was found that the tendency of the calculated temperature distribution agreed with that of the temperature distribution measured by the hardness method.
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Nobushige TAMAKI, Hiroshi ASANO, Keisuke SEO, Tatsuhiko IHARA
Article type: Article
Session ID: 2415
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Photo-catalyst, which is coated at wall of buildings, is widely used for self-cleaning of it The purpose of this study is to improve combustion efficiency by adding active oxygen generated by photo-catalyst to combustion air. In this paper, the effects of existence of photo-catalyst, moisture within combustion air and irradiation of ultra-violent rays on combustion of carbon monoxide for fuel were investigated. Moreover, the effect of active oxygen generated by reaction of photo-catalyst on combustion of fuel. was considered. As the results, it can be seen that moisture within combustion air strongly affects combustion of fuel, maximum concentration of carbon dioxide CO_2 at combustion air with moisture was greater than one of without moisture.
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Shimpei TERASHIMA, Yoshiharu TSUJIKAWA, Ken-ichi KANEKO
Article type: Article
Session ID: 2416
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The performances of the energy systems using Atmospheric Pressure Turbine (APT) which is based on Inverted Brayton cycle in order to use high-temperature and atmospheric-pressure energy sources (for example, exhaust gas from a conventional gas-turbine) directly, have been analyzed in this paper. The exergy loss distribution has also been made clear.
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Bunji ONO, Kenji NAKASHIMA, Toshinobu SHIGEMATSU
Article type: Article
Session ID: 2417
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The AUV (Autonomous Under-water Vehicle), which is used for the present seabed investigations, has obtained the thrust with the screw driven by the battery. However, it has a disadvantage because of its size and cost. Therefore, this research is carried out to propose the Bubble Jet Engine (BJE) as a new propulsion device. It can directly transform combustion energy into speed energy, so it is expected that BJE rises propulsion efficiency too. This research aims at measuring exhale flow and thrust to design ejectors, which become the core of BJE, and exploring practical use possibility of BJE. Ejector is the element in which gas is mixed with water, and the improvements in the propulsion efficiency are realized by taking in ejector as much water as possible. Vertical type gas-water ejector experimental apparatus for measuring water entrainment was employed in order to understand the characteristics of operation conditions, such as inlet distance, nozzle pressure, diameter of nozzle, and so on. In addition, experiments for measuring the thrust in the condition of ejector were actually executed with horizontal type apparatus in water. At present, however, the influence of the ejector to improve thrust can't have been recognized yet.
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Takashi TSUCHIYA, Tatsuya INOUE
Article type: Article
Session ID: 2418
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The performance of various types of control systems for an electric governor of a diesel engine was examined. The amount of fuel injection of diesel engine is usually controlled by an electric governor system in these decades, and a PID controller is installed for the electric governor. Even when the optimal parameters for PID controller are well tuned, it is difficult to keep constant rotating speed of the engine, because the applied load to generators may vary according to its running conditions. In this research, a neural network was applied to regulate the parameters in PID controller to control the amount of fuel injection. Experimental studies show that the parameter regulation system using neural network presented here had good performance under various running conditions.
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Kyohei Yamaguchi, Tomoaki Mukai, Jin Kusaka, Yasuhiro Daisho
Article type: Article
Session ID: 2419
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper deals with improvements of power and exhaust gas emissions in a passenger car diesel engine by Premixed Compression Ignition (PCI) combustion and two stage super charging. A low compression ratio type piston was used to assure suitable ignition delay which sufficient air was introduced into the spray plume to suppress NOx and smoke formation. As a result, PCI combustion successfully controls NOx and smoke emissions simultaneously at low loads. At high loads in which it is difficult to utilize PCI combustion, combustion which combined high boost pressure by two stage super charging and high EGR rate, favorably reduce NOx emission with no degradation in smoke emission and torque. In addition, the low compression ratio led to higher specific power, because it suppressed the peak pressure.
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Takayuki ITO, Takaaki KITAMURA, Gen SUGIYAMA
Article type: Article
Session ID: 2420
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This work investigates the soot formation process in premixed diesel combustion using comprehensive soot model implemented into the KIVA-3V multidimensional CFD code. The numerical model is based on the KIVA code which is modified to use CHEMKIN as the chemistry solver. The soot model includes the particle inception, coagulation, surface growth and oxidation processes. It has been investigated that the effects of intake oxygen concentration and injection pressure on soot formation process in the premixed compression ignition (PCI) combustion with injection timing close to top dead center. The simulation results showed good levels of agreement with the measured in-cylinder heat release rate and soot emission. Also, the temporal profiles of in-cylinder soot mass were revealed.
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Seitaro TASHIMA, Naoto HORIBE, Takuji ISHIYAMA, Masahiro SHIOJI
Article type: Article
Session ID: 2421
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The objective of present work is to obtain a strategy for adapting injection conditions to varied engine speeds in two-stage direct-injection PCCI operation in a diesel engine. To this end, an experimental study was conducted using a single-cylinder test engine varying first- and second-injection timings. The results indicate that problems of high maximum pressure rise rate at a low engine speed and low thermal efficiency at a high engine speed can be solved by adjusting injection timing. However, under a high engine speed condition, there remains a problem of increased CO emission.
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Masanobu KANNO, Yukihiro NISHIZAWA, Yuki NAGATA, Yudai YAMASAKI, Shige ...
Article type: Article
Session ID: 2422
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In this study, ignition and combustion characteristic of biomass gas in a HCCI engine was investigated experimentally. 1.6L gas engine for 13A fuel was remodeled to 24.6 compression ratio and rigged up an air heater for HCCI combustion. Fuel was assumed biomass gas consisted of CH_4, H_2, CO, CO_2 and N_2. In experiments, fuel composition was changed H_2 or CO of this biomass gas. As results, a HCCI engine moved in indicated thermal efficiency 37%. Higher H_2 composition made ignition timing of a HCCI engine advanced and lower CO composition made it delayed.
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Taiki KATAYAMA, Yoshifumi YAMAZAKI, Hiroki KASUYA, Akira IIJIMA, Hideo ...
Article type: Article
Session ID: 2423
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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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, 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 were varied and examined their respective influence on HCCI combustion. The results indicated that the application of internal EGR retarded the ignition timing, with the result that the combustion reaction speed was moderated.
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Masaru OGAWA, Haruo NAKAMURA
Article type: Article
Session ID: 2501
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Ryo MORITA
Article type: Article
Session ID: 2502
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Liquid droplet impingement erosion (LDI) is defined as an erosion phenomenon caused by high-speed droplet attack in a steam flow. In a power plant, pipe wall thinning by LDI is observed steam piping system. Because LDI usually occur very locally and is difficult to detect, a prediction of LDI location is required for the safety of the plant system. Therefore, as ultimate objectives, we set the development of the prediction tool of LDI location that can use in power plants easily (LDI Prediction Code). In previous researches, we achieved to enable the evaluation of all the local flow conditions that affect LDI materially. However, to make the LDI prediction code the useful tool in the actual powerplant, more improvement of the present flow evaluation methods are required to be applicable to the wider steam conditions and enable the faster calculations. In this presentation, we tried to improve the correlation equation of the droplet diameter with incorporating the wetness into the equation by the steam experiments.
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Haruo Nakamura, Takayuki Nishikawa
Article type: Article
Session ID: 2503
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Kimitoshi YONEDA, Ryo MORITA, Fumio INADA
Article type: Article
Session ID: 2504
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Flow Accelerated Corrosion (FAC) requires considerable attention in plant piping management, for its potential of catastrophic pipe rupture of main piping systems. In view of fluid dynamics, the most essential factor to be considered is mass transfer at the inner surface of the pipe. Mass transfer coefficients are determined by fluid properties and piping geometry, however, no universal correlation exists, which is adaptable to various types of piping elements with strong turbulence. In this study, 4 models of mass transfer coefficient was derived based on Chilton-Colburn analogy and utilizing "Effective Friction velocity" from the hydraulics in the viscous sub-layer along the wall. FAC experiments with PWR condensate water condition and CFD for the flow were conducted with a contracted rectangular duct. By comparing the 4 models, verified with the experiments and calculations, the appropriate way of considering friction velocity and turbulent velocity into the mass transfer coefficient was found.
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Yoshihisa NISHI, Izumi KINOSHITA
Article type: Article
Session ID: 2505
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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An innovative plate-type steam generator (SG) concept is proposing by CRIEPI. The SG is composed with many layers of rectangular tube fabricated by the HIP (hot isostatic pressing) method. The sodium layer and water/steam layer are alternately piled up, and the leakage detection layer has been installed between those. In this report, the results of the evaluations of the crack propagation of the leakage detection layer wall were described.
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Kotaro Masuda, Haruo Nakamura
Article type: Article
Session ID: 2506
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Yasuo Koizumi, Hiroyashu Otake, Youhei kusama
Article type: Article
Session ID: 2507
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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When liquid flows down into a liquid pool as a jet flow or a film flow on a wall, it sometimes accompanies gas into the pool. If the penetrated gas drifts up and leaves from the pool surface, the phenomenon is harmless. However, when the pool is highly agitated or strong flow exists from the pool, the mingled gas in liquid is carried out from the pool. The mixed gas in the coolant may reach the reactor core such as the light water reactor or the fast bleeder reactor. It severely affects the reactivity. Thus, the carry-under of gas into the water pool by the liquid down-flow is important issue for nuclear reactors. In the present study, air carry-under into the water pool is examined. A water jet from the nozzle of 5 mm diameter plunges into the water pool. Flow behavior in the water pool is recorded. From the recorded pictures, the air carry-under volume and the penetration depth are obtained. A flow stare of the jet flow is also recorded. The relation between the jet flow situation and the air carry-under is analyzed.
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Yasuharu NAKAJIMA, Hideyuki SHIROTA, Katsuya MAEDA, Kunihiro HOSHINO, ...
Article type: Article
Session ID: 2601
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Ocean storage of carbon dioxide (CO_2) is one of greenhouse gas control technologies, where CO_2 is captured from the flue gas of fossil fuels and stored on deep seafloor below the depth of 3500m. The authors developed a double-tube nozzle for an offshore CO_2 releasing system, where a mixture of liquid CO_2 and dry ice, CO_2 slurry, should be released from the inner tube of the nozzle while liquid CO_2 is released from the outer nozzle. CO_2 slurry releasing experiments using a slurry injection unit were carried out to demonstrate the effectiveness of the double-tube nozzle. CO_2 slurry was prepared by injecting liquid CO_2 into dry ice powders in a chamber of the injection unit, and successfully released into water at 5MPa. Then, the nozzle shape and slurry injection rate were improved to make CO_2 slurry drops. CO_2 slurry drops were formed by extruding slurry column from the nozzle followed by instantaneous stopping of slurry. injection.
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Yuki MATSUMOTO, Akiko FUJIWARA, Yutaka ABE, Kenji YAMANE
Article type: Article
Session ID: 2602
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The objective of the present study is to elucidate the conditions which influence on CO_2 hydrate nucleation. In this study, we measured the induction time which is the time from putting liquid CO_2 droplet into the pressure chamber to forming the hydrate film to clarify the effect of the surrounding water conditions. Two types conditons of ion-exchanged water were filled in a pressure chamber under the pressure and temperature conditions of 40 MPa and 3〜5℃, respectively. In the case of using the water that had previously frozen as ice and melted at atmospheric pressure, hydrate formation was not observed. On the other hand, in the case of using the water that had previously frozen as ice and melted at hydrate formation pressure of 40 MPa, hydrate formation was identified. In addition the ratio of melted water weight was changed from 0 to 5 %. The lager the ratio of melted water induced the shorter the induction time. The relation between induction time and surrounding water conditions and mechanism of it are discussed.
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Se-Min JEONG, Toru SATO, Baixin CHEN
Article type: Article
Session ID: 2603
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The direct injection of CO_2 into the deep ocean with a pipe towed by a moving ship is considered to be a feasible way to mitigate global warming and expected to minimize its environmental impacts on marine organisms in the vicinity of the injection points. In this study, a numerical study was carried out for the dispersion of CO_2 concentration in the deep ocean by using a fixed mesoscale and a moving small-scale grid systems, where the nested small-scale domain moves in the mesoscale domain along the trajectory of the moving ship. To overcome the artificial diffusion of mass concentration at the interfaces of two different grid systems, a particle diffusion model was developed for anisotropic diffusion in the ocean. The developed techniques demonstrated its efficiencies and applicability to give an outline for the optimization of the CO_2 ocean sequestration system, by which biological impacts should be minimized and insignificant.
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Masanori ARITOMI, Ryujin OMASA, Daisuke ITO
Article type: Article
Session ID: 2604
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Masanori ARITOMI, Ryujin OMASA, Hiroshi AKATSUKA
Article type: Article
Session ID: 2605
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Toshiyuki TOSHA, Yasuko OKUYAMA, Atsunao MARUI, Miki TAKAHASHI, Xingli ...
Article type: Article
Session ID: 2606
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The global warming is one of the most serious environmental problems of the day and the Japanese Government announced a proposal of "Cool Earth 50" that will reduce half of CO_2 emission by 2050. Energy saving, use of the renewable energy and increase of electricity produced by low CO_2 emission power supply and nuclear power plant are necessary and important. It is, however, impossible to produce all the amount of energy to be used by the renewable and nuclear energies at present. We need a bridge technology to use fossil energy to keep the economic activities and to reduce the emission of CO_2 into the atmosphere. CO_2 capture and storage (CCS) is one of the most feasible methods among the bridge technologies. There are also several options to store CO_2. Geological storage, where CO_2 is stored into subsurface layers, is one of the storage options. In order to store CO_2 into the geological layers there need several technological innovations. AIST started a research project to realize CO_2 geological storage in saline aquifer. The research project contained several technologies to be developed such as technology to predict groundwater movement around depths of CO_2 storage, CO_2 monitoring technology using seismic wave, technology to evaluate the sealing abilities at cap rocks and geochemical technology using the geochemical simulator to predict reactions in the saline aquifer. We will present several results on the geological storage of CO_2 into saline aquifer and discuss further studies to commercialize the CO_2 geological storage.
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Chiaki SHINOHARA, Tsukasa KUMAGAI
Article type: Article
Session ID: 2607
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper describes evaluation results of several monitoring methods for potential CO_2 leakage from an offshore sub-seabed carbon dioxide (CO_2) storage project in the Southeast Asia. The study consists of three parts: literature review of background data of seawater in the region, selection of monitoring parameters and methods, and verification of the methods for a hypothetical leak scenario. Inorganic carbon parameters, especially pCO_2, are selected for this study and their background data are collected. The use of pCO_2 sensor loaded Autonomous Underwater Vehicle (AUV) is discussed and suggested as a monitoring method in order to cover the broad target area, which is possibly several square kilometers. Applicability of the above monitoring method is preliminarily studied using a hypothetical leak scenario in a previous study and a simple diffusion model.
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Takashi FUJII, Yuichi SUGAI, Kyuro SASAKI, Toshiyuki HASHIDA
Article type: Article
Session ID: 2608
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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It is an important step to understand the capacity of host reservoir rocks for CO_2 storage in order to assess the potential of CO_2 geological sequestration. In this study, CO_2 sorption capacity of rocks (granite and sandstone) under air dry and water saturated conditions was evaluated experimentally at temperatures of 33, 40 and 50℃, and pressures up to 20 MPa using a volumetric method. As a result, sorption isotherms for CO_2 showed that the CO_2 sorption capacity of both the rocks increased with the increasing CO_2 pressure, and decreased with the increasing temperature under both the air dry and water saturated conditions. The amount of CO_2 sorption are significantly larger than theoretical value based on a solubility model, which assumes that CO_2 injected within water-filled reservoir will dissolve into pore water. These CO_2 sorption capacities could not fully be explained by CO_2 dissolution in water alone. Furthermore, it has been shown very interestingly that the amount of CO_2 sorption measured for the air dry condition was close to that obtained for water saturated condition. The amount of CO_2 sorption for the sandstone is approximately two times larger than that of the granite. This investigation may point out the significance of CO_2 sorption onto rock minerals for the possible mechanism in CO_2 geological sequestration.
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Takuya MATSUMOTO, Tetsuya SUEKANE
Article type: Article
Session ID: 2609
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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To utilize aquifers without proven seal structures as CO_2 storage reservoir, CO_2 should be trapped by residual gas trapping and solubility trapping as well as physical trapping by cap-rock. We investigated the mechanism of the residual gas trapping from a microscopic point of view by means of micro-focus X-ray CT. First, we imaged trapped air bubbles in a Berea sandstone chip after spontaneous imbibition. Next, distributions of trapped bubbles in Berea sandstone were imaged in core-flooding. With a packed bed of glass beads, the effects of capillary number and the injected water volume are discussed. The trapped bubbles consist of two-type; one occupies the center of pore with a pore-scale size and the other has a pore-network scale size.
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Tetsuya SUEKANE, Masumi MATSUDA
Article type: Article
Session ID: 2610
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Residual gas trapping as well as physical trapping by cap-rock is an important process to keep CO_2 in aquifers against buoyancy. In this paper, we numerically analyzed the residual gas trapping by means of a lattice Boltzmann method from a microscopic point of views. CO_2 bubbles were trapped in porous media by interfacial tension and wettability. The trapped bubbles consist of two-type; one occupies the center of pore with a pore-scale size and the other has a pore-network scale size. With a decrease in porosity, the increase in the number of pore-network bubbles results in the increase in the residual gas saturation.
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Hiroyasu TAKASE, Tatsunori SAKURAI, Tsukasa KUMAGAI, Hidemitsu SHIMADA ...
Article type: Article
Session ID: 2611
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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There are a variety of stakeholders concerning CCS including the general public who may not have relevant scientific knowledge. Although CCS is an issue for everyone, only a few people have or have access to knowledge that is required as a basis for a rationally motivated consensus. In order to resolve the situation, a mechanism that allows efficient dissemination of knowledge and expedites discussion among the stakeholders is required. The objective of this study is to develop a prototype of such a mechanism, making use of information technologies and to test its practicality.
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Rencai CHU, Mika MUKOUJIMA, Tsutomu HATANAKA, Kouichi ISIDA
Article type: Article
Session ID: 2613
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In this paper, a thermoelectric generator (TEG) with a new compact structure was developed. The TEG composed of two heat transfer exchangers for heating and twelve heat transfer exchangers for cooling, and twenty thermoelectric modules between them. An experiment evaluating the performance of the TEG was carried out. As the result, 34W of electric power was realized at 2.4A current for two thermoelectric modules in series and totally 359W of electric power was obtained in this TEG with a compact volume of only 3 liter. That means the density of generating electric power is more than 100W/L. It is a remarkable improvement comparing with usual TEG less than 40w/L up to now.
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Yasuhiro Yamauchi, Atsushi Morii, Hiromu Takastuka, Kenji Tagashira, N ...
Article type: Article
Session ID: 2614
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Daisuke YAMAZAKI, Yukihiro NISHIZAWA, Yuki NAGATA, Yudai YAMASAKI, Shi ...
Article type: Article
Session ID: 2615
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Biomass resources are effective energy sources against global warming. In order to utilize biomass resources effectively, the automotive engine as a small-distributed generation system is one of the effective methods. In this study, a small size engine fueled by biomass gas based on automotive engine has been realized. Operating experiment fueled by low calorie gas simulating biomass gas gave knowledge about combustion characteristics and requirement for stable operation. 26% thermal efficiency was accomplished under appropriate conditions. An engine plant fueled by real biomass gas supplied from gasifying plant generated 19kW at its maximum. Then, auto control program was applied to the system. The control of air-fuel ratio and ignition timings realized stable rotational speed and power generation.
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Naoki TSURU, Yasuki KANSHA, Chihiro FUSHIMI, Kaoru SHIMOGAWARA, Atsush ...
Article type: Article
Session ID: 2616
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Reduction of energy consumption is one of the most considerable issues from the viewpoints of increasing fuel cost and environmental protection. Although the pinch technology is a widely-used method to recuperate heat and to reduce plenty of energy consumption, a heat-integrated system still has a problem that the conventional processes need external heat sources for heating up and exhaust energy as low-quality heat (exergy loss). In this paper, we propose an innovative self-heat recuperation system using pressure changing, which can achieve heat circulation without any furnaces. The result shows the required energy decreased drastically compared with the system using a fired heater to heat stream.
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Takashi OKAZAKI, Yohei KATO, Tomoyoshi OBAYASHI, Toshiro ABE
Article type: Article
Session ID: 2617
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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New heat pump water heater system using CO_2 has been developed to spread the electrical heat pump water heater from the point of view of the global warming prevention. The developed system consists of a water tank, the refrigeration circuit with a suction line heat exchanger (SLHX), a bypass line and heat recovery heat exchanger (HRHX) for the defrost. This system has three operating modes; hot water storage mode, heating up mode and defrost mode using HRHX. The SLHX can make the inlet quality of the evaporator lower than the conventional cycle without the SLHX, therefore amount of excessive refrigerant can be stored in the air side heat exchanger (evaporator) without accumulator under the various condition. In the defrost mode, the HRHX makes defrosting capacity increase and the air heat exchanger are used as the condenser.
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