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Yasutaka KITAMURA, Naoto HORIBE, Yoshimitsu HARADA, Sung-Sub KEE, Hiro ...
Article type: Article
Session ID: 4732
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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An ignition and combustion model has been constructed for DI-PCCI combustion employing a stochastic turbulent mixing model with a reduced chemical kinetic scheme. The presented chemical kinetic model reproduced ignition delays and temperature histories of homogeneous mixtures predicted by a detailed reaction model. In PCCI combustion under constant volume condition, calculated heat release rate histories coincide with experimental results including the effects of injection conditions. From the analysis of relationship between equivalence ratio and temperature in mixture, the reason for delayed ignition due to enhanced fuel-air mixing was clarified.
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Hiroyuki YAMADA, Atsumu TEZAKI, Yuichi GOTO
Article type: Article
Session ID: 4733
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The transition process from cool flame to thermal flame in homogeneous charge compression ignition is discussed It was confirmed in a simulation that an autoignition process exhibits three peaks in an Anhenius plot of heat release by a difference of key reaction or reaction mechanism so that low temperature oxidation, H_2O_2 decomposition reaction and H+O_2 reaction forming OH+O. A shoulder of H_2O_2 peak exhibits linear shape and an activation energy agrees with that of H_2O_2 decomposition under various fuels. In experiments, although broadened high temperature peak obscures the intermediate peak, other features obtained by simulations were observed From these observations, transition process from cool flame to thermal flame can be explained by thermal explosion theory in which rate determining reaction is H_2O_2 decomposition.
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Yoshihiro Sukegawa, Eiichiro Oohata, Shiro Yamaoka
Article type: Article
Session ID: 4734
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A fluid numerical simulation in the induction system of the diesel engine was done to make uniform cylinder distributions of EGR-gas. The finite volume method was used to solve 3-dimensional unsteady flow of the mixture and EGR gas in the diesel induction system. The one-dimensional engine simulator was also used to get the transient boundary conditions of the 3d simulations. EGR ratio of each cylinder on the real engine was measured by means of the exhaust gas component analysis. In the experiment, CO2 gas was used as quasi-EGR-gas and the engine was rotated by the electric motor. The simulation and experimental results showed that EGR ratio in the edge cylinders was lower than it in the central cylinders when EGR-gas was induced at the center of the induction pipe. The cylinder-to-cylinder EGR deviation was reduced with a hollow distribution of EGR-gas density at the collector inlet section.
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Shinji NAKAYA, Kazuo HATORI, Mitsuhiro TSUE, Michikata KONO, Daisuke S ...
Article type: Article
Session ID: 4735
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Numerical analysis on the process of the flame kernel initiation in spark ignition for methane/air combustible mixtures has been conducted. Spark energy near the minimum ignition energy is applied in the electrode gap and the early stage of the flame kernel initiation in investigated. The peak of minimum ignition energy for equivalence ratio of methane/air mixtures is located in the region of lean mixtures. When ignition energy is slight bigger than the minimum one, flame kernel initiation requires a certain period of time. In addition, hot gas spurts from the electrode gap at early stage of spark ignition processes and gradually quenches. In hot gas region, a local equivalence ratio is higher than that of the ambient gas at the latter stage of the flame kernel development.
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Masaya MUTO, Jun ARAI, Nobuyuki OSHIMA, Marie OSHIMA, Masato KUBOTA
Article type: Article
Session ID: 4736
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Changes in diffusion of spray particles in turbulent flow was investigated by means of spray 2D visualized images. Time sequence of Probability Density Functions (PDFs) of light intensity is used to investigate diffusion of spray. Each PDFs are obtained from light intensity distributions in time sequence of spray images. Spray is injected into turbulent flow, which is generated in the wind tunnel. As a result, it is showed that diffusion of spray is expressed with a concise procedure, in which measurement instrument doesn't need to resolve each particles in a spray image. And it is observed that the spray diffusion is enhanced associated with an increase in turbulent intensity.
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Jun ARAI, Hisashi ITOU, Nobuyuki OSHIMA, Marie OSHIMA, Masato KUBOTA
Article type: Article
Session ID: 4737
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Spray injection to turbulent duct flows was investigated by the combination of Large Eddy Simulation (LES) and Lagrangian Discrete Droplet Method (DDM). In this study we assume droplets are injected from a slit injector. This type of injector is used in some direct injection gasoline engines. Turbulence is generated by putting three cylinders in the duct. LES can resolve eddies induced by the momentum of the spray itself. As a result spray inner structures or irregular distribution of droplets were calculated. Conventional Reynolds Averaged Navier-Stokes (RANS) simulations can not treat such structures or irregularity, because all the effect of the turbulence are averaged. But these phenomena are important to enable stable stratified combustion under wide operating conditions in developing direct injection gasoline engines.
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Takafumi KOJIMA, Kazuie NISHIWAKI
Article type: Article
Session ID: 4738
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We analyzed the interrelationship between mixture heterogeneity and reaction in a homogeneous charge compression ignition (HCCI) combustion, using the Large Eddy Simulation (LES) in conjunction with a reaction kinetics model. The aim of this analysis is to find the statistical characteristics of the mixture heterogeneity in turbulent flow field for moderating the HCCI combustion and for increasing an output limit, which is restricted by an intense knock. Several different initial conditions of EGR gas heterogeneity were given at the intake valve closing time. The auto-ignition and combustion behaviors were analyzed for several different sets of the rms of the fluctuations in the EGR gas fraction and temperature. The analyses show that the heterogeneous distribution of an EGR gas gives a considerable effect to make the combustion slower, even when a fuel-air mixture is homogeneous in equivalence ratio.
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Toshinari IKEGAMI, Katsuhiko YOKOTA, Hiroshi SASAKI, Kazuhiro Ogawa, A ...
Article type: Article
Session ID: 4801
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Catalyst cannot easily decompose the exhaust gas of diesel engines because of lower exhaust gas temperature. In this study, the decomposition of NO_x in the modulated exhaust gas was studied with plasma discharge reactor as the method. Results showed that NO in N_2 as the dilution gas could be decomposed as much as 80% by this method in an optimized condition, but the decomposition was seriously obstructed by the addition of O_2 in the gas or even NO_x was increased with the increase of O_2 concentration and plasma energy. In addition, it has been understood that the amount of NO_x reduction depends on power consumption and an initial NO level. Moreover the additions of CO_2, HC were studied and analyzed.
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Tomohiko FURUHATA, Hironobu KOGA, Masataka ARAI
Article type: Article
Session ID: 4802
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this study, DeNO_x process in a tubular reactor with corona discharge was investigated numerically using elementary reactions for NO-N_2 system. N, N_2, NO, NO_2, N_2O, O, O_2, NO_3 and O_3 were considered in this calculation. Formation rate of N radical by corona discharge was assumed to be proportional to electric current and N_2 concentration. The effects of initial NO concentration and gas flow rate on the DeNO_x performance were investigated. From the calculated results, it seems that the decrease of NO was caused by the reduction reactions of NO such as NO+N→N_2+O, rather than the oxidation reactions of NO such as NO+O→NO_2 or the reduction reaction of NO_2 such as NO_2+O→NO+O_2. Moreover, it was shown that the calculation model developed in this study can described the characteristics of DeNO_x process obtained by the experiment using the tubular reactor.
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Takayuki YAMADA, Tomoyasu AIHARA
Article type: Article
Session ID: 4803
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Polycyclic aromatic hydrocarbon (PAH) is suggested as an origin of particulate matter (PM) in exhaust gas of diesel engine. In present study, aggregation processes of chemical species in the exhaust gas are numerically simulated by molecular dynamics (MD) method. The simulated exhaust gas consists of H_2O, CO_2, N_2, O_2 and Coronene. Aggregation kinetics of chemical species is quantified by internal energy under constant temperature and volume ensemble. The aggregation rates of Coronene, H_2O and CO_2 decrease with temperature. No chemical species aggregate over 450K except for Coronene. The aggregation rate increases with molar fraction of Coronene.
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Kenjiro NAKAMA, Jin KUSAKA, Yasuhiro DAISHO
Article type: Article
Session ID: 4804
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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To suppress knock in gasoline engines, the coolant flow of a single-cylinder engine was improved by using two methods: a multi-dimensional knock calculation and a method for predicting combustion chamber wall temperature based on a thermo-fluid calculation. Through these calculations, the head gasket geometry was modified to change the coolant flow and thereby improve the distribution of wall temperatures on the head side. By decreasing the wall temperature on the exhaust side by about 10K while maintaining the wall temperature on the intake side, it was possible to advance the spark timing by about 1°CA and improve the thermal efficiency by 0.4% over the whole speed range.
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Motohiro TAKAI
Article type: Article
Session ID: 4805
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In-cylinder pressure measurements are one of the most important tools for investigating the internal process in internal combustion engine. The correct position of TDC (Top Dead Center) is of crucial important in calculating IMEP or heat release rate. Since the calculation of these values are very sensitive to error in TDC determination. In this paper, the method of the correction of the position of the TDC was presented and was used to correct the position of TDC of the two types marine diesel engines.
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Hiroki MURAKAMI, Toshiaki KONOMI, Akira OTSUKA
Article type: Article
Session ID: 4807
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this paper, we have analyzed electric current distribution on an electrode of PEFC. We measure both electric current under rib and channel areas, and thereby calculate current ratio between them. Since the separator is pressed directly on the GDL, contact resistance is possibly small. On the other hand, smoothly supplied fuel in the channel area possibly leads to active reaction. In order to obtain the current ratio, we prepare 3 types of the GDL. First one is prepared by removing the rib area. Second one is prepared by removing the channel area. And last one is used without any treatment. We compare the performances of them and calculate ohmic resistances under the rib and under the channel. From the ohmic resistance ratio, it seems that about 84% of electricity is generated under the rib area.
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Hideaki TACHIBANA, Hironori NAKAJIMA, Toshiaki KONOMI
Article type: Article
Session ID: 4808
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We have investigated the behavior of a polymer electrolyte fuel cell (PEFC) operated with supplying carbon monoxide (CO) in addition hydrogen (H_2) into the anode in order to develop the PEFC diagnosis method for anode CO poisoning. Using current-voltage (I-V) curves and electrochemical impedance spectroscopy (EIS), we analyze the overvoltage, electrooxidation of CO and phenomena of CO adsorption/desorption at the anode. I-V curves show that the output voltage decreases owing to the CO poisoning when anode potential is lower than CO electrooxidation potential. EIS shows that a PEFC can be simulated with an equivalent circuit model consisting of several elements ; activation and concentration overvoltages and adsorption/desorption. Their characteristic values can be used for the diagnosis of the CO poisoning.
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Junichi NAKAZONO, Tatsumi KITAHARA, Toshiaki KONOMI
Article type: Article
Session ID: 4809
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The influence of GDL (Gas Diffusion Layer) on the PEFC (Polymer Electrolyte Fuel Cell) performance varies greatly depending on gas humidity condition. Under moderate humidity condition, the higher performance can be obtained when using the GDL with no treatment rather than MPL coating. This is because the GDL with no treatment has higher air permeability, compared with MPL coating, thereby reducing the concentration over voltage. Under high humidity condition, on the other hand, the PEFC performance obtained for the GDL with PTFE-hydrophobic treatment is higher than that with no treatment. Further improvement can be obtained with PTFE treatment followed by MPL coating with a carbon black and PTFE. The MPL coating is effective in reducing flooding on electrode, thereby decreasing the concentration over voltage. The reduction of flooding with the MPL coating is enhanced by increasing porosity of the carbon paper substrate.
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Koichi HIRATA, Yasuyuki Imai, Masakuni KAWADA, Teruyuki AKAZAWA, Sator ...
Article type: Article
Session ID: 4810
Published: September 15, 2006
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. We have tried to develop a heat recovery system with a Stirling engine generator. When the ship is at sea, the Stirling engine generator operates with the exhaust heat of the Diesel engine, and charges batteries in the ship. When the ship is at anchor in the harbor, the charged batteries supply the electric energy into the ship without the operation of the Diesel engine generator. This system is expected that the harbor area is kept clean, because the exhaust gas of the Diesel engine decreases in the area. In this paper, we report structure and performance of an experimental Stirling engine for the system. The engine has target power of 500W, and it can operate using heat source of 400 deg C.
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Koichi HIRATA, Yasuyuki Imai, Masakuni KAWADA, Teruyuki AKAZAWA, Keiji ...
Article type: Article
Session ID: 4811
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In order to prevent global warming and keep energy conservation, we need a compact and high efficient power source. A Stirling engine, which has excellent characteristics such as high ideal efficiency and low pollution, is one of the suitable power sources for a comfortable life in the future. In this study, we aim to develop a high efficient Stirling engine. And a ceramics heat exchanger is developed. It has high heatproof performance and high heat conduction, then the Stirling engine can have higher operating temperature. We discuss about performance of the ceramics heat exchanger based on the test results of a prototype Stilring engine.
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Hidekazu SUZUKI, Yasukazu BABA, Tsuneaki ISHIMA, Tomio OBOKATA
Article type: Article
Session ID: 4812
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Oil consumption is caused by the evaporation of oil film left on the cylinder wall or by the combustion of oil flowing out to the combustion camber through the piston ring gap. This study focusedd on oil outflow through the piston ring gap under a high vacuum operating condition in the intake manifold. Moreover, the oil film was visualized to determine oil film thickness. As a result, the oil flowed out steadily from the piston ring gaps at this operating condition, and moved through the surface of the top land to the combustion chamber. It was also found that the amount of oil outflow and the oil consumption were affected by the end gap design of the top ring.
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Oluwole AMIDA, Hironobu UEKI, Masahiro ISHIDA, Daisaku SAKAGUCHI
Article type: Article
Session ID: 4813
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The atomization of diesel fuel injected intermittently into the atmosphere was measured using a laser 2-focus velocimeter (L2F). The micro-scale probe nature of the L2F makes it possible to measure simultaneously the velocity and size of droplets. Measurements were taken at 10 and 30mm down the nozzle orifice and the result was compared with the result of KIVA-3 analysis which uses the ETAB model as droplet breakup model. It is confirmed that probability density distributions of velocity and size could be simulated accurately by adopting suitable parent-product droplet size ratio. As a result, it is clarified that unstable droplets in the region of stripping breakup still exist near the nozzle orifice, also, droplet breakup is dominated by bag breakup at 30mm down the nozzle exit.
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Yoshimitsu WADA, Jiro SENDA
Article type: Article
Session ID: 4814
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A new primary breakup model of fuel spray with multi-component is proposed by considering the turbulent energy induced by the cavitation bubble. The model proposed here deals with bubble behavior inside nozzle, namely, the process of the growth, the shrinkage and the collapse processes are taken into account by applying Rayleigh-Plesset equation. The resultant energy contributes to the enhancement of initial perturbations on the spray surface and the perturbations grow under the action of aerodynamic force. The model proposed is implemented into KIVA-3V code in order to validate the effect of energy generated by the cavitation on the primary breakup of the discharging jet.
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Shuji KAMATA, Hiroki NAKAGAWA, Tsukasa HORI, Jiro SENDA, Hajime FUJIMO ...
Article type: Article
Session ID: 4815
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A new photographic method is developed to be able to take a whole shape of a diesel spray in the wide visual field with the high spatial resolution. The photographic system is composed of a self-made high-magnified projector and a large format silver halide film. The high-magnified projector has two objective lenses with long-working distance and high spatial resolution. Using large format film, this enables the measurement of each droplet in wide visual field. In the experiment, laser transmitted light has been developed to investigate the droplet diameter of diesel spray. The light source was the second harmonic of Nd: YAG laser. As a result, the fine image of a spray periphery was taken by this system. There is the possibility of measurements the droplet diameter of the whole spray by using photographic system.
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Motohiro OSHIMA, Tomoya TSUCHIDA, Akiko KOMEDA, Koji TOMINAGA, Motoi N ...
Article type: Article
Session ID: 4816
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The novel chemical vapor deposition CVD is proposed to improve several kind of problems such as the adhesion precursor particle inside precursor supply line and formed film quality. In the novel CVD named Flashing Spray CVD(FS-CVD), liquid precursor through the injector directly to CVD chamber with lower chamber pressure as intermitted spray and flash boiling spray. Normally, the ambient pressure is kept the lowest in the chamber because the vapor pressure of precursor is low. The low saturated pressure precursor can be converted into high saturated pressure properties by mixing the solution due to the vapor-liquid equilibrium through two phase region in P-T diagram. In this study, TEOS and n-pentane were used as mixed solution. The vapor formation speed and distribution of flashing spray was observed by the image of LIF and Mie scattering. As the result, the vapor formation speed of flashing spray form the injector become to constant speed at the lowest ambient pressure. Further, the flash boiling was promoted due to optimum spray shape.
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Kenji ISHII, Zhili CHEN
Article type: Article
Session ID: 4817
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this study, simulation of mixture formation in a PCI engine was calculated by using GTT code, and the results of the simulation was compared with those of experiment with an experimental engine. The factor of HC exhaust was demonstrated in terms of spray, and how to decrease HC exhaust was analyzed. In addition, multipurpose utilization of GTT code was also discussed.
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Takashi YONEZAWA, Kazuhiko KAWAJIRI
Article type: Article
Session ID: 4818
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The amount of adhesion fuel on a flat plate which was formed through spray-flat plate impingement was measured to investigate the fuel spray adhesion behavior in a port fuel injection engine. It was shown that the amount of adhesion fuel was affected by ambient temperature, injector-plate distance and wall inclination angle. Especially, the wall inclination angle was more effective when the injector was close to a plate.
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Keiya NISHIDA, Tetsuya MANABE, Wu ZHANG
Article type: Article
Session ID: 4819
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The mixture formation process of a D.I. Diesel spray injected by a micro hole nozzle and a high pressure fuel injection system was characterized by means of the laser absorption and scattering (LAS) technique. The LAS technique provides the quantitative measurements of the liquid and vapor phase concentration distributions in the fuel spray, and the spray and mixture properties such as the Sauter mean diameter of the spray, the mass of ambient gas entrained into the spray, the mass of fuel vapor in the spray, and the mean equivalence ratio of the fuel and so on. The injection duration was set to the same for any diameter hole nozzle examined under the same injection pressure. Comparing to the conventional nozzle hole size (0.16mm in diameter) and fuel injection pressure (100MPa), combining the micro hole (80μm in diameter) nozzle and the high pressure (300MPa) fuel injection produces the spray having much smaller Sauter mean diameter, much higher evaporation rate, and much leaner fuel and ambient gas mixture due to the enhanced ambient gas entrainment per unit fuel in the spray.
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Yoshimi MIZUTA, Nobutoshi NAKACHI, Masato MIKAMI, Naoya KOJIMA
Article type: Article
Session ID: 4820
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The combustion of the fuel spray/air mixture, termed "premixed spray", was experimentally studied in counterflow field. The liquid-fuel spray with air stream was introduced from the lower duct to the combustion zone, and the air stream was blown from the upper duct. N-decane was used as a liquid fuel with low volatility. The premixed-spray flame was established near stagnation region within a specific range of the mean droplet diameter. The flame spread among droplets was observed by an intensified high-speed video. The stabilization of the premixed-flame was discussed based on the observation of the flame-spread behavior. The flame spread among droplets and formation of the group flame contributed the flame stabilization.
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Nobushige TAMAKI, Jyun TAKAYAMA, Kenji TANAKA
Article type: Article
Session ID: 4821
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The atomization enhancement nozzle, which is able to obtain the excellent spray characteristics under the low-injection pressure, was invented in the previous study. The purpose of this study is to apply this nozzle to the actual Diesel injector. It is necessary to obtain the flow rate corresponded to the high-injection pressure at the low-injection pressure. In this paper, the effects of geometric shapes and measurements of the atomization enhancement nozzle on the atomization characteristics and the flow characteristics were investigated. As the results, the shorter breakup length and the larger spray angle were obtained and the injection flow rate increased comparing with the nozzle invented in the previous study. The atomization characteristics and the flow characteristics were improved.
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Nao NINOMIYA, Takayuki SASAKI
Article type: Article
Session ID: 5001
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In order to achieve high-efficiency combustion or clean combustion without toxic emission, it is very important to control the combustion mechanism. Thus, it is necessary to measure or estimate the temperature and the mass fractions of major or minor chemical species. With the recent progress in computational capabilities, many kinds of the direct numerical simulations of the chemical reaction have been carried out and the resulting database can be used for the prediction of combustion. But, there have been incorporated many kinds of assumption and approximation in the real simulations. Presently, the authors of this study have tested two major simulation codes, which are CEA and OPPDIF, and compared the results to quantify the effect of approximations on the resulting database.
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Nobuhiro SHIWAKU, Yuzuru NADA, Mamoru TANAHASHI, Toshio MIYAUCHI
Article type: Article
Session ID: 5002
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A new SGS combustion model is proposed based on hierarchical structure of turbulent premixed flames. The hierarchical structure is clarified by the detailed analysis of direct numerical simulation (DNS) data of three-dimensional hydrogen-air turbulent premixed flame. SGS flame surface area strongly correlates with GS strain rate of turbulent velocity field, which is related to the cluster of coherent fine scale eddy. As the GS strain rate of the turbulent combustion field includes dilatation effects intrinsically, a physical consideration is introduced to give the lower limit of dilatation effects in GS. To represent the relation between GS flame surface area and GS strain rate, a new SGS combustion model is proposed under assumptions of fractal characteristics of flame fronts and the scale separation of turbulence. The results predicted by the proposed model coincide very well with DNS results.
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Kiyoshi TERAKADO, Eisuke HINODE, Mamoru TANAHASHI, Toshio MIYAUCHI
Article type: Article
Session ID: 5003
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Direct numerical simulations of ignition and propagation of hydrogen-air premixed flame in two-dimensional homogeneous isotropic turbulence are conducted to investigate effects of turbulence on the ignition and propagation process. In the ignition process, eddies stretch the high temperature region and disturb its evolution. In the propagation process, strong eddies prevent propagation of the flame, and the flame propagates along the edge of eddies. Ignition delay tends to increase with the increase of mean strain rate in the initial high temperature region. If the high temperature region is separated by the strong eddies in the ignition process, the ignition delays significantly.
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Kazuya TSUBOI, Shinnosuke NISHIKI, Yoshihiro NOMURA, Tatsuya HASEGAWA
Article type: Article
Session ID: 5004
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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An analysis of flame area was performed for DNS database of turbulent premixed flames. A local flame front at a prescribed progress variable was identified as a local three-dimensional polygon. The polygon was divided into some triangles and local flame area was evaluated. The turbulent burning velocity was evaluated using the ratio of the total turbulent flame area to the planar flame area and compared with that obtained by the reaction rate.
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Susumu NODA, Yoji HORII
Article type: Article
Session ID: 5005
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Comparative study of modeling jet nonpremixed flame has been implemented to evaluate the capability of the Reynolds stress model to the conventional κ-ε two equation model. H3 flame which is opened on website of the international workshop and is composed of a hydrogen/nitrogen mixture is chosen as a target flame. As a matter of course, the Reynolds stress model has predicted anisopropic phenomenon, the κ-ε two equation model being unable, to lead to fair good agreement with experimental results. This however strongly depends on empirical constants and requires further researches for definite insight.
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Shigeki TOMOMATSU, Hidenori TASAKA
Article type: Article
Session ID: 5006
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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To clarify the mechanism of turbulent combustion from the viewpoint of physical data, premixed turbulent combustion in a constant volume combustion chamber was researched. Flame shape was measured as cross sectional image by laser sheet method. As preparation of evaluation of flame shape, the most suitable method for extraction of flame front was examined. Gradient, Laplacian and template matching method were used as popular image processing method. In addition, Wavelet and FFT was examined as frequency filter of image. The results showed that the image processing method using frequency filter was suitable for extraction of correct flame front.
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Masaya NAKAHARA, Hiroyuki KIDO, Takamori SHIRASUNA, Koichi HIRATA
Article type: Article
Pages
357-358
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The influence of the addition of hydrogen to propane mixtures on its local burning velocity is investigated directly. Hydrogen added lean and rich propane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen are prepared. A two-dimensional sequential laser tomography technique is used to obtain the temporal statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity S_F is quantitatively obtained as the key parameters of the turbulent combustion. The obtained S_F is also discussed by the concept of Markstein number.
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Masaya NAKAHARA, Hiroyuki KIDO
Article type: Article
Session ID: 5008
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This study is attempted to establish a prediction model of turbulent burning velocity for hydrogen mixtures as a reference of the mean local burning velocity S_L estimated by taking account of the preferential diffusion effect, instead of the laminar burning velocity S_<L0>. The S_L is estimated for the specific mixtures having the same S_<L0> by adding nitrogen to hydrogen-air mixtures, where S_<L0> as well as the equivalence ratio are varied extensively, in order to confirm the effect of u'/S_<L0> on S_L. It is found that accuracy of the proposed simple mode can be improved by using S_L with respect to u'/S_<L0>.
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Yuji NAKAMURA, Satoshi MANOME, Naoki HAYASHI, Hiroshi YAMASHITA
Article type: Article
Session ID: 5009
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes the applicability of acetone-OH simultaneous PLIF approach (scheme) to the diagnostics of the near-extinction flame behavior. This scheme is recently developed by authors and showed qualitative and quantitative accuracy for the laminar flames. By means of one laser and one detector combination (i.e. the simplest PLIF set), this approach gives us three different quantities of the local flamelet ; such as flame curvature, flame thickness, relative OH fluorescence intensity in the laser sheet plane. Successive imaging of locally-quenched features in 2-D plane is achieved and frequent extinction is observed at convex toward burned side. Local curvature-OH correlation shows positive indicating the qualitative consistency with the previous works done by Chen & Bilger (2002) and Thevenin (2005). This fact ensures that the present scheme could have a potential to work on extinction flame imaging and could be powerful tools for controlling the actual combustor.
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Kazunori HAMASAKI, Satoshi SHIMONOKADO, Eiji KINOSHITA, Hidefumi KAKUR ...
Article type: Article
Session ID: 5010
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In order to use a low quality biodiesel as a burner fuel, the combustion characteristics and exhaust emissions of an agricultural warm air furnace operated with a low quality Rapeseed Oil Methyl Ester (RME_L) are investigated by comparing with a high quality one (RME_H) and Bunker A. RME_L and RME_H have the lower NO_x, SO_2 and Smoke emissions compared with Bunker A. The thermal efficiency and exhaust emissions of RME_L are almost the same as that of RME_H. Also, the carbon deposit of RME_L on the heat exchanger outlet of the agricultural warm air furnace is lower than that of Bunker A. From the experimental results, RME_L can be used as an alternative fuel for agricultural warm air furnaces.
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Jun HASHIMOTO
Article type: Article
Session ID: 5011
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this study, combustion mechanisms and effects of flame stretch on the burning velocity of two-component fuel mixtures of hydrogen and hydrocarbon are investigated by chemical kinetics computations. Lean and rich Mixtures having nearly the same laminar burning velocity S_<L0> are prepared by adding nitrogen to two-component fuel mixtures where the hydrogen additional rate δ and S_<L0> are varied from 0 to 1 and 15 to 35cm/s, respectively. As a result, it is elucidated that Markstein numbers of lean flames are changed monotonically from the value of the hydrocarbon flame to that of the hydrogen flame with increasing δ, however, those of rich flames show a complicated trend. These phenomena are explained qualitatively in light of the production rate of OH and HO_2.
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Shingo FUKUSHIGE, Shigenori NISHIO, Susumu NODA
Article type: Article
Session ID: 5012
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Flame characteristics configured flames can be strongly dominated by the combination of the burner and furnace. In this study, the effect of the flow field has been examined in terms of the emission of NO_x by LDV measurements furnace. The experiment was conducted in a variety of condition of the inner diameter of the cylindrical furnace,the global equivalence ratio and the turbulence at the flame boundary in the configuration of jet diffusion flames in cylindrical furnaces. As a result, it was found that increasing these parameter enhances recirculation of burned gas, and decreases the emission of NO_x.
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Yasutomo ZENMAN, Zvonko HRISTOV, Susumu NODA
Article type: Article
Session ID: 5013
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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An experimental investigation of the effect of the distance between the fuel and air nozzles on NO_x emission at different temperatures and oxygen concentrations of the oxidizer in high air temperature combustion cylindrical furnace was conducted. Highly preheated oxidizer (air and nitrogen) was injected in the furnace through an oxidizer nozzle positioned at the center of the base of the cylindrical furnace. Propane was injected through three different sets of fuel nozzles, one set working at a time. As a result, the emission of NO_x decreased as the distance between the fuel nozzles and the oxidizer nozzle increased. At lower preheating temperatures and lower O2 concentrations of the oxidizer, the emission of NO_x tends to become lower.
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Sang-Chul BAE, Yang YANG, Yasuyuki IKEGAMI, Masanori MONDE
Article type: Article
Session ID: 5015
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The effective thermal conductivities of TL-492 (Mm (La_<0.6-0.8>)Ni_<4.0>Mn_<0.2>Al_<0.2>) with hydrogen and helium have been examined at pressure from 0 to 2MPa, with before activation, after activation and oxidized status of metal hydrides. Experiment results show that pressure has great influence on effective thermal conductivity in low pressure range (<0.3MPa). And that influence decreases rapidly with increase of gas pressure. Metal coating method has been considered as an easy and efficient method to enhance the poor thermal conductivity of metal hydrides. At the present research, effective thermal conductivity of pure LaNi_<4.7>Al_<0.3> and its Cu metal coated alternative which have two weight percentages have been tested and compared with carbon fiber. It has shown that this method is not as effective as carbon fiber because its highest improvement is only 1.67 times comparing to pure LaNi_<4.7>Al_<0.3>, less than 1/3 of the efficiency of carbon fiber mixing method, and it takes much more additives.
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Hidefumi OISHI, Masanori MONDE, Tatsuhiro MURAKAMI, Yuichi MITSUTAKE
Article type: Article
Session ID: 5016
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Hybrid hydrogen storage tank is a high pressure hydrogen tank combined with metal hydrogen absorbing material to increase hydrogen mass stored per tank volume. It becomes an essential technology to supply hydrogen gas to fuel cell vehicles. However, poor heat transmission in MH bed during exoergic hydride forming reaction causes a long hydrogen charging time. This study shows basic characteristics of hydrogen charging rate and MH temperatures during hydrogen charging of a hybrid tank. Radial fin arrangement in cylindrical MH cartridge hydrogen charging enhances heat transfer in MH and reduces considerably hydrogen absorption time. The optimum fin number is also given by 2D numerical analysis.
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Shu MORIMOTO, Masanori MONDE, Peter WOODFIELD, Yuichi MITSUTAKE
Article type: Article
Session ID: 5017
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The increase in temperature of a gas has been measured during filling at a high pressure. Heat transfer between the compressed gas and the tank affects the strength of CFRP gas tanks which should be operated below 80℃. The experimental conditions are that filling gas is Hydrogen at 35MPa and at a filling mass flow rate of 50-180g/min. The temperatures are measured either vertically or horizontally at five positions in the tank. The characteristic of the gas temperature increase during filling and after filling are categorized into 4 regions. Coefficient of natural convective heat transfer is also given for different filling rates and for Hydrogen and Nitrogen.
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Takumi KONISHO, Tomoya KAWASE, Takuya WATANABE, Ichiro UENO
Article type: Article
Session ID: 5018
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The present authors carried out an experimental study with a special interest upon the dynamics of the fluid in the vicinity of the boundary line of three phases ; solid-liquid-gas interface, which is so-called 'contact line.' The moving droplet on the solid substrate is accompanied with the movement of the boundary line of three phases ; solid-liquid-gas interface, which is so-called macroscopic 'contact line.' Existing studies have indicated there is a thin liquid film known as 'precursor film' ahead the contact line of the droplet. In the present study the precursor film was detected by applying conventional ellipsometer, and its existing length was evaluated as a function of a dimensionless Capillary number. The present authors also indicate the effect of tiny particle sitting on the solid surface upon the traveling droplet and precursor film dynamics.
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Kazunori KOCHIYA, Ichiro UENO
Article type: Article
Session ID: 5019
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Behavior of particles depositing in the vicinity of solid-liquid-gas boundary line (contact line) of a volatile droplet sitting on solid substrate is focused. This phenomenon is called as 'coffee stain problem.' The present paper discusses two major topics under the conditions with and without solutocapillary convection ; (1) morphological pattern formation by the particles stuck on the solid surface after the dryout of the droplet and (2) spatio-temporal particle motion in the evaporating droplet.
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Shinichi TSUDA, Shu TAKAGI, Yoichiro MATSUMOTO
Article type: Article
Session ID: 5020
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this study, we investigate the growth mechanism of bubble nuclei and the exponent forcoarsening rate of the mean radiususing microcanonical molecular dynamics simulation. The coarsening process of the bubble nuclei such as Ostwald ripening occurs in the case of one-component liquid while it is not observed clearly in the case that noncondensable gas forms bubble nuclei. Although the same coarsening rate (n=1/2) is obtained, we confirm the different characteristics of the change of the total radius and the decrease of the bubble nuclei with coarsening. We describe the differences reflect the characteristics of the radius change of each nucleus and the size distribution function.
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Junichiro SHIOMI, Shigeo MARUYAMA
Article type: Article
Session ID: 5021
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Molecular dynamics simulations were performed to investigate the transport and phase change of a water cluster confined in a single-walled carbon nanotube. It is demonstrated that the water cluster can be transported along the temperature gradient due to the temperature dependence of the interactive potential energy of water molecules. The efficiency of the transport takes advantage of the hydrophobic water-carbon interface. Furthermore, the first order phase change of the water cluster to ice-nanotube is investigated in terms of the dependence of the freezing temperature on the diameter of the carbon nanotube. It is shown that the freezing temperature exhibits a maximum value, about room temperature, for nanotube diameter of d=1.1nm, where the ice-nanotube consists of 5-membered rings. Analyses of the potential energy indicate that the freezing temperature is mainly determined by the structural stability of the ice crystal.
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Shohei CHIASHI, Yuhei MIYAUCHI, Masamichi KOHNO, Shigeo MARUYAMA
Article type: Article
Session ID: 5022
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Raman scattering from various SWNTs (single-walled carbon nanotubes) samples were measured with three excitation laser wavelengths (488.0, 514.5 and 632.8nm) at various temperatures (4〜1000K). The G-band and D-band peaks showed clear temperature dependences: the downshift of Raman shift ; the broadening of peak width ; and the decrease of intensity with increase in temperature. The G^+ peak, which is the strongest peak in the G-band, showed the universal temperature dependence for three different excitation laser wavelengths and for various SWNTs samples. Hence, the temperature of SWNTs can be conveniently measured by Raman shift of the G^+ peak. With this temperature measurement technique by Raman scattering, in-situ temperature measurement of SWNTs during laser-heated CVD process was performed.
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Genki TAKEUCHI, Takeshi SOMEYA, Yutaka SUZUKI, Yutaka ABE
Article type: Article
Session ID: 5023
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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It is requested to develop a small and highly efficient heat exchanger for small size energy equipment such as fuel cells and CO_2 heat pumps. In the present study, the high pressure resistant micro-channel stacked heat exchanger had been developed. The heat transfer area for each volume of this device is quite large. Since the distance between the micro-channels in the device is small, the thermal resistance is small. This device can bear for very high pressure condition since the device is main factored by the diffused bond method. Due to the very high pressure resistance, this device can be used for high flow rate condition As the results, it is clarified that above features make the device to achive very high performance more than hundred times larger heat transfer rate than the existing heat exchanger.
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Hiroyuki HIRANO, Xian WANG, Naotaka OKAMOTO
Article type: Article
Session ID: 5024
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Numerical calculation of the two-phase flow in a microchannel was carried out. HS-MAC and PLIC-VOF algorithms and CSF model were employed. The program developed in the present study could capture the sharp interface well. Water and an organic fluid were injected from the two lateral channels and led into the main channel. The segment of each liquid was produced alternatively and periodically. In the present calculation, the length of each fluid was almost equal and unchanged. The flow mode is almost independent of the contact angle which is smaller than 90°. According to the dimensional analysis, the Capillary number was concluded to be important in this phenomena. As Capillary number becomes large, the segment length of each fluid becomes small. The T-typed microchannel provides the shorter segment in the present conditions. The segment length depends on the junction angle.
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