JSME International Journal Series B Fluids and Thermal Engineering
Online ISSN : 1347-5371
Print ISSN : 1340-8054
ISSN-L : 1340-8054
Volume 42 , Issue 4
Showing 1-26 articles out of 26 articles from the selected issue
  • Andrea PROSPERETTI
    1999 Volume 42 Issue 4 Pages 573-585
    Published: November 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The first part of the paper addresses some questions concerning the interpretation of averaged-equations descriptions of multiphase flows. A general result on the connection between hyperbolicity and stability is presented and its implications discussed. Exact expressions for the momentum equations applicable to dilute suspensions of spheres in potential flow and in Stokes flow are then presented. These results are only accurate to first order in the disperse-phase volume fraction, but they are nevertheless valuable due to the paucity of exact relations in disperse flows. Finally, the issue of the mixture pressure in a disperse flow is addressed, and some non-dilute results obtained by means of numerical simulations are described. The Appendix contains a summary of a recently developed ensemble-averaging formulation.
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  • Tamotsu IGARASHI
    1999 Volume 42 Issue 4 Pages 586-595
    Published: November 15, 1999
    Released: February 18, 2008
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    Experimental studies were carried out on the performance of three vortex shedders used for vortex flowmeter in a circular pipe : one is a trapezoidal cylinder used as a practical device and the other two types are a circular cylinder with a two-dimansional slit along the diameter and a triangular-semicylinder which accompanies alternative boundary layer suction and blowing. The vortex shedding frequency was obtained on the basis of measured fluctuating pressure on the surface of the vortex shedder. The pressure loss of the two shedders with a slit are reduced by 50% compared to that of a trapezoidal cylinder, and the two shedders are superior in linearity, regularity, sensitivity and range ability to the trapezoidal cylinder.
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  • Akiyoshi IIDA, Toshio OTAGURO, Chisachi KATO, Shinichi SHIMODE
    1999 Volume 42 Issue 4 Pages 596-604
    Published: November 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The objective of this investigation is to develop a method for detecting the aerodynamic sound source in a low-Mach number turbulent wake. We therefore introduced coherent output power (COP) in terms of surface pressure and vorticity fluctuation to evaluate vorticity contribution to aerodynamic sound generation. Moreover, aerodynamic sound source was calculated by using a modified Lighthill-Curle's equation ; that is, surface pressure fluctuation was replaced by COP. It was found that the intensity of COP corresponds to the distribution of the aerodynamic sound source caused by unsteady vorticity fluctuation. It therefore more directily reflects the aerodynamic aspects of the sound source. And we measured the distribution of aerodynamic sound source in the wake of a circular cylinder with Reynolds number of 4.0×104. This measurements show that aerodynamic sound is generated near the formation region of Karman vortices. It is therefore concluded that the separated shear layers play an important role in generating aerodynamic sound. Moreover, our identification method by using COP can successfully evaluate aerodynamic properties of a sound source.
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  • Tetuya KAWAMURA, Makiko KAN, Tsutomu HAYASHI
    1999 Volume 42 Issue 4 Pages 605-611
    Published: November 15, 1999
    Released: February 18, 2008
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    The flow around a circular cylinder standing on the sand is computed numerically and the movement of the sand is investigated. The numerical method employed in this study can be divided into three parts : (1) calculation of the air flow around the cylinder using MAC method with a generalized coordinate system ; (2) estimation of the sand transfer caused by the flow through the friction ; (3) determination of the shape of the ground. Since the computational area changes at step (3), this procedure has to be repeated at each time step. Results show that the horseshoe vortex scoops out the ground in front of the cylinder and the wake makes the sand accumulate in the rear region. The dented region becomes deeper as the cylinder leans windward.
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  • Mohammed Rafiuddion AHMED, Yasuaki KOHAMA
    1999 Volume 42 Issue 4 Pages 612-618
    Published: November 15, 1999
    Released: February 18, 2008
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    Influence of ground clearance and angle of attack on the aerodynamic characteristics of a tandem wing configuration with a variable distance between them and held together by two flat end plates, is studied experimentally. A moving belt system was used to simulate the true ground effect. Both the wing sections were having SYM-1B profile, which is known to have excellent aerodynamic characteristics in ground effect. It was found that the ground clearance of the wings and the angles of attack to the wings have a very strong influence on the aerodynamic performance of the tandem wings. A strong interference effect between the wake of the front wing and the rear wing affects the aerodynamic performance of the tandem wing configuration, especially when the distance between the wings is shorter. The system showed high pitching instability for increased spacing between the tandem wings.
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  • Mohammed Rafiuddin AHMED, Hideyuki SIRAGANE, Yasuaki KOHAMA
    1999 Volume 42 Issue 4 Pages 619-625
    Published: November 15, 1999
    Released: February 18, 2008
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    Results from studies on the performance of a moving belt system are presented. Velocity measurements were performed above the moving belt with a hot-wire anemometer at a free-stream velocity of 15m / s. The belt speed was same as the free-stream velocity. Boundary layer suction was applied upstream of the moving belt to obtain a uniform free-stream. It is found that with the help of moving belt system, it is possible to minimize the growth of boundary layer. The boundary layer grew by only 1 mm over a distance of 700 mm. Such a system is highly desirable for studies on ground effect aerodynamics. Measurements of lift and drag forces are performed on a tandem wing configuration in ground effect using the system with and without the belt moving. Influence of angles of attack for the wings on the aerodynamic characteristics of a tandem wing configuration with a variable distance between them is also studied for the two cases, with a very small ground clearance.
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  • Nobuyuki SHIMA, Norikazu SAITO, Masayoshi OKAMOTO
    1999 Volume 42 Issue 4 Pages 626-633
    Published: November 15, 1999
    Released: February 18, 2008
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    A low-Reynolds-number second-moment closure which completely eliminates wall-reflection redistribution terms is tested in turbulent flows with wall blowing and suction. The turbulence model was previously shown to give good predictions for fully developed channel flow, boundary layers in zero, adverse and favorable pressure gradients, and plane and round jets. In the present study, the model is used to calculate three boundary layers with blowing, two boundary layers with suction, and a channel flow with blowing and suction. The predictions are generally in good agreement with experimental data and direct numerical simulation data. The result encourages further testing of the model in various turbulent flows to establish a second-moment closure without wall-reflection redistribution terms.
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  • Shujun LIU, Toshiaki IKOHAGI
    1999 Volume 42 Issue 4 Pages 634-640
    Published: November 15, 1999
    Released: February 18, 2008
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    In this study, cavitation-induced sonoluminescence under conditions of cathodic protection was measured and examined in three percent sodium sulfate solution using an electrostrictive vibratory apparatus. It was found that the relative intensity of sonoluminescence increases as the cathodic current becomes larger. This because the hydrogen gas bubbles which evolve can also give off sonoluminescence in the sams way as cavitation bulbble. This fact suggests that cavitation accompanied by an electrolytic reaction can result in more intense sonoluminescence.
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  • Shujun LIU, Jiro HIGUCHI, Toshiaki IKOHAGI
    1999 Volume 42 Issue 4 Pages 641-648
    Published: November 15, 1999
    Released: February 18, 2008
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    To obtain information on the cavity flow behavior, an experimental study of the external and internal flows of a cavity occurring on a 2-D hydrofoil was performed in a closed-type cavitation tunnel. The liquid phase velocities and their fluctuations in the flow field inside and outside the cavity were measured by using a Laser Doppler Velocimeter (LDV) in different cavitation states. In addition, the corresponding cavitation aspects were observed photographically by means of a xenon flach lamp with an exposure time of 1 μs and a high-speed video. The results show that the averaged velocity profiles inside the cavity are similar to those in the single phase boundary layer. However, strong fluctuation and intermittent reverse flow occur within the cavity, especially in the region near the bottom.
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  • Guoyu WANG, Shujun LIU, Masayuki SHINTANI, Toshiaki IKOHAGI
    1999 Volume 42 Issue 4 Pages 649-657
    Published: November 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In this paper, to make clear the mechanism of cavitation damage around a hollow-jet valve, cavitation damage test was conducted in a hollow-jet model valve. The eroded surfaces of specimens were observed by Scanning Electron Microscope (SEM) at different times of the test. Cavitation aspects were also observed photographically by a high-speed camera. It was found that the damage occurs in cavitating flows around a hollow-jet valve with two patterns. One is characterized by a big plastic crater, which seems to be generated by one blow event of cavitating vortex collapse near a specimen surface. Another is due to a small brittle irregular pit formed by the cumulative effects of many weaker blows. The former is the main cause to lead serious damage. The high-speed photographic observations of the cavitation aspects showed that more cavitating vortices in middle cavitation number state occur than these in other states. The damage tests also illustrated that the middle state is the most dangerous for cavitation damage around a hollw-jet valve.
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  • Koji MORI, Yoshiyuki KONDO, Masuo KAJI, Takuya YAGISHITA
    1999 Volume 42 Issue 4 Pages 658-666
    Published: November 15, 1999
    Released: February 18, 2008
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    In order to clarify the effects of liquid viscosity on the interfacial structure of the flow occurring in the transition region from plug flow to annular flow regimes, time-spatial measurements of liquid holdup were carried out using liquids with kinematic viscosity of 1×10-6, 10×10-6 and 20×10-6m2 / s. Based on these measurements, time-spatial maps of wave behavior were produced and the probability distributions of wave width, wave velocity and wave height were also determined. Close inspection of these data revealed that there appeared two types of waves, namely huge waves and disturbance waves, even in cases where the liquids with the kinematic viscosity of 10×10-6 and 20×10-6m2 / s were used. Moreover, the differences between these waves became greater with an increase in the kinematic viscosity of liquid. Furthermore, it was also clarified that the region, where the gas-liquid interface was covered with ripple-like waves, became wider with an increase in the kinematic viscosity of liquid.
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  • Shin-ichi NAKAO, Masaki TAKAMOTO
    1999 Volume 42 Issue 4 Pages 667-673
    Published: November 15, 1999
    Released: February 18, 2008
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    A calibration facility based on the gravimetric method has been developed at NRLM for small mass flow rates of gases. This calibration facility establishes a primary gas flow measurement standard in Japan with an expanded maximum uncertainty of ±0.12 percent for small mass flow rates from 0.1 g / min to 50 g / min for nitrogen gas. Five sonic Venturi nozzles were tested using this facility and the results showed that they can work well as a flow transfer standard for small mass flow rates. These sonic Venturi nozzles can be used to establish flow transfer standards within an expanded uncertainty of ±0.15 percent.
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  • Ki-hyung LEE, Chang-sik LEE, Young-cheol JOO
    1999 Volume 42 Issue 4 Pages 674-682
    Published: November 15, 1999
    Released: February 18, 2008
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    It has been known that the in-cylinder flow field structure at the time of ignition timing has an effect on the shape and propagating speed of initial flame. Particle image velocimetry (PIV), a planar measuring technique, is a very efficient tool for studying complicated flow fields such as in-cylinder flow and intake port flow, and relies on fast and efficient method to track numerous particles suspended in the flow. In this study, two-color scanning PIV is designed to measure the two-dimensional velocity data by using a rotating mirror and a beam splitter. This PIV method gives the information about the complex turbulent flow and vorticity including tumbling flow by using a spatial filtering technique. From this experimentation, we obtained the few-mm turbulent integral length scales with a high spatial resolution and showed that the mean velocity and the turbulence strength increased linearly with the increase of engine speed.
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  • Kunito OKUYAMA, Atsushi OGAWA, Yoshihiro IIDA
    1999 Volume 42 Issue 4 Pages 683-690
    Published: November 15, 1999
    Released: February 18, 2008
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    The endothermic reaction and heat transfer characteristics of a platinum-catalyst-coated fin which undergoes a methanol decomposition reaction are investigated experimentally. Fin base temperature is varied widely over the range of practical interst. The local temperature along the fin structure and the evolution rate of decomposed gas measured agree well with those predicted by the analytical model described in the previous paper (Reaction and Heat Transfer Characteristics of Catalyst-Coated Fins (Theoretical Analysis of Fins with an Endothermic Reaction), JSME Int.J., Ser.B, Vol.42, No.2(1999), p.255). For the ranges of dimensionaless parameters examined, the effects of the mass transfer of reactant species from bulk fluid onto the fin surface and the heat absorption by the reaction on fin efficiencies of the reaction rate and heat transfer are shown to be negligible. From theoretical consideration, for the case in which the reaction rate on the fin surface is not affected by the mass transfer onto the fin surface and the heat absorption by reaction in general, one dimensionless quantity, which is expressed as a function of dimensionless parameters, is shown to be dominant for fin efficiency of the reaction rate in the ranges of dimensionless parameters which are practically possible. The simple approximation of the fin efficiency of the reaction rate expressed in terms of the dominant dimensionless quantity well predicts the results obtained by the experiment.
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  • Shuhn-Shyurng HOU
    1999 Volume 42 Issue 4 Pages 691-698
    Published: November 15, 1999
    Released: February 18, 2008
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    The extinction of dilute spray flames under the influence of the external heat transfer existing in both upstream and downstream regions is studied using activation energy asymptotics. A completely prevaporized burning model and a partially prevaporized burning model are identified. The internal heat transfer embedded in the rich and lean spray respectively provides heat loss and heat gain for the system. However, the external heat transfer results in globally external heat loss and external heat gain, respectively, to the spray system with increasing wall temperature. The C-shaped and S-shaped extinction curves are clearly classified and mapped with parameters of the wall temperature, the initial droplet size and the external heat transfer coefficient. Characteristics differing from previous findings regarding upstream heat transfer are discussed. Furthermore, the phenomenon of reproducing an S-shaped extinction curve from the original C-shaped extinction curve is also presented and discussed.
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  • Hiroshi YAMASHITA, Dunja DJAMRAK, Tadao TAKAENO
    1999 Volume 42 Issue 4 Pages 699-707
    Published: November 15, 1999
    Released: February 18, 2008
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    A direct numerical simulation of two-dimensional fuel jet flames developed in a co-flowing air stream was made considering rather complex finite chemistry in order to clarify the role of elementary reactions in flame structure and its unsteady behavior. The governing equations were discretized and numerically integrated using the finite volume method. The temperature dependence of thermodynamical properties was taken into account and the transport properties were calculated according to the simplified transport model proposed by Smooke [Reduced Kinetic Mechanisms and Asymptotic Approximations for Methane-Air Flames, (1991), p.1-28, Springer-Verlag]. Chemical reactions were described by Smooke's skeletal methane-air reaction mechanism. It was found that large-scale fluctuations were produced in the downstream of the jet flame where a decrease in temperature occurred at some instant, leading to local extinction. Upon comparison with the results of a counterflow laminar diffusion flame, it was also found that the hypothesis of the laminar flamelet model could be accepted even for the case of the unsteady jet flame with local extinction. Furthermore, better understanding of the extinction mechanism was obtained : In the turbulent region of the flame, fuel is converted by large vortices into the reaction zone at high supply rates, inducing CH3, CH3O, CH2O and HCO production. At some instant, the increase in mixing rates will result in a decrease in temperature, causing the consumption of available active radicals due to the activity of some exothermic reactions, and the slowdown of the reactions producing new OH, O and H radicals. The radical pool is no longer available for chain reactions to proceed, resulting in an extinction.
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  • Nobuhiro YAMANISHI, Yoichiro MATSUMOTO
    1999 Volume 42 Issue 4 Pages 708-714
    Published: November 15, 1999
    Released: February 18, 2008
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    The Multistage model for diatomic molecules scattering from a solid surface is presented, which is based on a large body of data obtained from molecular dynamics simulations and molecular beam experiments. The molecular dynamics method is used for the numerical analysis of the scattering of an oxygen gas molecule from a clean graphite surface. The angular and velocity distributions agree well with experimental results, which were shown in our previous report. The scattering direction, translational energy and rotational energy of the gas molecule after each collision are saved as the data base. The basic idea of the model is to separate the collision into different stages. At each stage, the energy loss, the scattering direction and the trapping probability of the gas molecule are determined. The angular and velocity distribution of the model agrees with those of molecular beam experiments.
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  • Yukinobu TAKIGUCHI, Masahiko UEMATSU
    1999 Volume 42 Issue 4 Pages 715-722
    Published: November 15, 1999
    Released: February 18, 2008
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    A new equation of state for aqueous ethanol mixtures is proposed in the temperature range from 270 K to 420 K at pressures up to 200 MPa. The equation is expressed in a form of excess molar Gibbs free energy as a function of temperature, pressure and mole fraction of ethanol. The equation has been formulated based on the experimental data of excess molar volume measured by the present authors. Comparisons with the experimental data are reported in detail. Behaviors of excess molar Gibbs free energy and excess molar enthalpy as a function of mole fraction of ethanol are discussed in a wide range of temperatures and pressures.
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  • Masanobu IGETA, Takayoshi INOUE, John VARESI, Arun MAJUMDAR
    1999 Volume 42 Issue 4 Pages 723-730
    Published: November 15, 1999
    Released: February 18, 2008
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    An experimental study on microscopic scale measurements of thermal expansion and temperature by using the Scanning Joule Expansion Microscope (SJEM) based on the Atomic Force Microscope (AFM) was conducted. While the AFM is scanning on the sample heated by AC current, topographical and thermal expansion images are measured simultaneously by detecting DC and AC motions of the cantilever. In order to apply this technique to the temperature measurement in microscopic scale, the sample was covered with a thin film of polymer (PMMA) which has a high thermal expansion coefficient compared with metals and dielectric materials. Merits of this technique are (1) quite simplicity of measurement because of using the commercial cantilever instead of complicated thermal cantilever for the typical Scanning Thermal Microscopy (SThM) and (2) a higher spatial resolution of 20 nm which is restricted by the point contact scale between the cantilever and the sample.
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  • Zhen-Hua LIU, Yu-Ming CHEN
    1999 Volume 42 Issue 4 Pages 731-736
    Published: November 15, 1999
    Released: February 18, 2008
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    An experimental and theoretical study was carried out for the critical heat flux (CHF) during natural convective boiling in uniformly heated vertical tubes and vertical annular tubes submerged in saturated liquids. By adopting a simple mixing in-tube flow model, a generalized approximate formula was derived which agrees well with the CHF data of the tubes, annular tubes and rectangular channels submerged in water or other liquids under various pressure conditions. The common faults of various experimantal correlations were also discussed theoretically.
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  • Minoru HISODA, Shigefumi NISHIO, Ryo SHIRAKASHI
    1999 Volume 42 Issue 4 Pages 737-744
    Published: November 15, 1999
    Released: February 18, 2008
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    In the present paper, heat transport rates and fluid flow patterns of the meandering closed-loop heat-transport device (MCL-HTD) were experimentally and analytically investigated by using water as an operating liquid. MCL-HTD consists of a closed-looped-tube meandering between heating and cooling parts with operating liquid of a volume fraction in it. First, the effective thermal conductivity of the MCL-HTD was measured, which showed much higher value than that of copper. Next, observation of fluid flow in the MCL-HTD was conducted, and a simple periodic flow pattern appeared at a high value of volume fraction of liquid. This periodic flow pattern was numerically analyzed by a model, and the flow pattern induced liquid flow from the heating to cooling parts or contrariwise. Such liquid flow results in large temperature differences between the liquid and tube wall at the heating and cooling parts.
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  • Toshiro MAKINO, Akinari NAKAMURA, Hidenobu WAKABAYASHI
    1999 Volume 42 Issue 4 Pages 745-751
    Published: November 15, 1999
    Released: February 18, 2008
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    Directional distribution of bidirectional reflectance ρ for visible laser irradiation is investigated experimentally on rough metal surfaces. The reflection is found to be far from perfect-diffuse. Relationship of reflection characteristics and rms surface roughness Σ is not simple in case Σ is of an order of the wavelength of incident radiation. It is recommended to analyze the reflection characteristics on (ρ cos θR), where θR is the zenithal angle of reflection. What has been called 'off-specular' peak does not appear in this case. A reflection model for describing the directional distribution is presented for heat transfer applications. The model can evaluate the values of the specular component RS and the perfect-diffuse component Rd of the hemispherical reflectance RH for directional incidence. It is interesting that calculated values of the specularly reflected energy ratio (RS / RH) do not always fit with our impression on the specularity in the directional distribution of ρ.
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  • Takamitsu YOSHIMOTO, Tatsuyuki OKAMOTO, Toshimi TAKAGI, Masashi KATSUK ...
    1999 Volume 42 Issue 4 Pages 752-759
    Published: November 15, 1999
    Released: February 18, 2008
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    Numerical simulations of heat transfer in a furnace of practical scale were carried out, coupled with a prediction of the flame. Radiative heat transfer was computed taking its nongray characteristic into account. Convective heat transfer to the furnace wall was incorporated as well. The numerical computations were conducted based upon the conservation equations of mass, momentum, energy and species together with the k-ε turbulence model and the eddy dissipation model for estimating the combustion rate and the effective viscosity. Radiative heat transfer was computed using the radiant heat ray method in combination with a weighted-sum-of-gray-gas model or a wide-band model. Predicted results were compared with experimental data. Comparisons showed that the profiles of temperature and species concentration can be predicted fairly well and that the weighted-sum-of-gray-gas model as well as the wide-band model gives a good prediction of heat flux to the furnace wall. The influence of soot on furnace heat transfer was also estimated.
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  • Taketoshi FUJIKAWA, Yoshiaki HATTORI, Makoto KOIKE, Kazuhiro AKIHIMA, ...
    1999 Volume 42 Issue 4 Pages 760-767
    Published: November 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    To improve the accuracy of fuel concentration measurements in a direct-injection gasoline engine by LIF (laser-induced fluorescence) technique, two approaches have been couducted. The combination of acetone as the fluorescence tracer of fuel and 266 nm as the excitation wavelength was used for the first approach in order to minimize the error caused by the temperature dependence of the LIF intensity. The second approach was the correction of the equivalence ratio obtained from the raw LIF image for the severe temperature distribution caused by evaporation and superheating of the injected fuel. The temperature distribution in the mixture was calculated ; then the equivalence ratio was corrected for the effects of air density variation and the remaining LIF temperature dependence. This improved techanique was applied to the quantitative analysis of the mixture formation process in a visualized direct-injection gasoline engine both under early and late injection conditions.
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  • Takeshi HASHIZUME, Hisashi AKAGAAWA, Kinji TSUJIMURA
    1999 Volume 42 Issue 4 Pages 768-775
    Published: November 15, 1999
    Released: February 18, 2008
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    Emissions characteristics of a new low-NOx diesel combustion concept termed MULDIC (MULtiple stage DIesel Combustion), were examined under high load conditions. In conventional diesel combustion, a near-stoichiometric mixture is formed during the ignition delay, which results in a large amount of NOx generated during the ensuing premixed combustion. Moreover, there is also a region of stoichiometric mixture formed when fuel mixes with air in diffusion combustion, where NOx is also produced. In MULDIC, premixed combustion and diffusion combustion are separated in time, and optimized independently. As a result, NOx emissions from MULDIC were reduced to less than half the values typical of conventional diesel combustion, at the same fuel consumption.
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  • Takashi FUKUI, Toshio SHIRAISHI, Tamotsu MURAKAMI, Naomasa NAKAJIMA
    1999 Volume 42 Issue 4 Pages 776-782
    Published: November 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In this paper we describe the new design methods of micro-Stirling engines. By setting the phase angle of two engines at 90 degrees instead of 180 degrees, the engines, which we named TF4 (torque flattening four-cylinder) engines, generate continuous positive and smooth torque, so they do not need a flywheel to supplement negative torque. Although raising the buffer pressure effectively improves the power of the Stirling engines, it is difficult to apply mechanical seals to micro-Stirling engines. Instead of mechanical seals, we suggest the use of magnetic clutches that transmit engine torque without contact. Using magnetic clutches, it is possible to avoid the use of rotary seal parts and decrease friction loss. Based on the proposed methods, we fabricated high specific power miniaturized alpha-type Stirling engines of 0.074 cc swept volume, whose maximum frequency is 317 Hz. We also demonstrate the efficiency of the engines and magnetic clutches.
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