JSME International Journal Series B Fluids and Thermal Engineering
Online ISSN : 1347-5371
Print ISSN : 1340-8054
ISSN-L : 1340-8054
Volume 48 , Issue 1
Special Issue on Experimental Mechanics in Heat and Fluid Flow
Showing 1-22 articles out of 22 articles from the selected issue
PAPERS
  • Toshiaki KITAGAWA
    2005 Volume 48 Issue 1 Pages 2-8
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    Spherically propagating laminar flames at elevated pressures in a large volume bomb were studied for propane-air mixtures. The effects of the initial mixture pressure on the burning velocity and flame instabilities were investigated varying the initial pressure from 0.10 to 0.50MPa. The Markstein number decreased with the increase in the initial pressure. The burning velocities at elevated pressures are affected not only by the change in the unstretched burning velocity but also by the variation in the Markstein number, or the variation in the sensitivity of the burning velocity to the flame stretch. The flame with a low Markstein number was unstable. Cellular flame structure developed earlier in such cases. Cellular structure accelerated the flame propagation. The burning velocity was affected by the flame instabilities in addition to the above two factors.
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  • Tsutomu HAYASHI, Yan LI, Yutaka HARA
    2005 Volume 48 Issue 1 Pages 9-16
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    In order to decrease the torque variation of a Savonius rotor and improve the starting characteristics, a new type of Savonius rotor, which has three stages with 120-degree bucket phase shift between the adjacent stages, has been designed and made. Wind tunnel tests make it clear that both the static and dynamic torque variations in one revolution of this three-stage rotor have been greatly smoothed in comparison with an ordinary one-stage rotor, which means the improvement of the starting characteristics. The torque characteristics of the rotors with guide vanes were also measured. The guide vanes increased the torque coefficient on the average in the low tip speed ratio but decreased the torque coefficient in high tip speed ratio. Although the present three-stage rotor needs improvement of the aspect ratio of each stage, the three-stage rotor with no guide vane had better torque characteristics than the one-stage rotor with guide vanes for tip speed ratio larger than 0.8.
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  • Chen-I HUNG, Ke-Chin WANG, Chin-Kwun CHYOU
    2005 Volume 48 Issue 1 Pages 17-24
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    The complete mixing of two or more different fluids in the microscopic scale within a reasonable time period plays an important role in the Micro-Total-Analysis-System (μTAS ). The objective of this study is to propose a new design of a passive micromixer by using flow-field simulations through Computational Fluid Dynamics (CFD) techniques. The primary idea of designing the micromixer is to add feedback side-channels on both sides of the main channel. Through the feedback side-channels, the fluids are guided to flow back into the main channel and to push the main stream and, therefore, the mixing effect will be produced and enhanced. By simulating the flow field in the micromixer, the important design parameters and the operational conditions, such as the channel geometry, the position of side-channel, and the inlet velocity, can be examined.
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  • Gyeong Rae CHO, Masaaki KAWAHASHI, Hiroyuki HIRAHARA, Michio KITADUME
    2005 Volume 48 Issue 1 Pages 25-33
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    An experimental analysis of the 3D velocity field of flow is very effective for the understanding of the physical significance of complex flow and for the practical design of fluid machinery. Under the currently circumstance, stereoscopic particle image velocimetry (SPIV) is one of the promising techniques for the experimental analysis. Although the development of algorithms and the feasibility studies of SPIV have been realized, the accumulation of techniques for applications leading to the design of practical fluid machineries or devices is not yet sufficient. To establish practical techniques for the experimental analysis of 3D flow in fluid machinery by SPIV, the detailed 3D analysis of flow using a utility model of multiblade fans used in automobile air-conditioning systems has been carried out. The stereo view camera arrangement and laser-light-sheet illumination for the complex shape of the fan and for the 3D flow through it have been investigated, and the visualization of experimental results for the understanding of the flow structure has also been discussed. The results obtained using the practical techniques applied in this experiment provide knowledge useful in the understanding of flow through the fan and in improving it.
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  • Yojiro ISHINO, Norio OHIWA
    2005 Volume 48 Issue 1 Pages 34-40
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    The advanced CT (computerized tomography) reconstruction technique for measuring an instantaneous three-dimensional distribution of chemiluminescence of a turbulent premixed flame is accomplished. In the technique, first, instantaneous two-dimensional images (‘projection’ images) of an objective flame are simultaneously taken from forty horizontal directions with a forty-lens camera. Next four hundred horizontal CT images, which are reconstructed from the ‘projection’ images by MLEM (maximum likelihood expectation maximization) algorithm, are vertically accumulated, resulting in an instantaneous three-dimensional distribution of flame-chemiluminescence. Results for a propane-air fuel-rich-premixed turbulent flame are as follows. The flame front is observed to be a thin wrinkled luminous region of 0.6mm in thickness. The three-dimensional result clearly shows that the cusps observed in horizontal cross-sections correspond to ridges of the three-dimensional flame front. The luminosity is quenched at the ridges by Lewis number effect. Finally, various types of display of three-dimensional distribution are performed to demonstrate the three-dimensionality of data acquisition.
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  • Masatoshi DAIKOKU, Hitoshi FURUDATE, Takao INAMURA
    2005 Volume 48 Issue 1 Pages 41-47
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    A new type of Y-jet airblast atomizer was developed to control mean droplet diameter over a wide range of liquid flow rates. This atomizer employs a fluid amplifier system that controls the liquid delivery to two kinds of injection ports having different inner diameters. In order to clarify the effect of amplifier dimensions on spray characteristics, the relationship between flow rate characteristics and spray characteristics was investigated and flow visualization of the flow inside the fluid amplifier was performed. When the main flow rates were 3.0g/s and 4.0g/s, the flow rate characteristics of the amplifier were improved, and good spray characteristics were obtained.
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  • Fujio INASAKA, Masaki ADACHI, Kohki SHIOZAKI, Izuo AYA, Hideki NARIAI
    2005 Volume 48 Issue 1 Pages 48-55
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    We investigated the water hammer caused by striking of water mass pushed up by a rapidly growing bubble and its scale effects using two cylindrical model containment vessels of 1.0 and 0.428m diameters. We also closely observed the movement of water mass and the growing bubble in the vessels. In these experiments, rapid bubble growth was simulated by injecting high-pressure air into a water pool. It was clarified that the water mass was pushed up without any air penetration until the water level reached a certain elevation. On the basis of all data, experimental correlations for estimating the height and striking velocity of the water mass with coherency were proposed, and the water hammer pressure for exerting large forces on the structures was quantitatively evaluated.
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  • You Hwan SHIN, Kwang Ho KIM, Chang Sik KANG
    2005 Volume 48 Issue 1 Pages 56-64
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    This study presents some measurement results on the unsteady pressure fields around rotor under stable and unstable operating conditions of an axial flow fan. The unsteady static pressure of rotor passage was measured by using high frequency pressure transducers mounted on the casing wall. The measurements on the unsteady total pressure at rotor inlet and outlet were also conducted with specially designed high frequency total pressure probe. Double Phase-Locked Ensemble Averaging Technique was used for analysis of pressure fluctuations around the rotor at rotating stall onset point. From the results, the unsteady pressure fields during stable and unstable operations of the axial fan were investigated and compared with each other. Particularly one period of rotating stall could be divided into two regions, stalled flow and unstalled flow region respectively. Furthermore the former could be also classified into two zones, bubbled and disturbed region by their features. The flow characteristics for each zone were described in detail and the static and total pressure fields were also analyzed in terms of the pressure distribution along pressure side and suction side on the blade tip profile.
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  • Shinji KIMIJIMA, Nobuhide KASAGI
    2005 Volume 48 Issue 1 Pages 65-74
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    A hybrid system based on a micro gas turbine (µGT) and a high-temperature fuel cell, i.e., molten carbonate fuel cell (MCFC) or solid oxide fuel cell (SOFC), is expected to achieve a much higher efficiency than conventional distributed power generation systems. In this study, a cycle analysis method and the performance evaluation of a µGT-MCFC hybrid system, of which the power output is 30kW, are investigated to clarify its feasibility. We developed a general design strategy in which a low fuel input to a combustor and higher MCFC operating temperature result in a high power generation efficiency. A high recuperator temperature effectiveness and a moderate steam-carbon ratio are the requirements for obtaining a high material strength in a turbine. In addition, by employing a combustor for complete oxidation of MCFC effluents without additional fuel input, i.e., a catalytic combustor, the power generation efficiency of a µGT-MCFC is achieved at over 60%(LHV).
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  • Susumu NODA, Hisaya MORI, Yusuke HONGO, Makoto NISHIOKA
    2005 Volume 48 Issue 1 Pages 75-82
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    Nonpremixed flamelet statistics at the flame base of lifted turbulent nonpremixed flames are investigated experimentally using a planar temperature Rayleigh scattering method. A methane/hydrogen mixture is supplied from a tube of 3.2mm I.D. into the surrounding air flow so as to form two lifted turbulent nonpremixed flames having exit velocities of 50m/s (Re=4200) and 80m/s (Re=6700), respectively. Temperature data are related to maximum temperature at several flame positions based on the instantaneous flame base tip as containing information on the reaction region of each nonpremixed flamelet at each position. The statistics in terms of maximum temperature, thermal dissipation rate, scalar dissipation rate, and flame brush are discussed with reference to the modeling of the flame base structure. The scalar dissipation rate has log-normal statistics and the quenching scalar dissipation rate is lower than the critical value predicted using the uniformly strained counter nonpremixed flame. These statistics are compared to those obtained using a model proposed by Müller et al., which combines the flamelet model and the scalar field variable to predict lifted turbulent nonpremixed flames. The comparison has shown that the model can qualitatively predict lifted turbulent nonpremixed flames, but modification is required in order to obtain more accurate quantitative prediction taking into account the edge flame structure, the statistics of scalar dissipation rate, and the statistics of flame brush.
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  • Ryuji YAMAKITA, Katsuya MIURA, Yojiro ISHINO, Norio OHIWA
    2005 Volume 48 Issue 1 Pages 83-91
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    Thermal recycling of recycled plastic resin is focused in this investigation. Fine grinding of plastic resin and preparation of high temperature oxidizing atmosphere are indispensable for effective and successful burn-up of plastic resin. Polyethylene terephthalate resin powder is employed and high temperature oxidizing atmosphere is generated downstream an annular burner. Through a circular nozzle set coaxially in the closed bottom end of the annular burner, PET-powder and propane-air mixture are issued vertically upward into the high temperature oxidizing atmosphere. Temperature and O2 concentration fields downstream the annular burner are first examined by varying the circular jet equivalence ratio with the air flow rate kept constant and without PET-powder supply. PET-powder having a mass-median diameter of either 89.7µm or 145µm is then issued into the high temperature region along with propane-air mixture by varying the PET-powder mass flow rate. Appearances of the PET-powder flame are observed using a high-speed CCD video camera and unburnt PET particles are traced during their passages in the high temperature region. Variation of O2 concentration fields due to PET-powder combustion is also measured in the PET flame. According to the results, overall limit conditions for effective burn-up of PET-powder are finally discussed.
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  • Tae Woo LIM, Jun Hyo KIM
    2005 Volume 48 Issue 1 Pages 92-98
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    Experimental investigation of pressure drop for pure refrigerants R134a and R123 and their mixtures as test fluids was carried out for both an adiabatic and a diabatic two-phase flow in a horizontal tube. The measured frictional pressure drop in the adiabatic experiments increased in the S-shaped curve as equilibrium vapor quality was increased. These data were compared to various correlations proposed in the past for the frictional pressure drop. The homogeneous model considerally underpredicted the present data both for pure fluids and their mixtures in the entire mass flux range 150 to 600kg/m2s covered in the measurements, while Friedel correlation was found rather well to correlate the frictional pressure drop data among compared correlations. However a detailed examination showed Friedel correlation underpredicted the present data in the stratified and stratified-wavy flow regions at low vapor quality and overpredicted in the annular flow region at high quality. A new two-phase multiplier was developed from a dimensional analysis of the frictional pressure drop data measured in the adiabatic experiment. This new multiplier was found successfully to correlate the frictional pressure drop measured in the diabatic flow boiling experiments of pure refrigerants and their mixtures almost with a mean deviation of 20%.
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  • Yasuhide TANI, Hideto INAGAKI, Akinori SAITO, Takashi SUZUKI
    2005 Volume 48 Issue 1 Pages 99-105
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    Exhaust emission and fuel consumption of a vehicle engine can be reduced by improving fuel atomization of an injection nozzle. Authors have already reported development of a new type of nozzle called Silicon Plate Nozzle (SPN) in order to improve fuel atomization by adopting micro-machining. This paper discusses combination of two SPNs which resulted in drastic improvement of fuel atomization. By combining two SPNs so that each rectangular aperture crossed with other, the fan-like spray was obtained. As a result, obtained Sauter Mean Diameter (SMD) of the fuel spray was 50µ m or less at fuel pressure of 300kPa. This experimental results were confirmed by numerical analysis.
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  • Kazunori SHIODA, Susumu YAMANAKA, Fukuo MAEDA, Kazunori IWABUCHI, Tosh ...
    2005 Volume 48 Issue 1 Pages 106-113
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    Combustion oscillation stabilization by Helmholtz resonator has been investigated for gas turbine combustor, and mechanism of oscillation control has been discussed in terms of analysis model of Helmholtz oscillation, excited between combustor and fuel injector. Amplitude of oscillation pressure is stabilized corresponding to resonator parameters, such as throat diameter and length, and calculated results on combustion oscillation stabilization are compared with experimental results by atmospheric combustion apparatus. In case Helmholtz resonator equipped to combustor is in resonance to combustor chamber, it is shown that amplitude of oscillation pressure can be minimized. However, effectiveness of the resonator may be lessened with decrease of throat diameter or increase of throat length, while throat diameter and length are both tuning parameters of the resonator. Throat resistance, which is determined by both of throat diameter and length, is actually one of the major parameters in Helmholtz oscillation control. Resonator parameters must be optimized in terms of attenuation characteristics as well as resonance frequency.
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  • Katsuhide OHIRA, Kenji NAKAMICHI, Yuichi KIHARA
    2005 Volume 48 Issue 1 Pages 114-121
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    Slush hydrogen is a two-phase solid-liquid cryogenic fluid consisting of solid hydrogen particles in liquid hydrogen, and various applications are anticipated such as fuel for reusable space shuttles. At a solid mass ratio (solid fraction) of within 50%, piped transport can be conducted in the same manner as for normal fluids. A new method is proposed for measuring the slush hydrogen mass flow rate using a microwave method. Noting the slight fluctuation in the distribution of solid hydrogen particles in slush hydrogen, i.e., slush hydrogen density, waveguide-type densimeters are placed at two locations along the piped flow to measure the density and to detect the density fluctuations. The flow velocity is also calculated from the densimeter distance and the delay time when the cross correlation function of the two density signals is at a maximum. This waveguide-type flowmeter has no moving mechanical parts in the flow stream. This paper reports the development of a new slush hydrogen waveguide-type flowmeter, together with the fabrication of required test apparatus and the confirmation of flowmeter accuracy.
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  • Masakazu SHIRAKAWA, Masashi NAKAMOTO, Shunji HOSAKA
    2005 Volume 48 Issue 1 Pages 122-128
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    This paper treats the development of a dynamic simulation model and its application to the optimization of a start-up process for a combined cycle power plant. Generally, the plant system design is complicated, and the control design is difficult to establish without dynamic simulation. The comparison of the simulation results and the plant data is reported. The obtained results demonstrate that the simulation is reliable to evaluate the plant dynamic phenomenon and available to predict the operational processes. However, not only an analytical method but also the development of a design method is important to determine the optimal operational procedure. In this paper, the dynamic simulation and the nonlinear programming are combined, and it proposes the design method that optimizes the operational parameters.
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  • Shuichi UMEZAWA
    2005 Volume 48 Issue 1 Pages 129-135
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    A new optical torque measurement method is proposed for diagnosis of thermal efficiency of combined cycle power plants. In the case that the plant comprises a steam turbine and a gas turbine, both of which are connected to the same generator, it is difficult to identify which turbine causes deterioration of performance when the plant efficiency is reduced. Therefore, an optical torque sensor has been developed to measure the output of each turbine, which are important data to analyze performance of each machineries in a plant. The sensor measures axial distortion caused by power transmission by use of He-Ne laser beams, small stainless steel reflectors having bar-code patterns, and a technique of signal processing featuring high frequency. It was applied to TOKYO ELECTRIC POWER COMPANY (TEPCO) commercial plants. Following system improvements, it is concluded that error factors can be eliminated and sensor performance can reach a practical use level.
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  • Shijie GUO, Yoshiyuki MARUTA
    2005 Volume 48 Issue 1 Pages 136-143
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    The pressure fluctuations acting on the impeller and the impeller vibration excited by the fluctuations were investigated in a centrifugal pump with several vaned diffusers. Firstly, the pressures both acting on the impeller and in the volute were measured simultaneously. It was demonstrated that both the volute static pressure and the pressure fluctuations on the impeller are uneven circumferentially (not uniform) under off-design operating conditions. At high flow rates, the pressure fluctuations are large in the front of the volute exit, where the static pressure is low. Secondly, the impeller vibration excited by the fluctuations was measured. It was found that resonance can be excited even when the resonance condition of rotor-stator interaction is not satisfied and sidebands occur in frequency spectra because of the circumferential unevenness of the fluctuations. Resonance can also be excited when a natural frequency of the impeller coincides with the frequencies of sidebands. Furthermore, the vibration wave is a traveling wave in the circumferential direction when resonance of a nodal diameter mode is excited, and the resonant frequency may depend on the traveling direction of the wave due to the inertia effect (added mass) of water.
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  • Daisuke NAKAMURA, Harunori NAGATA, Tsuyoshi TOTANI, Isao KUDO
    2005 Volume 48 Issue 1 Pages 144-150
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    The authors have proposed the use of a hydrogen concentration probe as a new simple method of evaluating hydrogen concentration. We propose a method of evaluating the rate of change of catalytic heat release in order to evaluate hydrogen concentration history for the condition under which the boundary layer is likely to be immature. By using a shock tube, the rate of increase of heat budget of platinum wire was investigated experimentally. Experimental results indicate that the rate of increase of difference due to catalytic heat release is the maximum value when the hydrogen concentration is 30%, which agrees well with a previous result. As a result, this method can be used to evaluate the rate of increase of difference due to catalytic heat release. It is clear that the rate of change due to catalytic heat release is strongly correlated with the rate of change of hydrogen concentration.
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  • Seiichi TAKEUCHI, Noriyoshi DOUHARA
    2005 Volume 48 Issue 1 Pages 151-155
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    The present study was conducted in order to clarify the effects of airflow turbulence on the spray combustion. Methanol was atomized with the two-fluid-type nozzle in order to generate the spray flame, and the turbulence characteristic of the flame was varied by inserting a mesh near the tip of the nozzle. Droplets in the spray flame were measured using a PDPA system in a reaction field, and changes in the turbulence characteristic were measured using a hot-wire anemometer in a no-reaction field in order to clarify the effects of turbulence on combustion behavior. Inserting a finer mesh promoted droplet evaporation and enhanced the dispersion characteristic. Regarding changes in the turbulence characteristic, the integral time scale increased and the energy spectrum decreased as the inserted mesh became finer. Based on the obtained results, we determined that a finer mesh causes vortexes to be more persistent and enhances the dispersion characteristic of the droplets.
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  • Takao MAEDA, Hideyuki KAWABUCHI
    2005 Volume 48 Issue 1 Pages 156-163
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    This paper shows the pressure distribution at the 50%radial section of a rotor blade of 10m-diameter wind turbine in yawed operation. The pressure sensors were mounted on the blade, and local inflow angle and local dynamic pressure were measured with the use of five hole Pitot tubes at 1 chord length upwind of the blade leading edge. It was found that the normal force coefficient in yawed condition decreases compared to that for non-yawed condition. Even if local angle of attack and the relative inflow velocity are the same, pressure distribution shows differences due to the local slip angle. The tufts flow-visualization on the rotating blade was carried out by setting a video camera on the rotating system. Separation in the region of middle chord to trailing edge on suction surface is thought to be the main reason of the reduction of normal force coefficients.
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  • Masaya NAKAHARA, Hiroyuki KIDO, Kenshiro NAKASHIMA
    2005 Volume 48 Issue 1 Pages 164-171
    Published: 2005
    Released: August 15, 2005
    JOURNALS FREE ACCESS
    The local flame properties of turbulent propagating flames with respect to the ratio of the turbulence intensity to the laminar burning velocity u’/SL0 in the flamelet regime have been investigated experimentally for methane, propane and hydrogen mixtures having nearly the same laminar burning velocity with different equivalence ratios. u’/SL0 is varied as 1.4 and 2.3. A 2D laser tomography technique is used to obtain the flame configuration and movement in a constant-volume vessel and then the local flame displacement velocity SF is quantitatively measured as a key parameter of turbulent combustion. As a result, the mean value of SF shows to be affected by u’/SL0, which indicates a relation between the characteristic chemical reaction time and the characteristic flow time, to some extent, especially for leaner and richer mixtures. SF is also discussed by the concept of preferential diffusion and Markstein number which can affect the local burning velocity characteristics.
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