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野村, 友和 ; 高橋, 易資 ; 武田, 親士 ; 石間, 経章 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Characteristics of the flow inside an engine cylinder model have been evaluated by a particle image velocimetry (PIV) and a laser Doppler anemometer (LDA). Verifications of the results by Partial
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Cells in Cartesian coordinate method numerical simulation have been also made by the experiment results. The model engine head that has two intake valves and transparent cylinder are used in the steady state flow condition. The tests are conducted by single- and dual- valve open condition with 8mm valve lift in-1470 Pa suction gauge pressure. The comparisons between the PIV and the LDA experiments show almost the same tendencies for mean velocities and turbulence intensities in the whole experimental regien qualitatively and also quantitatively. The differences in the valve open condition are clearly observed in the integral length and time scales that are estimated from the PIV and LDA data respectively. It is shown that the PIV results are useful for verification of numerical results, which agree reasonably with those of experiments.
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野村, 友和 ; 高橋, 易資 ; 石間, 経章 ; 小保方, 富夫
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application/pdf<br />Journal Article<br />Boundary layer flow over a multi-holed plate is analyzed in this paper. Two perforated plates which have different diameter of holes and a flat plate are tested in the rectangular duct. The
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diameters of holes are 20mm or 40mm in staggered arrangement and the all plates are 10mm in thickness. These studies are carried out by means of two-dimensional LDA (laser Doppler anemometer) and numerical simulation with Partial Cell method. The mean flow velocity and the relative turbulence intensity are 4.5m/s and 2% respectively in both the experiment and the calculation. Comparisons of flows over the three plates are made for the mean velocity, turbulence intensity and Reynolds stress. In addition, the difference in turbulence flow structure depending on the diameter of holes has been discussed by experimental results.
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細谷, 肇 ; 小保方, 富夫
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application/pdf<br />Journal Article<br />There have been many experiments to characterize Diesel fuel spray under steady-state conditions. However, the appropriate number of holes and the hole position on the sac to be used in the
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experiment are not clear. To address this subject, we investigate Diesel type spray flows using a laser Doppler anemometer (LDA) and a phase Doppler anemometer (PDA). Spray flow characteristics such as mean and fluctuating two-component velocities, two-dimensional distribution of particle diameter and the variation of three parameters at the log-hyperbolic fitting for particle size distribution are given from measured data. Spray jets from four varieties of Diesel nozzle are compared with each other to clarity the differences in spray characteristics between them. The results show that the spray from the single-hole nozzle on top of the sac is distinct from the others.
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小保方, 富夫 ; 橋本, 徹 ; 五十木, 慎一 ; 柄沢, 隆夫 ; 志賀, 聖一 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />The swirl and axial components of gas velocity in the disk-type combustion cha
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mber of a firing engine were measured by an LDA. The engine was operated under the conditions of a speed of 1500rpm, η_υ=0.5, φ=1.4 and ignition timing of 30°BTDC. The gas velocities at 9 points on a diameter at midheight of the combustion chamber were analyzed by the cycle-resolved method. The bulk (mean) velocity was determined by the frequency discrimination method with the cut-off frequency of 667Hz. The flame propagation pattern was detected by ionization probes set at 17 points on the piston. It has been observed that, in the case of fired operation, the turbulence intensity is higher, the integral length and micro length scales are longer and the swirl flow is weaker and is eccentrically shifted compared with the case of motored operation. These results show that it should be noted that there are remarkable differences in the gas flow between motored operation and fired opeation.
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細谷, 肇 ; 小保方, 富夫
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application/pdf<br />Journal Article<br />Diesel fuel spray from a single-hole-type injection nozzle is investigated under steady and atmospheric conditions in order to understand the unsteady Diesel spray. Axial and radial
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velocity components of the spray at two constant injection pressures of 9.8MPa and 4.9MPa are measured by laser Doppler anemometer (LDA), and turbulence characteristics of the spray flow velocities are analyzed. Distributions of mean velocity and turbulence characteristics in the spray flow are compared with gas jets and other spray flows. It is found that the injected spray is accelerated in the region close to the nozzle exit, and this phenomenon may be estimated as a kind of cavitation caused by expansion of dissolved gas in the fuel. The decrease in centerline velocity along the nozzle axis is very small and the air entrainment factor is also shown to take a smaller value than in previous experiments.
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小保方, 富夫 ; Bopp, Stefan ; Tropea, Cam
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application/pdf<br />Journal Article<br />A simple adapter for a two-dimensional, backscatter, fiber-optic laser Droppler anemometer probe consisting of two glass plates has been developed to measure the spatial
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correlation of velocity fluctuations. A conventional two-color, four-beam LDA probe has been modified by reversing the placement of two of the fibers so that both the green and the blue control volumes measure the same velocity component. An adapter for beam separation is ten mounted behind the front lens to separate the two control volumes. In the present work, the measuring point separation was varied up to 3 mm in the lateral and vertical directions. By using only one glass plate 10 mm thick, it was also possible to achieve in-line (Axial) displacements of the control volumes of up to 3.5 mm. spatial correlations were performed in an intermittent jet flow in which the convective flow velocity could be deduced from the offset of the cross-correlation function.
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藤沢, 延行 ; 白井, 紘行
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application/pdf<br />Journal Article<br />The sructure of turbulence in a wall jet along a plane surface is investigated by measuring the balance of turbulence energy. With the aid of a hot-wire anemometer system, convection velocities of
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small-scale turbulent motion are measured as well as other time-averaged flow properties and turbulence characteristics. It is found that the convection velocity of small-scale turbulence deviates significantly from the mean flow velocity, that is, Taylor's hypothesis is not valid for the present wall jet, and the present results on turbulence energy balance agree much better with theoretical predictions by the turbulence model than do those based on Taylor's hypothesis.
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藤沢, 延行 ; 白井, 紘行
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application/pdf<br />Journal Article<br />Stability analysis for the occurrence of Taylor-Gortler vortices in turbulent wall jets along concave surfaces is studied by comparative experiment. The eddy viscosity expression in the
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perturbation equations are determined from a modified version of a tw
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| 9.
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藤沢, 延行
概要:
application/pdf<br />Journal Article<br />2方程式乱流モデルを用いて, 平面壁, 凹面壁, 凸面壁に沿う二次元乱流壁面噴流の平均流および乱流特性を予測する方法を示し, それらの特性に対する曲率の影響
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を検討した. 曲率b/R(ただし, b:半値幅, R:曲率半径)が-0.1～0.1の範囲において, 予測結果は実験と一致する. 乱れエネルギバランスの対流・生成・散逸を実験と対比し, 曲面壁面噴流に対するモデルの適用限界について考察している.
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