日本機械学会論文集 B編
Online ISSN : 1884-8346
Print ISSN : 0387-5016
67 巻, 662 号
選択された号の論文の33件中1~33を表示しています
  • 森西 晃嗣
    2001 年 67 巻 662 号 p. 2389-2396
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Two gridless type methods for evaluating the second derivatives are presented. In the first method, the second derivatives are evaluated with evaluating the first derivatives of the derivatives. On the other hand, Laplace operators as well as the second derivatives are directly evaluated in the second method. The methods can be applied to numerical solutions of any partial differential equations on Cartesian grids, structured grids, and unstructured grids. In this paper, the methods are applied to Poisson equations. Numerical solutions are obtained and compared with analytic solutions on several levels of point density so that grid convergence studies of L2 errors are carried out. The second order accuracy is confirmed for both the gridless methods, while the directly evaluating method of the Laplace operator is more effective than the successive evaluating method.
  • 加村 圭市郎, 戸田 和之, 山本 誠
    2001 年 67 巻 662 号 p. 2397-2404
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Sand erosion is a phenomenon in which solid particles impinging to a wall cause a damage to a part of the wall. It occurs on the walls of a lot of machines such as airplane, ship and pump. It is well known that performance and lifetime of the equipment are deteriorated due to sand erosion. In the present study, computations of sand erosion phenomena around a 2 dimensional airfoil are carried out to clarify the change of geometry and flowfield with proceeding the erosion. Surface roughness is taken into account using a wall function, and the influence of surface roughness is investigated numerically. Moreover, the effects of different wall materials are studied.
  • 鈴木 正己, 荒川 忠一
    2001 年 67 巻 662 号 p. 2405-2411
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Wells turbine has the cascade whose stagger angle is 90 degrees, namely the blades are perpendicular to the axial velocity. The blades can rotate in the same direction irrespective of reciprocating airflow. The good performance is required from 0 to 90 degrees of attack angle because the turbine is operated in the oscillating airflow produced with wave energy. Furthermore, very interesting and complex flows are experimentally observed by the oil film method with a water tunnel in the large attack angle where the performance such as self-starting is strongly influenced. In order to understand these phenomena in detail, CFD code is developed by authors with SIMPLE algorithm and domain decomposition. This paper tries to analyze the mechanism of these three dimensional flows around the turbine with the numerical analysis, focusing on the off design condition.
  • 水沼 博, 杉山 恒, 熊谷 武
    2001 年 67 巻 662 号 p. 2412-2419
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Vortex stretching flow was investigated using an orifice-type and a rotating-nozzle device. The surfactant solutions showed remarkable vortex inhibition effect. It was indicated that the high resistance of the stretching flow for twisting shear produced the vortex inhibition. In the rotating-nozzle device, a core region of twisting shear appeared along the centerline. The method of viscometry was derived for the twisting shear in the nozzle core. In turbulent flow, the high resistance of the stretching flow for the twisting shear would have influence on energy cascade from large scale to small scale turbulence and have a close relationship to the suppression of transverse turbulence.
  • 古川 明徳, 石坂 公一, 渡邉 聡
    2001 年 67 巻 662 号 p. 2420-2424
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    An attachment of inducer is a powerful method to improve the cavitation performance of a turbo-pump. Cavitation surge phenomena, occurring under the severe suction pressure at partial flow rate, is focused in the present paper. Flow measurements were carried out at the inlet and outlet sections of a flat-plate helical inducer with the solidity of 2.0 and tip blade angle of 11 degrees by using a total-head yawmeter with a phase locked sampling method to the cavitation oscillation. Change of the flow distributions during the oscillation is clarified with observed cavitation behaviors. After the results are compared with those at conditions just before and after the oscillation, the fluctuating blade forces are estimated from the blade to blade distributions of casing wall pressures measured at these conditions.
  • 古川 明徳, 石坂 公一, 渡邉 聡
    2001 年 67 巻 662 号 p. 2425-2430
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Cavitation tests have been carried out for helical inducer with various blade lengths. Effects of inducer blade lengths on head characteristics and cavitation induced oscillation phenomena are described in the present paper. The oscillation occurring in the case of inducers with lower solidity less than 1.0 differs from that with the solidity of 2.0. Change of the flow distributions during the oscillation is measured from by using a single hole yawmeter with the phase locked sampling method to the oscillation. By compared with the results for higher solidity inducer, the behaviors of cavitation induced oscillation are clarified.
  • 杉井 康彦, 中野 厚史, 西尾 茂, 南山 求
    2001 年 67 巻 662 号 p. 2431-2436
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Particle image velocimetry (PIV) has been the quantitative measurement method of instantaneous velocity fields in experimental fluid mechanics. The authors have proposed the adaptive PIV technique using the gradient-based sub-pixel analysis, in which a pixel unit displacement is obtained using the iterative cross-correlation method while a sub-pixel displacement is calculated by the use of the so-called spatio-temporal derivative method. The present method can achieve high accuracy of measurement and high spatial resolution compatibly. In this paper, the proposed method is applied to visualized images of the arteriole in the rat mesentery using the intravital-microscope and the high-speed digital video system. Time-series of the volocity profiles of the arteriole is obtained. Averaged velocity profiles show the blood flow volume is constant at five vessel cross-sections. The arteriole velocity profiles are blunt at the center region of the vessel cross-section and sharp profiles at near wall region, this suggests the shear stress on the vessel wall is higher than expected one. The results show that the proposed method is very useful to measure the blood flow velocity profiles with highly accuracy of measurement, and high temporal and spatial resolution.
  • 川口 達也, 前田 昌信
    2001 年 67 巻 662 号 p. 2437-2442
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    The paper describes the concentration measurement technique for unsteady flow fields by employing the laser absorption in conjunction with a Computer Tomography technique. The technique can measure the three dimensional concentration distribution and provide an information about the entire structure of the fluid, while conventional LIF imaging techniques give a cross section of the field. The method will contribute to the investigation of the transport phenomena and the dynamic interaction among them in combination with other measurement technique for experimental study.
  • 森岡 禎, 齋藤 学, 本阿弥 真治
    2001 年 67 巻 662 号 p. 2443-2448
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    The general goal of this study is to construct the closed loop control system of the reattachment process in a backward facing step flow by a row of the vortex generator jets. A row of injection holes which covers full span is located upstream of the step. Optimal conditions are studied experimentally by systematic variation of two parameters, injection hole pitch and jet velocity ratio. A micro wall flow sensor was used for measurement of forward flow fraction. It is found that the reattachment line is almost parallel to the spanwise direction in the range of the pitch of 10 d to 20 d, although the discrete disturbance by jet injection is provided at the step. The velocity ratio is one of the most effective manipulated variables in the control system of the reattachment process.
  • 伊東 明俊, 樋田 英紀, 早乙女 康典
    2001 年 67 巻 662 号 p. 2449-2454
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    This study investigates how to control the stream of bioconvection. Bioconvection is a phenomenon that is autonomously generated by the high density culture media of microorganisms. In this study, "negative galvano-taxis" of microorganisms are used to control the downward stream of bioconvection. For that purpose, an array of 15 negative electrodes is installed at the top of the observation pool. The basic effects of electrical field on bioconvection was investigated. The result shows that the status of bioconvection classifies three different regions by the strength of electrical field. The lower area is "natural convection region" in which bioconvection is not changed by electrical field. Middle area is "convection control region" in which down flow stream near the negative electrode is brought to just under the negative electrode. The higher area is "forced convection region" in which the down flow stream that is generated under negative electrode dominates whole of convection stream and original bioconvection stream is disappeared. This controlled downward flow has a possibility as a driving source for micro fluid machines.
  • 岡田 吉弘, 酒井 康彦, 小林 紀久
    2001 年 67 巻 662 号 p. 2455-2461
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    The axial velocity, radial velocity and concentration of a high Schmidt number matter were measured simultaneously in an axisymmetric turbulent jet. The diffusing fluid is a water solution of the commercial dye (Schmidt number Sc≃3800), and an issuing Reynolds number is 6400. A combined probe of a fiber optic concentration sensor and a X type hot film was used to measure the axial velocity, radial velocity and concentration simultaneously. The normalized axial and radial mass flux show similar profiles. Eddy diffusivities are the function of only r/LU (the radial distance normalized by the half width of axial mean velocity). The effect of the axial concentration gradient is dominant for the axial mass flux near the jet centerline, and also the effect of the radial concentration gradient becomes significant far from the jet centerline.
  • 杉浦 崇之, 中川 勝文
    2001 年 67 巻 662 号 p. 2462-2469
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    The nozzle used in total-flow system has an important role to convert the thermal energy of low temperature heat to the kinetic energy. As the flow in the nozzle is suspending small droplets, there exist velocity and temperature relaxation between gas and liquid phase. The shock waves caused by the velocity and the temperature relaxation in the nozzle are researched theoretically in this paper. It is shown that shock waves appear in the divergent section of the nozzle where the frozen Mach number is less than unity and the equilibrium Mach number is greater than unity. Those shock waves in subsonic mist flow behave as dispersed shock waves when velocity relaxation time is small, and pseudo-like-shock waves for large relaxation time.
  • 田中 靖幸, 菊地 勝浩, 飯田 雅宣, 高橋 亮一
    2001 年 67 巻 662 号 p. 2470-2477
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    When a train enters or leaves a tunnel at high speed, several pressure waves are radiated from the portals, of which we are especially concerned with two pressure waves in this paper. One is that radiated from the entrance when the train enters the tunnel, and the other radiated from the exit when the train leaves. Here, we call the former a tunnel entry wave, and the latter a tunnel exit wave. This paper reports the results of a field measurement performed at a Shinkansen tunnel to investigate the fundamental characteristics of tunnel entry/exit wave. The results of the field measurement show a good agreement with those of simple acoustic analysis regarding velocity dependency and distance attenuation. However, the agreement regarding directivity is not so good although qualitative tendency is consistent. The tunnel entry/exit wave is weaker when the train has a smaller crosssection and a slender nose shape. The peak pressure magnitude of the tunnel entry/exit wave is proportional to the pressure gradient of pressure wave in the tunnel and low frequency components below 10Hz are dominant, which is a similar tendency to that of the micro-pressure wave.
  • 高石 武久, 善田 康雄, 佐川 明朗, 長倉 清
    2001 年 67 巻 662 号 p. 2478-2486
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    In order to simulate the flow under high speed trains, a pair of mirror image models are placed symmetrically, with the symmetric plane assumed to be the moving ground. At the bogie section whose aeproacoustic noise is larger than that from any other sources at lower parts of the train, the shear flow separated at the leading edge is unstable and disturbance grows finally to touch the bottom of the cavity of the section. The cavity tone at the bogie section is modeled as being generated by the pressure fluctuation caused by the interaction of vortices with the trailing edge of the bogie section. When the Green's function adapted to the shape is introduced accompanying the ground regarded as an infinite plane wall, the result is nearly equal to the formula of sound generated by the mirror image models. Mirror image models are verified to be suitable, only if the shear flow at the open end of the cavity reproduceds the real flow under the train.
  • 織田 剛, 里深 信行, 西田 秀利
    2001 年 67 巻 662 号 p. 2487-2494
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    A numerical analysis method using the level set method has been developed to simulate the interface movement and growth with phase change which accompany a change of density. The multi phase flow and the temperature with the latent heat are solved by the finite volume method on a fixed non staggered Cartesian grid. Particular treatments added to the level set method to calculate the Stefan condition and the remedy added to the temperature equation to avoid the artificial temperature advection beyond the interface are described in detail. Our analysis method is capable of both the solid liquid and liquid gas phase changes. Good agreements of the interface location with other published results and better accuracy in temperature and velocity distributions are obtained, though some errors still exist in the growth rate of the interface in each direction from the effect of the Cartesian gird.
  • 有馬 博史, 門出 政則, 光武 雄一
    2001 年 67 巻 662 号 p. 2495-2502
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    An analytical method has been developed to solve an inverse problem for one-dimensional heat conduction in cylindrical and spherical coordinates by using Laplace transformation. This method successfully derives the inverse solution by which the surface temperature and heat flux can be predicted well for any kind of boundary condition with a constant initial condition. The inverse solution obtained by the temperatures at two different measuring points can predict the surface temperature and heat flux with higher accuracy than that at a single measuring point, although the single measuring point is enough for the cylindrical and spherical coordinates to predict them. The same order of accuracy of estimation has been maintained between cylindrical and spherical coordinate.
  • 藤井 哲, 田代 光男, 真喜志 治
    2001 年 67 巻 662 号 p. 2503-2509
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    This paper deals with an experimental study of free convection condensation of steam air mixture on a vertical tube. The experiment is made using two copper tubes of 6mm and 4mm in outer diameter. The range of concentration of air is 0.1∿0.9. Condensation rate is measured as well as overall heat transfer rate. The convection heat flux is obtained by subtracting the condensation heat flux from the heat flux at the cooling surface. The equations for predicting condensation mass flux, convective heat flux at the liquid vapor interface, and heat flux at the cooling surface are proposed by modifying corresponding equations for a vertical flat surface. The newly proposed equations correlate the respective experimental results within the error of several percents irrespectively of the wettability of the tube surface.
  • 王 華生, 本田 博司, 野津 滋
    2001 年 67 巻 662 号 p. 2510-2517
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    The previously proposed theoretical models of film condentation in helically grooved, horizontal microfin tubes have been modified to describe the characteristics of condensing two-phase flow more accurately. The stratified flow regime and the annular flow regime were considered. For the stratified flow regime, the previously proposed theoretical model was modified to take account of the curvature of vapor-liquid interface due to the surface tension force. For the annular flow regime, a more accurate expression for the interfacial shear stress was incorporated in the previously proposed theoretical model. Generally, the modified theoretical models predicted a lower circumferential average heat transfer coefficient than the previously proposed ones. Comparison of the theoretical predictions of the circumferential average heat transfer coefficient with available experimental data for six tubes and five refrigerants revealed that a good agreement (r.m.s. error of less than 21.1%) was obtained for all cases when the higher of the two theoretical predictions were adopted as the calculated value.
  • 川口 清司, 鈴木 昌彦
    2001 年 67 巻 662 号 p. 2518-2524
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    In recent years, the fan heater utilized in industry and residence has become smaller, lighter, and more silent as the result of improvement. But, there is a problem that the noise is loud due to air pressure loss of heat exchangers. We developed fan heaters, the blades of which are made of ceramic heater, and warmed by Joule heat. We investigated relationship with flow and heat transfer in the casing, and the optimum shape of casing. In result, we found that it was more silent as the result of decreasing pressure loss.
  • 中村 元, 亀本 喬司
    2001 年 67 巻 662 号 p. 2525-2532
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    A vortex element method based on Biot-Savalt law and the core spreading model was extended to analysis for unsteady heat transfer. Discrete heat elements were introduced into the flow field close to a wall surface in addition to nascent vortex elements. In this study, unsteady flow and heat transfer were calculated around a circular cylinder to a uniform flow in the range of Re=200∿1000, and Pr=0.71. From the result of the present calculation, the mechanism of unsteady heat transfer in the separated flow region of the cylinder was clarified.
  • 服部 篤, 岡田 昌志 /, Chaedong KANG
    2001 年 67 巻 662 号 p. 2533-2540
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    A water fine particle suspension with a uniform initial temperature and various initial concentration distributions in a rectangular vessel was heated from a vertical wall and cooled from the opposing vertical wall. The particle made of SiO2 had a narrow size distribution (mean diameter of 2.96μm, standard deviation of 0.023μm). In order to observe phenomena of the natural convection, the temperature distribution, local particle concentration of the suspension and position of first interface were measured under various temperature differences between the opposing vertical walls. To make the influence of initial particle concentration on the phenomena clear, natural convection of suspension with three patterns of concentration, i.e. a naturally or artificially formed gradient, or non-gradient, was investigated. The pattern of formation of layers was classified by Grashof number. Moreover, to make the influence of initial depth of suspension clear, the suspensions with three initial depths, 50, 100 or 160mm, were examined.
  • 能登 勝久, 松下 陽一, 中島 健
    2001 年 67 巻 662 号 p. 2541-2549
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    A positively buoyant wake from a circular cylinder at the Reynolds number 800∿940 is measured, discussed and found as follows : By heating an isothermal wake, turbulent energy and turbulent vorticity in the isothermal turbulent wake are conserved in the buoyant wake, and this buoyant wake certainly becomes a double structure combined non linearly with two kinds of large-scaled coherent motions, i.e. one is the vortex street motion and the other the plume swaying motion with extremely different frequencies each other. That is, the buoyant wake is a turbulent flow with a triple structure of free turbulence, vortex motion and swaying motion. Structural instability with abrupt change occurs certainly due to unbalance between two kinds of large scaled motions.
  • 呉田 昌俊, 秋本 肇
    2001 年 67 巻 662 号 p. 2550-2557
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    The purpose of this study is to propose the critical heat flux (CHF) correlation for narrow oneside heated rectangular channels. CHF of subcooled flow boiling of water in narrow rectangular channels under the atmospheric pressure was measured parametrically. Experimental test channels were rectangular channels heated from one side with channel gap of 0.2-3.0mm, channel of 7-22mm, and heated length of 50-100mm. CHF correlation for one-side heated rectangular channels was shown. Next, applicability of the correlation to the both-side heated rectangular channel, the half-circumferentially heated tube, and full-circumferentially heated tubes was examined. New CHF correlation for one-and both-side heated rectangular channels, and half-and full-circumferentially heated round tubes was proposed using critical quality, non-dimensional CHF parameter and heated perimeter ratio. Calculation error of the correlation is ±45% (Maximum 10 times better than the existing CHF evaluation equations which were proposed for the full-circumferentially heated tubes).
  • 小関 多賀美, 竹田 晴信, 飯嶋 和明, 村井 正光, 松藤 久良
    2001 年 67 巻 662 号 p. 2558-2566
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    It is investigated whether the application of the heat storage system with metal hydride (MH) is available for air conditioning of buildings or not. The trial system is composed of two heat storage vessels which is a "shell and tube type" heat exchanger with heat transfer fins and is filled with MH, and a compressor equipped for hydrogen transfer. The metal hydride generates heat at absorption process and absorbs heat at desorption process. The system proposed in this paper is simple because the vessel has two functions of heat source and heat storage, and suitable for environment because of no chlorofluorocarbon (CFC). In this paper, the performance of the heat storage vessel is evaluated experimentally by heat storage capacity, which is determined with heat quantity of cold water obtained by the transfer of hydrogen. As a result, cold water at 7°C is supplied for about 6 hours, and the capacity per unit vessel volume is 344MJ/m3 that is sufficiently high compared with the conventional system using water and/or ice.
  • 趙 黛青, 山下 博史
    2001 年 67 巻 662 号 p. 2567-2573
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    In order to clarify the rapid flame propagation mechanism along a vortex axis (the vortex bursting phenomenon), the steady state propagation characteristics of premixed flame in a vortex tube have been examined in detail by the numerical calculation. In this calculation, the flame is fixed in the computational domain by adding an axial flow to the unburnt premixed gas. The obtained results show quantitatively for various flow conditions that, with increasing the maximum tangential velocity, the flame propagation speed increases proportionally, and the flame diameter decreases and approaches to a constant value, and the results are independent of the kind of the vortex. Moreover, the results show that the variation of the pressure along the vortex axis occurs between the inflow part and the flame front and the pressure in the burnt region is almost uniform, and that the propagation speed corresponds to this pressure difference and it is estimated by the Bernoulli's equation.
  • 毛笠 明志
    2001 年 67 巻 662 号 p. 2574-2581
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Pulsed combustion, which applies spontaneous oscillating combustion, is well known and is utilized practically in liquid heating while taking advantage of its high heat transfer rate and low NOx emission. However, due to its high acoustic noise, the application is limited. We began this research with the idea that if oscillation was externally applied to combustion, advantages similar to those might be realized while controlling the noise level. Ruiz et al. and few other authors reported a decrease in NOx emission when air ratio was changed cyclically and the reason for which was attributed to the occurrence of periodical lean-rich combustion. The purpose of this study is to clarify whether combustion with oscillation driven externally can effectively reduce NOx emission, or whether its effectiveness may be limited to only exceptional conditions. Experiments were carried out in a high-temperature furnace, so that lower oscillation frequency could be realized. In addition, the oscillator was rebuilt so that conditions for fuel and air could be individually controlled.
  • 石野 洋二郎, 山口 譽起, 大岩 紀生
    2001 年 67 巻 662 号 p. 2582-2589
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Acoustic characteristics of a two dimensional valveless pulse combustion systems having various geometrical constructions are first measured and numerically analyzed under the cold and stagnant conditions, and effects of each acoustic element on the overall resonant properties of the pulse combustion systems are clearly estimated and explained. Comparison of the acoustic resonant behavior numerically analyzed with that experimentally measured yields a suitable set of the acoustic parameters for each system construction, such as the damping factor and reflection coefficient. Frequency characteristics of the resonant pressure fluctuation in the combustion chamber are then numerically estimated under a typical pulse combustion condition, by introducing not only the acoustic parameters obtained but also the longitudinal temperature profile measured. It is found that the resonant pressure exhibits a sinusoidal character and retards in phase by about 35 degree after the original pressure oscillation applied, being in good agreement with those measured in the proposed pulse combustor. It is also confirmed that, by applying it to another type of the pulse combustor, the proposed numerical method can clearly predict the variation in the profile of pressure fluctuation with the tailpipe length.
  • 坂下 直己, 天谷 賢児, 新井 雅隆
    2001 年 67 巻 662 号 p. 2590-2595
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Fuel droplet and vapor distributions in a spray flame formed in the hot air stream were measured by an exciplex fluorescence method. Kerosene was used as a test fuel. Kerosene was miscible with a small quantity of exciplex-forming dopants, TMPD (N, N, N', N'-tetramethyl-1, 4-phenylene diamine) and naphthalene. A Nd : YAG laser (355nm) was used for excitation of the fuel. The fuel spray was injected from a swirl atomizer into an air stream. Air temperature was changed from room temperature to 1000k which was higher than the self-ignition temperature of a kerosene spray. Distributions of the fuel droplets and vapor were strongly affected by the air temperature. Furthermore it was confirmed that the fuel vapor was transported into recirculating flow area formed on the flame holder.
  • 佐藤 博之, 天谷 賢児, 新井 雅隆
    2001 年 67 巻 662 号 p. 2596-2603
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Quantitative investigation of the gravity effect was performed for acetone and kerosene pool fires. A centrifuge was used to examine the gravity effect. Small-scale pool fires were observed under various high gravity fields. Regions of stable flame, puffing flame and irregular oscillatory flame were mapped with the gravity level and pool diameter. Flame height decreased and oscillatory frequency increased with an increase in the gravity level. Behavior of the flame height was agreed quantitatively with the scaling prediction presented by Orloff and Heskestad. Puffing phenomena observed under various gravity fields were summarized with the Strouhal number and Froude number. As the result, we could obtain an empirical equation of St=0.517Fr-0.502. From this equation, puffing frequency could be estimated for a flame of various pool diameter varying from 0.01 to 50 meters.
  • 高 〓男, 樅山 智裕, 新井 雅隆
    2001 年 67 巻 662 号 p. 2604-2610
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Diesel spray impinged normally on a flat wall was investigated. Spray tip penetration and spray volumes of before and after impingement were measured on high speed photographs of the sprays which were injected by a single shot injection system into a high pressure chamber of cold state. The effects of the spray tip penetration, spray volume, entrainment mass and air-fuel ratio were discussed on the sprays of before and after impingement. The volume of the post-impingement spray was calculated using axi-symmetrical model. It was greatly affected by the distance between the injection nozzle and the wall. When the impingement distance was shorter than the break-up length of the original spray, the entrainment mass as well as the volume of post-impingement spray was the larger than that of the original spray at the same inspection time. To calculate the average spray concentration of after impingement spray, the fuel film stuck on the wall was measured. The average air-fuel ratio of the impingement spray increased faster than the free spray because the spray concentration in a space decreased by the fuel stuck on the wall.
  • 金野 満, 梶谷 修一, 陳 之立, 渡部 泰幸
    2001 年 67 巻 662 号 p. 2611-2617
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    The Combustion characteristics of a direct injection C.I. engine fueled with dimethyl ether (DME) were investigated. The in cylinder observation of combustion process was conducted using high speed video camera. The concentration change of principal intermediate combustion products was traced by gas sampling. As the results, DME combustion was found to be non luminous because polycondensation reaction over C2 would not proceed. It was also found that ignition occurred in the down stream of the spray, where DME was perfectly gasified. DME evaporated immediately after injection, and in the evaporating zone low temperature oxidation reaction actively took place.
  • 光原 好人, / 中西 康文, 吉原 福全, 西脇 一宇, 平岡 正勝, Kazuie NISHIWAKI
    2001 年 67 巻 662 号 p. 2618-2624
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    A new thermal recycling system of waste plastics has been developed, in which plastic waste is melted and mixed with heavy oil A at temperatures around 200°C, producing the fuel for diesel engine generator systems. In experiments, polyethylene (PE), polypropylene (PP), and polystyrene (PS), having weight-average molecular weights (Mw) between 4000 to 300000, were used in the production of new fuels at mixing ratios of plastic to heavy oil A of between 5% and 40% by mass ratio. Physical property of the new polymer fuels was investigated. The polymer fuels produced by mixing ratios of 5% PE(Mw=60000), 25% PP(Mw=12000), 5% PP(Mw=120000) were tested in a diesel engine and the results showed that the performance exhibit by the new fuels was almost the same as that of heavy oil A.
  • 古谷 正広, 太田 安彦, 北口 佳範, 大崎 守, 村井 美樹, 磯貝 鉄也
    2001 年 67 巻 662 号 p. 2625-2631
    発行日: 2001/10/25
    公開日: 2008/03/28
    ジャーナル フリー
    Compression ignition of a stoichiometric iso octane/oxygen/argon mixture was observed using a shock tube and a rapid compression machine. Reducing the compression temperature, the activation energy for the shock compression ignition fell suddenly at the critical temperature the ignition delay exceeded around 1 ms. This peculiarity could be seen in the shock compression stoichiometric methane ignition with which mixture absolutely no cool flame low-temperature reactions accompanied. Shock wave diagrams indicated that the ignition was originated not at the end of the tube but to the inside of the tube. It resulted in the smaller activation energies in the lower temperature regions. This phenomenon was not due to the difference of chemical reaction mechanisms. IIigh-speed schlieren observations using another shock tube with visualization windows have allowed us to confirm the peculiarity that the earliest ignition sites were located apart from the tube end and the ignition initiation structure would change depending on the compression temperature.
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