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| 1.
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森田, 真一 ; 渡辺, 直樹 ; 古畑, 朋彦 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Six-stroke diesel engine proposed here has six processes in one cycle, i.e. intake, 1st compression, 1st combustion, 2nd compression, 2nd combustion and exhaust. By the direct EGR in the 2nd
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combustion process, NO emission could be expected to decrease. However, much Soot was exhausted by a weak mixing in the 2nd combustion process. A high pressure injection with a common rail was introduced into the engine to improve the mixing in the second combustion process. As a result, more NO was exhausted while Soot was decreased due to better mixing. In this study, to decrease NO and Soot simultaneously, two stage fuel injection was applied to the 1st combustion. When the main injection timing for the 1st combustion process was extremely delayed, NO and Soot were decreased. It was considered that NO reduction was due to the 1st combustion of low temperature and EGR effect in the 2nd combustion. Also, Soot reduction was due to a relatively long ignition delay for the 2nd combustion
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| 2.
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倉持, 大輔 ; 川口, 知宏 ; 古畑, 朋彦 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Ignition and combustion characteristics of diesel spray impinged on an extrude
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d wall, which was a top of cylindrical column, were experimentally investigated. Appearance positions of OH and C_2 radical luminosities and luminous flame kernel were stereoscopically observed using a two-way fiber optical system. The extruded column was fixed in a high temperature and high pressure combustion chamber. A diesel spray was impinged vertically to the extruded wall. Effects of cylindrical column diameter (D=5,10,15mm, ∞(flat wall)) on ignition and combustion characteristics were investigated. As the result, appearance position of OH luminosity was observed near the spray tip except for D=∞ (flat wall). The maximum volume of luminous flame impinged on the extruded wall was strongly influenced by the diameter of the column. In a condition of low-ambient temperature, the maximum volume of blue flame on the extruded column of 10 mm diameter was larger than those on other columns.
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| 3.
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川口, 知宏 ; 長瀧, 翼 ; 天谷, 賢児 ; 古畑, 朋彦 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Ignition and combustion characteristics of diesel spray impinging on a wall were experimentally investigated. Ignition position and appearance position of the luminous flame
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kernel were stereoscopically observed using a two-way fiber optical system. Flat
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| 4.
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林, 義裕 ; 若林, 千裕 ; 古畑, 朋彦 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Mixture formation of diesel spray impinged on an extruded surface, which was a top of cylindrical column, was investigated experimentally. A diesel spray was impinged vertically to the
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extruded surface. The behaviors of impinged spray were observed using a high-speed drum camera. A spray volume was estimated from the photographs. Effect of cylindrical column diameter on spray behavior was investigated. Adhering fuel was measured by a primitive ""wiping by paper and mass measuring"" method under various conditions. Air-fuel ratio in spray was calculated from spray volume and adhering fuel. As the result, the behavior of diesel spray impinged on an extruded column was strongly influenced by the diameter of the extruded column. From the measured results, it is clear that the air-fuel ratio in spray in the extruded column diameter of 45mm was larger than those in the other columns.
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| 5.
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高, 炅男 ; 樅山, 智裕 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />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
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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.
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| 6.
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江原, 拓未 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />In this paper, behaviors of diesel spray injected along a wall were experimentally investigated. In order to clarify the wall effect on spray structure, the geometry of the wall and its
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relative position to the spray axis were varied. Structures of spray injected into a high-pressure atmosphere were recorded by high-speed photographs. Results shows that the asymmetrically large vortexes in the spray were induced by the wall effect, and the spray penetrating along the wall was deviated to the wall surface. This phenomenon is called the Coanda effect in the field of fluid dynamics. The growth orientation of spray was defined by image analysis. Maldistribution ratio of spray area was defined for the quantitative estimation of the spray deviation behavior. The spray deviating conditions such as the geometry of the wall and its relative position to the spray axis were fined.
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| 7.
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隆, 武強 ; 石間, 経章 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />To study the characteristics of velocity in a large-angle conical spray proposed for a premixed combustion type Diesel engine, steady and unsteady conical sprays were analyzed using a laser
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Doppler anemometer (LDA). The injection pressure for the steady conical spray was varied in three steps. For the unsteady conical spray, it was 19.6MPa, where the amount of injected fuel was 25.6mg per cycle, and the injection frequency was 20.7Hz. As a result, the radial distributions of mean axial-velocity for both conical sprays were similar to the Goertler distribution. The Shapes of the turbulence intensity distributions of the conical sprays and a radial gas jet were similar. Their values for the steady conical spray were smaller than that for the radial gas jet, and those for the unsteady conical spray were almost the same as that for the radial gas jet in the whole experimental region. The Reynolds stress distributions for the steady conical spray and the radial gas jet were similar but the maximum value of steady conical spray was half that of the radial gas jet. The unsteady conical spray had a value of the same order of magnitude as that of radial gas jet in the whole experimental region. The rate of decrease of the unsteady conical spray velocity was 3 times that of the steady conical spray velocity but 1/6 that of the radial gas jet velocity. The rate of air entrainment into the unsteady conical spray was half that for the steady conical spray.
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| 8.
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高橋, 秀夫 ; 柳沢, 洋樹 ; 志賀, 聖一 ; 柄沢, 隆夫 ; 中村, 壽雄
概要:
application/pdf<br />Journal Article<br />The atomization behavior of an intermittent fuel spray from a diesel nozzle was clearly observed by means of shadowgraphy using an image-converting camera with the framing rate of 10^5
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f.p.s. and an image-intensified CCD camera with high-speed gating. A rather wide range of valve-opening pressure (5 to 70 MPa) was covered, and simultaneous measurement of the injection pressure inside the nozzle sac was also attempted to clarify the atomization mechanisms at its very early stage of injection. At the beginning of injection, the emergence of a liquid column was observed. Initially, it has almost the same diameter as the nozzle hole and then spreads radially, forming the spray angle in the vicinity of the nozzle exit. The timing of this spray-angle formation becomes earlier with the increase in valve opening pressure, even if the pressure inside the nozzle sac at this moment does not vary. This pressure approximately corresponds to that of the transition region in an atomization regime of a steady jet.
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| 9.
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隆, 武強 ; 大塚, 博行 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />To study the characteristics of flow and particle diameters in large-angle con
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ical spray proposed for Diesel engines of premixed combustion, unsteady conical spray in the air has been analyzed using a phase Doppler anemometer (PDA). In experiments, the frequency of injction is 20.8 Hz and the amount of injection fuel is 10.3 mg in each cycle. Axial and radial distributions of bulk velocity and mean diameter of particles are obtained. As a result, it is found that the profile of mean velocity distribution is close to the Goertler distribution, and the Sauter mean diameter of droplets in the conical spray is as small as 30μm. Correlation between particle diameter and velocity in the entire spray is negative and unusual, but is found to be normal if the spray is divided into parts and studied. We also find that particles with small diameter (20μm) which are emitted at high speed (60m/s) at the earliest stage lose velocity rapidly, merge into bigger particles, and are overtaken by bigger but slower particles which are emitted at the later stage. Particles with large diameter (50μm) gather at the tip of the spray as they travel farther from the nozzle exit.
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| 10.
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高橋, 秀夫 ; 柳沢, 洋樹 ; 志賀, 聖一 ; 柄沢, 隆夫 ; 中村, 壽雄
概要:
application/pdf<br />Journal Article<br />The development of a high-pressure diesel spray in its very early stage is examined through enlarged shadowgraphs in both atmospheric and pressurized conditions. A rather wide range of valve
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opening pressure was covered to clarify the mechanisms of the initial stage of development. At 0.3 ms after the start of injection, there is a region where the tip penetration is insensitive to the ambient pressure and it becomes shorter with the increase in valve opening pressure. This characteristic feature of the spray formation process is related to the eddy motion generated in the spray. The transition of the atomization regime from a wavy jet to a fully developed spray is also shown, and it is suggested that the pressure history in the nozzle sac is closely related to this phenomenon.
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