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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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星野, 浩之 ; 満山, 陽平 ; 齊藤, 正浩 ; 古畑, 朋彦 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />In order to reveal the soot removal mechanism in Electric Diesel Particulate Trap (E-DPT), mechanism of soot trapping and re-burning of soot particles in exhaust gas was investigated using
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one channel electric diesel particulate trap (1 channel E-DPT). The E-DPT is capable to trap soot particles by applying DC electric field between electro-plates. The results showed that soot particles like a whisker grew up from negative electrode side toward positive one. Soot particles trapped on the plates formed many soot bridges in narrow space between electro-plates. Formation of soot particles depended on electric intensity. In the condition of F=200 kV/m, lumps of soot were observed instead of whisker like soot bridges and soot trapping and soot re-burning were balanced. Ignition of the soot lump was occurred at the contact point between the lump and electro-plate, however re-burning of whole the lump was rarely observed. Remained soot drifted to down stream. It is thought that many remained soot particles were discharged from the E-DPT. Incomplete reburning of soot lump caused soot removal efficiency deterioration of E-DPT. In the case of narrow space and high electric intensity (F=600kV/m, L=0.5mm), however, soot bridge re-burning was main phenomenon and soot lump re-burning was controlled
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| 3.
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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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| 4.
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橋本, 健 ; 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. intaka, 1st compression, 1st combustion, 2nd compression, 2nd combustion and exhaust. By the effect of direct EGR in the
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2nd combustion process, NO concentration could be expected to decrease. However, by a weak mixing in the 2nd combustion process, much soot was exhausted and NO concentration was hardly decreased compared with the conventional four-stroke diesel engine. To improve the fuel/air mixing at the 2nd combustion process, high pressure injection with common rail system was applied to the engine. As the result, NO concentration was increased owing to the increase of premixed combustion of 1st combustion process, although soot was reduced. Therefore, the 1st injection timing was extremely advanced to control the 1st combustion process. It changed 1st combustion process into HCCI-like combustion, and NO concentration was greatly decreased. Moreover, soot was reduced with no increase of NO concentration in the 2nd combustion process. As the result, trade-off curve of NO and soot was improved compared with the conventional four-stroke diesel engine. But CO concentration was increased.
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| 5.
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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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| 6.
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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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| 7.
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ARAI, Masataka ; AMAGAI, Kenji ; NAKAJI, Takayuki ; HAYASHI, Shinji
概要:
application/pdf<br />Journal Article<br />Particulate matter (PM) emission exhausted from diesel engine should be reduced to keep the clean air environment. PM emission was considered that it consisted of coarse and
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aggregate particles, and nuclei-mode particles of which diameter was less than 50nm. However the detail characteristics about these particles of the PM were still unknown and they were needed for more physically accurate measurement and more effective reduction of exhaust PM emission. In this study, the size distributions of solid particles in PM emission were reported. PMs in the tail-pipe emission were sampled from three type diesel engines. Sampled PM was chemically treated to separate the solid carbon fraction from other fractions such as soluble organic fraction (SOF). The electron microscopic and optical-manual size measurement procedures were used to determine the size distribution of primary particles those were formed through coagulation process from nuclei-mode particles and consisted in aggregate particles. The centrifugal sedimentation method was applied to measure the Stokes diameter of dry-soot. Aerodynamic diameters of nano and aggregate particles were measured with scanning mobility particle sizer (SMPS). The peak aggregate diameters detected by SMPS were fallen in the same size regime as the Stokes diameter of dry-soot. Both of primary and Stokes diameters of dry-soot decreased with increases of engine speed and excess air ratio. Also, the effects of fuel properties and engine types on primary and aggregate particle diameters were discussed.
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| 8.
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新井, 雅隆 ; 天谷, 賢児 ; 長瀧, 翼 ; 沖田, 秀樹
概要:
application/pdf<br />Journal Article<br />Ignition and combustion characteristics of diesel spray impinging on an inclined wall were experimentally investigated. Ignition position and appearance position of the
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luminous flame kernel were stereoscopically observed using a two-way fiber optical system. Flat impingement wall was fixed in a high temperature, high pressure combustion chamber. Inclined angle of the flat wall was set at 30 degees or right angle against the center axis of the injection spray. Distance from nozzle tip to the impingement point on the wall was set at 50mm. Effect of ambient temperature on ignition position was investigated. As the result, ignition positions were observed near the spray periphery in the both cases of 30 degrees and right angle impingements. However, the luminous flame appeared near the wall surface at downword side of inclined wall because the fuel rich region was formed around the downword side of spray impingement point.
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| 9.
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林田, 守正 ; 成澤, 和幸 ; 倉嶌, 大輔 ; 紙屋, 雄史
概要:
application/pdf<br />Journal Article<br />The driving conditions of suburban transit buses were investigated with a chartered bus. Based on this data, a series hybrid system was designed for transit buses from the viewpoint of the
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acceleration performance and the energy saving. In order to measure the electric energy flow on board, the dynamometer bench tests and the static simulated experiments were carried out with storage batteries and ultra capacitors. It was clarified that the charge discharge loss in the storage devices can be estimated by the calculation using the internal resistance and current. And, the energy efficiency of the series hybrid system was evaluated in compared with conventional engine-powered buses for a trial.
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| 10.
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河野, 雅文 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Effect of cetane number on ignition delay and ignition location of disesel spray was experimentally investigated. Five kinds of fuels, which had different cetane numbers of light fraction and
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heavy fraction of fuel, were used. As a result, the ignition delay was not so affected by the change of cetane number, however, the ignition location was strongly affected by a cetane number. When the light fraction cetane number was low, the ignition was not observed near the nozzle. And when the heavy fraction cetane number was high, the ignition was observed at the position far from the nozzle. Ignition position had an effect on flame development. When the ignition occurred near the nozzle, flame development rate was slow. When the ignition occurred at the position far from the nozzle, flame development rate was fast. In case of the ignition position was far from the nozzle, effect of the cetane number on flame development was remarkable.
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| 11.
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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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| 12.
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岩崎, 浩二 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Combustion characteristics and engine performances of a swirl-chamber type IDI diesel engine using two-stage injection were experimentally investigated. The injection timing and fuel allocation ratio
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between first and second injections were widely varied. Heat release rate was analyzed to evaluate the combustion phenomena in the engine. As the result, ignition delay period for two-stage injection became longer than that for single-stage injection when the amount of fuel in the first stage injection was small. However, when the amount of fuel in the first injection was large, there was no difference of ignition delay period between two-stage injection and single-stage injection. NO and Smoke emissions and fuel consumption were improved by two-stage injection when ingition delay period became long.
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| 13.
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岩崎, 浩二 ; 荻原, 五郎 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Combustion characteristics and engine performances of a two-stage injection DI diesel engine were experimentally investigated. Two-stage injection was achieved by using two injection pumps.
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Injection timing and fuel allocation ratio between first and second injection were widely controlled. Engine performance of a two-stage injection diesel engine was compared with that of a single injection diesel engine with early timing injection. The heat release rate was analyzed to understand the combustion phenomena in a two-stage injection diesel engine. As a result, NO emission of two-stage injeciton diesel engine was improved when the first injection timing is early. The various pattern of heat release rate appeared with the change of a fuel allocation ratio. It was greatly affected by the first injection spray impinged on the cylinder wall or the piston top. The trade-off tendency between NO and smoke was influenced by the fuel allocation ratio of sub-injection pump was high.
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| 14.
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岡本, 雄一郎 ; 荻原, 五郎 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />A six-stroke diesel engine which was proposed by authors had second compression and second combustion strokes which were added on a four-stroke diesel engine. Numerical prediction and experiments
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on six-stroke engine which were carried out previously, showed that a six-stroke diesel engine could reduce NO concentration and shorter ignition delay could be attained in second combustion. Using various fuels on second combustion, it might be possible to improve more the emission characteristics. In this report, Methanol was used in the second combustion to improve the six-stroke engine performance. As the result, NO concentration in the exhaust gas decreased with delaying of the injection timing at second combustion and increased with an increase of the heat allocation ratio of second combustion stroke when the injection timing at first combustion stroke was fixed. Smoke wasn't exhausted at all when Methanol was put into the second combustion stroke. NO concentrations were affected by the heat allocation ratio and related with gas temperature. It was confirmed that the NO concentration of the Diesel fuel-Methanol engine become lower compared with that of the Diesel fuel engine.
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| 15.
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江原, 拓未 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />In the previous paper, the authors clarified that an impingement spray have the slip flow region near the impingement point on the wall. Then, behavior of a diesel spray impinging on an
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inclined wall was modeled to make an empirical formula of impingement spray tip penetration. To introduce a new model of spray growth behavior, uniform velocity penetration of the spray growth behavior in the slip region were framed and included into the traditional formula about the free spray. The momentum conservation theory was applied to the spray of after slipping. The growth behavior of an impingement spray was expressed as the function of wall distance and inclined wall angle. Spray path length calcurated from this formula showed qualititaively well agreement with an actual measurement.
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| 16.
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岡本, 雄一郎 ; 荻原, 五郎 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />A Six-stroke diesel engine was developed and its performance was evaluated. This engine had second compression and second combustion strokes which were added on the four stroke diesel engine.
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To control the fuel injection ratio and injection timings for first and second combustion strokes independently, two fuel pumps were attached to the engine. Effect of the fuel allocation ratio between first and second combustion strokes on the engine performance was investigated. Engine performance of the six stroke diesel engine was compared with that of the four stroke diesel engine which was the base engine of the six stroke engine. As a result, NO concentration in the exhaust gas decreased with a delaying of injection timing at second combustion stroke, but the injection timing at first combustion stroke didn't influence NO concentration. NO concentration decreased with an increase of allocation fuel ratio into the second combustion stroke. A trade-off relation between NO and soot concentration was observed against the change of allocation ratio. From the comparison between six and four stroke engine, it was confirmed that the NO concentration of the six stroke engine becomes lower than that of the four stroke engine.
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| 17.
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江原, 拓未 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />In this paper, behavior of a diesel spray impinging on an inclined wall was experimentally investigated in a pressurized vessel. In order to clarify the wall effect on a diesel spray
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structure, a relative angle of the inclined wall to the spray axis was varied. Spray penetration along the wall was observed optically and compared with that of a free spray. To observe an internal structure of the spray, it was visualized by a YAG laser sheet light and its tomographic image was captured on a film. The photo-image on a film was taken into an image analyzing computer using a high resolved image scanner. High density ridges in the tomographic image were extracted to clarify the internal structure of an impingement spray. Further, the growth characteristics of impingement spray was observed by a high speed photograph. To evaluate various spray motion quantitatively, a spray path penetration which described a development of a spray tip along the wall was used. As the result, the slip flow region of spray was found near the impingement point on the wall. It seemed that the injected fuel does not make a mixture and slipped on the wall surface in this slip region. The length of this region was measured in various impingement wall condition.
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| 18.
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廣安, 博之 ; 小田, 晴己 ; 西田, 恵哉 ; 鈴木, 護 ; 吉川, 滋 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />An experimental study on emission formation processes, such as particulate, nitric oxide and total hydrocarbon, in a small D. I. diesel engine was carried out by using a newly developed total
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in-cylinder sampling technique. The sampling method was composed of rapidly opening a blowdown valve attached to the bottom of the piston cavity, and quickly transferring most of the in-cylinder contents into a large sampling chamber below the piston. The sampling experiment gave a history of spatially averaged emission concentrations in the cylinder. The effects of several engine variables on the emission formation processes were investigated.
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| 19.
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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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| 20.
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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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| 21.
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天谷, 賢児 ; 張, 峰 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />The performance of a six stroke diesel engine which has been proposed by the authors was experimentally investigated using a cyclical rapid-compression-expansion machine. The ignition delay and the
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maximum heat release rate in the first and second combustion processes were measured under the various conditions of wall temperature of the engine cylinder. An optical fiber probe connected to a photo sensor was installed into a combustion chamber to measure the ignition delay and to obtain the luminosity of soot exidation in the second compression process. The experimental data were compared with the numerical predictions from the 1st report. As a result, the soot oxidation phenomenon in the second compression process was numerically and experimentally confirmed. It was clarified that the experimental data of the wall temperature effect on ignition delay qualitatively agreed with the numerical prediction.
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| 22.
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新井, 雅隆 ; 井田, 祐一 ; 天谷, 賢児
概要:
application/pdf<br />Journal Article<br />The performance of a six-stroke diesel engine which has been proposed by the authers was numerically predicted using a phenomenological model developed in the previous study. Concentrations of nitric
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oxide and soot are calculated from the simple phenomeno
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| 23.
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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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| 24.
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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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| 25.
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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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| 26.
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新井, 雅隆 ; 井田, 祐一 ; 天谷, 賢児
概要:
application/pdf<br />Journal Article<br />The performance of a 6-stroke diesel engine was numerically analyzed by means of a simple thermodynamical model. Since the 6-stroke diesel engine proposed in this report has two combustion
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processes in one cycle, it will offer new methods of the Combustion Control which could not be attained in an ordinary 4-stroke diesel engine. For example, the second combustion stroke provides the oxidation process of the soot that formed in the first combustion stroke. With this method, the in-cylinder gas temperature related to the NO_x and soot formation in the combustion processes was predicted. It was confirmed that under various conditions, the maximum gas temperature of the 6-stroke diesel engine was lower than that of the 4-stroke engine. Furthermore, a 6-stroke low-heat-rejection diesel engine was analyzed. It was predicted that in comparison with the temperature in an ordinary 4-stroke engine, a higher thermal efficiency would be attained with a lower in-cylinder gas temperature.
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| 27.
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細谷, 肇 ; 小保方, 富夫
概要:
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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| 28.
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吉津, 文嗣 ; 中山, 満茂
概要:
application/pdf<br />Journal Article<br />A new type of pilot injector for low emission combustion in DI diesel engine has been developed by applying the authors' creative conception which are an active control of the time-dependent
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spray penetration and an appropriate radial distribution of local Sauter Mean Diameter during the ignition lag. The concept was realized in the new-type pilot injector where the opening pressure of the second stage (main injection) was higher than that of the first stage (pilot injection). In this paper, the new spray concept and the relationship between the design factors of the Dodge Plunger set in the injector and the fundamental injection characteristics were made clear.
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| 29.
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細谷, 肇 ; 小保方, 富夫
概要:
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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| 30.
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TABATA, Michihiko ; FUJII, Hiroshi ; ARAI, Masataka ; HIROYASU, Hiroyuki
概要:
application/pdf<br />Journal Article<br />The Sauter mean diameter and size distribution of a diesel spray in a vaporizing process were studied to obtain detailed information of the diameter change of the spray in an
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elevated-temperature and-pressure environment. In this study, direct photographs of the diffracted light from particles or spray drops were taken using a pulsed laser and analyzed directly. The mean particle size could be measured even if the diffracted light from particles passed through a high-ambient-temperature and-pressure environment. The liquids used for studying a vaporizing diesel spray were diesel fuel and n-heptane. The Sauter mean diameter increased to a maximum, then decreased with a further increase of the ambient temperature. The change of the Sauter mean diameter was different for different fuel evaporation rates. The increase of the Sauter mean diameter of n-heptane spray occurred at a lower ambient temperature condition than did that for the diesel spray.
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| 31.
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清水, 正則 ; 新井, 雅隆 ; 廣安, 博之
概要:
application/pdf<br />Journal Article<br />In order to elucidate the disintegrating mechanisms of a diesel spray, the breakup length was measured by an electric resistance method. A reattachment distance of separated liquid flow
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in a nozzle and a spray were observed photographically. The mechanism of the two disintegrating processes of the jet was investigated by separating an ambient effect from a disturbed effect of the nozzle. The atomizing mechanism of the jet was governed by both the initial disturbance due to the nozzle geometry and an interfacial force between the jet and the environment. If a strong disturbance was given to the internal flow in a nozzle, the jet would be broken up into a spray flow.
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| 32.
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高橋, 秀夫 ; 志賀, 聖一 ; 小柴, 英俊 ; 柄沢, 隆夫 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />The purpose of this study is to clarify the characteristics of diesel spray with higher and unsteady injection pressure under an elevated pressure condition and an elevated pressure and
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temperature condition. A Bosch-type injection system and a rapid compression machine were used. The behavior of the spray until 2 ms after the beginning of injection, which corresponds to the period of the ignition delay of most diesel engines, was observed by high-speed photography. Under the less evaporating condition, the spray penetrations of higher and normal injection pressure are almost the same, whereas, under the evaporating condition, those penetrations are not the same. Thus, the penetration of the normal injection pressure is affected by the ambient temperature, while the penetration of the higher injection pressure is little affected by the evaporation. The same tendency was observed in the behavior of spray cone angle development. It is also shown that the spray generates small eddies and the spray pattern is affected by the growth and dissipation of those eddies.
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| 33.
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高橋, 秀夫 ; 志賀, 聖一 ; 柄沢, 隆夫 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />A rapid-compression machine is developed for fundamental studies of diesel combustion. Low-pressure compressed air and a stainless-steel membrane are employed to drive the piston. This is
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similar to the principle of a shock tube and is quite simple compared with other machines. The combustion chamber has a 120 mm bore and is 20 mm in depth. These dimensions were determined to avoid the impingement of the spray within 2ms, which seems to be a typical ignition delay period. Compression time and polytropic exponent are about 38ms and 1.30, respectively. High-speed photographs were taken to observe the spray development for both evaporating and non evaporating spray, and the effect of evaporation could be shown clearly. A combustion test was also carried out, and a pressure rise due to combustion was recognized. Thus, it is shown that this machine has sufficient performance for the study of diesel combustion. A simple simulation technique to design the machine is also presented and its availability is verified.
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| 34.
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柄沢, 隆夫 ; 川口, 暁生 ; 志賀, 聖一 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />This paper presents an experimental study being aimed at revealing the ignition assistance effect of a hot surface in an alcohol-fueled diesel engine and its mechanism. A single shot of spray was
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injected into a motored diesel engine. Ignition lag was measured and was split into two regimes, physical lag and chemical lag, by applying a statistical technique presented by S. Kumagai. High-speed direct photographs were also taken. The dependence of those ignition lags were classified into three regions on their Arrhenius plots. In lower hot-surface temperatures, the ignition lags decrease exponentially with increasing the hot-surface temperature. In higher temperature regions, the ignition lags tend to have constant values, passing through the transient region. By combining the high-speed photographs, it is suggested that the hot surface does not initiate flame propagation, but supplies heat to assist the spontaneous ignition as the assistance mechanism.
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| 35.
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志賀, 聖一 ; 柄沢, 隆夫 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />To predict the shape of a flame in a vessel is one of very important problems in the field of combustion. But it is difficult because the shape is strongly influenced by the flow which is affected
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not only by the surrounding walls but also by the expansion of gas due to combustion. The mechanism of formation of a wedge shaped flame in a constant volume combustion chamber has longtime been a target of many researchers since Ellis pointed it out in 1928. Several hypotheses have been proposed but they do not clearly present a complete mechanism. Modern techniques of measurement are giving new data about the combustion gases. In this report, a two dimensional LDV and some other measuring techniques are used to check the hypotheses mentioned above, and a new idea on the mechanism of formation of a wedge shaped flame is proposed.
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