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| 1.
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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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| 2.
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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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| 3.
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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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| 4.
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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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| 5.
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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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| 6.
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小保方, 富夫 ; 柄沢, 隆夫 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />The bulk velocity and turbulence of air swirl flow in the dish type combustion
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chamber of a motored engine were measured by an LDA. The LDA was modified with optical finers for easy operation and was improved to form a smaller measuring space 0.29 mm in length. The engine was operated at a speed of 1 000 rpm. The gas velocity at a mid section of the combustion chamber was analyzed by the stationary time average method. The radial distribution of mean swirl flow and turbulence characteristics such as turbulence intensity (u'), integral time and spacial scale (L_t, L) and micro time and spatial acale (λ_t, λ) were obtained, and time depending properties of such flow data were investigated. It has been revealed that the mean swirl velocity and swirl ratio almost agree with those of previous reports, but u' is higher and scales of turblence are lower than the data given by the hot-wire anemometer.
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| 7.
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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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| 8.
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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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| 9.
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志賀, 聖一 ; 江原, 秀治 ; 柄沢, 隆夫 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />This paper presents one of the studies which aim to reveal the capability of controlling diesel combustion by exhaust gas recirculation (EGR). In a previous paper, the effect of EGR on soot emission
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was examined, and it was shown that soot emission is suppressed under the condition that the mass fraction burned by spontaneous (pre-mixed) combustion is increased. In a present paper, diesel knock intensity is defined as a sound pressure distributed over 1-1.5kHz, and the effect of EGR on the diesel knock intensity is examined. The diesel knock intensity is remarkably reduced by EGR under the same operating condition as soot emission is reduced by EGR. By calculating the heat release rate based on the indicated pressure diagram, it was suggested that a reduction of knock intensity originates from the reduced reaction rate in the spontaneous ignition. The quantitative relationship between the diesel knock intensity and the maximum rate of pressure rise is also presented.
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| 10.
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志賀, 聖一 ; 江原, 秀治 ; 柄沢, 隆夫 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />In previous paper, it was suggested the effect of exhaust gas recirculation (EGR) on the diesel knock is relevant to the reaction rate of spontaneous ignition which occurs at the initial stage of
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diesel combustion. In a present study, this suggestion is verified by measuring the ignition lag and separating it into physical and chemical lags by applying the statistical technique presented by S. Kumagai. Under the operating condition used in this study, the physical lag is rather longer than the chemical lag and hardly changes with an increase in EGR ratio. On the other hand, the chemical lag is considerably affected by EGR. Though the dependent behaviour of the chemical lag on EGR is not simple, it is clearly shown that the tendency of chemical lag versus EGR ratio is quite the reverse of that of the diesel knock intensity. This means that the diesel knock intensity with EGR is dominated by the reaction rate of spontaneous ignition.
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