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SIGA, Seiichi ; 志賀, 聖一
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Departmental Bulletin Paper
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椎名, 亮介 ; 荒木, 幹也 ; CHEN, Lai ; 中村, 壽雄 ; 志賀, 聖一 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />This paper presents basic combustion characteristics of a spark-ignition engine fuelled with three kinds of gaseous fuels; H_2, CO and CH_4. A single-cylinder engine was operated under WOT at
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1500min^<-1> condition. CO gas gives lower thermal efficiency than H_2 and CH_4, since the energy of the fuel can not be transferred to the pressure or the work, although it gives higher combustion temperature which makes the higher exhaust gas temperature and much higher NO_x emissions than those for CH_4. H_2 gives upper limit of flammability due to the occurrence of backfire and almost comparable thermal efficiency with that for CH_4 at its stoichiometric condition.
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| 3.
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椎名, 亮介 ; 荒木, 幹也 ; CHEN, Lai ; 中村, 壽雄 ; 志賀, 聖一 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />This paper presents basic combustion characteristics of a spark-ignition engine fuelled with three kinds of gaseous fuels; H_2, CO and CH_4. A single-cylinder engine was operated under WOT at
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1500min^<-1> condition. CO gas gives lower thermal efficiency than H_2 and CH_4, since the energy of the fuel can not be transferred to the pressure or the work, although it gives higher combustion temperature which makes the higher exhaust gas temperature and much higher NO_x emissions than those for CH_4. H_2 gives upper limit of flammability due to the occurrence of backfire and almost comparable thermal efficiency with that for CH_4 at its stoichiometric condition.
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田村, 貴洋 ; 荒木, 幹也 ; 山田, 秀志 ; 志賀, 聖一 ; 林, 茂 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Droplet size and spray dispersion characteristics of an impingement jet type jet engine fuel injector are investigated experimentally. The fuel injector is consisted of a pintle,
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intermediate ring, and outer ring, forming co-axial air flow channels with co-swirlers. Compressed air at room temperature is supplied with a blower, and is injected into the atmosphere through the co-axial channels. Distilled water is supplied with a liquid pump, and is injected from hole nozzles mounted in the pintle. The number of nozzles is 8 and 16. The liquid jets impinge onto impingement walls mounted on the intermediate ring, forming a free liquid film. From the tip of the liquid film, fine droplets are formed. The droplet size is measured using an LDSA, and the spray cross section is visualized using time-average Mie scattering method. It is shown that the droplet size is almost the same as the atomization of a simple wall impingement jet, which is much smaller than that for a conventional air-blast fuel injector, and it is observed that a relatively uniform spray is formed using the fuel injector.
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| 5.
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田村, 貴洋 ; 荒木, 幹也 ; 山田, 秀志 ; 志賀, 聖一 ; 林, 茂 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Droplet size and spray dispersion characteristics of an impingement jet type jet engine fuel injector are investigated experimentally. The fuel injector is consisted of a pintle,
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intermediate ring, and outer ring, forming co-axial air flow channels with co-swirlers. Compressed air at room temperature is supplied with a blower, and is injected into the atmosphere through the co-axial channels. Distilled water is supplied with a liquid pump, and is injected from hole nozzles mounted in the pintle. The number of nozzles is 8 and 16. The liquid jets impinge onto impingement walls mounted on the intermediate ring, forming a free liquid film. From the tip of the liquid film, fine droplets are formed. The droplet size is measured using an LDSA, and the spray cross section is visualized using time-average Mie scattering method. It is shown that the droplet size is almost the same as the atomization of a simple wall impingement jet, which is much smaller than that for a conventional air-blast fuel injector, and it is observed that a relatively uniform spray is formed using the fuel injector.
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| 6.
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荒木, 幹也 ; 岸本, 秀雄 ; 中島, 邦明 ; 前原, 充宏 ; 志賀, 聖一 ; 中村, 壽雄 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Performance of a 2 stroke cycle engine fuelled with CNG (Compressed natural ga
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s) using intermittent fuel injection from a scavenging port is investigated experimentally. The test engine is a 2 cylinder, 398 cm^3, 2 stroke cycle spark ignition engine. Gaseous fuel injectors are attached at the cylinder block, and a CNG is injected into the scavenging passage through a fuel injection pipe. The fuel injection pressure is set at 0.255 MPa, and the fuel is injected intermittently during the scavenging process. The length and tip geometry of the fuel injection pipe are varied, and the effect on the engine performance is investigated. Using the scavenging port fuel injection, the BSFC is reduced by 25%, and the lean burn limit extends from λ = 1.2 to 1.46, at the maximum. The peak of the NO_x emission shifts to leaner side, and the THC emission is reduced by 47% at the maximum. It is considered that the intermittent fuel injection from a scavenging port is effective to achieve stratified combustion and reduction in fuel short circuiting through the cylinder.
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| 7.
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荒木, 幹也 ; 藤原, 康裕 ; 志賀, 聖一 ; 中村, 壽雄 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Accuracy of an injection rate measurement of a gaseous fuel injector was improved by modification of equations and static pressure correction. A production gaseous fuel injector for an NGV
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(Natural gas vehicle) was used, which is for an intake port fuel injection. The injection pressure was set at 255 kPa (g), and the injection duration was varied from 5 to 20 ms. Nitrogen gas was used as the test gas. The test gas was injected into a pipe from the injector, and the static pressure history was acquired with a piezoelectronic pressure transducer. One-dimensional, compressible, inviscid, adiabatic flow was assumed, and the instantaneous mass flow rate inside the pipe was estimated using newly modified equations. The pressure gradient due to pipe friction was corrected using Darcy-Weisbach equation. By integrating the injection rate during the injection duration, the total amount of mass flow per one stroke was calculated. The data obtained by the injection rate meter are compared to that of the calibration test, and it is shown that the injection rate measurement was carried out within the error of 2 to 3%.
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| 8.
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荒木, 幹也 ; 藤原, 康裕 ; 志賀, 聖一 ; 中村, 壽雄 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Injection rate of a gaseous fuel injector was calculated by measuring the needle valve lift history. In our lab, a gaseous fuel injection rate meter using 1-dimensional pipe flow was developed.
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In the present study, the measurement accuracy of the injection rate meter was examined by comparing the theoretical injection rate estimated from the needle valve lift history. The needle valve lift was measured using an optical method. A small beam cut plate is attached to the needle valve of the gaseous fuel injector. A laser beam passes through the beam cut plate, and the variation of the beam intensity was measured with a photo sensor. From the beam intensity, the needle valve lift history was estimated. One-dimensional, compressible, inviscid, adiabatic flow was assumed, and the instantaneous mass flow rate through the needle valve sheet, the injector sack, and the injection hole was estimated. The estimated injection rate was compared with that obtained with the gaseous fuel injection rate meter. The estimated and measured injection rates agree relatively well even at transient duration. It is shown that the injection rate meter has high reliability and accuracy.
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| 9.
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荒木, 幹也 ; 曽根, 祐輔 ; 小島, 孝之 ; 志賀, 聖一 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Supersonic jet noise was visualized using a newly developed optical CT (Computed Tomography) method. From a converging round nozzle whose exit diameter is 8.0 mm, air is injected into the
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atmosphere. The pressure ratio is set at 2.25 (M_j=1.14), and an under-expanded jet is formed. A sound wave is pressure fluctuation, and the density fluctuates at the same time, Using a kind of schlieren method, the fluctuation of the density gradient is detected. A He-Ne laser beam passes through the supersonic jej, and the beam direction is slightly refracted due to the density gradient inside and around the supersonic jet. The beam refraction is converted to a brightness signal using a knife edge and a photo sensor. The signal obtained with the photo sensor is the integrated value along the laser beam path. Using a modified Abel inversion, the local refraction of the laser beam is calculated and the tomogram is re-constructed. It is shown that, using the optical CT method, nonintrusive acoustic measurement is possible even inside the supersonic jet. It is shown that the sound source of the screech tone exists around the 4th shock cell of the under-expanded jet, and that intensive fluctuation is observed not only in the shear layer but also along the center axis of the jet, implying the existence of the traveling shock wave.
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荒木, 幹也 ; 小保方, 富夫 ; 石間, 経章 ; 志賀, 聖一 ; 増渕, 匡彦 ; 杉本, 知士郎
概要:
application/pdf<br />Journal Article<br />Effects of horn geometry on the atomization characteristics of an ultrasonic f
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uel injector using a micro nozzle array were investigated experimentally. Micro nozzles whose exit diameter d=3μm are mounted on a thin metal film. The number of the micro nozzles is from 2.0×10^4 to 1.2×10^5. Using an ultrasonic oscillator, gasoline is periodically pushed out from the micro nozzles at a frequency from 62 to 65kHz. A disk type PZT is used as an ultrasonic oscillator, and the oscillation is amplified using a step-type horn. The input voltage to the PZT is varied from 0 to 200V. To increase the fuel flow rate, the horn small end diameter Ds is increased from 10.5 to 25mm, while the large end diameter is fixed at 30mm. To prevent forming a liquid film on the micro nozzle array, gutters are machined on the small end of the horn. It is shown that the SMD (Sauter mean diameter) of the spray is almost uniform around 10 to 14μm, regardless of the horn small end diameter. The fuel flow rate increases, at the maximum, 2.8 times larger when compared to the original horn geometry.
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| 11.
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荒木, 幹也 ; 藤原, 康裕 ; 志賀, 聖一 ; 中村, 壽雄 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Injection rate measurement of a gaseous fuel injector was carried out by use of one-dimensional pipe flow. A production gaseous fuel injector for an NGV (Natural gas vehicle) was used,
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which is for an intake port fuel injection. The injection pressure was set at 255 kPa, and the injection duration was varied from 3.4 to 20 ms. Nitrogen gas was used as the test gas. The test gas was injected into a pipe from the injector, and the static pressure history was acquired with a piezoelectronic pressure transducer. One-dimensional, compressible, inviscid, adiabatic flow was assumed, and the instantaneous mass flow rate inside the pipe was estimated. By integrating the injection rate during the injection duration, the total amount of mass flow per one stroke was calculated. Caliburation test was carried out by use of a pressure vessel, from which the total mass flow during one stroke was estimated. Both data are compared, and it is shown that the injection rate measurement was carried out with an error of about 10%.
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荒木, 幹也 ; 堀越, 順 ; 山田, 秀志 ; 志賀, 聖一 ; 林, 茂 ; 中村, 壽雄 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Effects of a wall impingement jet on atomization characteristics of a jet engine fuel injector were investigated experimentally. Liquid is injected from 0.2mm-diam nozzles and the liquid
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columns impinge onto a wall. The liquid forms thin films on the impingement wall and fine droplets can be produced. Several kinds of impingement wall geometries, such as slope, parallel and cylinder types, were examined and the droplet size and atomization mode were investigated. The droplet size was measured with an LDSA. For the slope type, two kinds of atomization mode, namely, ""air blast atomization"" and ""pressure atomization"" modes were observed. The pressure atomization mode is preferable, since it leads to the atomization improvement of a jet engine in low load operations. For parallel types, the atomization characteristics were similar to that for the slope type. For cylinder types, pressure atomization mode can be realized with a small liquid injection pressure. And the droplet size in the pressure atomization mode is smaller when compared with the parallel types.
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荒木, 幹也 ; 桑原, 孝輔 ; 新井, 正明 ; 石間, 経章 ; 志賀, 聖一 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />Effects of gas injection from a nozzle wall on screech reduction of a supersonic under expanded jet are investigated experimentally. From a converging round nozzle, air is injected into the
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atmosphere (Main jet) at a pressure ratio of 2.25 (M=1.14). The exit diameter of the main jet nozzle is 8.0mm. From small nozzles mounted in the main jet nozzle wall, air is injected in the normal direction to the main jet (Secondary jet). The exit diameter of the secondary nozzles is 1.0mm. The number of the secondary nozzles is selected to be 2 or 4, and the mass flow rate of each secondary jet is set at 2.0% or 4.0% of the main jet. With the secondary jets, the screech SPL is reduced by 23 dB at the maximum, and the frequency profile of the broadband noise is also influenced. And with the secondary jets, the total pressure of the main jet is slightly decreased with the increase in the total mass flow rate of the secondary jets. Consequently, it is shown that the gas injection method is effective in screech reduction with a small loss in the total pressure.
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荒木, 幹也 ; 許, 成軍 ; 志賀, 聖一 ; 山田, 秀志 ; 林, 茂 ; 中村, 壽雄
概要:
application/pdf<br />Journal Article<br />Atomization characteristics of a liquid film were investigated, experimentally
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, A liquid jet emerging from a straight-type hole nozzle is impinged onto a solid wall, forming a liquid film. Effects of three independent parameters were investigated, namely, injection pressure P_0, impingement angle α and impingement wall diameter d. The liquid film velocity V_2 was measured with a PDPA. The SMD of the droplets was measured with an LDSA. It is shown that the SMD decreases linearly with the increase in the liquid film velocity V_2, and that the gradient of the line decreases with the increase in the impingement angle α. For the case that the impingement angle α is 30deg, the SMD of the droplets is proportional to V_2^<-0.63>. For the case that the impingement angle α is 90deg, the SMD of the droplets is proportional to V_2^<-0.51>. For the case that V_2<300m/s, the SMD of the droplets is smaller than that for a liquid jet. It is shown that by use of a liquid film, atomization is enhanced compared with a liquid jet.
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山田, 秀志 ; 松本, 裕 ; 林, 茂 ; 志賀, 聖一 ; 荒木, 幹也 ; 堀越, 順 ; 中村, 壽雄 ; 小保方, 富夫
概要:
application/pdf<br />Journal Article<br />The effect of pressure atomization with wall impingement on the atomization characteristics was examined in a real scale jet engine burner. The air velocity was set from 41 to 92m/s, and the
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liquid injection pressure was from 0.5 to 7.5MPa. Two laser faci
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| 16.
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長屋, 幸助 ; 鈴木, 孝明 ; 今井, 勝仁 ; 今井, 康博 ; 志賀, 聖一
概要:
application/pdf<br />Journal Article<br />An engine valve timing control system is presented. The system consists of a new-type planetary gear mechanism and a control motor. In order to detect a cam rotation angle, this paper also presents
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a sensor consisting of a permanent magnet chip and a coil. The control motor controls the phase between the inlet valve and the exhaust valve. The control algorithm is presented. To validate the present mechanism and the control system, experimental tests have been carried out for the valve system of a real automobile engine head. It is clarified that the present system has advantages as compared to the control system using oil pressure, which has been used in resent automobiles.
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周, 斌 ; Machacon, H.T.C. ; 志賀, 聖一 ; 譚, 達明 ; 柄澤, 隆夫 ; 小保方, 富夫 ; 中村, 寿雄
概要:
application/pdf<br />Journal Article<br />In this study a neural network prediction method that can be used in predicting engine behavior is proposed. Using data from a series of characteristic experiments, this method eliminates
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the need for complicated mathematical calculations used in prediction models. To test this method exhaust emissions and engine performance data from intake gas composition variation experiments were taken and compared with the predicted data from this network. The method has been tested and found effective in predicting engine exhaust emissions and engine performance. This technique can be a valuable tool in engine research.
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岡井, 敬一 ; 小野, 豊 ; 森上, 修 ; 芝, 世弐 ; 荒木, 幹也 ; 野村, 浩司 ; 志賀, 聖一 ; 津江, 光洋 ; 河野, 通方
概要:
application/pdf<br />Journal Article<br />Experimental investigation was conducted on two droplet-array combustion of methanol and methanol/dodecanol mixture fuels in microgravity. For methanol, effects of ambient pressure and
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droplet spacing were examined. Results show that the droplet lifetime decreases with increasing spacing at relatively low pressure and the droplet lifetime becomes independent of spacing at higher-subcritical and supercritical pressures. For methanol/dodecanol mixture, effects of pressure, fuel composition were investigated in terms of occurence of disruption. Disruption of droplet during combustion was demonstrated both for single droplet and droplet pairs.
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| 19.
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志賀, 聖一 ; 八木, 静夫 ; 盛田, 宗宏 ; 松本, 隆 ; 柄沢, 隆夫 ; 中村, 寿雄
概要:
application/pdf<br />Journal Article<br />In this paper we present the first stage of a study on the effect of early-closing of intake-valve on the engine performance in a spark-ignition engine. A four-valve single-cylinder engine was
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used with several values of expansion ratio and a half early-closing intake cam. The half early closing leads to almost a half of the volumetric efficiency and the BMEP for all cases of the expansion ratio. It can realize an improvement of about 7% in thermal efficiency under WOT,and about 4% under partial load of BMEP=0.2 MPa. These beneficial results are considered to be mainly caused by the effect of the more-expansion. The ratio of expansion to compression ratios was estimated to be around. 1.4 on the basis of motoring pressure analyses. Under the early-closing condition, an increase in the residual gas fraction was suggested and verified by a heat release analysis using a two-zone combustion model.
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| 20.
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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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| 21.
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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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| 22.
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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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| 23.
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志賀, 聖一 ; Heywood, John B ; Chun, Kwang M
概要:
application/pdf<br />Journal Article<br />This study aims to clarify the importance of chamber wall temperature in the knocking characteristics of a spark-ignition engine. To vary the chamber wall temperature, two procedures were
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used, one is to change the coolant temperature and the other is to raise the exhaust valve surface temperature by substituting a ceramic surface layer for the original steel layer. Although the coolant temperature change had no influence on the flame propagation process, it fairly affected the knocking process, such as mean knock intensity and mean knock occurrence timing. This is caused by both the change of bulk mixture temperature of the end gas and the temperature uniformity within the end gas region. Cycle-by-cycle based knocking behaviour can also be influenced by the coolant temperature, which is considered to be based on the temperature uniformity in the whole chamber region. Exhaust valve surface temperature change did not affect any knocking characteristics. It suggests the importance of the wall temperature in the end gas region.
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| 24.
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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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| 25.
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高橋, 秀夫 ; 志賀, 聖一 ; 柄沢, 隆夫 ; 倉林, 俊雄
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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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| 26.
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柄沢, 隆夫 ; 川口, 暁生 ; 志賀, 聖一 ; 倉林, 俊雄
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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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| 27.
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志賀, 聖一 ; 柄沢, 隆夫 ; 倉林, 俊雄
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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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| 28.
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柄沢, 隆夫 ; 志賀, 聖一 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />A simple method for producing uniform-size droplets has been proposed. A thin rectangular nozzle can generate a chain-type jet and, under some conditions, the jet disintegrates into droplets
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of high uniformity. The previous paper reported on the mechanism of uniform-droplet formation, and showed that the imposition of sound vibration to the jet can remarkably stabilize the phenomenon and extend the producible range. In the present paper, experiments are carried out using suger and ethanol solutions to reveal the effect of liquid properties, such as viscosity and surface tension, on the producible range of uniform-droplet. The results showed that both the increased viscosity and the isreased surface tention have a tendency to extend the producible range, though far increased viscosity has a negative effect. The producible range lies over Weber Number W_e=20~3000 and stability number S_b=0.003~0.08.
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| 29.
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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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| 30.
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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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| 31.
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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 />By using a direct injection diesel engine, the effect of exhaust gas recirculation (EGR) on soot emission was investigated. It was revealed that EGR had both effects of soot promotion and
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suppression. Soot emission was suppressed when the premixed (initial rapid) combustion fraction of the two combustion patterns was increased, which was accomplished by throttling the intake valve equipped the engine or advancing the injection timing. It was also suggested that the effect of EGR on soot emission should not ascribe only the physical or thermal properties of the inert gases within the exhaust gas, but some chemical properties of CO_2. Because it was shown that only CO_2 had the effect of soot suppression under some conditions.
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| 32.
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志賀, 聖一 ; 河野, 通方 ; 飯沼, 一男
概要:
application/pdf<br />Journal Article<br />火花点火可能な急速圧縮機によってノックを再現し,得られた指圧線図から求めた圧力振動振幅によってノック強さを定義した.このノック強さに影響する重要な要因として
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火炎伝ばによる燃焼質量割合が存在すること,また圧縮比,当量比の影響などを明らかにした.円筒形燃焼室においてノック強さが大きく変動するのは,ガス振動モードの節線位置が試行ごとに変化するためであることが2種の実験手法によって確認された.
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| 33.
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志賀, 聖一 ; 河野, 通方 ; 飯沼, 一男
概要:
application/pdf<br />Journal Article<br />急速圧縮機において再現した火花点火機関のノックを,直接およびシュリーレンの高速度撮影によって観察した結果,以下の知見が得られた.すべての混合気が自発点火する
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ときのガス振動の発生は,熱炎発生の不均一性による.自発点火における2段点火の1段めは局部的熱炎発生によるものではなく冷炎によるものである.火炎伝ぱをともなう場合の末端ガスの点火現象は,すべての混合気が自発点火する場合の点火過程と同等である.
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| 34.
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柄沢, 隆夫 ; 志賀, 聖一 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />This paper presents the experimental study on the phenomena of evaporation and
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ignition of the fuel-droplet impinged upon a hot surface. The experiment was made on the seven kinds of fuel. It was revealed that cool flame is generated in η-Heptane and diethyl-Ether at a surface temperature range which is 300-400 K below that of hot flame generation. The surface temperatures at which the cool and hot flames were generated were measured by applying a statistic method. Their delay times were also measured and then divided into physical and chemical delays by applying the statistic technique which was presented by S.Kumagai et al. Based upon these investigations, the natures of both the cool and hot flames were clarified and the difference between the surface temperature of hot flame generation and the ignition temperatures measured by using the crucible method was discussed.
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