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論文
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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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| 2.
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論文
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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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| 3.
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論文
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小保方, 富夫 ; 花田, 尚喜 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />The intensity and structure of turbulence in a flame front may be changed by expansion flow due to combustion. Therefore the velocity and turbulence in a combustion chamber of a spark
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ignition engine are measured by mans of a laser Doppler anemometer with fiber-optic pick-up under firing conditions. The engine is operated at a speed of 2500 rpm with propane-air mixtures. Data acquisition window width affects the turbulence intensity (u') and integral time scale of turbulence (Lt) of the analysis. In the experiment, a short (0.67 ms) and long (4 ms) window are selected and compared with each other. In the combustion period, twice the intensity of u' and an increase of 40 % in Lt are observed in the case of short window analysis. A stronger u' and larger Lt are observed in the long window analysis and it is shown that the Lt expands laterally during the compression stroke and vertically during the expansion stroke.
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論文
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小保方, 富夫 ; 花田, 尚喜 ; 倉林, 俊雄
概要:
application/pdf<br />Journal Article<br />To improve the adaptability of LDA (laser Doppler anemometer) for measuring velocities in an engine, an optical fiber system composed of a couple of single mode, polarization-preserving
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optical fibers has been made to transmit the incident beams. Though the total transmitting efficiency of this optical system is about 24 %, it has been confirmed that a fiber-optic LDA system with a 25 mW He-Ne laser is applicable to the real-time measurement of gas velocity in the combustion chamber of a small-sized two-stroke spark ignition engine. The ensemble-averaged mean velocities obtained by using this optical system show that the gas velocity rapidly decreases just before the flame front arrival and suddenly increases after passing of the flame. It is also shown that a new bulk flow is generated in the chamber by the gas expansion due to combustion.
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