著者

石井 一洋

出版者

一般社団法人 日本燃焼学会

雑誌

日本燃焼学会誌 (ISSN:13471864)

巻号頁・発行日

vol.55, no.174, pp.329-336, 2013 (Released:2018-01-26)

参考文献数

47

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Generally combustion of premixed mixtures is divided into two modes; deflagration and detonation. These two modes have completely different properties and can be easily distinguished from their travelling speed and propagation mechanism. If a mixture is ignited by a weak ignition source, a deflagration wave is obtained. Under appropriate conditions, a deflagration wave accelerates, resulting in an abrupt transition into a detonation wave. This type of detonation initiation is referred to as deflagration to detonation transition, DDT. In this paper, one-dimensional depiction of DDT phenomena is made, which is followed by the milestone visualization of onset of detonation by Urtiew and Oppenheim. Some reviews are focused on DDT in a smoothed tube and in an obstacle laden tube, including recent progress in these fields. Mechanism of detonation initiation is mentioned on the basis of new findings in numerical works.

著者

野嶋 新斗 石井 一洋

出版者

一般社団法人日本機械学会

雑誌

日本機械学会関東支部総会講演会講演論文集

巻号頁・発行日

vol.2015, no.21, pp."10907-1"-"10907-2", 2015-03-20

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In this study, operating conditions of a rotating detonation engine with internal mixing has been studied. Hydrogen and oxygen are supplied separately from gas storage tanks and mixed in an annular combustion chamber. The mixture is initiated by a spark discharge placed at the chamber wall surface. As a result, a strong deflagration after ignition is initially generated in the combustion chamber. The experimental results show that the following stages are involved to achieve stable propagation of the rotating detonation : i) a deflagration wave moves to the downstream, ii) a DDT process occurs in the downstream, iii) a detonation wave propagates in the upstream direction, iv) a rotating detonation is stabilized in the combustion chamber.

著者

石原 咲子 石井 一洋 片岡 秀文

出版者

一般社団法人 日本燃焼学会

雑誌

日本燃焼学会誌 (ISSN:13471864)

巻号頁・発行日

vol.56, no.178, pp.355-363, 2014 (Released:2018-01-26)

参考文献数

18

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For deflagration to detonation transition (DDT), several explanations on initiation have been given. Nevertheless, the knowledge on DDT is still insufficient for predicting where and when detonation occurs. In order to improve the reproducibility, an ethylene oxygen mixture was ignited forcibly by spark discharge behind an incident shock wave near the wall. The process of flame development was visualized by Schlieren imaging and analyzed by drawing several wave element trajectories on the shock waves ahead of the flame. As a result of varying the timing of spark discharge, detonation initiation was promoted as the boundary layer Reynolds number Reign increases. For Reign of more than 5.0 × 106, DDT was caused at 45 ± 10 μs. The processes of flame development were classified as Mode 1 and 2, which denote Reign of less than transition Reynolds number and more than it, respectively. Although the times for detonation initiation were markedly different in Mode 1 and 2, it was found that the both flame developments were similar. The accelerated flame near the wall propagates in upstream direction along the wall, resulting in approaching the shock wave front. This makes the shock stronger by coalescing of numerous compression waves. As the strengthened shock compresses the unburned gas, the flame was more accelerated, so that at the position where the flame front reached the shock front detonation initiation occurred. The difference of flame development between Mode 1 and 2 was observed in the initial stage in particular in the early 20 μs. Detonation initiation was caused at the position where following three conditions were satisfied: (1) A local Mach number reaches 2.4. (2) The flame front approaches and reaches the shock front ahead of it. (3) A concavity is generated on the flame/shock front, compressing the unburned gas coming into the point.

著者

坪井 孝夫 小川 輝繁 宇高 義郎 三宅 淳巳 石井 一洋

出版者

横浜国立大学

雑誌

基盤研究(B)

巻号頁・発行日

1999

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炉心溶融時に生ずる水素に起因するデトネーションに関して、3年間に以下の研究成果を得た。(1)炉心溶融時の雰囲気中に存在する水蒸気がデトネーションへの遷移(DDT)に及ぼす影響を実験的に調査するために、水蒸気濃度を0%から4-5%へと変化させた結果、全長13mのデトネーション管では3-8%の水蒸気を含む混合気ではDDTが生じなかった。実験条件によりこの限界は変化した。衝撃波管を用いた実験では、DDTが生ずるまでの誘導時間は、水蒸気濃度と初期温度に強く依存した。(2)局部的に混合気濃度が異なる場合、すす膜観測より、通常のすす膜構造と異なる規則的模様が観測され、複数の燃焼形態か混在することが観察された。(3)生じたデトネーションが構造物間の狭い空間を伝播する際の挙動については、間隙長一定の場合に、デトネーションのセルサイズが同一であっても混合気の組成によって伝播形態が大きく異なった。さらに混合気の組成(当量比、窒素およびアルゴン希釈割合)を大きく変化させた場合は、同一のセルサイズに対しては水素過剰混合気の方が速度欠損が大きかった。同一希釈量では、窒素希釈の方がアルゴン希釈よりも間隙内速度欠損が大きかった。(4)デトネーション管端にステンレスチューブを複数本最密になるよう挿入し、チューブ内径および長さがDDT過程に及ぼす影響について調べた結果、チューブの挿入によりDDT距離が大幅に短縮された。本研究の遂行にあたり、石井一洋、三宅淳巳、坪井孝夫と同行の大学院生がアーヘン工科大学を訪れ、アーヘン大学のオリビエ教授、シュミット助手、ビークリング助手、グレーニッヒ教授を招聘し、研究打ち合わせ並びに共同実験を行った。