著者

吉村 一樹 保坂 知幸 安川 義人 石井 英二 小倉 清隆 澤田 恵介

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.84, no.861, pp.18-00068-18-00068, 2018 (Released:2018-05-25)

参考文献数

19

---

Reduction of particulate matter (PM) in exhaust gas from automobile engines is in high demand. Fuel stuck on the engine wall causes incomplete combustion, and generates a large amount of PM. To prevent this, shape of fuel injection spray must be controlled with precision. We focused on the valve offset of the injector as a factor influencing the spray shape. Computational analysis was conducted to investigate the effects of the valve offset on inner nozzle flow and spray shape (spray direction and liquid penetration). Simulated spray behavior image, footprint, and liquid penetration agreed well with experimental results. From the inner nozzle flow simulation results with the valve offset, it was found that fuel tends to flow in the direction of the valve offset near a sac in the nozzle to provide the fuel to the holes. This flow was caused by the smaller flow path fomed in the valve offset direction. From the spray simulation results, shifts in the spray direction of the plumes were caused by the flows near the sac. Some plumes were injected in the direction opposite to the valve offset. The holes with larger drill angle located in the valve offset direction, and larger valve offset caused larger changes of spray directions. Furthermore, liquid penetration was investigated. We showed that the flow separation in the holes caused by the valve offset affects the velocity distribution at the hole outlet and results in changes of the penetration length when the drill angle is small. It was found that the valve offset causes the change in the inner nozzle flow, and results in the change of the spray shape. We concluded that the correlation of nozzle geometry and valve offset is important for controlling the spray shape.

著者

松田 淳 大津 広敬 藤田 和央 鈴木 俊之 澤田 恵介 安部 隆士

出版者

宇宙航空研究開発機構

雑誌

宇宙航空研究開発機構研究開発報告 (ISSN:13491113)

巻号頁・発行日

vol.5, pp.1-18, 2006-03

---

USERSミッションでは再突入フェーズを利用して,再突入時に発生する衝撃層内の輻射光の分光スペクトル取得実験が行われた.再突入カプセルの先端ノーズ部半径は0.55mで,再突入速度は約7.5km/sであった.高度約90km付近で取得されたスペクトルからは,従来の予測では考慮されていなかったOH,NH,CH等のアブレータと大気構成化学種との反応生成化学種からの発光が支配的であった.そこで,アブレーションを考慮したCFD解析を行い,その影響についての評価を試みた.その結果,壁面付近ではアブレータ起源化学種と大気構成化学種の反応化学種からの発光が無視できないほどの強度になることが示唆された.

著者

佐藤 潤一 澤田 恵介 松山 新吾 大西 直文

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2003, pp.114-115, 2003-07-28

---

Three-dimensional numerical simulations of an accretion disc in a close binary system were performed by solving the Euler equations with radiative transfer. We used the one-dimensional (tangent-slab) approximation to calculate the radiative transfer for the vertical directions of the disc. The cooling effect of the disc is considered by discharging energy in only this directions. The influence of radiative cooling has been accounted for by assuming a specific heat ratio γ which is smaller than that of a mono-atomic gas (=5/3). In the present study, the specific heat ratio was assumed to be constant while radiative cooling effect was included as the non-adiabatic process. Our numerical simulations with radiative transfer demonstrated that spiral shocks existed in three-dimensional disc. It was found that its feature approached in the case of a lower γ but its tendency was weaker than that of two-dimensional simulation.

著者

石向 桂一 大西 直文 澤田 恵介

出版者

日本流体力学会

雑誌

ながれ : 日本流体力学会誌 (ISSN:02863154)

巻号頁・発行日

vol.24, no.5, pp.515-523, 2005-10-25

被引用文献数

2

---

近年, DengらによってWeighted Compact Nonlinear Scheme (WCNS)と呼ばれる高次精度スキームが開発された.このWCNSは, 数値振動を生じることなく衝撃波を単調に捉えることができるため, 陰的LESに適用できると考えられる.本研究では, WCNSを用いた陰的LESによりBurgers乱流の数値計算を行い, エネルギースペクトルを求めた.得られたエネルギースペクトルはDNSの結果と良い一致を示したが, 従来型のLESでは, 高波数域に非物理的な振る舞いが現れた.