著者

松永 拓也 越塚 誠一 保坂 知幸 石井 英二

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.85, no.877, pp.19-00186, 2019 (Released:2019-09-25)

参考文献数

37

被引用文献数

1

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In this paper, we proposed a new particle method for numerical simulation of droplet dynamics. In the proposed method, the moving surface mesh is used to define interface between gas and liquid. The volume enclosed by the mesh represents the liquid droplet, and the outer domain is inactive gas with constant pressure. The incompressible liquid flow is calculated using a particle method, in which spatial derivatives are evaluated using an arbitrary high order accurate scheme. On the free surface, the surface stress balance equations, including surface tension and viscous stress, are adopted for the boundary conditions. Deformation of the gas-liquid interface is explicitly calculated by surface nodes that move in a Lagrangian fashion. Surface tension force is directly evaluated with high accuracy on each node utilizing the mesh shape. As numerical verification, simulations of three benchmark problems, namely circular patch test, Laplace pressure test and 2D droplet (liquid column) oscillation problems with different oscillation modes, have been carried out. The computation results were compared with the theoretical solutions, and excellent agreements were obtained. As a result, high accuracy and validity of the proposed computational method were confirmed.

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

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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.