1995 Fiscal Year Final Research Report Summary
Combustion of Transient Gas Fuel Jet and Process of Entrainment of Ambient Air into Jet
| Project/Area Number |
06650248
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Thermal engineering
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| Research Institution | Okayama University |
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Principal Investigator |
YOSHIYAMA Sadami Okayama University, Faculty of Engineering, Research Associate., 工学部, 助手 (80210780)
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| Co-Investigator(Kenkyū-buntansha) |
HAMAMOTO Yoshisuke Okayama University, Faculty of Engineering, Professor., 工学部, 教授 (60025955)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Jet / Transient Jet / Visualization / Impinging Jet / Laser-aided Diagnostics / Air Mass Entrained / Diffusion Flame / Turbulent Mixing |
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| Research Abstract |
It is well known that the process of mixture formation in direct injection engine such as diesel engine has great influence on the combustion in the cylinder. It is very important to understand the entrainment process of amibient air into the jet or spray in detail. However, few studies have been done on the entrainment process. The fuel injected into the cylinder with high pressure and high temperature in a diesel engine evaporates and goes through with entraining the ambient air. Therefore, for understanding the phenomena easily, a gas was injected for the reason of ignoring the evaporation process and the entrainment process is investigated under the amibient air with atmospheric pressure and room temperature.
In this study, a laser sheet was passed through the cross section of the jet that contained the jet axis or was perpendicular to the jet axis. The instantaneous image of the transient jet and the movement of the ambient air were visualized with fine particles and micro-balloons
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, respectively. A path line method for micro-balloons utilizing a CCD shutter camera was applied for obtaining the air mass entrained into a transient gas jet approximately. In the case of the flame, which was formed by igniting the hydrogen jet at the initiation of the jet, the air flowed into the jet was as the same sa in the jet without combustion. However, the rate of air flowed into the jet per unit surface area was smaller and decreased with time. When the timing of the ignition was delayd after the initiation of the jet injection, the combustible mixture was formed in advance and the air flowed into the jet increased because of turbulent diffusion due to the rapid combustion.
It is also said that the combustible mixture increases in impinging on a wall because of turbulent diffusion. The same method was applied to the jet impinging on a flat wall in order to inveatigate the entrainment of the ambient air into the jet. As a result, the air mass flowed into the jet impinging on a flat wall increased after the impingement for a while, but was almost the same when the time passed more and more even in the injection period. It was found that the rolled up region near the jet tip casused the ambient air flow into the jet. The compact structures that would correspond to the scale of the vortex were disposed regularly near the rolled up region. Less
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