Numerical Analyses of Film Cooling and Conjugate Heat Transfer for a Three-dimensional Thrust-vectoring Nozzle

• Main Authors: Chung-YuTien, 田崇佑
• Other Authors: Tsung-Leo Jiang
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/r6s7ax

碩士 === 國立成功大學 === 航空太空工程學系 === 104 === Modern fighters, such as USAF F-35, use 3D thrust-vectoring nozzles to enhance maneuverability and flexibility. Although the design improves fighter maneuverability, it causes thermal problem due to high-temperature flow strike. The internal flows of a 3D thrust-vectoring nozzle are analyzed in this study through numerical simulation. The characteristics that this research concerned include the thrust of the nozzle, the maximum wall temperature, and the detail flow in the cooling channel. In order to improve cooling benefit, three sensitive parameters, such as cooling mass flow rate of main flow, angle of cooling air injection, and slot length of cooling air injection, are analyzed. In the present study, the commercial CFD software, ANSYS FLUENT, employing the SST k-ω turbulence model and DO radiation model, was applied to analyzing the nozzle thrust variations. The simulation results of previous studies indicated that high temperature flow impacted the upper deflection wall. But surprisingly, this study indicates that upper deflection wall temperature is not as originally expected to be higher than the lower one. This is because the deflection section can deploy such that the upper wall has more cooling area for cooling down the nozzle wall. According to this reason, we need to concentrate cooling effect on the lower deflection wall. First, when the 3D thrust-vectoring nozzle deflects to 90 degree, the higher pressure at deflection upper area will cause lower quantity of cooling air injected to the main flow smoothly. Rich quantity of cooling air interacts intensely with the main flow, causing the thrust loss. Second, cooling-air injection angle is a main factor. If the channel direction is more vertical between the main flow and the cooling air, it will affect the thrust performance strongly. Due to the cooling channel geometry, the tilt angle model causes more heat transfer through the inner wall. Third, cooling injection slot length influences the cooling-air injection quantity of the upper site and the lower site when the 3D thrust-vectoring nozzle deflects to 90 degree. It will affect the temperature decreasing rate of high temperature decreasing rate temperature area seriously. Therefore, the cooling channel geometry design is a major factor for cooling effect and thrust performance.