稀薄噴流流場量測及模擬技術研究

Abstract

由於噴流在火箭推進、燃料噴射器、太空飛行體姿態控制等等的應用，因此在過去有相當多的相關研究。然而大部份的研究均注重在連續流區域。如果背壓相當低（如在太空中），將使流場現象（包括連續流、過渡流及自由流）變得相當複雜。如果噴嘴設計不良可能造成衛星本体遭受汙染、姿態控制準確性受到干擾等等問題發生，進而縮短任務生命及影響任務達成。然而在掌握噴流及衛星間之交互作用之前，須要針對噴流基本擴散流場（expanding flow）有所了解。並藉著噴流實驗結果建立相關流場之模擬能力，此對於未來國內衛星姿態控制系統設計自主能力之建立將有所貢獻。本研究最主要目的在利用太空計劃室籌備處即將建置完成之小型熱真空腔系統，提供高真空環境，量測噴流流場性質並與DSMC模擬結果比對，驗証數值模擬能力。因此本計畫提議針對單一噴流，以實驗及數值分析的方法做一詳細的探討與研究。總結來說，提議之研究計畫以一年時間來進行。簡要整理如下： 1.在前半年建議利用本實驗室已發展完成之平行化、三維、具非結構網格的蒙地卡羅直接模擬法（Direct Simulation Monte Carlo）程式進行噴流流場模擬。 2.在後半年以pitot tube量測全壓力分佈及流角（flow angle）。並與模擬結果，驗証程式的準確性。

關鍵詞：噴流、衛星、平行化、直接蒙地卡羅模擬法、姿態控制、全壓力

Jet plume has been the focus of numerous research efforts in the past due to its fruitful applications in rocket exhausts, fuel injectors, space-vehicle maneuvering thruster and aeroaccoustive and aerothermodynamic experiments. Most researches were conducted in the continuum regime. However, the flow field may become very complicated involving continuum, transitional and even free-molecular flows if the environmental pressure is very low. Ill-conditioned jet plume may cause the severe contamination of critical surface such as solar array and affect the accuracy of attitude control by improper plume impingement on spacecraft. This will definitely shorten the mission life and of course affect the planned mission. Thus, it is indispensable to understand the fundamentals of jet plume in vacuum environment if proper design of nozzle is desired. Experimental and numerical investigation of the jet plume will help Taiwan to establish its own capability of design the reaction control system of satellite.Therefore, the purpose of the current proposal is to measure the flow field of a jet plume in a to-be-completed small thermal vacuum chamber at National Space Program Office and to compare with the numerical results by direct simulation Monte Carlo (DSMC) method. In summary, we propose: 1.to use the completed parallel, three-dimensional, unstructured-mesh DSMC code to simulate the flow field of the jet plume; 2.to measure the distribution of total pressure and flow angle; 3.to compare the experimental and numerical results. Keywords？HHGjet plume, direct simulation Monte Carlo, parallel, unstructured-mesh, total pressure.