- 學位論文
高熱通量下延遲加熱控制對雙熱氣泡成長動力之相互影響
The Dynamic Interactions of Dual Thermal Bubbles with Delayed Heating Pulse under High Heat Flux
摘要
此研究當中藉由控制延遲時間，來了解複雜的雙氣泡之間相互影響，其中的影響可由最大的氣泡體積、速度流場變化、氣泡壓力及有效的能量來討論。延遲時間DT=0μs時，兩個氣泡同時產生，同時也產生壓力波相互抑制對方的成長。延遲時間DT=2μs時，右邊氣泡剛成長時所產的壓力波影響左邊氣泡的成長，導致於左邊的氣泡慢於單一成長的氣泡，當左邊氣泡萎縮時造成一個沉流，促進右邊氣泡的成長。延遲時間DT=8μs時，左邊氣泡維持單一氣泡的狀況，沒有受到任何影響，當左邊氣泡產生rebound，造成右邊的氣泡偏離原本預期的單一氣泡的曲線。 高熱通率的熱氣泡動態會所輸入的熱能所侷限，調整雙氣泡之間的延遲時間，讓氣泡之間的消長能有效率傳遞能量，從一顆氣泡傳遞到另一顆氣泡身上，此方式打破以往單一氣泡所能承載能量限制。實驗結果顯示若將兩氣泡的延遲時間設定在2μs及3μs之間，就能有效率的從一顆氣泡傳遞40%的能量轉移給另一顆氣泡。若是以整體能量來計算，雙氣泡系統所產生的能量會比兩倍的單一氣泡所產生的能量多20%。這樣的現象提供一個新的方式，能有效的轉移或集中能量給所需要的氣泡。
並列摘要
In this study, delay times of explosive dual microbubbles are controlled precisely to understand the complex and dynamic phenomenon of dual bubbles interactions. The interactions have been characterized in terms of maximal bubble size, sink/source flow, bubble pressure, and useful work. For DT = 0 μs, dual bubbles are produced simultaneously,and the produced pressures inhibit the growth ofeach other. The sizes of those are slightly smaller than thatof a single bubble. For DT = 2 μs, the pressure generated from the second (right) bubble affects the growth of the first (left) bubble in the beginning and poses the first bubble growth slower than the single bubble. When the first (left) bubble starts to collapse, the surrounding flow field induces a sink flow to promote the growth of the second (right) bubble. As the first (left) bubble rebounds, the peak pressure produced by the rebound leads to a rapid collapse of the second (right) bubble. For DT = 8 μs, the first (right) bubble keeps following the history of the single bubble because there is no influence from the second(right) one. As the first bubble rebounds in the same condition, the volume history of the second bubble drops and deviates from the original track of the single bubble. The dynamics of a high heat flux thermal bubble is constrained by the thermal energy carried on the bubble surface right after the bubble formation because of thermal isolation of vapor. This paper proposes a way by assigning time delays between dual bubbles to effectively transfer energy from one bubble into the other, thus breaks energy limitation that one single bubble can usually carry. Experiment result has demonstrated that the useful work as large as 40% can be transferred from one bubble into the other for the ignition time delay set between 2 and 3 μs in a dual bubble system. At the same time, the total extractable useful work in a dual bubble system is 20% higher than twice that of a single bubble system with the same input heat energy. This phenomenon opens up a new way to transfer or concentrate energies from distributed energy sources with limit energy density into a much higher one for higher power application.