碩士生: 高孝瑄
畢業年分: 2022年7月
論文名稱: 碳氫預混火焰在不鏽鋼−鉑分段式反應器之燃燒特性與性能優化研究(中文) / Study on combustion characteristics and performance optimization of hydrocarbon premixed flames in stainless steel−platinum segmentation reactor(英文)
中文摘要:
本研究主要探討具有穿孔之不鏽鋼/白金觸媒微管燃燒器的燃燒性能與優化研究。由於燃燒過程會伴隨著化學反應、熱傳導與質量擴散等不可逆性的過程發生，而這些不可逆性的過程稱之為熵。熵之生成會造成能量損失，然而這些能量損失無法藉由實驗測得求得，因此需要藉著模擬之幫助以探討微反應器內部能量損失之來源。藉著分析熵生成率之後，可以進一步求得微燃燒器的熱力學第二定律效率，以判別燃燒器性能。
繼前人的研究得知，帶有穿孔式的不鏽鋼/白金觸媒微管將有利於火焰穩住於微反應器中，其原因在於孔洞的設計能提供微反應器一個低速帶且有利於內、外兩流道之流體混合。然而，孔洞數量與孔徑大小之研究尚未深入探討，因此本研究提出三種不同之燃燒器設計，依固定白金面積設計出4個與6個孔洞數量，旨在探討白金用量相近的情況下，孔洞數量對於燃燒性能之影響，並以4個孔洞之設計探討孔徑大小，孔徑直徑分別為1公厘和1.5公厘。
然而，本研究提出3種燃燒器的孔洞設計以及針對會影響燃燒效率的四種參數進行探討，其中討論的參數包含甲烷/空氣的流速、氫氣/空氣的流速、甲烷/空氣的當量比，以及氫氣/空氣的當量比。隨著操作區間的搭配，將會有許多參數組合，若要探討所有排列組合條件的性能，勢必會浪費許多時間與金錢。因此本研究利用克里金代理優化模型協助以較少的組數得到然燃燒效率的趨勢，並且能以一定量的實驗組數去建立優化模型。其中，所建立的克里金代理優化模型可以成功預測3種燃燒器的燃燒效率，以及其燃燒模態的區間界定。例如，在六個孔洞設計中，氫氣/空氣速度、甲烷/空氣速度、甲烷/空氣的當量比與氫氣/空氣的當量比的敏感性係數值分別為 -1.7、-0.22、0.4 和 0.15。代表氫氣/空氣的當量比在六個孔洞設計中將影響燃燒效率甚大。
英文摘要:
This study focuses on the combustion performance and optimization of a perforated stainless steel/platinum catalytic micro-tube burner. The combustion process involves irreversible processes such as chemical reactions, heat conduction, and mass diffusion, collectively known as entropy. The generation of entropy leads to energy losses that cannot be measured experimentally, necessitating simulation to investigate the sources of energy loss within the micro-reactor. By analyzing the entropy generation rate, the second law efficiency of thermodynamics for the micro-burner can be determined, which helps in assessing the burner's performance.
Previous research has shown that perforated stainless steel/platinum catalytic micro-tubes stabilize flames within the micro-reactor. This is because the perforations create a low-velocity zone that enhances fluid mixing between the inner and outer flow channels. However, the effects of the number and size of these perforations have not been thoroughly explored. This study proposes three different burner designs with either 4 or 6 perforations, keeping the platinum surface area constant, to examine how the number of perforations affects combustion performance. Additionally, the impact of perforation diameter (1 mm and 1.5 mm) on the design with 4 perforations is investigated.
The study examines three burner designs and four parameters that affect combustion efficiency: methane/air flow rate, hydrogen/air flow rate, methane/air equivalence ratio, and hydrogen/air equivalence ratio. Considering the various combinations of operating conditions, exploring all permutations would be time-consuming and costly. Therefore, the Kriging surrogate optimization model is used to identify trends in combustion efficiency with fewer experimental runs. This model helps predict the combustion efficiency and delineate the combustion mode intervals for the three burner designs.
For example, in the design with six perforations, the sensitivity coefficients for hydrogen/air flow rate, methane/air flow rate, methane/air equivalence ratio, and hydrogen/air equivalence ratio are -1.7, -0.22, 0.4, and 0.15, respectively. This indicates that the hydrogen/air equivalence ratio significantly impacts combustion efficiency in the six-perforation design. The Kriging model effectively predicts combustion efficiency and guides optimization, demonstrating its utility in designing efficient micro-burners.
