| 摘要: | 本論文在已建立的三維十字型風扇擾動雙腔體燃燒器，它可於中央實驗區產生一近似等向性紊流場，實驗使用氨/氫/空氣預混燃氣來探討在不同燃氣當量比(u′ = 0.8、1.0 和 1.2)下之氫氣添加量對常溫常壓氨/氫/空氣層流燃燒速度的影響。此外，由於在 p = 1 atm 和 T = 300K 條件下，化學計量(equivelence ratio = 1.0)的甲烷/空氣層流燃燒速度(SL)為0.37 m/s，介於氫氣添加量在 40% ~ 50%的氨/氫/空氣 SL值之間；由實驗量測結果顯示，在相同條件下(equivelence ratio = 1.0, p = 1 atm, T = 300 K)，當氫氣添加量 45%時，氨/氫/空氣的 SL ≈ 0.34 m/s，與甲烷SL ≈ 0.37 m/s 相近。因此，本文進一步對氫氣添加量 45%之氨/氫/空氣預混燃氣進行了一系列量測，探討燃氣當量比(equivelence ratio = 0.5~1.5)、紊流(u′ = 0.7~2.8 m/s)和壓力(p = 1~5 atm)對 SL和紊流燃燒速度(ST)的影響，並利用先前各研究團隊所提出的正規化紊流燃燒速度之一般通式，進行了比較和分析。研究結果包含以下五點：(1)對於在本研究燃氣當量比( = 0.8, 1.0, 1.2)之氨/氫/空氣預混燃氣而言，層流燃燒速度均會隨氫氣添加量增加而呈指數型增加，其提升幅度在富油條件( = 1.2)下最為明顯。(2)氫氣添加量 45%之氨/氫/空氣預混燃氣在 p = 1 atm 和 T = 300 K 條件下，其 SL值在貧油(0.5 ≤ < 1.0)和化學計量( = 1.0)都與甲烷/空氣 SL值相近，但在富油(1.0 < ≤ 1.5)條件下，其SL值高於甲烷/空氣 SL值，這可能是因為氫/空氣燃氣在 = 1.8 有最高之 SL值。(3)氫氣添加量 45%之化學計量氨/氫/空氣燃氣之 SL 值與壓力的冪次關係為 SL ~ p-0.40，其冪次與化學計量甲烷/空氣燃氣之 SL ~ p-0.43相近。(4)利用紊流可大幅提升氨/氫/空氣之燃燒速度，常溫常壓下，在方均根紊流擾動速度 u = 2.8 m/s 時，可使 = 1.0 之氫氣添加量 45%氨/氫/空氣預混燃氣燃燒速度(ST,c̅=0.5)達 3.05 m/s，約是相同條件下 SL ≈ 0.34 m/s 的 9 倍。(5)利用先前 Kobayashi et al. (1998)、Bradely et al. (2005)、Chaudhuri et al. (2012)、Shy et al. (2019)、Wang et al. (2020)及Lhuillier et al. (2021)等團隊所提出之六個一 般 通 式 進 行 正 規 化 分 析 ， 所 得 之 關 係 式 依 序 如 下 : ST,c̅=0.5/SL = 2.71[(u/SL)(p/p0)Le-1]0.39; ST,c̅=0.5/u = 0.65(KLe)-0.31; ST,c̅=0.5/SL = 0.33(ReT,flameLe 1)0.5; ST,c̅=0.5/u = 0.33(DaLe-1)0.5; ST,c̅=0.5/SL-1 = 0.23(ReT,flameLe-2)0.53 及
ST,c̅=0.5/SL*1/Da=0.1Ka1.02，六種一般通式分析之結果均具有不錯的自我相似性(吻合度R2 > 0.7) ， 尤 以 ST,c̅=0.5/SL = 0.33(ReT,flameLe-1)0.5, ST,c̅=0.5/SL-1 =
0.23(ReT,flameLe-2)0.53 和ST,c̅=0.5/SL*1/Da=0.1Ka1.02為更佳，其 R2 值分別為 0.84、0.91和 0.94。前述氨/氫/空氣之高壓層紊流燃燒速度的量測結果，應可提供未來引擎使用無碳氫/氨混合燃料有用的基礎知識。
;This thesis investigates the impact of hydrogen addition on the laminar burning velocity of ammonia/hydrogen/air premixed combustion in a pre established three-dimensional cross-shaped fan-stirred dual-chamber burner. The experimental setup facilitates the creation of a near-isotropic turbulent flow field in the central test region of the cruciform burner. Experiments are conducted using ammonia/hydrogen/air premixed mixtures to explore the effect of hydrogen addition percentages at different equivalence ratios ( = 0.8, 1.0, 1.2) on the laminar burning velocity under standard temperature and pressure conditions. Furthermore, it should be noted that under conditions of p = 1 atm and T = 300 K, the stoichiometric methane/air laminar burning velocity (SL) is about 0.37 m/s. This falls within the range of hydrogen addition percentages between 40% and
50% for values of SL of ammonia/hydrogen/air mixtures. Experimental results at the same conditions ( = 1.0, p = 1 atm, T = 300 K) reveal that with a 45% hydrogen addition, SL of ammonia/hydrogen/air is approximately 0.34 m/s, which
is closely matching that of methane fuel. Therefore, this study further conducts a series of measurements on ammonia/hydrogen/air premixed combustion with a 45% hydrogen addition. It explores the effects of (= 0.5-1.5), r.m.s. turbulent fluctuation velocity (u = 0.7-2.8 m/s), and pressure (p = 1-5 atm) on both SL and turbulent burning velocity (ST). Several general correlations for normalizing
turbulent flame speeds, as proposed by various research teams in the past, are utilized for comparative analyses and in-depth exploration. The research findings encompass the following five key points. (1) For ammonia/hydrogen/air premixed combustion at various investigated in this study ( = 0.8, 1.0, 1.2), values of SL reveal an exponential increase with the addition of hydrogen. This increase is most pronounced at = 1.2. (2) For ammonia/hydrogen/air mixtures with a 45% hydrogen addition under conditions of p = 1 atm and T = 300 K, values of SL are closely matching with those of methane/air mixtures for both lean (0.5 ≤ < 1.0) and stoichiometric ( = 1.0) conditions; however, values of SL at rich conditions (1.0 < ≤ 1.5) are larger than those of methane/air mixtures. This phenomenon may be attributed to the fact that hydrogen/air combustion exhibits the highest SL at = 1.8. (3) The relationship between SL of the stoichiometric ammonia/hydrogen/air mixture with a 45% hydrogen addition and pressure follows a power-law relationship SL ~ p-0.40, which closely approximates SL ~ p
-0.43 observed for the stoichiometric methane/air mixture. (4) The study demonstrates that turbulence significantly enhances the burning velocity of ammonia/hydrogen/air. Under standard temperature and pressure conditions, when u′ = 2.8 m/s, the burning velocity (ST,c̅=0.5) of ammonia/hydrogen/air with a 45% hydrogen addition at = 1.0 reaches 3.05 m/s, about nine times higher than SL≈0.34 m/s under the same conditions. (5) Using six general correlations previously proposed by different research groups including Kobayashi et al.(1998), Bradely et al. (2005), Chaudhuri et al. (2012), Shy et al. (2019), Wang et al. (2020), and Lhuillier et al. (2021), this thesis performs relevant normalization
analyses. The resulting relationships are presented below in sequence of the aforesaid six research groups. ST,c̅=0.5/SL = 2.71[(u/SL)(p/p0)Le-1]0.39; ST,c̅=0.5/u = 0.65(KLe)-0.31; ST,c̅=0.5/SL = 0.33(ReT,flameLe-1)0.5; ST,c̅=0.5/u = 0.33(DaLe-1)0.5;ST,c̅=0.5/SL-1 = 0.23(ReT,flameLe-2)0.53
and ST,c̅=0.5/SL*1/Da=0.1Ka1.02. All six general correlation analyses exhibit reasonably good self-similarity where the goodness R2 > 0.7, with ST,c̅=0.5/SL = 0.33(ReT,flameLe-1)0.5
, ST,c̅=0.5/SL-1 = 0.23(ReT,flameLe-2)0.53 and ST,c̅=0.5/SL*1/Da=0.1Ka1.02 being particularly good, where the corresponding values of R2 are 0.84, 0.91, and 0.94, respectively. Finally, the present high-pressure SL and ST results for ammonia/hydrogen/air mixtures provide valuable fundamental knowledge for future engine applications utilizing carbon-free hydrogen/ammonia fuel blends. |
