| 摘要: | 預混紊流燃燒是燃燒學術領域一個仍不被完全了解且相當挑戰的主題，它具學術和應用的重要 性，因其與燃氣輪機、汽車引擎等內燃機息息相關，是推動現代燃燒研究的主因之一。即使是僅提升 內燃機燃燒效率1%，其所節省的燃料用量(減少汙染物和CO2 排放量)，即可對一國之經濟和環保有重 要的助益。而貧油預混紊流燃燒，已被證實可降低NOx 和提高燃燒效率，但其缺點是失效點火(misfire) 會增加，故目前汽車引擎仍大都是操作在微富油條件，這會產生較多的汙染物和CO2。預混紊流燃燒 涵蓋了空氣動力、熱力化學、化學動力和紊流等學科，目前對紊流的瞭解仍有許多不足之處，再加上 複雜的化學反應，以及實際汽車引擎和燃氣輪機等內燃機均操作在高溫高壓紊流條件下，使得此研究 深具挑戰性。本學術計畫，為了精準控制實驗條件(溫度、壓力、紊流特性、空燃比等)，特將非常複 雜的內燃機引燃和燃燒現象，簡化成可被詳細量測之實驗室研究，高溫高壓預混燃氣之引燃、爆炸和 紊焰傳播的實驗將於已建立之大型雙腔體定溫定壓預混紊流燃燒設備進行(如下圖所示)。在已有之高 溫高壓甲烷燃氣的基礎上[1,2]，此三年期計畫工作重點：(1)改善目前已有之常溫高壓火花引燃系統， 使其可應用至高溫高壓高紊流環境；(2)量測汽油主要參考燃料，異辛烷、正庚烷、甲苯之最小引燃能 量(minimum ignition energy, MIE)與溫度、壓力和紊流強度之關係；(3)量測90%異辛烷和10%正庚烷(約 等同汽油)之MIE 與溫度、壓力和紊流強度之關係；(4)量測各種氣態(氫氣、合成氣等)和液態燃料(異 辛烷、正庚烷、甲苯、汽油等)之層紊流燃燒速度；(5)分析前述結果之自我相似性(self-similarity)和建 立無因次化參數群通式。本計畫目標為建立高溫高壓預混紊流燃燒之引燃和火焰傳播的機制，產出具 學術和應用價值之研究成果，進一步提升主持人在國際預混紊流燃燒領域之學術地位。 ;Premixed turbulent combustion, a challenging subject in the combustion field, is of academic and industrial importance, because it is the corresponding burning mode in gas turbine combustors for power generation and spark ignition engines for transportation, which is the main driving force behind modern combustion research. Even a small 1% improvement of combustion efficiency in internal combustion engines has a significant impact on economy and environment due to fuel saving and thus reduction of pollutants and CO2 emissions. Lean premixed turbulent combustion has great potential to decrease NOx emissions and increase combustion efficiency, but its shortage is more misfires in engines. This is why the current auto engines are operated at slight rich fuel conditions that produce more pollutants and CO2 emissions. Premixed turbulent combustion covers multi disciplines such as aerodynamics, thermochemistry, chemical kinetics and turbulence. At present, turbulence is not fully understood, chemical reactions are quite complex, and real spark ignition engines and gas turbines are operated at high-pressure, high-temperature turbulent conditions, causing it difficult to study. For simplicity, we designed a well-controlled laboratory experiment to measure ignition, kernel formation, and flame propagation at high-pressure, high-temperature turbulent environment relevant to engine conditions. Experiments will be conducted in a large dual-chamber, constant-pressure, constant-temperture premixed turbulent combustion facility (see the figure in previous page) with new modifications using the newly-designed heating and insulation devices for high-temperature requirements (T = 298 ~ 523 K, p = 1 ~ 12 atm, and u′ = 0 ~ 8.42 m/s). The key working items of this three-year project are: (1) To further improve the already-established constant-temperature spark ignition system so that it can be used in high T, high p, high turbulent environment; (2) to measure the minimum ignition energy (MIE) of iso-octane and n-heptane (the primary reference fuel of gasoline) at various T, p, and u′; (3) to complete MIE measurements of 90% iso-octane and 10% n-heptane (the major components of gasoline) at various T, p, and u′; (4) to measure laminar and turbulent burning velocities of various gaseous and liquid fuels, such as hydrogen, syngas, iso-octane, n-heptane, toluene and gasoline, as functions of pressure, temperature, and turbulent intensity; (5) to analyze the self-similar behaviors of these aforesaid results and to establish normalized general correlations based on group non-dimensional parameters. The project goal is to establish high-temperature, high-pressure, turbulent lean premixed ignition and combustion mechanisms by unifying the above massive data for their possible fuel similarity. The expected results are of fundamental and practical importance, which are up front in the field of premixed turbulent combustion. |
