| 摘要: | 本台德國際合作計畫針對火花引燃引擎不易於貧油條件下操作之困難挑戰，提出一貧油高溫高壓 預混紊流燃燒技術之綜合研究，其可有效節省燃油、降低NOx 和提高熱效率，為一具節能減碳之前瞻 燃燒科技。目前文獻上已有之實驗和數值分析研究，絕大多數為常壓常溫，有些為高壓常溫，極少數 為高壓高溫。可是引擎和氣渦輪機均是在高壓高溫紊流條件下操作，是故如何開發接近實際引擎和燃 氣輪機操作條件之貧油預混紊流燃燒技術，將有重要學術和應用之價值。有鑒於此，我們提出此三年 期台德合作計畫『汽油和其替代品紊流火花引燃動力於貧油、高壓、高溫條件之綜合研究』，擬 開發前瞻高溫高壓貧油預混紊流燃燒技術，以建立其引燃相關機制。本計畫結合台德雙方研究能 量，由台灣團隊（中央機械）負責實驗量測和分析研究，而德國團隊(Karlsruher Institut für Technologie, Institut für Technische Thermodynamik)則負責數值模擬和化學動力學研究(reduced kinetics)，目標為建 立目前尚無之高溫高壓貧油預混紊流燃燒的引燃學理機制和其應用技術，並產出領先國際相關研究之 成果。我們將使用已開發成功之大型高壓高溫雙腔體預混紊流燃燒設備，此大型設施(在國際燃燒學術 領域具有創新性和獨特性)，其可控壓力範圍為0.1~10atm、可控溫度為25~250oC 和可控方均根紊流擾 動速度u′為0~8.42 m/s。近期設計之加熱設施擬用來執行實際引擎所用液態燃料(汽油和其替代品)的 火花引燃實驗和量測其後續發展之火焰燃燒速率，本計畫將有助於新世代高效率汽車引擎（操作在貧 油條件）之火花引燃系統的優化設計。三個年度工作項目依序重點條列如下：(1)改善目前已有之常溫 火花引燃系統，使其可以應用至高溫高壓高紊流環境；(2)量測貧油汽油（當量比φ = 0.8 或以下）及其 代替品：異辛烷(iso-octane)、正庚烷(n-heptane)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)量測貧油90%異辛烷和10%正庚烷（汽油主要參考燃料）之MIE 與溫度、 壓力和紊流強度之關係；(4)量測貧油異辛烷/正庚烷/甲苯（toluene）(約等同汽油)之MIE 與溫度、壓 力和紊流強度之關係；(5)所得結果與數值模擬 (含reduced kinetics 簡化化學動力學)相互驗證，目標為 建立貧油高溫高壓預混紊流火花引燃機制，期能解決火花引燃引擎不易於貧油條件下操作之挑戰問 題。此計畫攸關建立高效率和低汙染排放(低NOx)貧油預混紊流潔淨燃燒技術，應具學術和應用之價 值，將對航空/車用火花引燃引擎效率提升和降低NOx 以及節能減碳有重要之助益。有關數值模擬部 分，詳請見IM02 和IM03 之資料內容。 ;High-temperature, high-pressure lean premixed turbulent combustion, an advanced combustion method, is essential to the further development of auto engines and gas turbines because of its great potential to save fuels, reduce NOx, and increase thermal efficiency. However, so far in the available literatures, most experiments and simulations were conducted at normal temperature and pressure conditions, some at elevated pressures under room temperature condition, but very rare at high pressure and high temperature relevant to engines and gas turbines conditions. This motivates the present proposal, titled “A Comprehensive Study on Turbulent Spark Ignition Dynamics of Gasoline and Its Surrogate at Fuel-Lean, High Pressure, High Temperature Conditions”, which is a topic of wide interests with both academic and industrial importance. This three-year MOST-DFG proposal continues to unify the research capabilities between National Central University (NCU in Taiwan) and Karlsruher Institut für Technologie (KIT in Germany). The joint objective is to develop a challenging high temperature/high pressure lean premixed turbulent combustion technology at engine and gas turbine relevant conditions based on experimental measurements and numerical simulations. Hence, the associated ignition mechanisms can be established. The NCU team specialized in experiment is responsible for all experimental measurements and analyses, while the KITITT (Institut für Technische Thermodynamik) team specialized in both numerical simulations and laser-assisted measurements is responsible for numerical simulations and reduced chemical kinetics studies. Our goal is to establish spark ignition mechanisms of high-temperature, high-pressure lean premixed turbulent combustion, aiming to produce innovative research results in the field. Experiments will be conducted by the NCU team in a large dual-chamber, high-pressure premixed turbulent combustion facility that has newly-modified heating and insulation devices for high-temperature requirements. This innovative and unique large-scale facility allows us to perform experiments over very wide ranges of pressure (p = 0.1 ~ 10 atm), temperature (T = 25 ~ 250oC), and rms turbulent fluctuating velocity (u′ = 0 ~ 8.42 m/s). These newly-modified heating devices in and out a large 3D cruciform burner (inner chamber) should allow us to investigate spark ignition of various liquid fuels (gasoline and its surrogates) in high-temperature, high-pressure, high-Reynolds-number environment, which is crucial to the further development of high-efficiency gasoline engines. Simulations are to be performed by the KITITT team to develop the tractable nonlinear models, capable of describing spark ignition and its subsequent development under high-pressure, high-temperature turbulent conditions. This joint project implementation will allow us to create fundamental mathematical models, so that characteristics of ignition processes of lean gasoline and its surrogae mixtures relevant to engine conditions can be understood in more depth. These results are useful for optimization of ignition systems and development of fire safety standards in practical devices. The three-year key working items are as follows. For the experiment part: (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 lean gasoline (equivalence ratio φ = 0.8 or below) and its surrogates (iso-octane and n-heptane) at various T, p, and u′; (3) to complete MIE measurements of 90% iso-octane and 10% n-heptane (the primary reference fuel of gasoline) at various T, p, and u′; (4) to measure MIE of iso-octane/n-heptane/toluene mixtures as functions of pressure, temperature, and turbulent intensity; (5) to unify the above proposed massive data in attempt to establish the fuel similarity mechanisms and to produce results to further advance our knowledge in the field of premixed turbulent combustion. Concerning the content of numerical simulations and reduced kinetics development, please see IM02 and IM03 attached files. |
