An ignition control method with optimizations of the composition of mixture and turbulence characteristics based on molecular diffusion characteristics

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04311
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19020:Thermal engineering-related
• Research Institution: Ehime University
• Principal Investigator: Nakahara Masaya 愛媛大学, 理工学研究科(工学系), 教授 (20315112)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 予混合燃焼 / 着火促進 / 微小火炎 / 乱流場 / 燃焼速度 / 火炎伸長 / 水素 / ルイス数

Outline of Final Research Achievements

In this study, an ignition control method had been investigated for ultra-lean fueled mixtures and for high-intensive isotropic-homogeneous and swirl turbulent fields. First, from the investigation of the burning velocity of meso-scale flames in a laminar flow field (quiescence), it was clarified that the burning velocity SLl with the flame radius rf = 4 mm has a good linear correlation with the Lewis number regardless of the type of fuel (methane, propane and hydrogen), the type of diluent gas (nitrogen, argon and carbon dioxide), the hydrogen additional rate and the laminar burning velocity. Furthermore, from the investigation of the minimum ignition energy, MIE, in a turbulent field, it was found that the transition region of MIE in turbulence, where the ignition characteristics deteriorate rapidly, could be summarized by using the proposed turbulent Karlovitz number KaT4 based on SLl at rf = 4 mm in quiescence.

Free Research Field

熱工学　燃焼工学　科学教育

Academic Significance and Societal Importance of the Research Achievements

本研究で提案する微小層流火炎の火炎半径rf=4mmの燃焼速度SLlを基準とする乱流カーロビッツ数を用いると，乱流強度の増加に伴い悪化する着火特性を，安定的に着火できる領域と急激に着火特性が悪化する遷移領域を予測できる．この成果は，内燃機関であれば，炭化水素燃料の超希薄混合気でかつ高強度ガス流動場での着火特性を予測できることになり次世代エンジンの設計に有用な知見となる．さらに，水素利用社会においては，危険な燃焼特性を有する水素をどうすれば着火・爆発させずに安全に利用できるかを示す指針になり有用である．本研究成果は極めて学術的かつ社会的に意義は大きいと考える．