Ultra high-efficiency clean combustion engine fueled with DME

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K06185
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Thermal engineering
• Research Institution: Ibaraki University
• Principal Investigator: KONNO Mitsuru 茨城大学, 理工学研究科(工学野), 教授 (90205576)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: e-fuel / ジメチルエーテル / 内燃機関 / 合成燃料 / 改質 / キャビテーション

Outline of Final Research Achievements

Reforming characteristics of DME with engine exhaust gas were analyzed using a detailed elementary chemical reaction model. More hydrogen is generated by DME reforming at lower temperatures compared to gasoline reforming. DME reforming reaction was sensitive to DME/oxygen ratio. For a practical application of the DME reforming system, it is important to precisely keep the DME/exhaust mixing ratio adequate. Therefore, the flow behavior of DME in the fuel supply injector was examined in detail by high-speed visualization and numerical analysis. It was found that choking occurs at much lower pressure-difference than those of petroleum fuels, because the effective cross-sectional area of the flow passage decreases by cavitation due to DME’s high vapor pressure, and also because the sound speed decreases by a generation of gas-liquid two-phase flow.

Free Research Field

熱工学

Academic Significance and Societal Importance of the Research Achievements

DMEはCO2と再生可能エネルギーから製造可能なカーボンニュートラルに貢献する合成燃料である。本研究では、煤を排出しない性質、改質平衡温度の低さといった特色を活かし、排気熱によるDMEの改質反応を用いた内燃機関の高効率・クリーン化に取り組んだ。DMEの改質特性を明らかにするとともに、実用化の観点から、改質システムのDME／排気混合濃度の高精度化に必要なDMEインジェクタ流路内挙動を数値解析と可視化によって詳細に調べ、石油系燃料に比べて低い差圧でチョーク現象を起こすことを見出し、またその要因を明らかにした。これらの成果を通じてモビリティの脱石油化に向けてバッテリー以外の新たな可能性を示した。