每年專案

## 摘要

Laminar and turbulent minimum ignition energies (MIE_{L} and MIE_{T}) of a lean primary reference automobile fuel (PRF95; 95% isooctane/5% n-heptane) and air mixture at the equivalence ratio of 0.8 at 373 K with large Lewis number Le ≈ 2.95 >> 1 using small and large pin-to-pin electrode spark gaps (d_{gap}) are measured in a dual-chamber, constant temperature/pressure, fan-stirred 3D cruciform burner capable of generating near-isotropic turbulence. Each MIE datum is statistically determined at 50% ignitability by 18–30 repeated runs over a range of ignition energy (E_{ig}). We find two ignition transition (IT) modes. (1) A non-monotonic IT at small d_{gap} = 0.8 mm with the lowest MIE_{T} = 13.9 mJ (< MIE_{L} = 30.1 mJ) occurring at a critical u′_{c} ≈ 1.82 m/s due to the coupling effects between differential diffusion and turbulence, where u′ is the r.m.s. turbulent fluctuating velocity. When u′ > u′_{c}, MIE_{T} increases drastically (>> MIE_{L}), because turbulence re-asserts its dominant role. (2) A regular IT at large d_{gap} = 2 mm is found where MIE_{L} is only 2.05 mJ, in which the increasing slopes of MIE_{T} with u′ change from gradually to exponentially when u′ > u′_{c} ≈ 2.3 m/s. In the post-transition when u′ ≥ u′_{c}, the averaged ratio of MIE at d_{gap} = 0.8-mm and 2-mm (MIE_{0.8}/MIE_{2.0}) is 1.64 > 1, suggesting that using large d_{gap} = 2-mm has a higher ignition probability than using small d_{gap} = 0.8-mm for the lean-burn gasoline surrogate in intense turbulence. Finally, we estimate the uncertainties of burning velocities at u′ = 0 and 2.76 m/s, which are respectively less than 2% and 6% when using small/large E_{ig} ≈ MIE/70 mJ and/or d_{gap} = 0.8-mm/2-mm. These results are relevant to spark ignition gasoline engines operated in lean-burn turbulent condition.

原文 | ???core.languages.en_GB??? |
---|---|

頁（從 - 到） | 340-348 |

頁數 | 9 |

期刊 | Combustion and Flame |

卷 | 225 |

DOIs | |

出版狀態 | 已出版 - 3月 2021 |

## 指紋

深入研究「Two ignition transition modes at small and large distances between electrodes of a lean primary reference automobile fuel/air mixture at 373 K with Lewis number >> 1」主題。共同形成了獨特的指紋。## 專案

- 1 已完成