分会场

高效清洁燃烧

摘要

Ignition characteristics are of crucial importance for advanced internal combustion (IC) engines operating at low-temperature combustion modes. Recent work shows that fuel reforming has great potential in controlling combustion processes. In this work, cool flame oxidation as a reforming way was proposed and its potential in ignition characteristics was investigated under engine-relevant conditions. As a component of primary reference fuel (PRF), n-heptane was selected for investigations as it has pronounced low-temperature oxidation and cool flame behavior. Depending on fuel oxidation degree at various temperatures, two kinds of reforming products were classified, i.e. mild reforming and severe reforming, manifesting distinct fuel reactivity. Then the influence of forming conditions on reforming products was explored. The effects of reforming products on ignition characteristics of different blends were finally investigated, with detailed sensitivity analysis. The results show that the reforming products via cool flame oxidation are more sensitive to reforming temperature than reforming pressure and equivalence ratio. The majority of reforming products remain unchanged and only some free radicals show significant variations. The promotion effect on ignition processes becomes enhanced by the reforming products from higher temperature, higher pressure, leaner mixture, and severe reforming conditions. Affected by reforming products through cool flame oxidation, the ignition delay time is shortened under most operating conditions, except for some scenarios in the negative temperature coefficient (NTC) range where τ700k, mild>τ700k, severe>τ750k, severe>τ750k, mild, behaving a “cross-point” relation within 700 ~ 750 K.

关键词

冷焰氧化;燃料重整;着火滞燃期;重整产物;敏感性分析

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