柴油引燃氨/甲烷预混气着火及燃烧特性研究

Ignition and Combustion Characteristics of Diesel-Ignited Ammonia/Methane Premixed Gas

摘要

依托快速压缩膨胀机光学实验平台,建立火焰自然发光可视化测试系统,研究引燃柴油喷射正时、喷射量和喷射压力对氨/甲烷预混合气着火及燃烧特性的影响．通过分析火焰传播图像、滞燃期、火焰投影面积、缸内压力及放热率等参数,揭示不同喷射条件下的燃烧演化规律．结果表明,柴油引燃氨/甲烷预混合气燃烧可分为柴油主导的第 1 阶段和预混合气主导的第 2 阶段．喷射正时提前可提高缸压峰值和放热效率,最优喷射正时为上止点前 12°CA 至 9°CA；增加喷射量可缩短滞燃期并提高火焰面积和缸压峰值,最优喷射量为 10～12 mg；提高喷射压力在低当量比条件下可强化第 1 阶段放热,最优喷射压力为 100～120 MPa．掺混 40%甲烷显著提高混合气反应活性,使燃烧由柴油主导点火转变为协同促进燃烧．

Abstract

An optical rapid compression and expansion machine(RCEM)platform was used to establish a flame natural luminosity visualization system. The effects of pilot diesel injection timing,injection quantity,and injection pressure on the ignition and combustion characteristics of ammonia–methane premixed mixtures were investigated. Flame propagation images,ignition delay,flame projection area,in-cylinder pressure,and heat release rate were analyzed to reveal the combustion evolution under different injection conditions. The results show that the combustion process can be divided into two stages:a diesel-dominated first stage and a premixed-gas-dominated second stage. Advancing the injection timing increases the peak in-cylinder pressure and heat release efficiency. The optimal injection timing is from 12 to 9 crank angle degrees before top dead center. Increasing the injection quantity shortens the ignition delay and increases the flame area and peak cylinder pressure. The optimal injection quantity is 10 to 12 milligrams. Increasing the injection pressure strengthens the heat release in the first stage at low equivalence ratios. The optimal injection pressure is 100 to 120 megapascals. Adding 40% methane significantly increases the chemical reactivity of the mixture which shifts the combustion mode from diesel-dominated ignition to synergistically promoted combustion.

关键词

柴油引燃 / 氨/甲烷预混合气 / 燃烧特性 / 可视化实验

Key words

diesel ignition / ammonia/methane premixed gas / combustion characteristics / visualization experiment

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基金资助

奥托循环氨燃料发动机燃烧关键技术研究