摘要:
为探究清洁燃料乙炔在O2/CO2气氛下的可燃下限，在5L圆柱体爆炸反应装置中实验测得了乙炔的可燃下限。随CO2体积分数增加(14%-85%)，乙炔可燃下限的实验值从2.64%增长到3.93%，在较小的范围内呈线性增加。与其他烃类燃料相比，可燃下限呈现烷烃＞烯烃＞炔烃，表明炔烃具有更大燃烧范围。基于极限层流速度法计算模型，建立了适用于乙炔可燃下限的预测模型。通过实验数据的验证，该模型准确可靠。使用该模型讨论了CO2的热力学、化学、输运效应对可燃下限的影响机理。结果表明：热力学效应平均占比在64%，化学效应占比35%，输运效应占比1%。
Abstract:
Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. In order to grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different concentrations of CO2 on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5L cylindrical explosive reaction device. With the increase of CO2 concentration from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit presents alkanes > olefins > alkynes, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar flame velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC II combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. In order to explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit are discussed by using the model and modifying the combustion reaction mechanism of USC II to introduce the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.
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