Air–light hydrocarbon mixing gas is a new type of city gas which is composed of light hydrocarbon with the main component of n-pentane and air mixed in a certain proportion. To explore the dominant reactions for CO production of air–light hydrocarbon mixing gas with different mixing degrees at the critical equivalence ratios, a computational study was conducted on the combustion characteristics, including the ignition delay time, laminar flame speed, extinction residence time, and emission of air–light hydrocarbon mixing gas at atmospheric pressure and room temperature in the present study. The calculated results indicate that the ignition delay time of air–light hydrocarbon mixing gas at temperatures of 1000–1118 K is greater than that of n-pentane, while the opposite at temperatures of 1118–1600 K. From the study of the laminar flame speed and ignition delay time, it was found that the essence of air–light hydrocarbon mixing gas is that its attribute parameter is determined by the ratio of n-pentane to the total amount of air at the moment of combustion. The changes in the extinction residence time and the CO emission index of air–light hydrocarbon mixing gas are not synchronized, that is the CO emission index is not necessarily small for air–light hydrocarbon mixing gas with excellent extinction residence time. CO sensitivity analysis and CO rate of production identified key species and reactions that are primarily responsible for CO formation and annihilation. The mixing degree plays a key role in the CO emission index of air–light hydrocarbon mixing gas, which has a constructive opinion on the future experiment and application of air–light hydrocarbon mixing gas.

In the present study, the detailed mechanism of n-pentane combustion, including 697 species and 3214 reactions, is first simplified to a mechanism with only 26 species and 134 reactions, which is suitable for the pressure of 1 atm, temperatures of 1000–1600 K, and equivalent ratios of 0.5–1.6. However, when the equivalence ratio is 1.0, in the temperature range of 1000–1100 K, compared with the detailed mechanism, the maximum error of the ignition delay time predicted by the simplified mechanism exceeds 20%. Therefore, based on the method of temperature sensitivity analysis, the simplified mechanism is further utilized through reducing the A-factor of 2HO2 = H2O2 + O2 (−1) and 2HO2 = H2O2 + O2 (−2) by 10 times. By comparing with the detailed mechanism and predicting the ignition delay time, laminar flame speed, species profile, and extinction residence time, it is found that the optimized mechanism has good accuracy in the applicable range, and is fully capable of simulating the combustion process of light hydrocarbon gas.

Air–light hydrocarbon mixing gas with pentane as the main component is recognized as the “fourth urban gas” by the Chinese government. However, leakage may occur because of inadvertent human operation, and in this case, it is very easy to cause explosion. This paper mainly studies the changes in reactants, products, and free radicals during the explosion of pentane, especially the effects of oxygen and carbon monoxide concentrations on human body in this environment. In actual situations, excessive leakage of pentane is predominant. Once an explosion occurs, oxygen will be quickly consumed, and the concentration of carbon monoxide will rise abruptly. The high temperature resulting from the explosion can cause carbon dioxide to rarely react with carbon atoms to form carbon monoxide through the reaction of CO 2 + C = 2CO. The research studies on the three major free radicals including hydrogen radical, oxygen radical, and hydroxyl radical are performed to provide theoretical support for preventing the chain reaction from further expanding the impact of explosion.