Combustion mechanism of n-pentane, isopentane and neopentane as environmentally friendly working fluids: ReaxFF molecular dynamic simulations study.

A series of ReaxFF reactive molecular dynamic simulations are performed to investigate the combustion of n-pentane, isopentane and neopentane. The effects of temperature and the n-pentane-to-O2 ratio on the number of main radical and molecular products for the combustion of n-pentane are analyzed, the combustion characteristics of n-pentane, isopentane and neopentane are compared, and the spontaneous combustion characteristic of n-pentane is discussed in this work. The results indicated that the main reactions involved in the early stage of n-pentane, isopentane and neopentane combustion are the pyrolysis of these working fluids, and then, O2 molecules are involved in the oxidation reactions. The content of O2 in reaction systems has a very obvious effect on the combustion of n-pentane. With the increase in the O2 content, the consumption rate of n-pentane is significantly accelerated, and the rate of increase in the total fragments number is also significantly increased. Neopentane burns most intensely, followed by isopentane, and finally n-pentane. A faster heating rate will be accompanied by more intense spontaneous combustion of n-pentane and more product formation, which will cause greater harm to the surrounding area. Thus, in order to reduce the possibility of damage caused by leakage combustion of flammable working fluid, the heat source temperature and open flame around the organic Rankine cycle system should be strictly controlled, and some flame retardants are recommended to be added to the working fluid to reduce the flammability while ensuring the economy of the organic Rankine cycle. This study is conducive to the safety of n-pentane, isopentane and neopentane used in industrial fields. [ABSTRACT FROM AUTHOR]