Role of peroxy chemistry in the high-pressure ignition of n-butanol – Experiments and detailed kinetic modelling

Abstract

Due to its considerable advantages over lower alcohols such as ethanol, in particular with regard to its physical properties like volatility, corrosivity, and hygroscopicity, butanol has attracted considerable interest as a potential biofuel candidate. It has therefore been a target of a series of experimental studies probing its combustion characteristics. Nevertheless, its ignition behaviour at elevated pressures still remains widely unexplored. The present study investigates the oxidation of n-butanol at pressures near 80 bar. Ignition delays were determined experimentally in the temperature range of 795-1200 K between 61 and 92 bar.The time of ignition was determined by recording pressure and CH-emission time histories throughout the course of the experiments. The results display the first evidence of the influence of negative temperature coefficient (NTC) behaviour which was not observed in earlier ignition studies. The high pressure measurements show that NTC behaviour is enhanced as pressures are increased. The experimental results were modelled using an improved chemical kinetic mechanism which includes a simplified submechanism for butylperoxy formation and isomerisation reactions currently absent in n-butanol kinetic models.The detailed mechanism validated with the high pressure ignition results for realistic engine in-cylinder conditions can have significant impact on future advanced low temperature combustion engines.

Comparative Autoignition Trends in Butanol Isomers at Elevated Pressure

“…Nevertheless, the chemistry of the hydroxybutylperoxy species is important in the combustion of the other isomers of butanol as well. Using the high pressure shock tube at RWTH Aachen University, Vranckx et al 26 showed the importance of peroxy chemistry pathways in the autoignition of n-butanol. By adding a lumped peroxy model to an existing kinetic model for n-butanol combustion, they were able to substantially improve agreement of the model with their experiments at high pressure and low temperature.…”

“…Several studies of ignition delay of the butanol isomers have been conducted in both apparatuses, including work in shock tubes by Black et al, 21 Heufer et al, 22 Moss et al, 23 Noorani et al, 24 Stranic et al, 17 Vasu et al, 25 and Vranckx et al, 26 and work in RCMs by Karwat et al 27 and Weber et al 16 These studies have covered a wide range of temperature-pressure regimes for n-butanol, from 1-90 bar and 675-1800 K. However, only the shock tube studies from Moss et al 23 and Stranic et al 17 have studied all four isomers of butanol, over the more limited range of 1-48 atm and 1022-1825 K.…”

An experimental study on the formation of polycyclic aromatic hydrocarbons in laminar coflow non-premixed methane/air flames doped with four isomeric butanols

“…Several experimental studies focusing on the combustion characteristics of butyl alcohols have also been published by presenting a wealth of combustion data obtained in shock-tubes [2,[13][14][15][16], flow reactors [17,18], jet-stirred reactors [2,[19][20][21][22][23] and flames [17,22,[24][25][26][27][28]. Coupled to these experiments, kinetic modeling studies have been performed, which resulted in a detailed description of the high-temperature fuel chemistry [2,13,17,19,22,27].…”

Mixed butanols addition to gasoline surrogates: Shock tube ignition delay time measurements and chemical kinetic modeling

“…Combustion of the butanol isomers has been studied extensively in shock tubes [14][15][16][17][18][19][20][21][22][23][24]. This greatly contributed to the development of many chemical kinetic models [9,18,22,[24][25][26][27][28][29]. These chemical kinetic models provide a detailed description of the fuel ignition characteristics and hence a better understanding of the fuel/engine interactions through engine-combustion simulations.…”