Process Safety and Environmental Protection 1 1 1 ( 2 0 1 7 ) 94–101 Contents lists available at ScienceDirect Process Safety and Environmental Protection jou rn al hom epage: www.elsevier.com/locate/psep Pressure and temperature influence on propagation indices of n-butane–air gaseous mixtures Venera Giurcan a , Maria Mitu a , Domnina Razus a,* , Dumitru Oancea b a “Ilie Murgulescu” Institute of Physical Chemistry, 202 Spl.Independentei, 060021 Bucharest, Romania b University of Bucharest, Department of Physical Chemistry, 4-12 Blvd. Elisabeta, 030018, Bucharest, Romania a r t i c l e i n f o Article history: Received 13 April 2017 Received in revised form 20 June 2017 Accepted 28 June 2017 Available online 5 July 2017 Keywords: Combustion Closed vessel n-Butane Explosion pressure Rate of pressure rise Severity factor a b s t r a c t The combustion of n-butane–air in a closed spherical vessel with central ignition was stud- ied at various initial pressures within 0.3–1.3 bar and initial temperatures within 298–430 K, by means of transient pressure-time records. The propagation indices of confined deflagra- tions in the quiescent stoichiometric mixture are reported: the peak explosion pressure, the explosion time, the maximum rate of pressure rise and the related severity factor. The mea- sured propagation indices are compared with the propagation indices computed under the assumption of an adiabatic propagation. Based on explosion pressure variation with the ini- tial temperature, the heat of combustion of n-butane with air, corrected for the endothermic processes in the burned gas, was determined. © 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Butane, either alone or as component of Liquefied Petroleum Gas, is extensively used as fuel in automotive engines and domestic heaters. Prevention of fires and accidental explosions of n-butane–air gaseous mixtures, occurring under various conditions as self-ignition or forced ignition, requires the knowledge of several characteristic properties. For forced ignitions of mixtures within the flammability range, the explosion indices – peak explosion pressure, explosion time, maxi- mum rate of pressure rise and severity factor can be directly measured in closed vessels from the recorded pressure – time curves. Values of these indices, determined at ambient initial conditions, are available for the stoichiometric n-butane–air mixture (Bartknecht and Zwahlen, 1993; Brandes and Möller, 2003; Ogle, 1999). However, many processes are running with lean or rich butane–air mixtures, at temperatures and/or pressures different from ambient. Few data on n-butane–air explosions under confined conditions, at normal and/or elevated tem- peratures and pressures, are available (Holtappels, 2007; Holtappels et al., 2007; Razus et al., 2007a). The explosion pressures and sever- ity factors of n-butane with air, measured at 20, 100, 150 and 200 ◦ C and ∗ Corresponding author. E-mail addresses: drazus@icf.ro, drazus@yahoo.com (D. Razus). two initial pressures: 1 bar and 5 bar in a 6 L cylindrical vessel, were reported and discussed in comparison with the data characteristic for n-butane–oxygen mixtures (Holtappels, 2007; Holtappels et al., 2007). Combustion of n-butane–air at ambient initial temperature and vari- able initial pressures and equivalence ratios was studied in two closed vessels with central ignition: a spherical vessel of 10 cm diameter and a cylindrical vessel with 10 cm diameter and 15 cm height (Razus et al., 2007a). The propagation indices (peak explosion pressures, explosion times, maximum rates of pressure rise and severity factors) of mixtures with variable equivalence ratio within 0.82 and 1.52 were examined in connection with the initial pressure and the characteristics of the explosion vessel (volume, height/diameter ratio) which influence the heat losses during explosion propagation. Other studies aimed at deter- mining the normal burning velocity of n-butane–air mixtures in various conditions (initial composition, temperature and pressure) by differ- ent techniques and various flame configurations: stationary flames anchored on a burner (Sher and Ozdor, 1992; Bosschaart et al., 2004), stagnation flames (Davis and Law, 1998; Hirasawa et al., 2002), out- wardly spherically propagating flames (Marshall et al., 2010; Wu et al., 2014). A further comparison of experimental burning velocities with computed burning velocities obtained from the detailed chemical mod- http://dx.doi.org/10.1016/j.psep.2017.06.020 0957-5820/© 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.