Journal of Hazardous Materials 241–242 (2012) 32–54 Contents lists available at SciVerse ScienceDirect Journal of Hazardous Materials j ournal homepage: www.elsevier.com/locate/jhazmat Review Flammability limits: A review with emphasis on ethanol for aeronautical applications and description of the experimental procedure a b,∗ c c Christian J.R. Coronado , João A. Carvalho Jr. , José C. Andrade , Ely V. Cortez , a c b Felipe S. Carvalho , José C. Santos , Andrés Z. Mendiburu a Federal University of Itajubá – UNIFEI, Mechanical Engineering Institute – IEM Av BPS 1303, Itajubá, MG CEP 37500903, Brazil b São Paulo State University – UNESP, Campus of Guaratinguetá – FEG Av. Ariberto P. da Cunha 333, Guaratinguetá, SP CEP 12510410, Brazil c National Space Research Institute – INPE, Combustion and Propulsion Laboratory – LCP Rod. Pres. Dutra, km 39, Cachoeira Paulista, SP CEP 12630-000, Brazil h i g h l i g h t s Develops a comprehensive literature review on ethanol flammability limits. Difference in standard procedures lead to different experimental values of the flammability limits. Methodology for experiments to find the FL’s of ethanol for aeronautical applications. a r t i c l e i n f o a b s t r a c t Article history: The lower and upper flammability limits of a fuel are key tools for predicting fire, assessing the possibility Received 22 May 2012 of explosion, and designing protection systems. Knowledge about the risks involved with the explo- Received in revised form 23 August 2012 sion of both gaseous and vaporized liquid fuel mixtures with air is very important to guarantee safety Accepted 16 September 2012 in industrial, domestic, and aeronautical applications. Currently, most countries use various standard Available online 24 September 2012 experimental tests, which lead to different experimental values for these limits. A comprehensive liter- ature review of the flammability limits of combustible mixtures is developed here in order to organize Keywords: the theoretical and practical knowledge of the subject. The main focus of this paper is the review of Flammability limits Ethanol the flammability data of ethanol–air mixtures available in the literature. In addition, the description of methodology for experiments to find the upper and lower limits of flammability of ethanol for aero- Visual criterion Pressure and temperature dependence nautical applications is discussed. A heated spherical 20 L vessel was used. The mixtures were ignited with electrode rods placed in the center of the vessel, and the spark gap was 6.4 mm. LFL and the UFL ◦ were determined for ethanol (hydrated ethanol 96% INPM) as functions of temperature for atmospheric pressure to compare results with data published in the scientific literature. © 2012 Elsevier B.V. All rights reserved. Contents 1. Introduction . 33 1.1. Objectives and scope . 33 1.2. Flammability limits . 33 1.3. State of the art . 33 1.3.1. Theoretical methods to determine flammability limits. 35 2. Standard methodology for flammability determination . 36 2.1. Visual criterion . 36 2.2. Pressure criterion . 37 2.3. Brief description of flammability test methods discussed in this paper. 38 3. Influences of temperature, pressure, turbulence and ignition energy on flammability tests . 38 3.1. Temperature . 38 3.2. Pressure. 39 ∗ Corresponding author at: São Paulo State University – UNESP, Campus of Guaratinguetá – FEG, Av. Ariberto P. da Cunha 333, Guaratingueta, SP 12516-410, Brazil. Tel.: +55 12 31232838. E-mail addresses: [email protected], [email protected] (J.A. Carvalho Jr.). 0304-3894/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jhazmat.2012.09.035 C.J.R. Coronado et al. / Journal of Hazardous Materials 241–242 (2012) 32–54 33 3.3. Turbulence . 40 3.4. Comparison between the limits in air and in oxygen . 41 3.5. Ignition energy . 41 3.6. Flammability limits of fuel mixtures . 42 4. Flammability limits in the aeronautical industry. 42 4.1. Importance for the aeronautical industry . 42 4.2. Ignition . 43 4.3. Flammability properties of aviation fuels . 44 5. Tests for flammability limits of ethanol: review . 45 6. Experimental tests with ethanol . 47 6.1. Flammability apparatus . 47 6.2. Description of experimental procedure . 47 6.3. Mass of ethanol needed to form flammable mixtures with air . 50 6.4. Description of the procedure to calculate LFL and UFL from experimental data . 50 6.5. Results and discussion. 51 6.5.1. Behavior of flame propagation . ..