Combustion of Substances in a Cone Calorimeter - Assignment Example

Combustion of Substances in a Cone Calorimeter ABSTRACT The report summarizes the process of combustion of various substances in a cone calorimeter and the assessment of how these tested substances will contribute to the development of a room fire under given conditions. The study of the instrument, the basic process involved and other related scientific details are included. 1. INTRODUCTION Cone calorimeter is an instrument used to learn the fire behavior of various substances in condensed phase. It is widely used in Fire and Safety engineering. It is used to learn the scientific factors such as ignition time, mass loss and combustion products. The instrument allows the substance to be exposed to various heat fluxes and thus learn its burning behavior. The principle for measuring heat release is based on Hugget’s principle that the gross heat of combustion of any organic material is directly related to the amount of oxygen required for combustion. In many enclosure fires, the radiation from the surrounding burning fuel has a very significant role in the spreading, sustaining and control of heavy combustion. That is, to learn the fire behavior of various materials is very significant to control hazards. The most important factor to be measured is the amount of heat release. Many caloric methods were used for this purpose since 1950. But now, the most common and accurate way relied by the scientists is the cone calorimeter used internationally for both bench scale and large scale applications. 1.1 Aim: The aim of this experiment is to find out the fire behavior of the substances and to find out their individual contribution in bringing about room fire under given conditions. 1.2 Objectives: The objective of the experiment is to burn various substances in a cone calorimeter in the given experimental set up and find out their fire behavior. The result of the experiment will also conclude the role of each substance burnt in the calorimeter to make room fire. 1.3 Principle: The test is based on Hugget’s principle that the heat released during combustion can be found out from the amount of oxygen consumed in the process. For most of the combustible materials, for every 13.1 MJ of energy released, one kilogram of oxygen is consumed. For most substances, this variation is as negligible as ± 5 percent. The test materials are burnt in specific laboratory conditions and the heat released is measured by measuring the amount of oxygen consumed by determining the oxygen consumption rate and flow rate in the combustion stream. 2. DESCRIPTION OF THE EQUIPMENT Cone calorimeter can be generally described as a combination of various parts like a cone shaped electrical radiant heater, specimen holders, ignition device, radiation screen, weighing device for measuring specific mass, exhaust system, oxygen analyzer, heat flux meter, calibration burner, gas sampling apparatus a data collection and analysis system. The precise specifications of the instruments cannot be provided as the instrument is highly manufacturer specific. A schematic diagram of the instrument is given below. 3. EXPERIMENTAL MATERIALS The specimen used for the experiment is composite wooden laminated worktop. It consists of top lining of 2mm length and wooden chipboard which is 28mm thick. The laminate is positioned on top of wood which is 100mm long by 100mm wide by 30mm thick. The two materials are bonded together. The same specimen is employed in all tests only the heat flux varies in each test. The specimens are wound in aluminium foil with the lustrous side facing inwards to cover the exposed portions of the specimens. This is to prevent the falling of the specimen and therefore loss of mass. 4. PROCEDURE Before the experiment, the data acquisition system is operated and all initial information like initial mass, thickness and so on is entered. When all calibrations are performed, the specimen is placed on the appropriate holder and set in horizontal orientation. The spark plug is moved into its respective position and is turned on. Simultaneously, the ignition timer is put on. This procedure should be performed as fast as possible during specimen insertion. During the sustained combustion, the timing is noted and then the timer is stopped and the spark plug is turned off. The spark plug is moved out of flame. The data is collected until the signs of flame stops or twenty minutes whichever is earlier. The physical changes such as melting, cracking etc are noted. Any problems encountered during the experiment also must be noted. The heat flux during the first test, second test, third test and fourth test are set to 25kWm2, 35 kWm2, 45 kWm2 and 55 kWm2 respectively. 5. RESULTS The group of experiments was conducted to measure the following. The heat release rate Mass loss rate The effective heat of combustion Time to ignition Note the behavior of the substance when exposed to various heat fluxes and the dependence of heat release rate on heat flux. The number and nature of gases within is also measured so as to predict the fire toxicity. The specific initial mass, specimen thickness, time to ignition, flameout, end of test, total heat evolved, orientation, and total smoke released and mass lost with varied heat fluxes are noted down in the table given below. Heat Flux 25kW/m2 35kW/m2 45kW/m2 55kW/m2 Specimen Initial mass (grams) Specimen Thickness (mm) Time to ignition (Seconds) Flameout (Seconds) End of test (seconds) Total Heat Evolved Orientation Total Smoke Released Mass Lost (grams) Table 1 Different fire parameters measured The heat release rate, mass loss rate, effective heat of combustion, carbon monoxide yield and carbon dioxide yield with various heat fluxes are listed below. Heat flux 25 kW/m2 35 kW/m2 45 kW/m2 55 kW/m2 Time (Seconds) Heat Release Rate 60 120 180 240 300 360 Mass Loss Rate 60 120 180 240 300 360 Effective Heat of Combustion (MJ/kg) 60 120 180 240 300 360 Carbon Monoxide Yield (kg/kg) 60 120 180 240 300 360 Carbon Dioxide Yield (kg/kg) 60 120 180 240 300 360 Table 2 Average values of measured fire parameters at different times for different heat fluxes during the experiments 6. CONCLUSION 7. DISCUSSION AND CONCLUSION 7. REFERENCE 1. Babraskas, V., (1995) ‘The Cone Calorimeter’, The SFPE Handbook of Fire Protection Engineering, (2nd Edition), Ed: DiNenno, P.J., Society of Fire Protection Engineers, Boston, Massachusetts, USA 2. Babraskas, V., (1990) ‘The Cone Calorimeter – A New Tool for Fire Safety Engineering’, American Society for Testing and Materials, ASTM Standardisation News, USA 3. NFPA 264A, (1990) ‘Standard Method of Test for Heat Release Rate for Upholstered Furniture Components or Composites and Mattresses Using an Oxygen Consumption Calorimeter’, Technical Committee on Fire Tests, National Fire Protection Association (NFPA), USA 4. Janssens, M., (1995) ‘Calorimetry’, The SFPE Handbook of Fire Protection Engineering, (2nd Edition), Ed: DiNenno, P.J., Society of Fire Protection Engineers, Boston, Massachusetts, USA 5. International Standard ISO 5660-1 (1995) ‘Fire Test – Reaction to Fire Part 1: Heat Release Rate from Building Products (Cone Calorimeter Method)’, International Standard Organisation for Standardisation 6. Quintiere, J.G., and Rhodes, B., (1994) ‘Fire Growth Models for Materials’, National Institute of Standards and Technology (NIST), NIST-GCR-94-647, USA 7. Walton, W.D., and Twilley, W.H., (1984) ‘Heat Release and Mass Loss Rate Measurements for Selected Materials’, National Bureau of Standards, NBSIR 84-2960, Gaithersburg, USA 8. Brehob, E.G. and Kulkarni, A.K. (1993) ‘Time-dependent Mass Loss Rate Behavior of Wall Materials Under External Radiation’, Fire and Materials, Volume 17, pp. 249-254 9. Tewarson, A., (1995) ‘Generation of Heat and Chemical Compounds in Fires’, The SFPE Handbook of Fire Protection Engineering, (2nd Edition), Ed: DiNenno, P.J., Society of Fire Protection Engineers, Boston, Massachusetts, USA 10. Foley, M. and Drysdale, D., (1994) ‘Smoke Measurement and the Cone Calorimeter’, Fire and Materials, Volume 18, pp.385-387 11. Babraskas, V., (1995) ‘Burning Rates’, The SFPE Handbook of Fire Protection Engineering, (2nd Edition), Ed: DiNenno, P.J., Society of Fire Protection Engineers, Boston, Massachusetts, USA 12. Quintiere, J. Q (1997) ‘Principles of fire behaviour’ Delmar Publishers, USA 13. Drysdale, D. (1998) ‘An introduction to fire dynamics’ Second Edition, Wiley 14. Fire Safety Journal, Official Journal of the International Association for Fire Safety Science [available in the library and online] http://www.sciencedirect.com 15. Fire and Materials - is an international journal for scientific and technological communications directed at the fire properties of materials and the products into which they are made 16. BFRL Publications Online - This web site contains about 3000 document abstracts and complete publications produced by or for BFRL staff since 1993 and a selected number of documents published since 1978.................. http://fire.nist.gov/bfrlpubs 17. Wikipedia – This webpage contains the basic data about cone calorimeter. http://en.wikipedia.org/wiki/Cone_calorimeter Read More