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ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
STUDY OF FLAME ACCELERATION IN A CLOSED DUCT USING EFFECTIVE LEWIS AND ZELDOVICH NUMBERS AS PARAMETERS
Submission Author:
Guilherme Cardoso , RS , Brazil
Co-Authors:
Guilherme Cardoso, Carlos Henrique Lauermann, Rafael Quines, Manuel Nzinga, Thamy Cristina Hayashi, Andrés Armando Mendiburu Zevallos
Presenter: Guilherme Cardoso
doi://10.26678/ABCM.ENCIT2022.CIT22-0366
Abstract
The research involving alternative fuels is of key importance to guarantee the energy sustainability of practical application. Recently, there is interest in fuels involving hydrogen, natural gas, biomethane and their mixtures. It is indispensable to study the flame propagation behavior of the alternative fuels, in order to adopt the correct safety measures for their use. A premixed flame propagating inside a duct shows several characteristics of the flame mixture, as for example, its acceleration during the early stages of the propagation. The flame acceleration is relevant, because, under certain conditions, a deflagration could turn into a detonation, representing great danger for practical applications. The objective of the present work is to characterize the flame acceleration stage of premixed flames propagating inside closed ducts. Therefore, experiments were realized in order to measure the flame propagation velocity and to observe the acceleration of this flame. Characterizing the flame acceleration of alternative fuels is not an easy task, given the great variety of mixtures that are realizable. Therefore, in the present work, the mixtures are classified by their Lewis and Zeldovich numbers, on this way the authors try to obtain general observations that are applicable to alternative fuels of similar Lewis and Zeldovich number. This study analyzed the correlation of the acceleration with Zeldovich number and effective Lewis number. The mixtures were prepared with different concentrations of natural gas, hydrogen and helium and they were selected according to their effective Lewis number. The Lewis numbers of the mixtures ranged from 0.609 to 1.364 and the Zeldovich numbers ranged from 4.249 to 8.458. Furthermore, the tests were performed with no obstacles inside the duct and afterwards, the same mixtures were tested in the duct with two orifice plates obstacles, located near the ignition end, which had a blockage ratio of 0.75. All experiments were conducted at initial pressures of 40 kPa, initial temperatures of 310 K and the equivalence ratio of 1.0.
Keywords
flame acceleration, Lewis number, Zeldovich number
