High-Speed Flame Propagation in a Channel and Transition to Detonation
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AND MASS TRANSFER AND PHYSICAL GASDYNAMICS
High-Speed Flame Propagation in a Channel and Transition to Detonation A. D. Kiverina, * and I. S. Yakovenkoa a
Joint Institute for High Temperatures, Russian Academy of Science, Moscow, 125412 Russia *e-mail: [email protected] Received February 20, 2020; revised February 20, 2020; accepted March 10, 2020
Abstract—The physical mechanisms controlling the development of a flame prior to transition to detonation in a channel filled with a combustible gaseous mixture are systemized and analyzed. The features of the development of the accelerated flame in a channel are demonstrated with the results of numerical simulation for smooth and obstructed channels. This analysis makes it possible to formulate the criteria for a detonation onset induced by the development of an accelerated flame. Estimations on the basis of the proposed criteria predict with reasonable accuracy the limits of detonation initiation in hydrogen-based combustible mixtures. DOI: 10.1134/S0018151X20040070
INTRODUCTION The main objectives in the field of explosion safety at industrial facilities, the operation of which involves the risk of the generation, release, and subsequent ignition of gaseous combustible mixtures, are to predict and assess potential scenarios of the development of an explosion [1] and to design systems to prevent explosions and mitigate their consequences [2]. In light of the specifics of the development of gas explosions at different industrial facilities, including mines, combustible gas storage and transportation systems, nuclear power stations, chemical industry facilities, etc., flexible procedures are needed to assess the risk of explosion in the implementation of a given emergency scenario in a wide range of external conditions. This, in its turn, requires a detailed investigation into the characteristics of combustion development and, in particular, the basic physical mechanisms controlling the development of a particular combustion mode. The main combustion mode for premixed gaseous mixtures is deflagration combustion. It propagates through the combustible mixture in the form of a flame front and is accompanied by the development of gas-dynamic processes caused by the expansion of combustion products, propagation of the flame front itself, and the development of its surface as a result of various types of instabilities. These physical processes make the deflagration flame unsteady. In open spaces, the flame is accelerated due to the development of front instability [3] and, as a consequence, “autoturbulization” of the flame [4]. In closed volumes, the effects of medium compressibility become important. The expansion of combustion products in a confined space leads to compression of the unreacted mixture, thereby accelerating the combustion process. More-
over, in some cases, additional compression may induce self-ignition of the mixture in the preflame zone [5]. The development of an unsteady wave process in a compressible medium generates compression waves, the evolut
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