High-temperature ignition of a reactive material by a hot inert particle with a finite heat reserve

Abstract

The initiation of a reactive material by an inert particle at a high initial temperature and with a limited heat reserve is studied numerically. The possibility of using known ignition criteria to study the process are analyzed. The effect of burnout on hightemperature ignition by a particle with a limited heat reserve is studied. Four regimes of the process and the critical parameters separating these regimes are determined.Investigation of the initiation of reactive materials (RMs) by a hot inert inclusion involves the solution of questions of fire and explosion safety of various technological processes and the sensitivity of materials to external nonthermal actions. For example, during welding, an explosion hazard can occur when heated particles comes in contact with a material capable of explosive transformation. Local hot spots arise during radiation absorption by optical inhomogeneities present in a RM transparent to radiation or during adiabatic compression of gas inclusions under impact [1].The theoretical investigation of the thermal part of the problem reduces to solving the problem of ignition of a RM by a hot inclusion with a finite heat reserve. The ignition of a RM by hot inert bodies of various shapes have been studied numerically [2][3][4][5][6][7]. Vilyunov and Kolchin [2] considered the case of ignition by a hot inert plate with a low thermal conductivity [2]. The critical conditions (limiting plate width) and ignition parameters with an insignificant effect of the burnout of the RM were determined by approximate theoretical solution and numerically. Grishin and Subbotin [3] considered the opposite limiting case of ignition of a RM by a high-conducting hot inert body of symmetrical shape. The low-temperature and high-temperature ignition regimes and conjugate heat transfer between the hot inert body and RM were studied. Approximation formulas were determined that describe the critical particle size separating the regimes of ignition of the 1 Tomsk State University, Tomsk 634050; roza@ftf.tsu.ru. RM and gradual cooling of the inert body. Gol'dshliger et al. [4] and Loskutov and Sandrykina[5] studied the ignition by a hot inert particle of symmetrical shape taking into account the particle temperature distribution. The critical particle size and the effect exerted on it by the temperature distribution in an inert particle were determined. The heat exchange between an inert particle and a RM and heterogeneous chemical reactions on the inert particle surface were studied in [5]. Kuzntesov et al. [6,7] performed a numerical analysis of the ignition of a condensed material by a particle heated to high temperatures taking into account twodimensional heat transfer in the neighborhood of the region of contact of the particle with the material. An asymptotic analysis of the critical conditions of ignition of a material by a body with a finite heat reserve was performed by Berman and Ryazantsev [8]. In the cited studies, the burnout of the RM was not taken into account [4,[6][7][8] or was considered in a l...

Research of Macroscopic Regularities of Heat and Mass Transfer at the Ignition Condition of a Liquid High-Energy Material by an Immersed Source with a Limited Energy Capacity

“…It has been shown [1][2][3][4][5][6][7] that inertial processes of heat and mass transfer play leading role rather than rapid oxidation reactions, as could have been supposed. The integral ignition characteristics have been found to be dependent on a large group of factors [1][2][3][4][5][6][7] that determine the conditions of warming and subsequent ignition of HEM. Possible regimes of igniting HEM by local heating have been determined [1][2][3][4], as well as the peculiarities of location of the leading oxidation zone with respect to the contact boundary between the HEM and the local energy source [4][5][6].…”

“…Recent years, a fairly comprehensive analysis of macroscopic regularities was done for ignition processes of solid [1][2][3] and liquid [4][5][6][7][8][9] HEM at local heating induced by typical sources with a limited energy capacity (in particular, by intensely heated metallic and nonmetallic particles of different physical nature). It has been shown [1][2][3][4][5][6][7] that inertial processes of heat and mass transfer play leading role rather than rapid oxidation reactions, as could have been supposed. The integral ignition characteristics have been found to be dependent on a large group of factors [1][2][3][4][5][6][7] that determine the conditions of warming and subsequent ignition of HEM.…”

“…The integral ignition characteristics have been found to be dependent on a large group of factors [1][2][3][4][5][6][7] that determine the conditions of warming and subsequent ignition of HEM. Possible regimes of igniting HEM by local heating have been determined [1][2][3][4], as well as the peculiarities of location of the leading oxidation zone with respect to the contact boundary between the HEM and the local energy source [4][5][6]. It was noticed that the basic consideration has been made for the conditions of an "ideal" contact (without roughness, unevenness, cavities of energy source) at the boundary "local energy source-HEM" [1][2][3] and for the conditions of partial embedding of a small heat source into the near-surface layer of HEM [4][5][6][7].…”

“…Possible regimes of igniting HEM by local heating have been determined [1][2][3][4], as well as the peculiarities of location of the leading oxidation zone with respect to the contact boundary between the HEM and the local energy source [4][5][6]. It was noticed that the basic consideration has been made for the conditions of an "ideal" contact (without roughness, unevenness, cavities of energy source) at the boundary "local energy source-HEM" [1][2][3] and for the conditions of partial embedding of a small heat source into the near-surface layer of HEM [4][5][6][7]. At the same time, there exist conditions that permit a complete immersion of local sources with a limited energy capacity into HEM (in particular, liquid and gelatinous combustibles).…”

Characteristics of heat and mass transfer at ignition of a thin film of condensed liquid substance by hot particles of different configuration

“…has made it possible to make conclusion on some important characteristics of implementation of the latter variant [2][3][4][5][6]. In particular, the influence of the intensity of heat conduction, convection, radiation, diffusion, vaporization, gasification, decomposition, and crystallization processes on the ignition characteristics of typical solid (powder, wood, mix composites) and liquid (benzene, kerosene, diesel fuel, and fuel oil) condensed substances was assessed [2][3][4][5][6]. The influence of sizes and initial temperature of the energy sources on the ignition conditions was also assessed.…”