An Asymptotic Analysis of Radiant and Hypergolic Heterogeneous Ignition of Solid Propellants

Abstract

Abstract-An asymptotic analysis, in the limit of large activation energies, is presented for the ignition of a solid propellant undergoing an exothermic heterogeneous Arrhenius reaction with a gaseous oxidizer. The analysis is carried out for hypergolic or shock tube ignition conditions, and also for ignition under a radiant flux with in-depth absorption of the radiation.The asymptotic analysis illustrates how, for sufficiently large radiant fluxes, a short reaction stage, ending in thermal runaway, follows a much longer inert heating stage. A closed form expression is found to relate the ignition time to the radiant flux and physico-chemical propellant characteristics. An analytical expression is also found for the ignition time under hypergolic or shock tube ignition conditions.The existing numerical calculations of the ignition time, for hypergolic ignition cases and for ignition under a radiant flux with surface absorption, are very accurately correlated by the closed form expressions resulting from this asymptotic analysis. These expressions take also into account the effects of in-depth absorption.

Fluid–solid coupled simulation of the ignition transient of solid rocket motor

“…Under rapid pressurization rate in the motor ignition transient, the propellant dynamic burning rate can be significantly different from the burning rate predicted by the quasi-steady combustion model because of the thermal relaxation effect in the solid [14,18]. Ignition models of different complexity have been presented and used previously in numerical simulations [14,[18][19][20].…”

“…Ignition models of different complexity have been presented and used previously in numerical simulations [14,[18][19][20]. The simplest model switches on the burning boundary condition when the temperature of hot gases flowing over the propellant surface reaches a critical ignition temperature and an empirical formulation was utilized to calculate the mass flow rate of the combustion products.…”

Modeling of combustion and ignition of solid-propellant ingredients

“…Heterogeneous reaction models [190][191][192][193][194][195][196][197][198] assume that heterogeneous reactions at the propellant surface are responsible for ignition due to the molecular diffusion of ambient oxidizer species to the propellant surface. The formulation takes into account the condensed-phase conservation equations of energy and species concentration along with interfacial boundary conditions.…”

“…In the liquid, thermal decomposition and subsequent reactions, as well as phase transition, take place, generating gas Table 15 Theoretical models of solid-propellant ignition, adopted from Ref. [21] Solid-phase reaction model Heterogeneous reaction model Gas-phase reaction model [190][191][192][193][194][195][196][197][198] [199][200][201][202][203][204][205][206] Remarks Suitable for condensed-phase controlled materials, such as double-based propellants Suitable for gas-phase controlled material, such as low vulnerability ammunition (LOVA) propellants Effect of pressure is under-estimated since condensed-phase process is insensitive to pressure Suitable for the surface-reaction controlled material, such as polymers, hypergolic systems, etc.…”

Ignition of a Porous Solid Fuel by Convective Heat and Mass Transfer at the Fuel Surface

“…This model is distinguished from other existing ones (e.g. Bradley (1970), Hicks (1954), Linan and Williams (1971), Linan and Crespo (1972), Merzhanov and Averson (1971), Price et al (1966), Waldman (1970), and Williams (1966)) by inclusion of the mass diffusion of the gaseous oxidant through the porous solid fuel. Kim and Chung (1976) employed the Laplace asymptotic method and analyzed the porous-fuel ignition caused by the constant heat and mass fluxes applied at the fuel surface.…”