Abstract
This paper presents a numerical investigation of ignition and combustion stabilization of a novel design of a solid-fuel ramjet (SFRJ) motor with and without swirl flow. The proposed design includes two solid fuels, retaining the simple design of the classic SFRJ. Numerical simulations of unsteady, turbulent, reactive, and swirling flow coupled with solid-fuel pyrolysis have been performed using an in-house CFD solver. Experiments on SFRJ were conducted via a connected-pipe test facility to validate the developed code. Furthermore, the code was validated for chemical reactions, heat diffusion, and swirl flow by using benchmark test cases of shock-induced, semi-infinite plate, and dump combustor with swirl flow, respectively. Then, the proposed and classic designs were simulated for the same inflow conditions and configurations, and the results were analyzed and discussed. It is found that the mixing degree, reactant residence time, mass flux, ignition delay time, and regression rate improve when using the proposed design. Moreover, the proposed design reveals interesting observations of a new flame being created and merged with the main flame.
Highlights
It is well known that a solid-fuel ramjet (SFRJ) uses ambient air as an oxidizer during its flight.This oxidizer reacts inside the combustor with the solid fuel at high flight speed, since the SFRJ starts working at supersonic conditions
In the swirl flow condition, the combustion characteristics of SFRJ is mainly determined by the flow field characteristics
The cases represent the classic and proposed designs of SFRJ with and without swirl flow. This is to explore the influence of swirl flow and combustor design on the ignition and combustion characteristics of SFRJ
Summary
It is well known that a solid-fuel ramjet (SFRJ) uses ambient air as an oxidizer during its flight.This oxidizer reacts inside the combustor with the solid fuel at high flight speed, since the SFRJ starts working at supersonic conditions. SFRJ does not start its operation from zero speed, but by using an auxiliary device to reach a certain speed, such as booster rocket or military airplane. This makes the ignition process challenging for designers and researchers, and a hotspot area of research. Solid-fuel ignition can be defined as a complex phenomenon that involves many physicochemical processes with a sequence of events that starts with energy transfer to the solid fuel by an external stimulus, heating and subsequent decomposition of the solid phase, diffusion of vaporized gases near the surface, and, subsurface, heterogeneous, and/or gas-phase reactions. Once the external stimulus is removed, a sustained combustion will follow the ignition, otherwise the ignition is incomplete
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