Gas-phase detonation propagation in mixture composition gradients

Area of Science:

• Combustion science
• Chemical engineering
• Fluid dynamics

Background:

• Detonations are critical phenomena in various combustion processes.
• Understanding detonation propagation in non-uniform mixtures is vital for safety and efficiency.
• Spatially varying fuel concentrations present complex challenges to detonation dynamics.

Purpose of the Study:

• To numerically investigate detonation propagation in fuel-air mixtures with spatial composition gradients.
• To analyze the impact of mixture gradients on detonation structure and cell formation.
• To explore detonation behavior in both low- and high-activation energy regimes.

Main Methods:

• Numerical simulations in two-dimensional channels.
• Utilizing a two-component, single-step reaction model.
• Calibrating the model to match one-dimensional detonation properties of hydrocarbon-air mixtures.

Main Results:

• Complex reaction zone structures observed, including curved detonations and decoupled shocks.
• Detonation cell sizes vary across the channel, influenced by stoichiometry.
• In high-activation energy mixtures, increased gradients slow or quench detonations.

Conclusions:

• Mixture gradients significantly alter detonation propagation and cell morphology.
• Channel size relative to detonation cell size can mitigate gradient effects.
• Detonation quenching is a possibility in strongly non-uniform, high-activation energy mixtures.