Combustion Science
Cool Flame
Warm Flame
Hot Flame
DDT Simulation
DDT Expriment
Deflagration to Detonation Transition (DDT)
This is a fundamental phenomenon in reactive flows, where a subsonic combustion wave (deflagration) accelerates and transitions into a supersonic detonation. The process is driven by the interaction between flame propagation, pressure waves, and turbulence. As the flame front accelerates, often due to confinement and obstacles, it generates compression waves that preheat and compress the unburned mixture ahead of the flame. This leads to increased reaction rates and pressure buildup.
Eventually, the pressure waves coalesce into a shock wave that couples with the exothermic chemical reactions occurring in the mixture. When this coupling becomes self-sustaining, a detonation wave forms—a shock wave closely followed by a reaction zone, propagating at supersonic speed. The transition is characterized by highly unsteady and nonlinear dynamics, involving rapid energy release, strong shock interactions, and instabilities in both the flame and flow field. Understanding the physics of DDT is crucial for applications in advanced propulsion, safety of fuel-air systems, and the design of detonation-based engines.
DDT w/o Plasma
DDT Simulation
Cool & Warm Flames
Cool and Warm Flames are low-temperature combustion phenomena that occur under specific pressure and mixture conditions, typically in fuel–air mixtures with low ignition energy. Unlike conventional flames, which are characterized by high temperatures and bright luminosity, cool and warm flames are partially oxidized reaction states with relatively low heat release and faint or no visible light.
DDT Expermient
Cool Flame
Warm Flame
Hot Flame
Cool flames occur at temperatures around 500–800 K and are governed by low-temperature chemical kinetics, primarily involving chain-branching reactions and intermediate species such as peroxides and aldehydes. These flames are often transient and can appear as precursors to hot ignition in autoignition processes. They are especially important in engine knock, thermal runaway, and fuel reactivity studies, particularly with hydrocarbons and oxygenated fuels.
Warm flames represent an intermediate regime between cool and hot flames, occurring at higher temperatures than cool flames but still below typical flame temperatures. They are often observed as a secondary stage following cool flame activity and exhibit more pronounced heat release and light emission.
These phenomena are essential for understanding low-temperature combustion, autoignition behavior, and advanced engine cycles such as HCCI (Homogeneous Charge Compression Ignition). Research in this area helps in developing cleaner and more efficient combustion strategies, especially under lean and low-temperature operating conditions.
Plasma Assisted Combustion
Plasma-Assisted Combustion is an advanced approach that leverages non-equilibrium plasma discharges to enhance and control combustion processes. By introducing plasma—typically via nanosecond pulsed discharges, dielectric barrier discharges (DBDs), or microwave excitation—energetic electrons are generated that initiate and accelerate chemical reactions in the fuel–air mixture, even at low temperatures and lean conditions.
DDT with Plasma
DDT process
Plasma-Assisted Combustion is particularly effective in low-temperature environments, where traditional combustion is sluggish or unstable. It holds promise for applications such as lean-burn engines, high-altitude propulsion, detonation initiation, and fuel-flexible systems. The integration of plasma technologies into combustion systems enables greater control, efficiency, and emission reduction, and is a key area of research in next-generation propulsion and energy systems.
The key physical mechanism lies in non-thermal excitation, where energetic electrons promote dissociation, ionization, and excitation of molecules without significantly raising the bulk gas temperature. This leads to the formation of highly reactive radicals (e.g., O, H, OH), which enhance ignition, stabilize flames, and extend lean flammability limits. Plasma can also modify reaction pathways, reduce ignition delay, and suppress pollutant formation by influencing intermediate species and combustion phasing.