Laminar Deflagrated Flame Interaction With A Fluidic Jet Flow For Deflagration-To-Detonation Flame Acceleration

Recently researchers have begun to understand the full potential of Pulse Detonation Engines (PDEs) to efficiently produce an immense amount of thrust due to the generated detonation wave. Numerous experimental PDE facilities have been engineered which successfully achieve detonation through the use of solid obstructions to induce turbulent combustion. These obstacles create recirculation regions within the propagating flame and reflect acoustic waves, both of which contribute to turbulence production within the flame. Despite success, the use of a solid object has numerous drawbacks including pressure losses and heat soaking. An alternate solution to induce turbulence is through the use of a fluidic-based jet. The goal of the current research is to investigate the fundamental physics governing the interaction of a laminar deflagrated flame with a fluidic jet. The fluidic jet is an efficient mechanism for inducing turbulence and flame acceleration relative to solid obstacles. Control of the jet velocity provides dynamic control of turbulent production mechanisms. Additionally, the jet eliminates pressure losses and heat soak effects induced by obstacles. A PDE experimental setup is utilized for the investigation. The effects of varying equivalence ratios of methane and air for the flame and jet, as well as varying jet momentum ratios, on the interaction are studied. The interaction is explored using non-invasive testing methods including Schlieren imaging and Particle Image Velocimetry (PIV). These techniques provide qualitative and quantitative data pertaining to the interaction, which are used to define the physics of the interaction

Flame–turbulence interaction of laminar premixed deflagrated flames

The demand for higher combustion efficiency and performance is attainable through pressure gain combustion. Pressure gain combustion exploits the pressure rise for high flow momentum and pressure augmentation. One possible mechanism for detonation is turbulence generation and induction to augment the deflagrated flame acceleration. The study examines the interaction mechanisms of the laminar deflagrated flame with turbulence induced by a fluidic jet, composed of a transverse slot. The mechanisms of the jet including, flame-flow restriction, jet entrainment, turbulent transport, and recirculation are examined to determine the flame–turbulence interaction modes and their influence on the propagating deflagrated flame. The flame interaction and acceleration are compared to that induced by traditional solid obstacles. The flame structural dynamics and reacting flowfield are characterized using simultaneous high-speed PIV and chemiluminescence measurements. Additionally, high-speed Schlieren is used for visualizing the interaction features. Higher flame acceleration is observed for the fluidic jet relative to the obstacle. The flame interaction with the jet turbulence is dominated by a cross-stream high turbulent transport mechanism; whereas, the interaction for the obstacle is driven by Kelvin–Helmholtz and Rayleigh–Taylor instabilities. The obtained results show the dynamic flame evolution phenomenon of the local flame regime (laminar – corrugated flamelet - thin reactions)