Blast Wave-Induced Mixing in a Laser Ignited Hypersonic Flow

Abstract

A laser ignition system suitable for a hypersonic scramjet engine is considered. Wall-modeled large eddy simulation (LES) is used to study a scramjet-like geometry with a single hydrogen injector on the inlet, at a Mach 8 flight condition with a total enthalpy of 2.5 MJ. Detailed chemical kinetics and high fidelity turbulence modeling are used. The laser forms a kernel of high temperature plasma inside the fuel plume that briefly ignites the flow and leads to massive disruption of the flow structures around the jet, due to the expanding plasma kernel driving a blast wave that collides with the surrounding flow. The blast wave produces vorticity as it passes through the fuel–air interface, but comparably less than that produced by the jetting of the hot gas affected by the laser as it expands outward into the crossflow. The remnant of the plasma rolls up into a powerful vortex ring and noticeably increases the fuel plume area and the volume of well mixed reactants present in the simulation. These results indicate that the laser ignition system does more than just supply the energy to ignite the flow; it also substantially alters the flow structure and the mixing process.

Hydrodynamic ejection caused by laser-induced optical breakdown

“…Such laser-seeded ignition is attractive because it deposits energy and radicals within a flow, away from material that might degrade, and with relatively precise control over timing and location (Ronney 1994;Phuoc 2006). Ignition in various flow configurations has been studied (Lacaze et al 2009;Brieschenk, O'Byrne & Kleine 2013a;Massa & Freund 2017;Gibbons et al 2018). Laser energy deposition has also been used in control for drag reduction (Riggins, Nelson & Johnson 1999) and controlling shock-shock interactions in supersonic flow (Kandala & Candler 2004;Adelgren et al 2005).…”

Effects of surface tension on the Richtmyer-Meshkov instability in fully compressible and inviscid fluids

“…The RMI is relevant to many applications. It is well-known to inhibit the attainment of fusion in inertial confinement fusion contexts [1]; it can enhance mixing in high-speed airbreathing engines [2]; and may also drive mixing in certain supernovae [3] and magnetic field amplification in supernova remnants travelling through the interstellar medium [4].…”