78th Annual Meeting of the APS Division of Fluid Dynamics (Nov 23 — 25, 2025)

V060: Laser-Driven Ignition in a Subscale Rocket Combustor

We investigate how fuel mass and spark timing govern laser induced ignition in a subscale rocket combustor. Complex turbulent mixing creates intricate flow structures with hairpin vortices and fluid ligaments, in turn making this problem difficult to understand and solve. To address this challenge, we combine experiments and large eddy simulations (LES) in a comprehensive study at the PSAAP III Stanford Center. The outcome is controlled by the fuel mass present at the combustor at the moment of laser spark. If the spark is too early the flame fails to anchor. Within an optimal window well before the combustor becomes choked, ignition is reliable. If the spark is too late the resulting overpressure compromises structural integrity. The video shows stages of the injection sequence in experiments and LES. The simulations resolve the flow evolution over a few milliseconds and involve trillions of arithmetic operations.