Work

Characterization of a scramjet reacting flow using two-point focused laser differential interferometry

Year: 2026

Type: article

Abstract: High-speed reacting flows typical of a scramjet are characterized by large density gradients, heterogeneous flow conditions, and complex shock structures. Typical diagnostic techniques are intrusive and may require complex seeding processes. These harsh conditions also merit the use of non-intrusive laser-based techniques. Two-point focused laser differential interferometry (2pFLDI) has been demonstrated as a viable, non-intrusive, seedless velocimetry and turbulence characterization technique for supersonic reacting flows and potentially for other types of reacting flows as well due to its good spatial resolution and high frequency response. The velocity of disturbances propagating through two closely-spaced measurement volumes ( ∼ 168 μ m in the flow direction) is calculated using the cross-correlation between FLDI signals. This technique is applied in a dual-mode scramjet combustor that replicates Mach 5 flight conditions by matching enthalpy, reaching stagnation temperatures of ∼ 1300 K. The scramjet is able to operate in multiple modes by changing its fuel injection strategy. Both thermally-choked mode and scramjet mode behavior are characterized by 2pFLDI. The technique captures the axial velocity and phase fluctuation profiles of both modes as well as statistical velocity distributions in the isolator and combustor. Novelty and significance statement: Multi-point Focused Laser Differential Interferometry (FLDI) has been applied in a variety of environments, but has been limited to non-reacting flows. Velocities deduced from FLDI signals have been limited to time-averaged measurements. The present work expands the application of the two-point FLDI (2pFLDI) technique to high-speed reacting flow relevant to ramjets/scramjets allowing for non-intrusive, point-based, spectrally-resolved disturbance velocity measurements and focuses on the mechanics of the technique, post-processing routine, and the nature of the obtained data. 2pFLDI provides a low-cost alternative to intrusive and complex velocimetry techniques which often require seeding the flow. It also has the potential to be applied in pressure gain combustion devices such as the rotating detonation engine (RDE), as well as plasma jets and wind tunnels.

Source: Proceedings of the Combustion Institute

DOI: 10.1016/j.proci.2026.106237

Authors: Andrew P. Ceruzzi, Mithuun Kanapathipillai, Kenneth H. Yu, Christopher P. Cadou

Institutions: University of Oxford, University of Maryland, College Park

Language: English

Topic: Fluid Dynamics and Turbulent Flows

Subfield: Computational Mechanics

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,570

Funder: Air Force Office of Scientific Research