Passive Control of Flow Instabilities in Propellant Manifolds and Combustion Chambers for Liquid-Liquid Rotating Detonation Engines

Rotating Detonation Combustors (RDCs) are a subject of great interest in the field of propulsion and power generation for their theoretical pressure gain and increased thermal efficiency and power density over conventional deflagrative combustors. This allows smaller, lighter and more efficient airbreathing and rocket propulsion systems, as well as conventional gas turbine based civil power generation plants.  DARPA has expressed interest in the H2O2/RP1 propellant combination, which yields very powerful detonations, often exceeding 100 atmospheres and damaging hardware. RDCs in general are still a low-maturity technology, thus much work is still required in achieving operational stability and reliability, as oftentimes undesirable operating modes, such as counterrotating detonation waves and parasitic deflagrative combustion are observed, which sap energy from designed detonation waves and reduce combustion efficiency. Additionally, Liquid-Liquid detonations are specifically notable for their high pressure ratios and heat fluxes in comparison to gas-gas detonations, which has resulted in substantial, undesired damage to combustion chambers in past experiments at Purdue and IN Space.  In phase I work, HySonic investigated and successfully demonstrated control of unwanted acoustic modes and spectral clean-up in gas-gas RDCs through implementation of acoustically absorptive chamber linings. Building on this, a 1-year base and second-year option work is proposed addressing four prime objectives: 1) eliminate chamber damage through careful shaping of injector and chamber geometry, 2) control detonative behavior by applying novel wall treatments to combustion chambers and propellant manifolding, 3) implement active propellant cooling in order to enable appreciable burn times, and 4) to mature LLRDE technology to TRL 6 by integrating all the former objectives into a single test article. ??????? Three generations of hardware will be designed, manufactured, and tested, in collaboration with IN Space and Purdue University, initially working with short burntimes on heat-sink cooled hardware, then gradually incorporating water cooling, then propellant cooling, and implementing prerequisite investigations of topics like warmed propellants, acoustic stability/coupling in propellant manifolding, and injection response to detonation waves. Hardware will be designed to integrate into the existing NASA ESI rig already implemented at Purdue's Zucrow Labs.