Propulsion and Energy

Rotating detonation engines at the forefront of pressure gain combustion

The Pressure Gain Combustion Technical Committee advances the investigation, development and application of pressure gain technologies for improving propulsion and power generation systems and achieving new mission capabilities.

Research and development of pressure gain combustion is driven by potential higher fuel efficiency at reduced weight and volume for both power generation and propulsion applications. The rotating detonation engine remained the frontrunner in pressure gain combustion technology this year. Worldwide contributions from government, industry and academic institutions continued to elevate the technical level of RDEs.

Research into power-generating applications of RDEs this year explored system implementation and emission reduction benefits. In May, the U.S. Department of Energy announced a $7 million award to GE Research in New York to design, develop and demonstrate a low-loss, hydrogen-fueled RDE with full turbomachinery integration at conditions relevant to 7FA turbines. From April to July, the Department of Energy’s National Energy Technology Laboratory in West Virginia conducted studies of a hydrogen-air-fired RDE and continued to demonstrate ultra-low nitrogen oxide emissions, showing further promise toward adopting this emerging technology for land-based power generation.

Investigations into liquid propellant operation for rotating detonation rocket engines, RDREs, are on the rise. In July, the Air Force Research Laboratory presented fundamental studies on the secondary breakup characteristics of 100-micron scale droplets due to a traveling detonation wave; preliminary analysis reveals accelerated liquid propellant atomization due to this interaction and provides valuable data for anchoring computational models used in detonative combustor design. In December 2021, researchers at Purdue University’s Zucrow Laboratories in Indiana showcased rotating detonations using liquid oxygen and RP-1 as propellants. Operation of RDRE using cryogenic liquid propellants represents a milestone in RDRE development toward flightlike hardware. Following the success of their July 2021 gas-gas propellant RDRE flight demonstrator, researchers in Japan, including Nagoya University, Muroran Institute of Technology, Keio University and the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Science, developed a new liquid ethanol-nitrous oxide RDRE. This configuration will be launched and demonstrated in space by sounding rocket S-520 in 2024, marking the first flight of a multiphase RDRE system. 

From June to August, engineers at NASA’s Marshall Space Flight Center in Alabama, in collaboration with IN Space LLC in Indiana, fired two regeneratively cooled RDREs at NASA Marshall over 17 discrete starts and a cumulative of 600 seconds of operation. They achieved multiple firings greater than 110 seconds in duration and a full throttle test (over 17,800 newtons of force) for 15 seconds. The project demonstrated active throttling with detonation modes, successful ignition without a predetonator and the use of novel copper/chromium/niobium alloy additive manufacturing hardware capable of surviving long firing durations.

For the past two years, the Air Force Research Laboratory has led a 15-participant group across academia, industry and national laboratories in the AIAA Model Validation for Propulsion Workshop to standardize procedures for RDRE experimental testing and computations, allowing consistent comparisons among participating research groups. As of July, all experimental participants had corroborated their results, with discussions between computational groups ongoing. This year, experimental efforts emphasized data reduction among the participants and led to the preparation of a manuscript summarizing the flow conditions and measurements to be submitted for publication in December. Between December 2021 and January, researchers at Argonne National Laboratory in Illinois completed several high-fidelity large eddy simulations leveraging adaptive mesh refinement as part of the MVP effort and demonstrated a high degree of qualitative and quantitative agreement with the experimental validation database. Heat release analysis of the Argonne simulation indicated the thrust obtained is closely linked to the total heat release distribution between detonative and deflagrative combustion. A panel is planned at AIAA’s 2023 SciTech forum to detail differences and similarities observed in the computational results and possible paths forward to isolate the mechanisms driving discrepancies.  

Contributors: Eric Bach and John W. Bennewitz

Rotating detonation engines at the forefront of pressure gain combustion