NETL researchers investigated rotating detonation engine (RDE) waves and discovered that what had been previously understood to be unstable behavior is actually a repeatable and persistent mode of operation observed over longer timeframes. This new information could help design more reliable and efficient power generation systems in the future that will help reach the nation’s decarbonization goals.

The study, “Limit Cycle Oscillating Detonation Wave Behavior Analysis Within a Rotating Detonation Engine” was recently published in the Journal of Propulsion and Power.

RDEs are an advanced type of propulsion system that could yield higher efficiency and performance compared to traditional power generation systems. They operate by creating continuous detonation waves that rotate inside a modified gas turbine combustion chamber, which allows them to theoretically avoid the pressure loss and resulting decrease in efficiency that occurs with conventional gas turbine engines.

The rotating detonation process allows more of the fuel’s energy to be captured and utilized, resulting in higher power output, less fuel being consumed, a smaller industrial footprint and reduced environmental impact.

Understanding the behavior of the detonation waves is critical to designing optimal RDEs.

“Previous literature identified what was referred to as galloping, and described it as unsteady, transitory wave behavior,” said Kristyn Johnson May, NETL researcher and lead author of the paper. “This behavior was thought to only represent short-term instabilities, but we found that under specific operating conditions the wave-to-wave spacings increase and decrease cyclically and persistently through long-duration testing of around 20 seconds.”

This predictable wave behavior is referred to as limit cycle oscillatory (LCO) behavior. Johnson May and her colleagues developed a method to help better detect and understand different types of LCO wave behaviors.

“What is most intriguing is the graceful acceleration and deceleration of waves, suspected to be a result of an interconnection between individual wave strength and the local height of the freshly injected fuel region, “Johnson May said. “It is precisely this attribute that allows for persistent LCO modes to be maintained seemingly indefinitely when the boundary conditions of the detonation channel remain consistent.”

The NETL team notes in the paper that the exact effects of the LCO dynamic states on the performance of an RDE are currently unknown. However, further research could help pinpoint how the wave behavior could affect pressure gain, changes in combustion efficiency, nitrogen oxide formation and exhaust flow.

NETL is a DOE national laboratory that drives innovation and delivers solutions for an environmentally sustainable and prosperous energy future. By using its world-class talent and research facilities, NETL is ensuring affordable, abundant and reliable energy that drives a robust economy and national security, while developing technologies to manage carbon across the full life cycle, enabling environmental sustainability for all Americans.