With around 430 gas-turbine engines on 129 of its ships burning about US$2 billion worth of fuel every year, the U.S. Navy is examining the potential of using Rotating Detonation Engines (RDEs) to improve fuel consumption and cut costs. Researchers at the Naval Research Laboratory (NRL) estimate that retrofitting RDEs to its fleet could save the Navy approximately 300 to 400 million dollars a year.
The U.S Navy currently relies heavily on gas-turbine engines because they are self-contained, relatively easy to maintain, and relatively small, yet scalable to large powers. They are used to provide propulsion and generate electricity for many of its ships and, being fundamentally similar to the engines used in commercial airplanes, they are also used in many Navy aircraft.
Even with the move towards “all-electric” propulsion systems for future ships, the NRL says gas-turbine engines will still be needed to generate electricity for the ships’ propulsion system and other critical systems.
The gas-turbine engines currently used by the Navy are based on the Brayton thermodynamic cycle, in which air is compressed and mixed with fuel and then combusted at a constant pressure. The resulting high velocity and volume gas flow is then directed through a nozzle over the turbine’s blades, spinning the turbine.
The NRL says that alternatives to the Brayton cycle need to be explored to improve the performance of gas-turbine engines. For the past decade it has contributed to the development of Pulse Detonation Engines (PDEs), which use pulsed detonation waves to combust the fuel and oxidizer mixture, but believes RDEs may offer the potential for even greater fuel efficiency.
RDEs are similar to PDEs, but produce axial thrust by using a detonation wave that continuously travels around to detonate the incoming propellants. The RDE would offer improved efficiency over PDEs because the combustion chamber doesn’t need to be purged between detonations (pulses), as is the case with PDEs.
Building on earlier work done on general detonations, the NRL researchers have constructed a model for simulating RDEs and will now focus on gaining a better understanding of how they work and what type of performance can be achieved in the real world. They believe RDEs could be a disruptive technology in ships and planes, potentially providing the ability to meet a 10 percent increase in power requirements while reducing fuel use in future Navy applications by 25 percent.