Rotating detonation engine
A rotating detonation engine (RDE) is a proposed engine using a form of pressure gain combustion, where one or more detonations continuously travel around an annular channel. Computational simulations and experimental results have shown that the RDE has potential in transport and other applications.
In detonative combustion, the results expand at supersonic speed. It is theoretically more efficient than conventional deflagrative combustion by as much as 25%. Such an efficiency gain would provide a major fuel savings.
Disadvantages include instability and noise.
The basic concept of an RDE is a detonation wave that travels around a circular channel (annulus). Fuel and oxidizer are injected into the channel, normally through small holes or slits. A detonation is initiated in the fuel/oxidizer mixture by some form of igniter. After the engine is started, the detonations are self-sustaining. One detonation ignites the fuel/oxidizer mixture, which releases the energy necessary to sustain the detonation. The combustion products expand out of the channel and are pushed out of the channel by the incoming fuel and oxidizer.
Although the RDE's design is similar to the pulse detonation engine (PDE), the RDE is superior because the waves cycle around the chamber, while the PDE requires the chambers to be purged after each pulse.
Several US organisations work on RDEs.
The US Navy is pushing development. Researchers at the Naval Research Laboratory (NRL) particular interest in detonation engines such as the RDE, capability to reduce the fuel consumption in their heavy vehicles. Several obstacles still remain to overcome in order to use the RDE in the field. NRL researchers are currently focusing on better understanding how the RDE works.
Daniel Paxson at the Glenn Research Center used simulations in computational fluid dynamics (CFD) to assess the RDE's detonation frame of reference and compares performance with the PDE. He found that an RDE can perform at least on the same level as a PDE. Furthermore, he found that RDE performance can be directly compared to the PDE as their performance was essentially the same.
According to Russian Vice Prime Minister Dmitry Rogozin, in mid-January 2018 NPO Energomash company completed the initial test phase of a 2-ton class liquid propelant RDE and plans to develop larger models for use in space launch vehicles.
Other experiments have used numerical procedures to better understand the flow-field of the RDE. In 2020 a study from University of Washington explored an experimental device that allowed control of parameters such as the size of the cylinder gap. Using a high-speed camera they were able to view it operating in extreme slow motion. Based on that they developed a mathematical model to describe the process.
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