Development of Plasma Assisted Active Control for Rotating Detonation Engines

Abstract

The Rotating Detonation Engine (RDE) utilizes detonation combustion at constant volume, as compared to deflagration combustion at constant pressure, in creating thrust for spacecraft. Constant volume combustion is favourable in terms of greatly increased thermodynamic efficiency with much greater exhaust velocities, opening the door to lighter and cheaper spacecraft. The RDE is, however, more complicated and largely unstudied as compared to the more popular deflagration engines, and has therefore lacked widespread presence in the current aerospace industry. Little research has been done into this propulsion concept, and the few in existence have found similar challenges in control and stabilization of the rotating detonation wave. Two of the major factors in consideration are ignition delay, i.e. the time from propellant injection to propellant ignition, and coupling of ignition and detonation wave. A propellant with a simple chemistry or in an excited state can be ignited easier and thus decrease the ignition delay time. This paper will combine both a fuel with simple chemistry (hydrogen) and utilize plasma to destabilize the propellant into active radicals. We will design a pulsed nanosecond plasma discharger, through which the fuel and oxidiser will flow into the combustion chamber. To increase the chances of a stable coupling between ignition and detonation wave, the plasma can be varied in live time to ensure that the propellant is reactive enough to ignite at the right time. This will be accomplished through the design of an active control system, utilizing closed-loop feedback, that will vary the plasma strength through altering the voltage to the plasma generator dependent upon the pressure in the combustion chamber as measured from a pressure sensor placed in the combustion chamber. This paper will not consider the effects due to curvature of the wall, nor the viscous interactions between the fluid and the cylindrical wall. All simulations will be simplified to a 2D rectangular domain representing an unrolled cylinder, and will be completed through Ansys Fluent.