Evidence of Carbon Driven Detonation Waves Within a Rotating Detonation Engine

Coal dust explosions can be hazardous; however, it is well known there is a significant increase in pressure during the phenomena and, as such, if harnessed correctly can lead to increased performance in combustors. With the addition of carbon, in this case, Carbon Black, lean limits, and an increase in detonation velocity have been realized in comparison to that of pure hydrogen regimes. Carbon particles with a diameter of 29 nm were injected through a radially fed air line, which induced a heterogenous pre-mixed line, whereas hydrogen gas was injected axially through discrete fueling injectors, thus creating a solid-gaseous phase combustor. In all operating parameters, a stoichiometric mixture (φ ≅ 1) is introduced into the combustors annulus, where when the concentration of carbon is increased, hydrogen is decreased correspondingly. Hydrogen is used to initiate and sustain the detonation wave until the carbon begins to drive the detonation wave. Operational conditions include: total mass flux injected into the annulus (≅200 kg/(s*m2)), variation in hydrogen concentrations (100 – 30%) by weight of fuel, and total concentrations of carbon (0 - 70%) by weight of fuel. High-speed backend imaging allowed for a Discrete Fourier Transform analysis to deduce detonation wave velocities. It was found that with the addition of Carbon Black, a delayed formation of deflagrations occurred where the coal particles would sustain a detonation into leaner hydrogen-air concentration ratios. In some cases, when the local hydrogen-air equivalence ratios (φh ≅ 0.9) with the addition of coal-air (φc ≅ 0.1) to equivocate to a global phi of one, detonation wave velocities were found to have increased over that of pure hydrogen-air concentrations. Thus, a one-to-one classification of the heat of reaction to that of various detonation wave velocities was formulated and discussed as to show their direct correlation, and describe detonation wave velocities before an operational point is run.