Abstract-
The present work investigates the applications of detonation waves to steady
and unsteady air-breathing propulsion systems. The efficiency of ideal
detonation-based propulsion systems is first investigated based on
thermodynamics and quasi one-dimensional flow. Steady detonation waves are
shown to be less desirable than deflagrations for steady propulsion systems but
unsteady detonations are found to have the potential for generating more work
than constant-pressure combustion. The subsequent work focuses on specific
engine concepts utilizing detonations in a steady and an unsteady mode. A flow
path analysis of ideal steady detonation engines is conducted and shows that
the performance of these engines is limited and poorer than that of the ideal
ramjet or turbojet engines. The limitations associated with the use of a steady
detonation in the combustor are drastic and such engines do not appear to be
practical. This leads us to focus on unsteady detonation engines, i.e., pulse
detonation engines. The unsteady generation of thrust in a pulse detonation
engine is first analyzed using gas dynamics and modeled in the simplest
configuration consisting of a straight detonation tube. The impulse of a
detonation tube is found to scale directly with the mass of explosive in the
tube and the square root of the energy release per unit mass of the mixture.
Impulse values for typical fuel-oxidizer mixtures are found to be on the order
of 160 s for hydrocarbon-oxygen mixtures and 120 s for fuel-air mixtures at
standard conditions. These results are then used as a basis to predict the
performance of a supersonic air-breathing pulse detonation engine with a single
straight tube. We show that hydrogen- and JP10-fueled pulse detonation engines
generate thrust up to a Mach number of 4 at 10,000 m altitude, and that the
specific impulse decreases quasi-linearly with increasng flight Mach number.
Finally, we find that the performance of our single-tube air-breathing pulse
detonation engine exceeds that of the ramjet below a Mach number of 1.35.
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