Performance Evaluation of an Unsteady Turbine Driven by a Pulsed Detonation Combustor

Abstract

Replacing a Brayton cycle near constant-pressure combustor with a pulsed detonation combustor (PDC) may take advantage of potential performance improvements from low-entropy, pressure-gain heat addition. In this paper, the radial turbine of a Garrett automotive turbocharger is coupled to a hydrogen fueled PDC. Unsteady turbine power is obtained with a conventional dynamometer technique. Sampling frequencies greater than 10 kHz resolve rapid flowfield transients of confined detonations which occur in less than a millisecond and include peak gas pressures exceeding 4 MPa and peak gas temperatures greater than 2,400 K. Results include 6 ms time histories of turbine inlet and exit temperature, pressure, mass flow, and enthalpy during blowdown of a PDC. The unsteady inlet flowfield included momentary reverse flow, which was not observed at the turbine exit. Full pulsed detonation cycle time histories of turbine power, rotor speed, rotational energy and net shaft torque are included to describe the turbine response to detonations. Rotor speed is periodic and net shaft torque oscillates in response to a detonation. Results are shown for fill fractions ranging from 0.5 to 1.0 with a 0.5 purge fraction. PDC operating frequencies in this study range from 10 Hz to 25 Hz.