Partial Fuel Filling in Pulse Detonation Engines

Abstract

Partial fuel filling in pulse detonation engines (PDEs) is a fuel-filling strategy in which only a part of the PDE tube is filled with a combustible mixture and the rest of the tube with a nonreactive mixture. The structures of the pressure waves in the flowfield in partially filled PDEs are illustrated in detail by systematic numerical simulations. The simulations show those pressure waves control the development of the flowfield and, hence, the thrust production of the PDE. Based on the pressure information from the simulations, performance analysis is also conducted. The analysis shows that for a fuel section of a given length the impulse increases with the length of the nonreactive section, eventually approaching an asymptotic value. Hence, the partial fuel filling in a PDE increases the fuel-based specific impulse I f sp, which represents an improvement in the fuel efficiency for air-breathing applications, similar to the benefit generated by the bypass air introduced in gas-turbine jet engines. However, it does carry a penalty of reducing the total-mixture-based specific impulse I m sp because less chemical energy is contained per unit volume. As a consequence, the total engine output from a PDE partially filled with the combustible mixture is lower compared to that from one fully filled with the combustible mixture. Lower I m sp also implies reduction in fuel efficiency for PDE rocket applications.