Performance on a Pulse Detonation Engine Under Subsonic and Supersonic Flight Conditions

Abstract

In a Pulse Detonation Engine (PDE), an exit nozzle enhances thrust generation, maintains operating pressure and also controls operating frequency. The performance of a PDE, under subsonic and supersonic flight conditions, was assessed using two parametric studies. The first of these parametric studies employs a 2D CFD model and quantifies the relative impact of four different but separate exit nozzle shapes namely a Converging and Diverging (CD) nozzle, a diverging nozzle, a straight nozzle and a converging nozzle where as a second parametric model uses a quasi-1D model for predicting the effect of a CD nozzle geometry parameters on the systems-level performance of a PDE. The 2D CFD performance model predictions for the subsonic flight (Mach number (Minf) = 0.8 and altitude (hinf) = 20 kft), using single pulse simulations of the detonation and the blowdown processes, show that the fuel-specific impulse Ispf, is higher for the case of a diverging nozzle when compared to all other nozzles. These results are in agreement with the results reported earlier [14,20] in the literature. The 2D CFD performance model predictions of a PDE under supersonic flight conditions (Minf = 3.0 and hinf = 30 kft), obtained using single pulse simulations of the detonation and the blowdown processes, show that the Ispf, total impulse and thrust generated are higher for the case of the diverging nozzle and the CD nozzle, when compared to the performance metrics of the straight nozzle or the diverging nozzle. A second parametric study employs the Q1D limit cycle model, and the exit CD nozzle contraction ratio (Rnc) is varied from 1.6 to 6.4. For the subsonic flight conditions, Ispf increases with increasing values of the exit nozzle contraction ratio and attains a constant value of 1600 for an exit nozzle contraction ratio of 3.0. For the supersonic flight conditions, Ispf increases with increasing values of the exit nozzle contraction ratio and attains a constant value of 1950 for Rnc > 5.0. The design choice of the optimum value for Rnc is predicted to be a compromise between optimizing the performance metric Ispf and generating the required thrust.