Thermodynamic Cycle Analysis of Pulse Detonation Engines

Pulse detonation engines (PDEs) are currently attracting considerable research and development attention because they promise performance improvements over existing airbreathing propulsion devices. Because of their inherently unsteady behavior, it has been difficult to conveniently classify and evaluate them relative to their steady-state counterparts. Consequently, most PDE studies employ unsteady gasdynamic calculations to determine the instantaneous pressures and forces acting on the surfaces of the device and integrate them over a cycle to determine thrust performance. A classical, closed thermodynamic cycle analysis of the PDE that is independent of time is presented. The most important result is the thermal efficiency of the PDE cycle, or the fraction of the heating value of the fuel that is converted to work that can be used to produce thrust. The cycle thermal efficiency is then used to find all of the traditional propulsion performance measures. The benefits of this approach are the following: the fundamental processes incorporated in PDEs are clarified; direct, quantitative comparisons with other cycles (e.g., Brayton or Humphrey) are easily made; that the influence of the entire ranges of the main parameters that influence PDE performance are easily explored; the ideal or upper limit of PDE performance capability is quantitatively established; and this analysis provides a basic building block for more complex PDE cycles. A comparison of cycle performance is made for ideal and real PDE, Brayton, and Humphrey cycles, utilizing realistic component loss models. (Author)