Resume of Nozzle Damping Theory
Technical memo. 1 Apr-20 Jun 1976
NAVAL WEAPONS CENTER CHINA LAKE CA
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This report is a brief survey of rocket nozzle damping which can provide a major source of damping in solid propellant motors. In a stability analysis it would be very advantageous to be able to assess nozzle damping. Unfortunately the state of the art precludes a reliable evaluation for many types of solid propellant motors. Nozzle damping theory was originally developed for liquid rockets. Typically, there is an injector at the head end of a cylindrical combustion chamber terminated by a nozzle, a geometry far simpler than that for a typical solid propellant rocket. The damping associated with a rocket nozzle, in many cases, reduces to evaluation of the acoustic admittance at the nozzle entrance plane. For small perturbations the sonic point in the nozzle is unique in that downstream of that point no wave energy will be reflected back to the chamber since the wave propagation velocity is less than or equal to the mean flow velocity. The analysis thus requires solving the flow field from the sonic point back to the nozzle entrance plane. Simpler treatments are available for axial modes when the convergence section of the nozzle is much shorter than the wave length and will be treated in a separate section.
- Numerical Mathematics
- Solid Propellant Rocket Engines