The reliable numerical evaluation of thermoacoustic stability is one of the most important unresolved problems in the development of liquid rocket engines. To provide data for code validation, a transonic cold-flow test facility was built, which comprises a rocket engine model for acoustic measurements. It consists of a cylindrical chamber with inflow through a perforated plate representing the faceplate and a choked nozzle at the exit. The flow is excited with a siren and complex eigenfrequencies, and the nozzle admittances for the most critical first-transverse mode are extracted from dynamic pressure measurements. These data are used to benchmark three stability assessment tools of widely varying numerical complexity. Results obtained with one- and three-dimensional methods based on the solution of the linearized Euler equations and results from nonlinear Navier-Stokes computations (unsteady Reynolds-averaged Navier-Stokes) are compared with the experimental data. All three codes reproduce the measured first-transverse-mode frequency, but only the two linearized Euler equation methods provide satisfactory values for first-transverse-mode damping and nozzle admittance. The nozzle admittances calculated from the unsteady Reynolds-averaged Navier-Stokes results exhibit large scatter, but the average of the data from 11 monitor points is close to the measured values and mode decomposition during data analysis is expected to reduce scatter further. However, the employed unsteady Reynolds-averaged Navier-Stokes method overpredicts nozzle damping.
Validation of Transverse Instability Damping Computations for Rocket Engines
Journal of propulsion and power ; 31 , 4
2015
Aufsatz (Zeitschrift)
Englisch
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