Abstract
An experimental combustor, designated BKH, is operated at DLR Lampoldshausen to investigate high-frequency combustion instability phenomena. The combustor operates with liquid oxygen (LOx) and gaseous or liquid hydrogen propellants at supercritical conditions analogous to real rocket engines. An externally imposed acoustic disturbance interacts with a series of 5 coaxial injection elements in the center of the chamber. A combination of experimental analysis and numerical modeling is used to provide further insight and understanding of the BKH experiments. Optical data from the BKH experiments are analyzed to extract the response of the flame at the excitation frequency. A new method for reconstructing the acoustic field inside the chamber from dynamic pressure sensor data is used to describe the evolution of the acoustic mode and the local disturbance in the flame zone. An Unsteady Reynolds-Averaged Navier–Stokes (URANS) model of a single BKH injection element subjected to representative transverse acoustic velocity excitation has been computed using a specialized release of the DLR TAU code. The single-element model reproduces the retraction of the dense LOx core during transverse velocity excitation as observed experimentally. The model also provides further insight into the flattening and flapping of the flame. The flapping is identified as the oxygen core being transported by the transverse acoustic velocity.
Highlights
High-frequency combustion instabilities refer to a coupling between acoustic and combustion processes which occurs inside combustion chambers
The response of the single injector to an imposed transverse acoustic velocity disturbance was modeled by subjecting the steady-state solution to a representative disturbance during an unsteady computation
Flattening, §apping, and retraction of the liquid oxidizer core from a coaxial injection element under transverse acoustic excitation have previously been identi¦ed in
Summary
High-frequency combustion instabilities refer to a coupling between acoustic and combustion processes which occurs inside combustion chambers. If unimpeded, this coupling may produce acoustic disturbances that can aect the operation and structural integrity of the combustion chamber. High-frequency combustion instabilities are not yet fully understood and cannot be predicted, increasing risk and necessitating extensive ground testing to verify the safe operation of new hardware designs and con¦gurations. The combustion instability experiments feature additional diagnostics and instrumentation to observe the response of a §ame to either natural or externally imposed disturbances. The data from such experiments may be used to validate combustion instability models. The models may be used to provide further insight into the experiments themselves and eventually as a tool for predicting combustion instabilities
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
