W. Konrad et al., COMBUSTION INSTABILITY INVESTIGATIONS ON THE BR710 JET ENGINE, Journal of engineering for gas turbines and power, 120(1), 1998, pp. 34-40
During the development of the BR710 jet engine, audible combustor inst
abilities (termed ''rumble'') occurred. Amplitudes measured with test
cell microphones were up to 130 dB at around 100 Hz. Disturbances of t
his amplitude are clearly undesirable, even if only present during sta
rt-up, and a research program was initiated to eliminate the problem.
Presented here is the methodical and structured approach used to ident
ify, understand, and remove the instability. Some reference is made to
theory, which was used for guidance, but the focus of the work is on
the research done to find the cause of the problem and to correct it.
The investigation followed two separate, but parallel, paths-one looki
ng in detail at individual components of the engine to identify possib
le involvement in the instability and the other looking at the pressur
e signals from various parts of a complete engine to help pinpoint the
source of the disturbance. The main cause of the BR710 combustor rumb
le was found to be a self-excited aerodynamic instability arising from
the design of the fuel injector head. In the end, minor modifications
lead to spray pattern changes, which greatly reduced the combustor no
ise. As a result of this work, new recommendations are made for reduci
ng the risk of combustion instabilities in jet engines.