Abstract
A low-order model is presented to study the propagation and interaction of acoustic and entropic
perturbations through a convergent-divergent nozzle. The calculations deal with choked, unchoked, as well
as compact and non-compact nozzles. In the choked case, a normal shock exists in the divergent section of
the nozzle. To validate the models developed, cylindrical configurations corresponding to Entropy-WaveGenerator
(EWG) and Hot-Acoustic-Testrig (HAT) of DLR are studied. For the EWG, an entropy wave is
generated upstream of a nozzle by an electrical heating device, and for the HAT a speaker is used to
generate pressure waves. In these two configurations and for the choked case, the supersonic region
between the nozzle throat and the normal shock is assumed to be acoustically compact. The results of the
low-order model are found to give excellent agreement with the experimental results of the EWG and HAT
rigs. To give insight into the physics, the model is used to undertake a parametric study for a range of nozzle
lengths and shock strengths. The low order model is finally used to calculate the direct to indirect (entropy
and vorticity) combustion noise ratio for an idealised thin-annular combustor. For this model combustor
the direct acoustic noise is found to dominate within the combustor while, the entropy indirect noise is
found to be the main source of noise downstream of the choked nozzle. The indirect vorticity noise has a
negligible contribution.
Original language | English |
---|---|
Number of pages | 12 |
Journal | AIAA Journal |
Early online date | 15 May 2017 |
DOIs | |
Publication status | Early online date - 15 May 2017 |