Assessment and Prediction of Helmholtz Resonator Performance Within Gas Turbine Combustion Systems

Abstract

This paper is concerned with the potential use of Helmholtz resonators to provide increased acoustic damping within aero gas turbine combustion systems. Experimental measurements were undertaken using a high intensity facility into which a three burner combustor sector (non-reacting) model could be incorporated. In this way the performance of various damper geometry combinations were assessed. The effect of incident noise levels was also considered along with the associated transition from linear absorption (i.e. where absorption is directly proportional to incident pressure magnitude) to nonlinear absorption (i.e. where the proportion of acoustic loss decreases with increasing noise levels). This complicates the performance comparison between different damping geometries and means care is required when relating laboratory to engine operating conditions. In addition, all the measurements were undertaken in the presence of fuel injectors and other realistic flow field features found within a combustion system and which could affect damping performance. Finally, experimental and numerical assessment was made of the noise levels at which ingestion of hot gas will occur into the resonator cavities with and without the presence of a purging flow. For the geometries investigated ingestion occurs when the fluid displacement in the neck during an acoustic cycle is approximately equal to, or greater than, the resonator neck length. The ratio of fluid displacement and neck length provides a limit for the noise levels at which hot gas is ingested into the cavity and hence the operating condition where damping performance and system mechanical integrity is significantly compromised.

Suppression of Combustion Instabilities in a Premixed Swirl Combustor with Acoustic Liner

“…Passive control methods do not involve any control algorithms and actuators thus the control system is simpler. Passive approaches typically include: (1) modulating the fuel supply to make operation states away from the instability boundary by artificial means; (2) adjusting the fuel injectors positions to change the fuel convective time delay thus making a damping effect [22] ; (3)dissipating acoustic energy with Helmholtz resonator [23,24], or acoustic liner [25][26][27]. The effective damping range (i.e.…”

Scattering to Higher Harmonics for Quarter Wave and Helmholtz Resonators

“…When the amplitude of the acoustic excitation rises and the purging flow rate is too low, hot gas can penetrate the resonator opening. This can detune the resonator and should thus be avoided, see e. g., the studies byĆosić et al 10 and Rupp et al 11 .…”