Investigation of the Response of an Air Blast Atomizer Combustion Chamber Configuration on Forced Modulation of Air Feed at Realistic Operating Conditions

Abstract

DLR investigated forced combustion oscillations of two liquid fuel burners in a research combustion chamber at elevated pressures simulating idle conditions of aircraft engine combustors. The work was performed in collaboration with MTU Munich. An existing combustion chamber with optical access, capable to operate up to 20 bar, was upgraded with an air flow pulsator, that bypasses air from the combustor plenum to the exhaust with a sinusoidal massflow variation up to 700 Hz. Pressure transducers in the plenum and the flame tube monitored the forced disturbances. A photomultiplier recorded the OH* chemiluminescence of the flame. For the agreed operating conditions frequency scans of these values were registered. Additionally images of the OH* chemiluminescence were taken at selected frequencies and evaluated in a statistical manner, to separate turbulent and periodic behavior. From the analysis of the pressure data, it can be concluded, that serious thermoacoustic feedback was not observed for both burners. However, burner 2 with the flame detached from the wall exhibited a higher fluctuation level as burner 1 with the wall attached flame. A resonant behavior was observed near the characteristic frequency of the sound room comprised of plenum, flame tube, and burner nozzle as connecting passage. The chemiluminescence images show different modes of spatial fluctuation for the burners and for burner 2 they also vary with the operating condition.

Dynamics and stability of lean-premixed swirl-stabilized combustion

“…Although considerable efforts have been devoted to studying forced shear layers and jets in the past few decades (Ho and Huerre [123], Panda and McLaughlin [128], Longmire and Eaton [176], Swanson and Richards [177], Cerecedo et al [178], Gallaire et al [132]), relatively limited investigations have been conducted to examine the response of a swirl injector to externally imposed excitations [179][180][181][182][183][184][185][186]. Cohen and Hibshman [179] studied the response of a two-passage swirl injector over a frequency range from 300 to 600 Hz.…”

Influence of Heat Transfer and Material Temperature on Combustion Instabilities in a Swirl Burner

“…[40] or Ref. [18]), the results indicate that the mode frequency changes between cases 1 and 2 due to the differences in sound speed in the plenum.…”

“…With increasing preheat temperature, the flame became more responsive to fuel flow rate modulations, which was mostly caused by a decrease of the evaporation and chemical time scale with higher temperatures. In the liquid fuel combustor investigated by Hassa et al [18], the resonance frequency of the system depended only on the preheat temperature, whereas the amplitude response of the system was strongly influenced by the burner geometry.…”

Thermoacoustically driven flame motion and heat release variation in a swirl-stabilized gas turbine burner investigated by LIF and chemiluminescence

“…Hubschmid et al (2002) and Schenker et al (2003). Hassa et al (2002) observed flame motion by means of OH* CL in a liquid fuel combustor operated at pressures up to 20 bar. In a premixed swirl-stabilized combustor a periodic motion of the flame was observed by Bellows et al (2007).…”