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.
The Aerospace Center 0 370 L'Enfant Promenade, SW 0 Washington, DC 20024-251 8 Amer~can lnstitwte of Aeronawtics an Downloaded by KUNGLIGA TEKNISKA HOGSKOLEN KTH on August 24, 2015 | http://arc.aiaa.org |Abstract DLR Cologne has built a thrust nozzle test facility for high temperature model tests on nozzles of hypersonic vihicles like ShJGER. The facility has been designed to simulate the aerothermodynamic flow field conditions within a ramjet at flight Mach numbers of about 3.5 to 7. The high temperature ramcombustor intake conditions will be generated by precombustors and the low pressure exhaust conditions will be provided by a diffuser working against atmospheric pressure. The total temperature up to 3000K will be achieved by hydrogen combustion. When fully operational, the facility will have the capability to measure flow parameters with laser diagnostics and thrust coefficients with a strain-gage balance. The connected pipe concept is described in detail and some statements to the test objects and to the accompanying fundamental research program are made.
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 behaviour. From the analysis of the pressure data, it can be concluded, that serious thermo-acoustic 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 behaviour 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.
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