Investigation of Combustion Instability in a Turbofan Mixed-Flow Augmentor
Final technical rept. 30 Jun 1970-31 Dec 1971
NORTHERN RESEARCH AND ENGINEERING CORP WOBURN MA
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An analytical and experimental investigation was conducted of combustion instability in a TF-30-P1 augmentor. A sustained oscillation was observed with a fuel zone combination which does not occur during normal engine operation. On cold days oscillation amplitudes above 35 per cent peak-to-mean were observed, but on hot days the amplitudes dropped below 10 per cent. NRECs previously developed combustion instability model correctly predicted an instability with the same frequency as that observed. Once the individual zones of combustion of the TF-30-P1 augmentor were modelled properly, the analysis correctly indicated the fuel zone combination during which the oscillation becomes most severe. The analytical model also correctly predicted the trends which were observed when engine geometry was modified, when AVGAS replaced JP-4, and when the engine inlet temperature was low. But to correlate predicted and observed amplitude levels, a stabilizing turbulent mixing effect had to be hypothesized to supplement the droplet vaporization effects which excite the instability.
- Combustion and Ignition
- Jet and Gas Turbine Engines