NOISE GENERATION IN HOT NOZZLE FLOW

Noise originating from the unsteady heat-release during the combustion process in the combustor of a gas turbine is well known. However, an effect known as indirect combustion noise has received considerable interest only recently. Indirect combustion noise will be generated, when entropy or vorticity fluctuations will be subject to a strong velocity gradient like in nozzle guide vane of the high pressure turbine. First experimental proof of this phenomenon could be obtained some years ago in a dedicated small-scale laboratory experiment. Recent experiments performed in the Hot Acoustic Test rig (HAT) by the German Aerospace Center (DLR) aim at further understanding of this phenomenon by investigating the sound propagation through a nozzle and sound generation when cold air spots are injected into a hot mean flow. The nozzle Mach number was varied from subsonic to sonic conditions. First results based on propagation time analysis reveal noise generation at the location of the nozzle. Parameter studies of nozzle Mach number, temperature of the cold streaks, and the way the cold air is injected (radial/axial blowing) have been performed

Kalibriermessungen von zwei Kistler-Sonden für akutische Messungen an Brennkammern

Im Rahmen der Arbeit wurden zwei Kistler-Sonden im Vergleich zu einem Kondensatormikrofon kalibriert, um Korrekturfaktoren für Amplitude und Phase zu bestimmen. Neben Betrachtungen zur Überströmung wurden die Sonden dabei auch untereinander verglichen