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Research Papers

Experimental Assessment of Noise Generation and Transmission in a High-Pressure Transonic Turbine Stage

[+] Author and Article Information
Karsten Knobloch

Department of Engine Acoustics,
Institute of Propulsion Technology,
German Aerospace Center (DLR),
Berlin D-10623, Germany
e-mail: karsten.knobloch@dlr.de

Lars Neuhaus

Department of Engine Acoustics,
Institute of Propulsion Technology,
German Aerospace Center (DLR),
Berlin D-10623, Germany
e-mail: lars.neuhaus@dlr.de

Friedrich Bake

Department of Engine Acoustics,
Institute of Propulsion Technology,
German Aerospace Center (DLR),
Berlin D-10623, Germany
e-mail: friedrich.bake@dlr.de

Paolo Gaetani

Laboratorio di Fluidodinamica delle Macchine,
Dipartimento di Energia,
Politecnico di Milano,
Milano I-20158, Italy
e-mail: paolo.gaetani@polimi.it

Giacomo Persico

Laboratorio di Fluidodinamica delle Macchine,
Dipartimento di Energia,
Politecnico di Milano,
Milano I-20158, Italy
e-mail: giacomo.persico@polimi.it

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received October 18, 2016; final manuscript received March 23, 2017; published online May 9, 2017. Editor: Kenneth Hall.

J. Turbomach 139(10), 101006 (May 09, 2017) (12 pages) Paper No: TURBO-16-1278; doi: 10.1115/1.4036344 History: Received October 18, 2016; Revised March 23, 2017

Noise originating from the core of an aero-engine is challenging to quantify since the understanding of its generation and propagation is less advanced than that for noise sources of other engine components. To overcome the difficulties associated with dynamic measurements in the crowded core region, dedicated experiments have been set up in order to investigate mainly two processes: the propagation of direct combustion noise through the subsequent turbine stage, and the generation of indirect combustion noise by the passage of inhomogeneities of entropy and vorticity through the turbine stage. In the current work, a transonic turbine stage was exposed to isolated and well-characterized acoustic, entropic, and vortical disturbances. The incoming and outgoing sound fields were analyzed in detail by two large arrays of microphones. The mean flow field and the disturbances were carefully mapped by several aerodynamic and thermal probes. The results include transmission and reflection characteristics of the turbine stage, the latter was found to be much lower than commonly assumed. The modal decomposition of the acoustic field in the upstream and downstream section shows additional modes besides the expected rotor–stator interaction modes. At the frequency of entropy or vorticity excitation, respectively, a significant increase of the overall sound power level was observed.

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Figures

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Fig. 1

Schematic view of the test setup for indirect combustion noise experiment in a HP turbine

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Fig. 2

Schematic view of the excitation generation device (EWG/VWG) used for indirect combustion noise experiments in the HP turbine

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Fig. 3

Stator-exit flow field in OP1

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Fig. 4

Spanwise profiles downstream of the stator

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Fig. 5

Rotating-frame time-mean rotor-exit flow field in OP1

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Fig. 6

Rotating-frame time-mean rotor-exit flow field in OP3

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Fig. 7

Spanwise profiles downstream of the rotor—absolute quantities

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Fig. 8

Shape and amplitude of entropy waves

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Fig. 9

Shape and amplitude of vorticity waves

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Fig. 10

Spectra of sound pressure level—averaged over full array for upstream and downstream side, OP1 and OP3

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Fig. 11

Modal distribution of sound power for OP1 in upstream and downstream section. Mean value and error bars (1×σ).

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Fig. 12

Transmission and reflection in downstream direction (upper plot) and energetic residual (lower plot) for OP1 and OP3. OP0 corresponds to fixed rotor, no flow.

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Fig. 13

Total sound power difference for unsteady excitation, upper two plots: 30 Hz, lower two plots: 90 Hz

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Fig. 14

Downstream propagating acoustic power ΔP2,Entropy+ generated by the entropy waves at operating conditions OP1 and OP3 for 30 HZ excitation

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