Numerical investigation of combustion noise generation in a full annular combustion chamber

2015 ◽  
Author(s):  
Thomas Livebardon ◽  
Stephane Moreau ◽  
Thierry Poinsot ◽  
Eric Bouty
Keyword(s):  
Combustion Chamber ◽  
Numerical Investigation ◽  
Combustion Noise ◽  
Noise Generation

scholarly journals Effects of Nozzle Helmholtz Number on Indirect Combustion Noise by Compositional Perturbations

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Luca Magri ◽  
Jeffrey O'Brien ◽  
Matthias Ihme
Keyword(s):  
Velocity Profile ◽  
Combustion Chamber ◽  
Transfer Functions ◽  
Mixture Fraction ◽  
Supersonic Nozzle ◽  
Noise Pollution ◽  
Combustion Noise ◽  
Dipole Source ◽  
Multicomponent Gas ◽  
Thermoacoustic Oscillations

By modeling a multicomponent gas, a new source of indirect combustion noise is identified, which is named compositional indirect noise. The advection of mixture inhomogeneities exiting the gas-turbine combustion chamber through subsonic and supersonic nozzles is shown to be an acoustic dipole source of sound. The level of mixture inhomogeneity is described by a difference in composition with the mixture fraction. An n-dodecane mixture, which is a kerosene fuel relevant to aeronautics, is used to evaluate the level of compositional noise. By relaxing the compact-nozzle assumption, the indirect noise is numerically calculated for Helmholtz numbers up to 2 in nozzles with linear velocity profile. The compact-nozzle limit is discussed. Only in this limit, it is possible to derive analytical transfer functions for (i) the noise emitted by the nozzle and (ii) the acoustics traveling back to the combustion chamber generated by accelerated compositional inhomogeneities. The former contributes to noise pollution, whereas the latter has the potential to induce thermoacoustic oscillations. It is shown that the compositional indirect noise can be at least as large as the direct noise and entropy noise in choked nozzles and lean mixtures. As the frequency with which the compositional inhomogeneities enter the nozzle increases, or as the nozzle spatial length increases, the level of compositional noise decreases, with a similar, but not equal, trend to the entropy noise. The noisiest configuration is found to be a compact supersonic nozzle.

Influence of Turbulent Combustion Noise on the Decrement Estimates of Gas Oscillations

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
V. Karmalita
Keyword(s):  
Combustion Chamber ◽  
Linear Model ◽  
Natural Frequency ◽  
Turbulent Combustion ◽  
Logarithmic Decrement ◽  
Combustion Noise ◽  
Vibrating Combustion ◽  
The Impact ◽  
Oscillation Decrement

This paper deals with the autoregression method to determine the logarithmic decrement and natural frequency of gas oscillations in a combustion chamber. The proposed approach to quantify the impact of combustion noise on the estimates of oscillation decrement is based on a linear model of the vibrating combustion phenomena. An application of the proposed approach for afterburner tests is presented as well.

Effects of Pilot Fuel and Liner Cooling on the Flame Structure in a Full Scale Swirl-Stabilized Combustion Setup

2009 ◽  
Author(s):  
Jens Fa¨rber ◽  
Rainer Koch ◽  
Hans-Jo¨rg Bauer ◽  
Matthias Hase ◽  
Werner Krebs
Keyword(s):  
Combustion Chamber ◽  
Fuel Injection ◽  
Flame Structure ◽  
Cone Angle ◽  
Flow Patterns ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Combustion Noise ◽  
Pilot Fuel ◽  
Combustor Liner

The flame structure and the limits of operation of a lean premixed swirl flame were experimentally investigated under piloted and non-piloted conditions. Flame stabilization and blow out limits are discussed with respect to pilot fuel injection and combustor liner cooling for lean operating conditions. Two distinctly different flow patterns are found to develop depending on piloting and liner cooling parameters. These flow patterns are characterized with respect to flame stability, blow out limits, combustion noise and emissions. The combustion system explored consists of a single burner similar to the burners used in Siemens annular combustion systems. The burner feeds a distinctively non-adiabatic combustion chamber operated with natural gas under atmospheric pressure. Liner cooling is mimicked by purely convective cooling and an additional flow of ‘leakage air’ injected into the combustion chamber. Both, this additional air flow and the pilot fuel ratio were found to have a strong influence on the flow structure and stability of the flame close to the lean blow off limit (LBO). It is shown by Laser Doppler Velocimetry (LDV) that the angle of the swirl cone is strongly affected by pilot fuel injection. Two distinct types of flow patterns are observed close to LBO in this large scale setup: While non-piloted flames exhibit tight cone angles and small inner recirculation zones (IRZ), sufficient piloting results in a wide cone angle and a large IRZ. Only in the latter case, the main flow becomes attached to the combustor liner. Flame structures deduced from flow fields and CH-Chemiluminescence images depend on both the pilot fuel injection and liner cooling.

Assessment of the Indirect Combustion Noise Generated in a Transonic High-Pressure Turbine Stage

2015 ◽  
Author(s):  
Dimitrios Papadogiannis ◽  
Florent Duchaine ◽  
Laurent Gicquel ◽  
Gaofeng Wang ◽  
Stéphane Moreau ◽  
...  
Keyword(s):  
High Pressure ◽  
Acoustic Waves ◽  
Gas Turbines ◽  
Guide Vane ◽  
Combustion Noise ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Noise Generation ◽  
Turbine Stage ◽  
High Pressure Turbine

Indirect combustion noise, generated by the acceleration and distortion of entropy waves through the turbine stages, has been shown to be the dominant noise source of gas turbines at low-frequencies and to impact the thermoacoustic behavior of the combustor. In the present work, indirect combustion noise generation is evaluated in the realistic, fully 3D transonic high-pressure turbine stage MT1 using Large-Eddy Simulations (LES). An analysis of the basic flow and the different turbine noise generation mechanisms is performed for two configurations: one with a steady inflow and a second with a pulsed inlet, where a plane entropy wave train at a given frequency is injected before propagating across the stage generating indirect noise. The noise is evaluated through the Dynamic Mode Decomposition of the flow field. It is compared with previous 2D simulations of a similar stator/rotor configuration, as well as with the compact theory of Cumpsty and Marble. Results show that the upstream propagating entropy noise is reduced due to the choked turbine nozzle guide vane. Downstream acoustic waves are found to be of similar strength to the 2D case, highlighting the potential impact of indirect combustion noise on the overall noise signature of the engine.

scholarly journals Numerical Prediction of Far-Field Combustion Noise from Aeronautical Engines

Acoustics ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 174-198 ◽  
Author(s):  
Mélissa Férand ◽  
Thomas Livebardon ◽  
Stéphane Moreau ◽  
Marlène Sanjosé
Keyword(s):  
Temperature Field ◽  
Low Power ◽  
Combustion Chamber ◽  
High Power ◽  
Acoustic Propagation ◽  
Combustion Noise ◽  
Far Field ◽  
Low Frequencies ◽  
Turboshaft Engine ◽  
Good Agreement

A hybrid methodology combining a detailed Large Eddy Simulation of a combustion chamber sector, an analytical propagation model of the extracted acoustic and entropy waves at the combustor exit through the turbine stages, and a far-field acoustic propagation through a variable exhaust temperature field was shown to predict far-field combustion noise from helicopter and aircraft propulsion systems accurately for the first time. For the single-stream turboshaft engine, the validation was achieved from engine core to the turbine exit. Propagation to the far field was then performed through a modeled axisymmetric jet. Its temperature modified the acoustic propagation of combustion noise significantly and a simple analytical model based on the Snell–Descarte law was shown to predict the directivity for axisymmetric single jet exhaust accurately. Good agreement with measured far-field spectra for all turboshaft-engine regimes below 2 kHz stresses that combustion noise is most likely the dominant noise source at low frequencies in such engines. For the more complex dual-stream turbofan engine, two regime computations showed that direct noise is mostly generated by the unsteady flame dynamics and the indirect combustion noise by the temperature stratification induced by the dilution holes in the combustion chamber, as found previously in the turboshaft case. However, in the turboengine, direct noise was found dominant at the combustor exit for the low power case and equivalent contributions of both combustion noise sources for the high power case. The propagation to the far-field was achieved through the temperature field provided by a Reynolds-Averaged Navier–Stokes simulation. Good agreement with measured spectra was also found at low frequencies for the low power turboengine case. At high power, however, turboengine jet noise overcomes combustion noise at low frequencies.

Noise Generation in Hot Nozzle Flow

2015 ◽  
Author(s):  
Karsten Knobloch ◽  
Tiago Werner ◽  
Friedrich Bake
Keyword(s):  
Mach Number ◽  
Guide Vane ◽  
Combustion Process ◽  
Combustion Noise ◽  
Small Scale ◽  
Propagation Time ◽  
Noise Generation ◽  
Mean Flow ◽  
Experimental Proof ◽  
Cold Air

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.

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