Pressure wave generation from perturbed premixed flames

2016 ◽  
Vol 797 ◽  
pp. 231-246 ◽  
Author(s):  
Mathieu Blanchard ◽  
Peter J. Schmid ◽  
Denis Sipp ◽  
Thierry Schuller
Keyword(s):  
Heat Release ◽  
Pressure Wave ◽  
Pressure Fluctuations ◽  
Premixed Flame ◽  
Noise Generation ◽  
Relative Importance ◽  
Acoustic Activity ◽  
Optimization Methodology ◽  
Acoustic Output ◽  
Axisymmetric Disturbances

Numerical simulations and perturbation analysis of a radially imploding laminar premixed flame are used to study the mechanisms responsible for the generation of pressure fluctuations at flame fronts for various Lewis numbers. The relative importance of mechanisms based on unsteady heat release and on vorticity is investigated using an optimization methodology. Particular attention is paid to the influence of non-axisymmetric conditions and local flame curvature. It is shown that vorticity-based noise generation prevails for high-wavenumber, non-axisymmetric disturbances at all curvatures, while heat-release-driven noise generation dominates the axisymmetric and low-wavenumber regimes. These results indicate that short-wavelength vorticity waves actively participate in flame acoustic activity and can surpass acoustic output mechanisms based on heat-release fluctuations in the vicinity of the flame front.

scholarly journals A Study on the Interaction between a Flame and a Pressure Wave : On the Response of a premixed Flame to an N-Wave

1979 ◽  
Vol 22 (166) ◽  
pp. 585-590
Author(s):  
Eiichi MAEDA ◽  
Haruo KAWADA ◽  
Yoshio YOSHIZAWA ◽  
Yuji FUJITA
Keyword(s):  
Pressure Wave ◽  
Premixed Flame ◽  
N Wave

scholarly journals Combustion Instability of Swirl Premixed Flame with Dielectric Barrier Discharge Plasma

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1405
Author(s):  
Kai Deng ◽  
Shenglang Zhao ◽  
Chenyang Xue ◽  
Jinlin Hu ◽  
Yi Zhong ◽  
...  
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Combustion Instability ◽  
Premixed Flame ◽  
Oh Radicals ◽  
Acoustic Frequency ◽  
Planar Laser ◽  
Barrier Discharge Plasma

The effects of plasma on the combustion instability of a methane swirling premixed flame under acoustic excitation were investigated. The flame image of OH planar laser-induced fluorescence and the fluctuation of flame transfer function showed the mechanism of plasma in combustion instability. The results show that when the acoustic frequency is less than 100 Hz, the gain in flame transfer function gradually increases with the frequency; when the acoustic frequency is 100~220 Hz, the flame transfer function shows a trend of first decreasing and then increasing with acoustic frequency. When the acoustic frequency is greater than 220 Hz, the flame transfer function gradually decreases with acoustic frequency. When the voltage exceeds the critical discharge value of 5.3 kV, the premixed gas is ionized and the heat release rate increases significantly, thereby reducing the gain in flame transfer function and enhancing flame stability. Plasma causes changes in the internal recirculation zone, compression, and curling degree of the flame, and thereby accelerates the rate of chemical reaction and leads to an increase in flame heat release rate. Eventually, the concentration of OH radicals changes, and the heat release rate changes accordingly, which ultimately changes the combustion instability of the swirling flame.

Measurements and calculations of formaldehyde concentrations in a methane/N2/air, non-premixed flame: Implications for heat release rate

2009 ◽  
Vol 32 (1) ◽  
pp. 1311-1318 ◽  
Author(s):  
S.B. Dworkin ◽  
A.M. Schaffer ◽  
B.C. Connelly ◽  
M.B. Long ◽  
M.D. Smooke ◽  
...  
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Premixed Flame

Nonlinear Heat-Release/Acoustic Model for Thermoacoustic Instability in Lean Premixed Combustors

1999 ◽  
Vol 121 (3) ◽  
pp. 415-421 ◽  
Author(s):  
A. A. Peracchio ◽  
W. M. Proscia
Keyword(s):  
Heat Release ◽  
Limit Cycle ◽  
Gas Turbines ◽  
Pressure Fluctuations ◽  
Parametric Model ◽  
Operating Conditions ◽  
Cycle Frequency ◽  
Thermoacoustic Instability ◽  
Lean Premixed ◽  
Industrial Gas Turbines

Lean premixed combustors, such as those used in industrial gas turbines to achieve low emissions, are often susceptible to the thermoacoustic combustion instabilities, which manifest themselves as pressure and heat release oscillations in the combustor. These oscillations can result in increased noise and decreased durability due to vibration and flame motion. A physically based nonlinear parametric model has been developed that captures this instability. It describes the coupling of combustor acoustics with the rate of heat release. The model represents this coupling by accounting for the effect of acoustic pressure fluctuations on the varying fuel/air ratio being delivered to the flame, causing a fluctuating heat release due to both fuel air ratio variations and flame front oscillations. If the phasing of the fluctuating heat release and pressure are proper, an instability results that grows into a limit cycle. The nonlinear nature of the model predicts the onset of the instability and additionally captures the resulting limit cycle. Tests of a lean premixed nozzle run at engine scale and engine operating conditions in the UTRC single nozzle rig, conducted under DARPA contract, exhibited instabilities. Parameters from the model were adjusted so that analytical results were consistent with relevant experimental data from this test. The parametric model captures the limit cycle behavior over a range of mean fuel air ratios, showing the instability amplitude (pressure and heat release) to increase and limit cycle frequency to decrease as mean fuel air ratio is reduced.

scholarly journals Experimental and numerical studies of sound generated by cavities

2019 ◽  
Vol 137 ◽  
pp. 01011
Author(s):  
Sebastian Rulik ◽  
Włodzimierz Wrόblewski ◽  
Mirosław Majkut ◽  
Michał Strozik ◽  
Krzysztof Rusin
Keyword(s):  
High Frequency ◽  
Measurement Techniques ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
High Amplitude ◽  
Noise Generation ◽  
Flow Conditions ◽  
Numerical Studies ◽  
Wide Range ◽  
Specific Frequency

Cavities and gaps are an important element in the construction of many devices and machines, including energy sector applications. This type of flow is usually coupled with strong pressure fluctuations inside the cavity, which are emitted into the far field in the form of a sound wave responsible for the noise generation. This applies to both subsonic and supersonic flows. Pressure fluctuations often have the character of single tones of a specific frequency and high amplitude and their generation is associated with a vortex shedding formed directly above the inlet and its interaction with the walls of the cavity. The presented work include description of developed test stand and applied measurement techniques dedicated to the analysis of high frequency phenomena. In addition, the adopted numerical model will be described, including conducted two-dimensional and three-dimensional analysis. The developed models will be validated based on experimental measurements concerning wide range of flow conditions.

Influence of the Blade Design Parameters on Hydraulic Noise Generation by a Low Specific Speed Radial Pump With Narrow Channel Flow

2021 ◽  
Author(s):  
Rajavamsi Gangipamula ◽  
Pritanshu Ranjan ◽  
Ranjit S. Patil
Keyword(s):  
Pressure Fluctuations ◽  
Narrow Channel ◽  
Design Parameters ◽  
Noise Generation ◽  
Blade Design ◽  
Acoustic Behavior ◽  
Blade Passage ◽  
Low Specific Speed ◽  
Radial Pump ◽  
Specific Speed

Abstract Present work aims to investigate the hydro acoustic behavior of a typical low specific speed radial type centrifugal pump with narrow channel impeller passage. The blade design parameters play an important role in hydraulic noise generation by a low specific speed radial pump with narrow impeller channels. Though, these pumps are hydraulically efficient for a given design point, the hydraulic noise production may be higher at duty point. The blade passage length along with the outlet width of the impeller are the two main design parameters of a radial impeller with narrow channels, which can impact the flow quality along the impeller blade passage. To understand the effect of the narrow channel, initially steady state simulation is conducted to predict and validate the hydraulic performance. Then transient simulations were conducted using Detached Eddy Simulation (DES) using STAR-CCM+ to predict the hydro acoustic behavior of the pump in terms of pressure fluctuations and far field noise spectra of the pump at specific points. The velocity profiles along the impeller channels, shows the formation of wake region, which strongly affects the jet wake flow phenomenon near impeller trailing edge. This results in high pressure fluctuations near impeller outlet.

Dynamics of an impinging jet. Part 2. The noise generation

1982 ◽  
Vol 116 ◽  
pp. 379-391 ◽  
Author(s):  
Nagy S. Nosseir ◽  
Chih-Ming Ho
Keyword(s):  
Coherent Structures ◽  
Near Field ◽  
Pressure Fluctuations ◽  
Aerodynamic Noise ◽  
Far Field ◽  
Noise Generation ◽  
Physical Mechanisms ◽  
Field Noise ◽  
Subsonic Jet ◽  
Jet Axis

The aerodynamic noise generated by a subsonic jet impinging on a flat plate is studied from measurements of near-field and surface-pressure fluctuations. The far-field noise measured at 90° to the jet axis is found to be generated by two different physical mechanisms. One mechanism is the impinging of the large coherent structures on the plate, and the other is associated with the initial instability of the shear layer. These two sources of noise radiate to the far field via different acoustical paths.

scholarly journals A Study on the Interactions between a Flame and a Pressure Wave : On the Response of a Premixed Flame to an N-Wave

1978 ◽  
Vol 44 (384) ◽  
pp. 2842-2850
Author(s):  
Eiichi MAEDA ◽  
Haruo KAWADA ◽  
Yoshio YOSHIZAWA ◽  
Yuji FUJITA
Keyword(s):  
Pressure Wave ◽  
Premixed Flame ◽  
N Wave

On Generation of Entropy Waves by a Premixed Flame

2016 ◽  
Author(s):  
Lin Strobio Chen ◽  
Thomas Steinbacher ◽  
Camilo Silva ◽  
Wolfgang Polifke
Keyword(s):  
Heat Release ◽  
Equivalence Ratio ◽  
Source Term ◽  
Combustion Products ◽  
Combustion Noise ◽  
Premixed Flame ◽  
Combustion Chambers ◽  
Thermoacoustic Instabilities ◽  
The One ◽  
Entropy Source

It is understood that so-called “entropy waves” can contribute to combustion noise and play a role in thermoacoustic instabilities in combustion chambers. The prevalent description of entropy waves generation regards the flame front as a source of heat at rest. Such a model leads — in its simplest form — to an entropy source term that depends exclusively on the unsteady response of the heat release rate and upstream velocity perturbations. However, in the case of a perfectly premixed flame, which has a constant and homogeneous fuel / air ratio and thus constant temperature of combustion products, generation of entropy waves (i.e. temperature inhomogeneities) across the flame is not expected. The present study analyzes and resolves this inconsistency, and proposes a modified version of the quasi 1-D jump relations, which regards the flame as a moving discontinuity, instead of a source at rest. It is shown that by giving up the hypothesis of a flame at rest, the entropy source term is related upto leading order in Mach number to changes in equivalence ratio only. To supplement the analytical results, numerical simulations of a Bunsen-type 2D premixed flame are analysed, with a focus on the correlations between surface area, heat release and position of the flame on the one hand, and entropy fluctuations downstream of the flame on the other. Both perfectly premixed as well as flames with fluctuating equivalence ratio are considered.

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