Acoustically Coupled Combustion of Liquid Fuel Droplets

2016 ◽  
Vol 68 (4) ◽  
Author(s):  
Ann R. Karagozian
Keyword(s):  
Flow Field ◽  
Liquid Fuel ◽  
Combustion Control ◽  
Engineering Systems ◽  
Combustion Instabilities ◽  
Fundamental Interaction ◽  
Fuel Droplets ◽  
Idealized Model ◽  
Practical Engineering

The dynamics of oscillatory flames is relevant to acoustically coupled combustion instabilities arising in many practical engineering systems. This paper reviews fundamental studies that pertain to the combustion of single liquid fuel droplets in an acoustically resonant environment. This flow field is not only an idealized model for the study of the fundamental interaction of reactive, evaporative, acoustic, and other transport-based timescales, but it may also be used to identify relevant phenomena in more complex or practical geometries that require a focus for future combustion control efforts. The nature of these phenomena is discussed in detail, in addition to their implications for broader issues associated with combustion instabilities.

Forced Oscillations in Combustors With Spray Atomizers

1999 ◽  
Vol 124 (1) ◽  
pp. 20-30 ◽  
Author(s):  
M. Zhu ◽  
A. P. Dowling ◽  
K. N. C. Bray
Keyword(s):  
Liquid Fuel ◽  
Pressure Fluctuations ◽  
Droplet Size Distribution ◽  
Forced Oscillations ◽  
Combustion Instabilities ◽  
Unsteady Combustion ◽  
Fuel Droplets ◽  
Rate Of Combustion ◽  
Flow Oscillations ◽  
Insight Into

Most types of combustion-driven devices experience combustion instabilities. For aeroengine combustors, the frequency of this oscillation is typically in the range 60–120 Hz and is commonly called “rumble.” The rumble oscillations involve coupling between the air and fuel supplies and unsteady flow in the combustor. Essentially pressure fluctuations alter the inlet fuel and air, thereby changing the rate of combustion, which at certain frequencies further enhances the pressure perturbation and so leads to self-excited oscillations. The large residence time of the liquid fuel droplets, at idle and subidle conditions, means that liquid and gaseous phases must both be considered. In the present work, we use a numerical model to investigate the forced unsteady combustion due to specified time-dependent variations in the fuel and air supplies. Harmonic variations in inlet air and fuel flows have been considered and the resulting unsteady combustion calculated. The influence of droplet size distribution has also been investigated. The calculations provide insight into the interaction between atomization, unsteady combustion, and flow oscillations.

Combustion Oscillations in Burners With Fuel Spray Atomisers

1999 ◽  
Author(s):  
M. Zhu ◽  
A. P. Dowling ◽  
K. N. C. Bray
Keyword(s):  
Liquid Fuel ◽  
Pressure Fluctuations ◽  
Droplet Size Distribution ◽  
Combustion Instabilities ◽  
Unsteady Combustion ◽  
Fuel Droplets ◽  
Rate Of Combustion ◽  
Aero Engine ◽  
Flow Oscillations ◽  
Insight Into

Most types of combustion-driven devices experience combustion instabilities. For aero-engine combustors, the frequency of this oscillation is typically in the range 60–120Hz and is commonly called ‘rumble’. The rumble oscillations involve coupling between the air and fuel supplies and unsteady flow in the combustor. Essentially pressure fluctuations alter the inlet fuel and air, thereby changing the rate of combustion, which at certain frequencies further enhances the pressure perturbation and so leads to self-excited oscillations. The large residence time of the liquid fuel droplets, at idle and sub-idle conditions, means that liquid and gaseous phases must both be considered. In the present work, we use a numerical model to investigate forced unsteady combustion due to specified time-dependent variations in the fuel and air supplies. Harmonic variations in inlet air and fuel flows have been considered and the resulting unsteady combustion calculated. The influence of droplet size distribution has also been investigated. The calculations provide insight into understanding the interaction between atomization, unsteady combustion and flow oscillations.

NONEQUILIBRIUM DIFFUSION COMBUSTION OF LIQUID FUEL DROPLETS AND SPRAYS MODELING

2012 ◽  
Vol 43 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Nickolay N. Smirnov ◽  
V. F. Nikitin ◽  
V. V. Tyurenkova
Keyword(s):  
Liquid Fuel ◽  
Diffusion Combustion ◽  
Fuel Droplets

Laser-Based Investigations of Periodic Combustion Instabilities in a Gas Turbine Model Combustor

2005 ◽  
Vol 127 (3) ◽  
pp. 492-496 ◽  
Author(s):  
R. Giezendanner ◽  
P. Weigand ◽  
X. R. Duan ◽  
W. Meier ◽  
U. Meier ◽  
...  
Keyword(s):  
Flow Field ◽  
Heat Release ◽  
Gas Turbine ◽  
Axial Velocity ◽  
Mixture Fraction ◽  
Oh Radicals ◽  
Driving Mechanism ◽  
Pulsation Period ◽  
Combustion Instabilities ◽  
Validation Data

The driving mechanism of pulsations in gas turbine combustors depends on a complex interaction between flow field, chemistry, heat release, and acoustics. Experimental data on all these factors are therefore required to obtain insight into the coupling mechanisms during a pulsation period. In order to develop a comprehensive experimental database to support a phenomenological understanding and to provide validation data for numerical simulation, a standard burner for optical investigations was established that exhibits strong self-excited oscillations. The burner was a swirl-stabilized nonpremixed model combustor designed for gas turbine applications and operated using methane as fuel at atmospheric pressure. It was mounted in a combustion chamber, which provides almost unobstructed optical access. The periodic combustion instabilities were studied by a variety of phase-resolved laser-based diagnostic techniques, locked to the frequency of the dominant pressure oscillation. Measurement techniques used were LDV for velocity measurements, planar laser-induced fluorescence for imaging of CH and OH radicals, and laser Raman scattering for the determination of the major species concentrations, temperature, and mixture fraction. The phase-resolved measurements revealed significant variations of all measured quantities in the vicinity of the nozzle exit, which trailed off quickly with increasing distance. A strong correlation of the heat release rate and axial velocity at the nozzle was observed, while the mean mixture fraction as well as the temperature in the periphery of the flame is phase shifted with respect to axial velocity oscillations. A qualitative interpretation of the experimental observations is given, which will help to form a better understanding of the interaction between flow field, mixing, heat release, and temperature in pulsating reacting flows, particularly when accompanied by corresponding CFD simulations that are currently underway.

scholarly journals Hydrodynamic Interactions between Bracket and Propeller of Podded Propulsor Based on Particle Image Velocimetry Test

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1142
Author(s):  
Dagang Zhao ◽  
Chunyu Guo ◽  
Tiecheng Wu ◽  
Wei Wang ◽  
Xunbin Yin
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Working Conditions ◽  
Cross Sections ◽  
Particle Image ◽  
Podded Propulsor ◽  
Image Velocimetry ◽  
Theoretical Significance ◽  
Practical Engineering ◽  
Flow Field Characteristics

In this study, particle image velocimetry was used to measure the fine flow-field characteristics of an L-type podded propulsor in various working conditions. The flow-field details at different cross-sections between the propeller and the inclined bracket were compared and analyzed, allowing for more intuitive comparison of the flow-field characteristics of L-type podded propulsors. The interference mechanisms among the propeller, pod, and bracket of the L-type podded propulsors at different advance coefficients, deflection angles, and deflection directions were investigated in depth. The results of this study can serve as reference material and provide technical support for the design and practical shipbuilding application of L-type podded propulsors. Therefore, the results have theoretical significance and practical engineering value.

Enhancing Broadband Vibration Energy Suppression Using Local Buckling Modes in Constrained Metamaterials

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Ryan L. Harne ◽  
Daniel C. Urbanek
Keyword(s):  
Vibration Suppression ◽  
Local Buckling ◽  
Engineering Systems ◽  
Buckling Modes ◽  
Dynamic Mass ◽  
Stiffness Reduction ◽  
Elastomeric Dampers ◽  
Practical Engineering ◽  
Post Buckling ◽  
Relative Change

Studies on dissipative metamaterials have uncovered means to suppress vibration and wave energy via resonant and bandgap phenomena through such engineered media, while global post-buckling of the infinitely periodic architectures is shown to tailor the attenuation properties and potentially magnify the effective damping effects. Yet, despite the promise suggested, the practical aspects of deploying metamaterials necessitates a focus on finite, periodic architectures, and the potential to therefore only trigger local buckling features when subjected to constraints. In addition, it is likely that metamaterials may be employed as devices within existing engineering systems, so as to motivate investigation on the usefulness of metamaterials when embedded within excited distributed or multidimensional structures. To illuminate these issues, this research undertakes complementary computational and experimental efforts. An elastomeric metamaterial, ideal for embedding into a practical engineering structure for vibration control, is introduced and studied for its relative change in broadband damping ability as constraint characteristics are modified. It is found that triggering a greater number of local buckling phenomena provides a valuable balance between stiffness reduction, corresponding to effective damping magnification, and demand for dynamic mass that may otherwise be diminished in globally post-buckled metamaterials. The concept of weakly constrained metamaterials is also shown to be uniformly more effective at broadband vibration suppression of the structure than solid elastomeric dampers of the same dimensions.

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