Low-frequency combustion instabilities of an airblast swirl injector in a liquid-fuel combustor

2018 ◽  
Vol 196 ◽  
pp. 424-438 ◽  
Author(s):  
Byeonguk Ahn ◽  
Jeongjae Lee ◽  
Seungchai Jung ◽  
Kyu Tae Kim
Keyword(s):  
Liquid Fuel ◽  
Low Frequency ◽  
Combustion Instabilities ◽  
Swirl Injector

Dynamic Characteristics of Simplex Swirl Injector in Low Frequency Range

2012 ◽  
Vol 28 (2) ◽  
pp. 323-333 ◽  
Author(s):  
Taeock Khil ◽  
Yunjae Chung ◽  
Vladimir G. Bazarov ◽  
Youngbin Yoon
Keyword(s):  
Dynamic Characteristics ◽  
Low Frequency ◽  
Frequency Range ◽  
Swirl Injector

On the Effect of Pressure Oscillations on Droplet Autoignition

2011 ◽  
Author(s):  
Christian Eigenbrod ◽  
Konstantin Klinkov ◽  
Fernando Filho Fachini
Keyword(s):  
High Frequency ◽  
Gas Turbines ◽  
Low Frequency ◽  
Combustion Instabilities ◽  
Driving Mechanisms ◽  
Temperature Oscillations ◽  
Large N ◽  
Main Driver ◽  
Droplet Sizes ◽  
Induction Times

The paper discusses the possible interaction between combustion instabilities and induction times of droplets (and sprays) to autoignition. It is shown that acoustic pressure/temperature oscillations significantly affect the induction times of n-heptane droplets. This may play an additional role in low frequency dynamics and might be the main driver of high frequency dynamics. Experiments on single droplets in an acoustic field were used to validate numerical simulations on the autoignition of large n-heptane droplets. The simulations were then extended towards technical droplet sizes and a gas turbine typical pressure range of 17 bar. It was found that the acoustic-scale changes of the pressure and temperature result in significant changes of the ignition delay. Applying numerical calculations to micro-sized droplets enabled to study the thermo-acoustic effects under conditions approximating real gas-turbines. The findings reveal the importance of thermo-acoustic effects on ignition processes in the instability-driving mechanisms of combustion and indicate that “acoustics-ignition”-interactions must be taken into account for low-frequency as well as for high-frequency dynamics; this in addition to the flow and mixture perturbations which are well known to drive combustion instabilities in gas-turbines.

Effect of Port Gas Injection on the Combustion Instabilities in a Spark-Ignition Lean-Burn Natural Gas Engine

2018 ◽  
Vol 28 (10) ◽  
pp. 1850124
Author(s):  
Li-Yuan Wang ◽  
Li-Ping Yang ◽  
En-Zhe Song ◽  
Chong Yao ◽  
Xiu-Zhen Ma
Keyword(s):  
Natural Gas ◽  
High Frequency ◽  
Gas Injection ◽  
Low Frequency ◽  
Combustion System ◽  
Combustion Instabilities ◽  
Lean Burn ◽  
Engine Load ◽  
Gas Engine ◽  
Natural Gas Engine

The combustion instabilities in a lean-burn natural gas engine have been studied. Using statistical analysis, phase-space reconstruction, and wavelet transforms, the effect of port gas injection on the dynamics of the indicated mean effective pressure (IMEP) fluctuations have been examined at a speed of 800[Formula: see text]rpm and engine load rates of 25% and 50%. The excessive air coefficient is 1.6 for each engine load, and the port gas injection timing (PGIT) ranges from 1 to 120 degrees of crankshaft angle ([Formula: see text]CA) after top dead center (ATDC) of the intake process. The results show that the PGIT has a significant effect on cyclic combustion fluctuations and the dynamics of the combustion system for all studied engine loads. An unreasonable PGIT leads to increased combustion fluctuations, and loosened and bifurcated structures of combustion system attractors. Furthermore, for both low and medium engine loads, the IMEP time series at earlier gas injections ([Formula: see text]CA and [Formula: see text]CA ATDC) undergoes low-frequency fluctuation together with high-frequency fluctuations in an intermittent fashion. For other PGITs, high-frequency intermittent fluctuations become persistent combined with weak low-frequency oscillations. Our results can be used to understand the oscillation characteristics and the complex dynamics of combustion system in a lean-burn natural gas engine. In addition, they may also be beneficial to the development of more sophisticated engine control strategies.

Vortex-driven acoustically coupled combustion instabilities

1987 ◽  
Vol 177 ◽  
pp. 265-292 ◽  
Author(s):  
Thierry J. Poinsot ◽  
Arnaud C. Trouve ◽  
Denis P. Veynante ◽  
Sebastien M. Candel ◽  
Emile J. Esposito
Keyword(s):  
Heat Release ◽  
Vortex Shedding ◽  
Combustion Instability ◽  
Low Frequency ◽  
Combustion Instabilities ◽  
Rayleigh Criterion ◽  
Phase Average ◽  
Steady Heat

Combustion instability is investigated in the case of a multiple inlet combustor with dump. It is shown that low-frequency instabilities are acoustically coupled and occur at the eigenfrequencies of the system. Using spark-schlieren and a special phase-average imaging of the C2-radical emission, the fluid-mechanical processes involved in a vortex-driven mode of instability are investigated. The phase-average images provide maps of the local non-steady heat release. From the data collected on the combustor the processes of vortex shedding, growth, interactions and burning are described. The phases between the pressure, velocity and heat-release fluctuations are determined. The implications of the global Rayleigh criterion are verified and a mechanism for low-frequency vortex-driven instabilities is proposed.

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.

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