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.

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.

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.

Spray Test of Fuel Nozzle for Lean Pre-Mixed Pre-Vaporized Combustor

2002 ◽  
Author(s):  
Tomoyoshi Nakae ◽  
Masao Saigo ◽  
Akihiro Santo ◽  
Atsushi Tanaka
Keyword(s):  
Liquid Fuel ◽  
Ambient Pressure ◽  
Droplet Size Distribution ◽  
Test Model ◽  
Air Velocity ◽  
Fuel Droplets ◽  
Fuel Flow ◽  
Fine Spray ◽  
Fuel Nozzle ◽  
Pdpa Measurement

An LPP (Lean Pre-mixed Pre-vaporized) combustor is one of the most promising systems to make it possible to reduce NOx emission drastically. To realize low NOx combustors using liquid fuel, uniformity and fine atomization of fuel droplets are essential requirements. Droplet diameters of a fuel nozzle designed for LPP combustor as determined by PDPA measurement system are presented in this paper. An annulus pre-mixing duct was employed for the LPP fuel nozzle test model. Spray tests were conducted at pressures from 0.18MPa to 0.53MPa. Pre-mixing air velocity was also varied. Data show that the test nozzle produces a fine spray. In this paper, fuel droplet size distribution and velocity are presented and effects of air pressure and velocity on atomization are discussed. SMD of fuel droplets increases with the increases of ambient pressure. This is inconsistent with the trend determined by other works. But when the effect of fuel flow rate (or fuel film thickness) is considered, these inconsistencies can be resolved.

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

Spinning Behaviour of Diametral Acoustic Modes in Deep Axisymmetric Cavities With Chamfered Edges

2014 ◽  
Author(s):  
Oleksandr Barannyk ◽  
Peter Oshkai
Keyword(s):  
Pressure Fluctuations ◽  
High Amplitude ◽  
Pronounced Change ◽  
Axisymmetric Cavity ◽  
Acoustic Modes ◽  
Splitter Plates ◽  
Flow Oscillations ◽  
Axisymmetric Cavities ◽  
Spinning Behaviour ◽  
Stationary Behaviour

Spinning behaviour of diametral acoustic modes associated with self-sustained flow oscillations in a deep, axisymmetric cavity located in a long pipeline was investigated experimentally. High-amplitude pressure fluctuations resulted from the excitation of the diametral acoustic modes by the fully-turbulent flow in the pipeline. The unsteady pressure was measured at three equally spaced azimuthal locations at the bottom of the cavity. This arrangement allowed calculation of the azimuthal orientation of the acoustic modes, which were classified as stationary, partially spinning or spinning. Introduction of shallow chamfers to the upstream and the downstream edges of the cavity resulted in changes of azimuthal orientation and spinning behaviour of the acoustic modes. In addition, introduction of splitter plates in the cavity led to pronounced change in the spatial orientation and the spinning behaviour of the acoustic modes. The short splitter plates changed the behaviour of the dominant acoustic modes from partially spinning to stationary, while the long splitter plates enforced the stationary behaviour across all resonant acoustic modes.

Spray Penetration and Drop Size Studies of Diesel Fuels

2005 ◽  
Author(s):  
Badih A. Jawad ◽  
Chris H. Riedel ◽  
Ahmad Bazzari
Keyword(s):  
Arrival Time ◽  
Injection Pressure ◽  
Diffraction Method ◽  
Droplet Size Distribution ◽  
Chamber Pressure ◽  
Spray Penetration ◽  
Digital Oscilloscope ◽  
Diesel Fuels ◽  
Atomization Mechanism ◽  
Insight Into

Understanding the disintegration mechanism, spray penetration, and spray motion is of great importance in the design of a high quality diesel engine. The atomization process that a liquid would undergo as it is injected into a high-temperature, high-pressure air, is investigated in this work. The purpose of this study is to gain further insight into the atomization mechanism, the variation over time in droplet size distribution and spray penetration. This is done based on effect of chamber pressure, injection pressure, and type of fuel. A laser diffraction method is used to determine droplet mean diameters, single injection with synchronized time mechanism allowed the time dependent studies. Obscuration signals are obtained through a digital oscilloscope from which arrival time of spray can be measured. The spray penetration correlation obtained is compared to other correlation’s obtained from different other techniques used in the literature.

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