Effect of Fuel Distribution on Spray Dynamics in a Two-Staged Multi-Injection Burner

2011 ◽  
Author(s):  
T. Providakis ◽  
L. Zimmer ◽  
P. Scouflaire ◽  
S. Ducruix
Keyword(s):  
Velocity Field ◽  
High Frequency ◽  
Gas Turbines ◽  
Low Frequency ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Reactive Flow ◽  
Mean Values ◽  
Fuel Distribution ◽  
Flame Dynamics

Burners operating in lean premixed prevaporized (LPP) regimes are considered as good candidates to reduce pollutant emissions from gas turbines. Lean combustion regimes result in lower burnt gas temperatures and therefore a reduction on the NOx emissions, one of the main pollutant species. However, these burners usually show strong flame dynamics, making them prone to various stabilization problems (combustion instabilities, flashback, flame extinction). To face this issue, multi-injection staged combustion can be envisaged. Staging procedures enable fuel distribution control, while multipoint injections can lead to a fast and efficient mixing. A laboratory-scale staged multipoint combustor is developed in the present study, in the framework of LPP combustion, with an injection device close to the industrial one. Using a staging procedure between the primary pilot stage and the secondary multipoint one, droplet and velocity field distributions can be varied in the spray that is formed at the entrance of the combustion chamber. Non-reactive and reactive flows are characterized through an extensive Phase Doppler Anemometry (PDA) campaign. Three staging values, corresponding to three different flame stabilization processes, are analyzed, while power is kept constant. It is shown that mean values and droplet distributions are affected by the staging procedure in the non-reactive as in the reactive situations. Using adequate post-processing, it is also possible to study non-reactive and reactive flow/flame dynamics. Spectral analysis shows that the non-reactive flow is strongly structured by a high frequency rotating structure that can clearly be associated with a precessing vortex core (PVC), while the reactive situation encounters a strong acoustic-flame coupling leading to a low frequency oscillation of both the velocity field and the spray droplet distribution. In this last situation, high frequency phenomena, which may be due to PVC, are still visible.

scholarly journals Characterization of the Acoustic Interactions in a Two-Staged Multi-Injection Combustor Fed With Liquid Fuel

2012 ◽  
Author(s):  
T. Providakis ◽  
L. Zimmer ◽  
P. Scouflaire ◽  
S. Ducruix
Keyword(s):  
Velocity Field ◽  
Acoustic Field ◽  
Gas Turbines ◽  
High Speed ◽  
Fuel Injection ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Mean Values ◽  
Fuel Distribution ◽  
Droplet Behavior

Burners operating in lean premixed prevaporized (LPP) regimes are considered as good candidates to reduce pollutant emissions from gas turbines. Lean combustion regimes result in lower burnt gas temperatures and therefore a reduction on the NOx emissions, one of the main pollutant species. However, these burners usually show strong flame dynamics, making them prone to various stabilization problems (combustion instabilities, flashback, flame extinction). To face this issue, multi-injection staged combustion can be envisaged. Staging procedures enable fuel distribution control, while multipoint injections can lead to a fast and efficient mixing. A laboratory-scale staged multipoint combustor is developed in the present study, in the framework of LPP combustion, with an injection device close to the industrial one. Using a staging procedure between the primary pilot stage and the secondary multipoint one, droplet and velocity field distributions can be varied in the spray that is formed at the entrance of the combustion chamber. The resulting spray and the flame are characterized using OH-Planar Laser Induced Fluorescence, High Speed Particle Image Velocimetry and Phase Doppler Anemometry measurements. Three staging values, corresponding to three different flame stabilization processes, are analyzed, while power is kept constant. It is shown that mean values are strongly influenced by the fuel distribution and the flame position. Using adequate post-processing, the interaction between the acoustic field and the droplet behavior is characterized. Spectral analysis reveals a strong acoustic-flame coupling leading to a low frequency oscillation of both the velocity field and the spray droplet distribution. In addition, acoustic measurements in the feeding line show that a strong oscillation of the acoustic field leading to a change in fuel injection, and hence droplet behavior.

scholarly journals Characterization of the Acoustic Interactions in a Two-Stage Multi-Injection Combustor Fed With Liquid Fuel

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Theodore Providakis ◽  
Laurent Zimmer ◽  
Philippe Scouflaire ◽  
Sébastien Ducruix
Keyword(s):  
Velocity Field ◽  
Acoustic Field ◽  
Gas Turbines ◽  
High Speed ◽  
Fuel Injection ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Mean Values ◽  
Fuel Distribution ◽  
Droplet Behavior

Burners operating in lean premixed prevaporized (LPP) regimes are considered as good candidates to reduce pollutant emissions from gas turbines. Lean combustion regimes result in lower burnt gas temperatures and therefore a reduction on the NOx emissions, one of the main pollutant species. However, these burners usually show strong flame dynamics, making them prone to various stabilization problems (combustion instabilities, flashback, flame extinction). To face this issue, multi-injection staged combustion can be envisaged. Staging procedures enable fuel distribution control, while multipoint injections can lead to a fast and efficient mixing. A laboratory-scale staged multipoint combustor is developed in the present study, in the framework of LPP combustion, with an injection device close to the industrial one. Using a staging procedure between the primary pilot stage and the secondary multipoint one, droplet and velocity field distributions can be varied in the spray that is formed at the entrance of the combustion chamber. The resulting spray and flame are characterized using OH-planar laser induced fluorescence, high speed particle image velocimetry, and phase Doppler anemometry measurements. Three staging values, corresponding to three different flame stabilization processes, are analyzed, while power is kept constant. It is shown that mean values are strongly influenced by the fuel distribution and the flame position. Using adequate postprocessing, the interaction between the acoustic field and the droplet behavior is characterized. Spectral analysis reveals a strong acoustic-flame coupling leading to a low frequency oscillation of both the velocity field and the spray droplet distribution. In addition, acoustic measurements in the feeding line show that a strong oscillation of the acoustic field leads to a change in fuel injection, and hence droplet behavior.

Effect of Swirl and Wall Geometry on the Emissions of Advanced Gas Turbine Combustors

1994 ◽  
Author(s):  
Gerald J. Micklow ◽  
Karthikeyan Shivaraman
Keyword(s):  
Numerical Study ◽  
Substantial Effect ◽  
Pollutant Emissions ◽  
Reactive Flow ◽  
Fuel Distribution ◽  
Lean Combustion ◽  
Liquid Spray ◽  
Fuel Nozzle ◽  
Interface Geometry ◽  
Wall Geometry

A numerical study was performed to investigate the chemically reactive flow with liquid spray injection in a staged combustor concept for reducing pollutant emissions. The staged combustor consists of an airblast atomizer, a rich bum section, a converging connecting pipe, a quick mix zone, a diverging connecting pipe, and a lean combustion zone. For computational efficiency, the combustor was split into two subsystems, i.e. the fuel nozzle/rich burn section and the quick quench/lean bum section. The current study investigates the effect of wall geometry and swirl direction, i.e. co- or counter-rotating swirl, on fuel distribution, temperature distribution, and emissions for the fuel nozzle/rich bum section at a cruise condition. At an equivalence ratio of 1.9, the nozzle-combustor (dome) interface geometry was varied from a flat wall (normal to the combustor wall) to a sloped wall of 45 degrees. It is seen that the sloped wall with co-rotating swirl direction had a substantial effect on combustor performance and reducing pollutant emissions.

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.

scholarly journals Evolution of low-frequency contribution in emission of steep-spectrum radio sources

2014 ◽  
Vol 11 (S308) ◽  
pp. 631-635
Author(s):  
Alla P. Miroshnichenko
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Radio Spectrum ◽  
Unified Model ◽  
Linear Size ◽  
Radio Sources ◽  
Mean Values ◽  
Spectrum Radio ◽  
Size Characteristic ◽  
The Mean

AbstractWe consider evolution properties of galaxies and quasars with steep radio spectrum at the decametre band from the UTR-2 catalogue. The ratios of source's monochromatic luminosities at the decametre and high-frequency bands display the dependence on the redshift, linear size, characteristic age of examined objects. At that, the mean values of corresponding ratios for considered galaxies and quasars have enough close quantities,testifying on the unified model of sources. We analyse obtained relations for two types of steep-spectrum sources (with linear steep spectrum (S) and low-frequency steepness after a break (C+)) from the UTR-2 catalogue.

LES Based CFD Investigation of the Ignition Process in Lean Spray Burner

2021 ◽  
Author(s):  
A. Andreini ◽  
M. Amerighi ◽  
L. Palanti ◽  
B. Facchini
Keyword(s):  
Gas Turbines ◽  
New Technologies ◽  
Direct Injection ◽  
Flame Structure ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Ignition Process ◽  
Promising Tool ◽  
New Formulation

Abstract During the last decades several new technologies were investigated in order to reduce the pollutant emissions and increase the overall engine efficiency. Unluckily, some of them including the lean direct injection spray combustion hinder the ignition performances of the combustor. Moreover, several expensive tests under very challenging operating conditions must be carried out to obtain the required certifications and assess the combustor behaviour with respect to the ignition process. Therefore, a deeper knowledge of the phenomena involved in the flame onset is mandatory to shorten the design process and achieve the required performances from the very beginning. In the last years, CFD simulations established as valid alternative to the experiments to investigate the complex phenomena involved in the ignition process. In fact, several examples are available in scientific literature about the use of simulations to predict the development of the flame starting from an initial kernel. In particular, LES proved to be a reliable tool to uncover new mechanisms of ignition and flame stabilization in gas turbines. In this work, two reactive LES of the ignition process were attempted using ANSYS Fluent 2019R1, with the aim of testing the Thickened Flame Model already implemented in the solver. In fact, compared to the previous versions, a new formulation for the efficiency function based on the pioneering work of Colin was made available. Such promising tool was validated against some detailed experimental results of a lean swirled flame, known as KIAI-CORIA spray flame. At first, a non-reactive and reactive LES were carried out to validate the cold field and the stabilized flame structure respectively. Finally, two ignition simulations were performed, from initial spark deposition up to flame stabilization or kernel quenching. All the obtained results have been extensively compared against the available experimental data showing that the employed simulation setup is fairly capable of describing the phenomena involved in the rig ignition.

Investigation of Flame Stability Characteristics of the EV Burner on the GT13E2 Engine

2008 ◽  
Author(s):  
F. Biagioli ◽  
P. Schiessel ◽  
L. Fischer
Keyword(s):  
Gas Turbines ◽  
Equivalence Ratio ◽  
Flame Temperature ◽  
Low Frequency ◽  
Stability Limit ◽  
Flame Stabilization ◽  
Turbulent Flames ◽  
Type Model ◽  
Characteristic Value ◽  
Ev Burner

The development and optimization of dry low NOx combustors for industrial gas turbines could largely benefit from better understanding of the way the burners stabilize lean premixed turbulent flames. This has motivated the present work where the stabilization properties of turbulent (partially) premixed flames in the annular combustor of the ALSTOM GT13E2 gas turbine equipped with the EnVironmental (EV) burner are studied. The study benefits from the results of a previous analysis where the flame anchoring properties have been determined in single EV burner configuration, using a one-dimensional boundary layer type model and Large Eddy Simulation (LES). These properties, which are confirmed by experiments on single burner atmospheric and high pressure test rigs, consist in two possible stabilization modes for the flame: a) anchored just downstream the exit of the burner or b) displaced inside it, depending if the bulk equivalence ratio is below or above a characteristic value. The change from one flame stabilization mode to the other implies a change in the NOx characteristic versus flame temperature due to different levels of unmixedness (higher when the flame is stabilized inside the burner). Such a change in the NOx characteristic is found also in the GT13E2, indicating that flames in the combustor of this engine have same stabilization properties as seen on single burner rigs. It is seen that low frequency pulsations—typically anticipating the approaching of the lean stability limit—becomes discernible on the GT13E2 as soon as the equivalence ratio falls below the characteristic value separating the two flame stabilization modes. This finding gives the opportunity of more effective extrapolation of single burner test rig data to engine conditions. Finally, a simple model which can determine the effect of propane content in natural gas on the conditions where the transition between the two stabilization modes takes place is developed.

Flame Stabilization and Emissions of a Natural Gas/Air Ceramic Porous Burner

2008 ◽  
Vol 47-50 ◽  
pp. 105-108 ◽  
Author(s):  
Neda Djordjevic ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis
Keyword(s):  
Gas Turbines ◽  
Premixed Flames ◽  
Stability Limit ◽  
Porous Matrix ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Inert Material ◽  
Flame Stability ◽  
Nox Emissions ◽  
Porous Burner

Increasingly stringent regulations for limiting pollutant emissions for both aircraft and industrial gas turbines enforce further reduction of NOx emissions while maintaining flame stability. Application of premixed flames offers the possibility to reduce these emissions, but nevertheless it is strongly connected with flame instability risks. A possible solution to ensure the stability of premixed flames is to provide enhanced heat recirculation employing porous inert material. Experimental determination of flame stability and emissions of a porous burner containing a reticulate ceramic sponge structure are reported and the influence of the structural properties of the porous matrix on stable operating range was investigated. It was found, that the flame stability limit was significantly higher compared with free flame burners and nitric oxide (NOx) emissions were below 10 ppm for all cases.

A Novel Reheat Combustor Experiment for the Analysis of High-Frequency Flame Dynamics: Concept and Experimental Validation

2018 ◽  
Author(s):  
Frederik M. Berger ◽  
Tobias Hummel ◽  
Pedro Romero Vega ◽  
Bruno Schuermans ◽  
Thomas Sattelmayer
Keyword(s):  
High Frequency ◽  
Dynamic Pressure ◽  
Combustion Regime ◽  
Flame Stabilization ◽  
Acoustic Properties ◽  
Transverse Resonance ◽  
Flame Dynamics ◽  
Auto Ignition ◽  
Pressure Dynamics ◽  
Face Plate

This paper presents a novel sequential combustor experiment for the study of reheat flame responses to high-frequency, transversal thermoacoustic oscillations. The reheat combustion chamber is of flat, quasi two-dimensional design to distinctly separate combustion areas dominated by auto-ignition and aerodynamic flame stabilization. This specific combustor setup furthermore promotes the occurrence of pressure pulsations at the first transverse resonance frequency, often referred to as screech. For investigation of combustion and acoustic properties, the reheat stage is equipped with pulsation probes at the face plate, and the entire combustion zone is optically accessible from all lateral sides to allow for (laser-) optical flame and flow diagnostics. In order to validate the qualification of the experimental setup for investigations of high-frequency flame dynamics, the reheat combustion regime and resulting transverse pressure dynamics are investigated. The desired flame shape with distinct auto-ignition and aerodynamic flame stabilization zones is achieved and can be sensibly controlled. Analyzing the frequency spectrum of the dynamic pressure measurements at the combustor face plate reveals the first transverse resonance at approximately 1600 Hz, which satisfies a key goal of the specific design. Overall, the setup qualifies for studying flame-acoustics interaction in reheat combustors and provides an experimental benchmark for modeling efforts and their validation. This will eventually contribute to design countermeasures to thermoacoustic pulsations for improved future generations of gas turbine combustors.

Is Frequency of Patient–Physician Clinic Contact Important in Peritoneal Dialysis Patients?

2009 ◽  
Vol 29 (2_suppl) ◽  
pp. 83-89 ◽  
Author(s):  
Ying Xu ◽  
Jie Dong ◽  
Li Zuo
Keyword(s):  
Peritoneal Dialysis ◽  
High Frequency ◽  
Low Frequency ◽  
Intermediate Frequency ◽  
Biochemical Data ◽  
Dialysis Adequacy ◽  
Mean Values ◽  
Frequency Group ◽  
Physician Contact ◽  
Baseline Demographic

Objective In a single-center retrospective cohort study, we investigated whether the frequency of clinic patient–physician contact (PPC) correlates with quality of care and can predict outcome in peritoneal dialysis (PD) patients. Patients and Methods We enrolled 307 incident PD patients who started PD from July 2002 to February 2007. All patients who visited the clinic at least once every 6 months and who lived for at least 6 months were followed until death, transfer to hemodialysis, renal transplantation, or February 2008 (censor date). Throughout the study period, an integrative follow-up strategy was used, including PPC and three other modes of contact between patients and non-physicians. Patients’ PPC frequency was divided into 3 categories: high frequency (monthly or more often), intermediate frequency (every 1 – 3 months), and low frequency (every 3 – 6 months). Baseline demographic and biochemical data were collected. Indices of diet, dialysis adequacy, biochemistry, and nutrition were measured at every visit and then calculated as mean values. Results We followed the 307 patients for a mean of 31.45 ± 13.62 months (range: 12 – 64 months). By PPC frequency, 127 patients (41.3%) were in the high-frequency group; 136 (44.3%), in the intermediate-frequency group; and 44 (14.3%), in the low-frequency group. We observed no difference of baseline demographic and biochemical data between the three groups ( p > 0.05). Patients in the low-frequency group had lower mean hemoglobin and total urea clearance rates, but higher serum phosphate than did patients in the intermediate- or high-frequency groups ( p < 0.05). Mean indices of nutrition, including serum albumin, daily protein and energy intake, and lean body mass were not different between the three groups ( p > 0.05). Frequency of PPC did not show an effect on the survival of PD patients ( p = 0.37 by Kaplan–Meier plot). Age ( p = 0.002), Charlson comorbidity score ( p = 0.001), and pre-dialysis albumin ( p = 0.019) were independent negative risk factors for death in multivariate Cox proportional hazard models, which were adjusted for sex, PPC frequency, baseline hemoglobin, and glomerular filtration rate. Conclusions Frequency of PPC did not predict outcome in PD patients after an integrative care strategy was implemented. Control of anemia and hyperphosphatemia needs to be strengthened in patients with a low frequency of PPC.

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