Experimental Investigation of the Stability Mechanism and Emissions of a Lifted Swirl Nonpremixed Flame

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Paris A. Fokaides ◽  
Plamen Kasabov ◽  
Nikolaos Zarzalis
Keyword(s):  
Experimental Investigation ◽  
Large Scale ◽  
Recirculation Zone ◽  
Laser Doppler Anemometry ◽  
Reverse Flow ◽  
Measurement Techniques ◽  
Turbulence Structure ◽  
Ignition Process ◽  
Nonpremixed Flame

We report on the experimental investigation of a confined lifted swirl nonpremixed flame by applying a novel Airblast nozzle (Zarzalis, N., et al., 2005, Fuel Injection Apparatus, Patent No. DE 10 2005 022 772.4, EP 06 009 563.5). 3D-laser doppler anemometry, a nonintrusive, laser-based measurement technique, is adapted for the measurement of all three mean velocity components and of the six Reynolds stress components. The determination of the temperature and mixture field occurs by employing in-flame measurement techniques. Valuable information concerning the mixing procedure, the temperature distribution, the turbulence level, and the velocity field of the flame is provided. The results demonstrate that there is sufficient residence time in the precombustion area of the lifted flame in order to achieve spatial and temporal uniformity of the mixture, leading to a quasi-premixed state. It was also found that hot reaction products, carried upstream by an annular zone of reverse flow, react with fresh unburnt mixture in a re-ignition process. The determination of the flow pattern revealed the presence of an inner weak recirculation zone in the nozzle vicinity and a dominant external recirculation zone. The examination of the probability density function of the velocity measurements was also found to be a very useful tool in terms of the analysis of the turbulence structure of the flow. The bimodal distribution in the shear layer between the downstream flow and the recirculated gases yields the existence of large scale eddies. Finally, the significant reduced NOx emissions in the lean area were also shown by means of emission measurements for elevated pressure conditions.

Experimental Investigation of the Stability Mechanism and Emissions of a Lifted Swirl Non-Premixed Flame

2007 ◽  
Author(s):  
Paris A. Fokaides ◽  
Plamen Kasabov ◽  
Nikolaos Zarzalis
Keyword(s):  
Experimental Investigation ◽  
Recirculation Zone ◽  
Laser Doppler Anemometry ◽  
Measurement Techniques ◽  
Bimodal Distribution ◽  
Premixed Flame ◽  
Turbulence Structure ◽  
Reaction Products ◽  
Mean Velocity

We report on the experimental investigation of a confined lifted swirl non-premixed flame by applying a novel Airblast nozzle [1]. 3D-Laser Doppler Anemometry, a non-intrusive, laser-based measurements technique, is adapted for the measurement of all three mean velocity components and of the six Reynolds stress components. The determination of the temperature and mixture field occurs by employing in-flame measurement techniques. Valuable information concerning the mixing procedure, the temperature distribution, the turbulence level and the velocity field of the flame is provided. The results demonstrate that there is sufficient residence time in the pre-combustion area of the lifted flame in order to achieve spatial and temporal uniformity of the mixture, leading to a quasi premixed state. It was also found that hot reaction products, carried upstream by large vortices along the jet, could possibly react with fresh unburnt mixture in a reignition process. The determination of the flow pattern revealed the presence of an inner weak recirculation zone in the nozzle vicinity and a dominant external recirculation zone. The examination of the probability density function (PDF) of the velocity-measurements was also found to be a very useful tool in terms of the analysis of the turbulence structure of the flow. The bimodal distribution yield the existence of large scaled eddies in the shear layer between the downstream flow and the recirculated gases. Finally, the significant reduced NOx emissions in the lean area were also shown by means of emission measurements for elevated pressure conditions.

Alternate Eddy Shedding Set Up by the Nonaxisymmetric Recirculation Zone at the Exhaust of a Cyclone Dust Separator

1998 ◽  
Vol 120 (1) ◽  
pp. 193-199 ◽  
Author(s):  
A. J. Griffiths ◽  
P. A. Yazdabadi ◽  
N. Syred
Keyword(s):  
Recirculation Zone ◽  
Laser Doppler Anemometry ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Time Dependent ◽  
Velocity Measurements ◽  
Flow Zone ◽  
Precessing Vortex Core ◽  
Dust Separator ◽  
Set Up

Two cyclone dust separators with geometric swirl numbers of 3.324 and 3.043 were used to analyze the motion of the complex three-dimensional time dependent motion set up in the free exhaust. A quantitative analysis of the flow was carried out, obtaining time dependent velocity measurements with the use of laser Doppler anemometry (L.D.A.) techniques. The investigations highlighted a eddy or vortex shedding mechanism in two distinct areas of the flow. This was in part caused by a reverse flow zone and a precessing vortex core within the exhaust region of the separator. Changes in the Reynolds number by a factor of 2 were observed to have no effect on the main characteristics of the flow. Some changes were seen in the flow structure with change in swirl number, particularly the size of the reverse flow zone and the position of the large engulfment vortices.

Numerical and Experimental Investigation of an Annular Jet Flow With Large Blockage

2004 ◽  
Vol 126 (3) ◽  
pp. 375-384 ◽  
Author(s):  
Christian Del Taglia ◽  
Lars Blum ◽  
Ju¨rg Gass ◽  
Yiannis Ventikos ◽  
Dimos Poulikakos
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Large Scale ◽  
Recirculation Zone ◽  
Blockage Ratio ◽  
Flow Conditions ◽  
Preferential Direction ◽  
Vortical Structures ◽  
Annular Jet ◽  
Unsteady Simulation

Unsteady 3-D numerical simulations and 3-D LDA measurements of an annular jet with a blockage ratio of 0.89 and Reynolds number 4400 are presented. At these flow conditions, the flow inside of the recirculation zone is asymmetric, with a preferential direction. Very good predictions of the velocity fluctuation values are achieved with the unsteady simulation technique in the same region, as the fluctuations are mainly large scale, structure dominated. A frequency near to 10 Hz is identified in the simulations, which is attributed to the principal shedding behavior of the vortical structures.

Effects of Combustor Aerodynamics on the Ignition of Solid Fuel

1994 ◽  
Author(s):  
Jing-Tang Yang ◽  
Cliff Yuh-Yih Wu ◽  
Hung-Tsann Yang
Keyword(s):  
Turbulence Intensity ◽  
Solid Fuel ◽  
High Speed ◽  
Recirculation Zone ◽  
Reverse Flow ◽  
Flow Characteristics ◽  
Video Camera ◽  
Sudden Expansion ◽  
Ignition Process ◽  
High Speed Video Camera

A traditional and a modified backward-facing steps were designed to investigate the effects of flow characteristics on the ignition of the solid fuel slab in a sudden expansion combustor. Experiments were conducted separately in the cold flow for the turbulent flow field and in a hot oxidizing flow stream for the ignition tests. The velocity flowfield was measured by a laser-Doppler anemometer (LDA) and the ignition process was observed by a high-speed video camera. The inlet flow velocity for the cold flowfield measurements was kept at 15 m/s, but was varied for the ignition tests, whereas the step height of the backstep was 29 mm. The results show that the higher turbulence intensity in the boundary layer near the separated point did not always cause a higher turbulence intensity in the recirculation zone. However, the combustor with a modified backstep generated greater reverse flow rate, turbulence intensity and Reynolds stress in the recirculation zone. As a result, the ignition delay of solid fuel in the modified combustor was significantly reduced as compared with the traditional combustor.

Large-scale Motion of Solar Filaments

2000 ◽  
Vol 179 ◽  
pp. 205-208
Author(s):  
Pavel Ambrož ◽  
Alfred Schroll
Keyword(s):  
Magnetic Flux ◽  
Proper Motion ◽  
Time Scale ◽  
Large Scale ◽  
Accuracy Of Measurements ◽  
Solar Filaments ◽  
General Movement ◽  
Scale Motion ◽  
Velocity Scatter

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.

Methods for the Quantification of Salivary Cortisol and of a-amylase in Biosensors and Portable Devices

2018 ◽  
Vol 68 (12) ◽  
pp. 2857-2859
Author(s):  
Cristina Mihaela Ghiciuc ◽  
Andreea Silvana Szalontay ◽  
Luminita Radulescu ◽  
Sebastian Cozma ◽  
Catalina Elena Lupusoru ◽  
...  
Keyword(s):  
Real Time ◽  
Medical Practice ◽  
Salivary Cortisol ◽  
Clinical Studies ◽  
Large Scale ◽  
Psychological Research ◽  
Portable Devices ◽  
Salivary Amylase ◽  
Specificity And Sensitivity

There is an increasing interest in the analysis of salivary biomarkers for medical practice. The objective of this article was to identify the specificity and sensitivity of quantification methods used in biosensors or portable devices for the determination of salivary cortisol and salivary a-amylase. There are no biosensors and portable devices for salivary amylase and cortisol that are used on a large scale in clinical studies. These devices would be useful in assessing more real-time psychological research in the future.

Identification of N-Substituted Triazolo-azetidines as Novel Antibacterials using pDualrep2 HTS Platform

2019 ◽  
Vol 22 (5) ◽  
pp. 346-354
Author(s):  
Yan A. Ivanenkov ◽  
Renat S. Yamidanov ◽  
Ilya A. Osterman ◽  
Petr V. Sergiev ◽  
Vladimir A. Aladinskiy ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Large Scale ◽  
Underlying Mechanism ◽  
Luciferase Assay ◽  
Reporter System ◽  
E Coli ◽  
Starting Point ◽  
High Concentrations ◽  
Mic Value

Aim and Objective: Antibiotic resistance is a serious constraint to the development of new effective antibacterials. Therefore, the discovery of the new antibacterials remains one of the main challenges in modern medicinal chemistry. This study was undertaken to identify novel molecules with antibacterial activity. Materials and Methods: Using our unique double-reporter system, in-house large-scale HTS campaign was conducted for the identification of antibacterial potency of small-molecule compounds. The construction allows us to visually assess the underlying mechanism of action. After the initial HTS and rescreen procedure, luciferase assay, C14-test, determination of MIC value and PrestoBlue test were carried out. Results: HTS rounds and rescreen campaign have revealed the antibacterial activity of a series of Nsubstituted triazolo-azetidines and their isosteric derivatives that has not been reported previously. Primary hit-molecule demonstrated a MIC value of 12.5 µg/mL against E. coli Δ tolC with signs of translation blockage and no SOS-response. Translation inhibition (26%, luciferase assay) was achieved at high concentrations up to 160 µg/mL, while no activity was found using C14-test. The compound did not demonstrate cytotoxicity in the PrestoBlue assay against a panel of eukaryotic cells. Within a series of direct structural analogues bearing the same or bioisosteric scaffold, compound 2 was found to have an improved antibacterial potency (MIC=6.25 µg/mL) close to Erythromycin (MIC=2.5-5 µg/mL) against the same strain. In contrast to the parent hit, this compound was more active and selective, and provided a robust IP position. Conclusion: N-substituted triazolo-azetidine scaffold may be used as a versatile starting point for the development of novel active and selective antibacterial compounds.

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