Comparison of the Flame Characteristics of Turbulent Circular and Elliptic Jets in a Crossflow

2002 ◽  
Vol 124 (3) ◽  
pp. 197-203 ◽  
Author(s):  
S. R. Gollahalli ◽  
D. Pardiwalla
Keyword(s):  
Flame Structure ◽  
Flux Ratio ◽  
Major Axis ◽  
Minor Axis ◽  
No Production ◽  
Sampling System ◽  
Computer Data ◽  
Rate Of Increase ◽  
Jet Velocity ◽  
Lower Limits

This study was directed to understand the coupling effects of the noncircular geometry of the burner and a crossflow on the combustion of gas jets. This paper compares the characteristics of turbulent propane jet flames from circular (diameter=0.45 cm) and elliptic (major axis/minor axis=3) burners of equivalent exit area in a crossflow. The elliptic burner was oriented with its major axis or minor axis aligned with the crossflow. Experiments were conducted in a wind tunnel provided with optical and probe access and capable of wind speeds up to 12.5 m/s. The burners were fabricated with metal tubes. Instrumentation included a Pt-Pt/13% Rh thermocouple, a quartz-probe gas sampling system, chemiluminescent and nondispersive infrared analyzers, a video-recorder, and a computer data acquisition system. The measurements consisted of the upper and lower limits of jet velocity for a stable flame, flame configuration, and visible length. Flame structure data including temperature profiles and concentration profiles of CO2,O2, CO, and NO were obtained in a two-zone flame configuration (at jet to crossflow momentum flux ratio=0.11), where a planar recirculation exists in the wake of the burner tube followed by an axisymmetric tail. The relative emission indicators of CO and NO were estimated from the composition data. Results show that the upper and lower limits of the fuel jet velocity increase with the crossflow velocity for all burners, and the rate of increase is highest for the elliptic burner with its minor axis aligned with the crossflow. That burner configuration also produces the longest flame. The relative emission indicators show that the CO production is lower and NO production is higher with elliptic burners than with circular burners in crossflow.

Comparison of the Flame Characteristics of Circular and Elliptic Jets in a Cross-Flow

2000 ◽  
Author(s):  
S. R. Gollahalli ◽  
D. Pardiwalla
Keyword(s):  
Cross Flow ◽  
Major Axis ◽  
Minor Axis ◽  
No Production ◽  
Sampling System ◽  
Computer Data ◽  
Rate Of Increase ◽  
Jet Velocity ◽  
The Cross ◽  
Lower Limits

Abstract This study was directed to understand the coupling effects of the noncircular geometry of the burner and a cross-flow on the combustion of gas jets. This paper compares the characteristics of propane jet flames from circular (diameter = 0.45 cm) and elliptic (major axis = 0.75 cm, minor axis = 0.26 cm) burners of equivalent exit area in a cross-flow. The elliptic burner was oriented with its major axis or minor axis aligned with the cross-flow. Experiments were conducted in a wind-tunnel provided with optical and probe access and capable of wind speeds up to 12.5 m/s. The burners were fabricated with metal tubes. Instrumentation included a Pt-Pt/13%Rh thermocouple, a quartz-probe gas sampling system, chemiluminescent and non-dispersive infrared analyzers, a video-recorder, and a computer data acquisition system. The measurements consisted of the upper and lower limits of jet velocity for a stable flame, flame configuration, and visible length. Flame structure data including temperature profiles and concentration profiles of CO2, O2, CO, and NO were obtained in a two-zone flame configuration where a planar recirculation exists in the wake of the burner tube followed by an axisymmetric tail. Emission indices of CO and NO were estimated from the composition data. Results indicate that the upper and lower limits of the fuel jet velocity increase with the cross-flow velocity for all burners, and the rate of increase is highest for the elliptic burner with its minor axis aligned with the cross-flow. That burner configuration also produces the longest flame. The emission indices show that the CO production is lower and NO production is higher for elliptic burners than for circular burners in cross-flow. Also, aligning the minor axis of the elliptic burner with the cross-stream is superior in terms of flame stability and emissions of NO and CO.

Flow and Thermal Structure of Burner-Wake Stabilized Elliptic Jet Flames in a Cross-Flow

2005 ◽  
Author(s):  
S. R. Gollahalli
Keyword(s):  
Momentum Flux ◽  
Thermal Structure ◽  
Flame Structure ◽  
Cross Flow ◽  
Flux Ratio ◽  
Major Axis ◽  
Minor Axis ◽  
Jet Flames ◽  
Zone Structure ◽  
Momentum Flux Ratio

This study was conducted to delineate the coupling effects of the elliptic geometry of the burner and a crossflow on the combustion of gas jets. This paper presents the flow and thermal structure of burner-wake stabilized turbulent propane jet flames from circular (diameter = 0.45 cm) and elliptic (major axis/minor axis = 3) burners of equivalent exit area in a crossflow of air. The elliptic burner was oriented with its major axis or minor axis aligned with the crossflow. Experiments were conducted in a wind tunnel provided with optical and probe access. Flame structure data including temperature profiles and concentration profiles of CO2, O2, CO, and NO were obtained in the single flame configuration (at jet to crossflow momentum flux ratio = 0.0067), where a planar recirculation zone exists completely stabilized in the wake of the burner tube. This study is complementary to our previous study with a two-zone structure flame at jet/crossflow momentum flux ratio of 0.11. Results show that in this flame configuration, the peak NO concentration in the circular burner is higher than that in the elliptic burner flames. Carbon monoxide concentration was approximately same in the flame with circular burner and the elliptic burner with its major axis aligned with cross-flow; the CO concentration in the elliptic flame with the minor axis of the burner aligned with cross-flow was slightly smaller.

Design of Turning Area for LNG Terminal Base on Computer Simulation

2012 ◽  
Vol 215-216 ◽  
pp. 1236-1240
Author(s):  
Yao Tian Fan
Keyword(s):  
Computer Simulation ◽  
Theoretical Calculation ◽  
Cost Effective ◽  
Major Axis ◽  
Minor Axis ◽  
Computer Simulator

Design of turning area for sea port is generally done according to the outcome of theoretical calculation or real-ship trial. However, these methods only take into account some limited respects for planning a port or are not so cost-effective. In this paper, computer simulator is used for optimizing the size of turning area for Yangshan LNG terminal. The outcome indicates that the major axis and minor axis of the turning area can meet the requirement of Q-Max LNG carrier berthing operation and it is suggested to do such maneuvering in some given conditions related to wind, current, tide, visibility and wave.

Hydrogen Blending Into Ansaldo Energia AE94.3A Gas Turbine: High Pressure Tests, Field Experience and Modelling Considerations

2021 ◽  
Author(s):  
A. Ciani ◽  
L. Tay-Wo-Chong ◽  
A. Amato ◽  
E. Bertolotto ◽  
G. Spataro
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Power Plants ◽  
Flame Structure ◽  
Flux Ratio ◽  
Fuel Blends ◽  
Pressure Tests ◽  
Fuel Staging ◽  
Combustion Tests ◽  
The Impact

Abstract Fuel flexibility in gas turbine development has become increasingly important and modern engines need to cope with a broad variety of fuels. The target to operate power plants with hydrogen-based fuels and low emissions will be of paramount importance in a future focusing on electric power decarbonization. Ansaldo Energia AE94.3A engine acquired broad experience with operation of various natural gas and hydrogen fuel blends, starting in 2006 in the Brindisi (Italy) power plant. Based on the exhaustive experience acquired in the field, this paper describes the latest advancements characterizing the operation of the AE94.3A burner with high pressure combustion tests adding hydrogen blends ranging from 0 to 40% in volume. The interpretation of the test results is supported by reactive and non-reactive simulations describing the effects of varying fuel reactivity on the flame structure as well as the impact of fuel / air momentum flux ratio on the fuel / air interaction and fuel distribution in the combustion chamber. As expected, increasing amounts of hydrogen in the fuel are also associated with higher amounts of NOx production, however this effect could be countered by optimization of the fuel staging strategy, based on the mentioned CFD considerations and feedback from high pressure tests.

Effect of Mach number on the acoustic field of 2:1 elliptic-slot jet

2001 ◽  
Vol 105 (1043) ◽  
pp. 9-16 ◽  
Author(s):  
S. B. Verma ◽  
E. Rathakrishnan
Keyword(s):  
Mach Number ◽  
Fundamental Frequency ◽  
Acoustic Field ◽  
Major Axis ◽  
Shock Structure ◽  
Minor Axis ◽  
Noise Levels ◽  
Underexpanded Jets ◽  
Barrel Shock ◽  
Mach Numbers

Abstract The shock-structure and the related acoustic field of underexpanded jets undergoes significant changes as the Mach number Mj is increased. The present investigation is carried out to study the effect of Mach number on an underexpanded 2:1 elliptic-slot jet. Experimental data are presented for fully expanded Mach numbers ranging from 1.3 to 2.0. It is observed that the ‘cross-over’ point at the end of the first cell at low Mach numbers gets replaced by a normal shock at a highly underexpanded condition resulting in the formation of a ‘barrel’ shock along the minor-axis side with a ‘bulb’ shock formed along the major-axis side. The above change in shock structure is accompanied by a related change in the acoustic field. The amplitude of fundamental frequency along the minor-axis side grows with Mj but falls beyond Mj = 1.75. Along the major-axis side, however, the fundamental frequency does not exist at low Mach numbers. It appears at Mj = 1.75 but then falls at Mj = 2.0. The related azimuthal directivity of overall noise levels (OASPL) shows significant changes with Mj.

Quantitative diagenetic analyses of Edmontosaurus regalis (Dinosauria: Hadrosauridae) postcranial elements from the Danek Bonebed, Upper Cretaceous Horseshoe Canyon Formation, Edmonton, Alberta, Canada: implications for allometric studies of fossil organisms

2014 ◽  
Vol 51 (11) ◽  
pp. 1007-1016 ◽  
Author(s):  
Mackenzie Baert ◽  
Michael E. Burns ◽  
Philip J. Currie
Keyword(s):  
Cross Section ◽  
Upper Cretaceous ◽  
Strong Relationship ◽  
Major Axis ◽  
Minor Axis ◽  
Morphological Features ◽  
Fossil Assemblages ◽  
Fossil Vertebrate ◽  
Horseshoe Canyon Formation ◽  
Upper Campanian

For fossil assemblages, quantitative size and shape studies are often complicated by diagenetic distortion. Different vertebrate elements, although subjected to similar burial stresses, exhibit deformations based upon their original shapes; this hypothesis is tested here by quantitatively comparing deformed humeri and femora from the Danek Bonebed (a monodominant Edmontosaurus regalis bonebed from the upper Campanian Horseshoe Canyon Formation in Edmonton, Alberta, Canada) with samples of undeformed humeri and femora from modern and fossil assemblages. Analyses suggest that at the Danek Bonebed a strong relationship exists between element length and circumference despite being distorted by crushing deformation. Major and minor axes of the midshaft cross section, however, were not uniformly distorted. Although their anatomical position did not change, the major axis became longer relative to the minor axis in distorted specimens. A regression based on the undeformed humeri was not able to accurately predict circumference in the Danek humeri. Further study might quantify the deformation of other bones in the Danek Bonebed and could be extended to other assemblages and genera. Caution should be taken when conducting studies in which diagenetic crushing may have altered morphological features of fossil vertebrate remains.

scholarly journals Effect of soaking process on physical properties of mature pepper berries (Piper nigrum L.)

Food Research ◽  
2020 ◽  
Vol 4 (S1) ◽  
pp. 116-123
Author(s):  
A.A.P.N. Megat ◽  
Rosnah Shamsudin ◽  
H. Che Man ◽  
M.E. Ya'acob
Keyword(s):  
Physical Properties ◽  
Water Uptake ◽  
Major Axis ◽  
Minor Axis ◽  
Piper Nigrum ◽  
Uptake Ratio ◽  
Fracture Force ◽  
Brown Colour

This study was carried out to determine the effect of the soaking process on the physical properties of the mature pepper berries. The soaking process was conducted by immersing pepper berries in water. The results showed the dimensions of the pepper berries before soaking was 5.24 mm (minor axis), 5.57 mm (medium axis) and 5.61 mm (major axis). The weight of pepper berries increased from day 1 (13.58%) until day 3 (16.92%) and decreased after day 4 (0.77%) until day 7 of soaking (13.08%). The water uptake ratio of soaked pepper berries increased from 1.14% (day 1) until 1.17% (day 3) and then decreased from 1.01% (day 4) until 0.87% (day 7). The fracture force required to fracture the pericarp was decreased starting from 67.21 N (day 1) decreased until 21.40 N (day 7). The colour of mature pepper berries was changed into black-brown colour (L= 34.16, a= 1.38, b= 1.40).

scholarly journals Less than the sum of its parts: the dust-corrected H α luminosity of star-forming galaxies explored at different spatial resolutions with MaNGA and MUSE

2020 ◽  
Vol 498 (3) ◽  
pp. 4205-4221
Author(s):  
N Vale Asari ◽  
V Wild ◽  
A L de Amorim ◽  
A Werle ◽  
Y Zheng ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Formation Rate ◽  
Flux Ratio ◽  
Star Forming ◽  
The Galaxy ◽  
Nearby Galaxies ◽  
Point To Point ◽  
Dust Attenuation ◽  
The Impact ◽  
Lower Limits

ABSTRACT The H α and H β emission-line luminosities measured in a single integrated spectrum are affected in non-trivial ways by point-to-point variations in dust attenuation in a galaxy. This work investigates the impact of this variation when estimating global H α luminosities corrected for the presence of dust by a global Balmer decrement. Analytical arguments show that the dust-corrected H α luminosity is always underestimated when using the global H α/H β flux ratio to correct for dust attenuation. We measure this effect on 156 face-on star-forming galaxies from the Mapping Nearby Galaxies at APO (MaNGA) survey. At 1–2 kpc spatial resolution, the effect is small but systematic, with the integrated dust-corrected H α luminosity underestimated by 2–4 per cent (and typically not more than by 10 per cent), and depends on the specific star formation rate of the galaxy. Given the spatial resolution of MaNGA, these are lower limits for the effect. From Multi Unit Spectroscopic Explorer (MUSE) observations of NGC 628 with a resolution of 36 pc, we find the discrepancy between the globally and the point-by-point dust-corrected H α luminosity to be 14 ± 1 per cent, which may still underestimate the true effect. We use toy models and simulations to show that the true difference depends strongly on the spatial variance of the H α/H β flux ratio, and on the slope of the relation between H αluminosity and dust attenuation within a galaxy. Larger samples of higher spatial resolution observations are required to quantify the dependence of this effect as a function of galaxy properties.

Flow field and acoustics characteristics of elliptical jet

2018 ◽  
Vol 90 (9) ◽  
pp. 1364-1371 ◽  
Author(s):  
S. Manigandan ◽  
Vijayaraja K.
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Rapid Change ◽  
Supersonic Jet ◽  
Major Axis ◽  
Minor Axis ◽  
Shock Cell ◽  
Potential Core ◽  
Content Type ◽  
Elliptical Jet

Purpose The purpose of this paper is to present the results of mixing promotion and screech frequency of controlled elliptical supersonic jet. Design/methodology/approach Flow field characteristics of low-aspect-ratio elliptical jets are examined at over-expanded, under-expanded and correctly expanded conditions. The tabs are placed at elliptical jet exit along the major and minor axes. Findings The results show that the mixing done by the minor axis is superior to the tabs along major axis. At all pressure ratios, the content of jet noise and the frequency are high for the tabs along the major axis because of increase in the amplitude of screech frequency. Further the tabs along minor axis show a dominance of large-scale vertical structures. In under-expanded conditions, the shock cell shows the rapid change because of the presence of tabs. The tabs along minor axis are making the shock weaker, hence no evidence of axis switching. Practical implications To achieve the greater performance of jet, the authors need to reduce the potential core length of the issuing jet. This can be achieved by implementing different types of tabs at the exit of the nozzle. Originality/value The present paper represents the flow of controlled jet using inverted triangular tabs. By achieving the controlled jet flow, the performance of propulsion systems can be improved. This can be used in systems such as combustion chamber, missile’s noise reduction and thrust vector control.

Effect of Nozzle Geometry on the Near-Field Flow Characteristics of High-Pressure Gas Leak Jets

2018 ◽  
Author(s):  
Xiaopeng Li ◽  
Fakun Zhuang ◽  
Rui Zhou ◽  
Yian Wang ◽  
Libo Wang ◽  
...  
Keyword(s):  
High Pressure ◽  
Nozzle Exit ◽  
Flow Behavior ◽  
Near Field ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Major Axis ◽  
Minor Axis ◽  
Nozzle Geometry ◽  
Square Jets

Three-dimensional large eddy simulations of high-pressure jets at the same nozzle pressure ratio of 5.60 but issuing from different nozzles are conducted. Four different nozzle geometries, i.e., the circular, elliptic, square, and rectangular nozzles, are used to investigate the effect of the nozzle geometry on the near-field jet flow behavior. A high-resolution, hexahedral, and block-structured grid containing about 31.8 million computational cells is applied. The compressible flow solver, astroFoam, which is developed based on the OpenFOAM C++ library, is used to perform the simulations. The time-averaged near-field shock structures and the mean axial density are compared with the experiment data to validate the fidelity of the LES results, and the reasonable agreement is observed. The results indicate that the remarkable differences exist in the near-field flow structures of the jets. In particular, the circular and square jets correspond to a three-dimensional helical instability mode, while the elliptic and rectangular jets have a two-dimensional lateral instability in their minor axis planes. A subsonic flow zone exists after the Mach disk in the circular and square jets, but is lacking in the elliptic and rectangular jets. The intercepting shocks in the circular jet originate near the nozzle exit, and appear to be circular in cross-section. The intercepting shocks in the square jet originate at the four corners of the nozzle exit at first, and then are observed along the major axis plane some distance downstream of the nozzle exit. However, the formation of the intercepting shock is observed in the major axis planes but is lacking in the minor axis planes for the elliptic and rectangular jets. In addition, the real mass flow rates and discharge coefficients for different jets are computed based on the LES modeling, and their differences are explored.

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