Experimental Studies of Reactive and Non-Reactive Flows in Dump Combustors

1990 ◽  
Author(s):  
A. S. Nejad ◽  
S. A. Ahmed ◽  
L. A. Roe ◽  
R. S. Gabruk
Keyword(s):  
Heat Release ◽  
High Speed ◽  
Equivalence Ratio ◽  
Experimental Studies ◽  
Recirculation Region ◽  
Experimental Program ◽  
High Speed Photography ◽  
Velocity Measurements ◽  
Dump Combustor ◽  
Dump Combustors

The objectives of this experimental program are two fold; first, to investigate, understand, and document the effects of heat release on the characteristics of a dump combustor flowfield; secondly, to provide a benchmark set of experimental data to aid the development of time averaged CFD codes. A limited number of velocity profiles are reported in this manuscript to illustrate the effects of combustion and heat release, at an equivalence ratio of 0.65, on dump combustor flows. High-speed photography and spectral analysis complemented velocity measurements and served to examine and characterize combustion instability limits. Results indicate that combustion altered the dump combustor flowfield and significantly reduced the length of the corner recirculation region.

scholarly journals Study of Lubricant Jet Flow Phenomena in Spur Gears—Out of Mesh Condition

1978 ◽  
Vol 100 (1) ◽  
pp. 61-68 ◽  
Author(s):  
D. P. Townsend ◽  
L. S. Akin
Keyword(s):  
High Speed ◽  
Gear Tooth ◽  
Velocity Ratio ◽  
Jet Impingement ◽  
Gear Ratio ◽  
Experimental Program ◽  
High Speed Photography ◽  
Gear Mesh ◽  
Mesh Condition ◽  
Oil Jet

An analysis was conducted for oil jet lubrication on the disengaging side of a gear mesh. Results of the analysis were computerized and used to determine the oil jet impingement depth for several gear ratios and oil jet to pitch line velocity ratios. An experimental program was conducted on the NASA gear test rig using high-speed photography to experimentally determine the oil jet impingement depth on the disengaging side of mesh. Impingement depth reaches a maximum at gear ratio near 1.5 where chopping by the leading gear tooth limits the impingement depth. The pinion impingement depth is zero above a gear ratio of 1.172 for a jet velocity to pitch time velocity ratio of 1.0 and is similar for other velocity ratios. The impingement depth for gear and pinion are equal and approximately one-half the maximum at a gear ratio of 1.0. Impingement depth on either the gear or pinion may be improved by relocation of the jet from the pitch line or by changing the jet angle. Results of the analysis were verified by experimental results using a high-speed camera and a well lighted oil jet.

Impact of Cooling Air Injection on the Primary Combustion Zone of a Swirl Burner

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
A. Marosky ◽  
V. Seidel ◽  
S. Bless ◽  
T. Sattelmayer ◽  
F. Magni
Keyword(s):  
Flow Field ◽  
Heat Release ◽  
High Speed ◽  
Equivalence Ratio ◽  
Swirling Flow ◽  
Water Channel ◽  
Combustion Stability ◽  
Flame Stability ◽  
Primary Zone ◽  
Cooling Air

In most dry, low NOx combustor designs, the front panel impingement cooling air is directly injected into the combustor primary zone. As this air partially mixes with the swirling flow of premixed reactants from the burner prior to completion of heat release, it reduces the effective equivalence ratio in the flame and has a beneficial effect on NOx emissions. However, the fluctuations of the equivalence ratio in the flame potentially increase heat release fluctuations and influence flame stability. Since both effects are not yet fully understood, isothermal experiments are made in a water channel, where high speed planar laser-induced fluorescence (HSPLIF) is applied to study the cooling air distribution and its fluctuations in the primary zone. In addition, the flow field is measured with high speed particle image velocimetry (HSPIV). Both mixing and flow field are also analyzed in numerical studies using isothermal large eddy simulation (LES), and the simulation results are compared with the experimental data. Of particular interest is the influence of the injection configuration and cooling air momentum variation on the cooling air penetration and dispersion. The spatial and temporal quality of mixing is quantified with probability density functions (PDF). Based on the results regarding the equivalence ratio fluctuations, regions with potential negative effects on combustion stability are identified. The strongest fluctuations are observed in the outer shear layer of the swirling flow, which exerts a strong suction effect on the cooling air. Interestingly, the cooling air dilutes the recirculation zone of the swirling flow. In the reacting case, this effect is expected to lead to a decrease of the temperature in the flame-anchoring zone below the adiabatic flame temperature of the premixed reactant, which may have an adverse effect on flame stability.

Liftoff behaviors and flame structure of dimethyl ether jet flame in CH4/air vitiated coflow

2019 ◽  
Vol 233 (8) ◽  
pp. 1039-1046 ◽  
Author(s):  
Wei Fu ◽  
Fengyu Li ◽  
Haitao Zhang ◽  
Bolun Yi ◽  
Yanju Liu ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
High Speed ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
High Speed Photography ◽  
Flame Stability ◽  
Jet Flames ◽  
Jet Flame ◽  
Field Temperature ◽  
Vitiated Coflow

The objective of this paper is to investigate the flame structure and liftoff behaviors of a dimethyl ether central jet in CH4/air vitiated coflow in a coflow burner. The liftoff behaviors of dimethyl ether jet flames in the air flow were studied firstly. The flame stability of the burner was analyzed by measuring the flow field temperature with thermocouples. By changing the coflow rate and CH4 equivalence ratio, the liftoff behaviors of dimethyl ether jet flames under different vitiated coflow environments were discussed. The jet flame structure was also analyzed qualitatively by high-speed photography.

Tensile Crack Speed in Brittle Rocks

2021 ◽  
Author(s):  
Mehdi Serati
Keyword(s):  
Size Effect ◽  
Rayleigh Wave ◽  
High Speed ◽  
Brazilian Test ◽  
Frame Rate ◽  
Experimental Program ◽  
High Speed Photography ◽  
Surface Mode ◽  
Crack Speed ◽  
Rock Types

<p>An important issue in rapid brittle fracture is the limiting speed of crack propagation. It is widely believed that brittle mode I crack cannot propagate faster than the Rayleigh wave speed, or the speed of sound on a solid surface. Mode II cracks are also limited by longitudinal speed wave. The origin for this belief stems from the predictions of continuum mechanics. Once the crack speed reaches a theoretical upper limit in a material, which is most often larger than one fifth of the Rayleigh wave velocity, branching of a propagating crack occurs. To verify this hypothesis, this paper presents the results of an experimental program aimed at disclosing the size effect on the crack velocity in the Splitting Tensile Strength indirect test (i.e. the Brazilian Test) using high-speed photography techniques. Over 100 Brazilian tests with more than 10 different rock types at various diameters were prepared and tested according to the ASTM standard recommendations using either a servo hydraulic machine or an electromechanical load frame at a wide ranges of load/displacement rates. By adopting a high frame rate of above 100,000 frames per second (fps), crack initiation, propagation, and coalescence were captured to study the size effect on the crack speed and failure mode on the Brazilian test results.</p>

Experimental Study of Aerodynamics Around Co-Rotating Blades in a Lawn Mower Deck

1999 ◽  
Author(s):  
W. Chon ◽  
P. Tetzlaff ◽  
R. S. Amano ◽  
A. Triscari ◽  
J. Torresin ◽  
...  
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Feeding System ◽  
Velocity Measurements ◽  
Forward Scatter ◽  
Lawn Mower ◽  
High Speed Video ◽  
Computational Fluid Dynamics Cfd ◽  
Blade Model

Abstract A combination of computational and experimental studies was performed on a 1.1m wide side discharge double-spindle lawn mower deck. For the experimental portion of the study air velocities were measured by using a forward-scatter LDV system. Velocity measurements were collected at several different tangential and axial sections inside the deck. In order to simulate the flow in real operating conditions, a grass feeding system was constructed in the laboratory. LDV test data were also validated by the conducting high-speed video taping of the experiments in several different running conditions. In the computational fluid dynamics (CFD) work, 2-D blade shapes at several arbitrary radial sections have been selected for flow computations around the blade model. The 2-D computational results were compared with the experimental results obtained in this study.

Effect of the Degree of Fuel-Air Mixing and Equivalence Ratio on the NOx Emission and Heat Release in a Dump Combustor

2009 ◽  
Vol 33 (9) ◽  
pp. 658-665
Author(s):  
Bong-Kug Cho ◽  
Do-Wook Choi ◽  
Gyu-Bo Kim ◽  
Young-June Chang ◽  
Ju-Hun Song ◽  
...  
Keyword(s):  
Heat Release ◽  
Equivalence Ratio ◽  
Nox Emission ◽  
Dump Combustor ◽  
Air Mixing

scholarly journals Bubbles with shock waves and ultrasound: a review

2015 ◽  
Vol 5 (5) ◽  
pp. 20150019 ◽  
Author(s):  
Siew-Wan Ohl ◽  
Evert Klaseboer ◽  
Boo Cheong Khoo
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Biomedical Applications ◽  
High Speed ◽  
Experimental Studies ◽  
High Intensity Focused Ultrasound ◽  
High Speed Photography ◽  
Sound Waves ◽  
Bubble Cloud ◽  
Bubble Interaction

The study of the interaction of bubbles with shock waves and ultrasound is sometimes termed ‘acoustic cavitation'. It is of importance in many biomedical applications where sound waves are applied. The use of shock waves and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics–bubble interactions, with a focus on shock wave–bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the ‘resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a shock wave complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving shock wave–bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead.

Analysis of Combustion in the Cetane-Rating Engine Using High-Speed Photography

1993 ◽  
Vol 207 (4) ◽  
pp. 317-328 ◽  
Author(s):  
N Ladommatos ◽  
M Parsi ◽  
N McGrath ◽  
S Mayne
Keyword(s):  
Heat Release ◽  
High Speed ◽  
Combustion Process ◽  
Injection System ◽  
Exhaust Emission ◽  
High Speed Photography ◽  
Diesel Fuels ◽  
Single Hole ◽  
Release Analysis

Modifications have been made to the injection system of the engine used for cetane-rating diesel fuels. These involved the replacement of the standard pintle nozzle with a single-hole orifice-type nozzle. The aim of the modifications was to improve the combustion process and thereby increase the precision of the cetane-rating test. The modifications to the injection system have been assessed using heat release analysis, exhaust emission measurements and high-speed photography of the combustion flames.

Numerical and Experimental Studies of Collapsing Cavitation Bubbles for Ballast Water Treatment

2018 ◽  
Author(s):  
Chang-Wei Kang ◽  
Tandiono Tandiono ◽  
Xin Lu ◽  
Cary K. Turangan ◽  
Hafiiz Osman ◽  
...  
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Hydrodynamic Cavitation ◽  
High Speed Photography ◽  
Gas Bubble ◽  
Liquid Pressure ◽  
Cfd Simulations ◽  
Bubble Cloud ◽  
Computational Fluid Dynamics Cfd ◽  
Sudden Jump

In this paper, we report both experimental and computational studies of hydrodynamic cavitation generated by accelerating liquid through a series of constrictions. The detailed process of cavitation generation is visualized using a high-speed photography. The cavitation is initiated when a gas bubble moves towards the constrictions. The gas bubble initially accelerates, expands and then splits into smaller bubbles when it moves along the constriction. As these bubbles migrate into a large liquid compartment, they collapse violently to form a bubble cloud, owing to a sudden jump in liquid pressure in the compartment. The experimental observation is further confirmed using computational fluid dynamics (CFD) simulations. We also present experimental evidence showing a significant reduction in gram-negative Escherichia coli concentration after it passes through the constrictions.

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