Effects of Nozzle Orientation on the Structure and Emissions of Spray Flames

1993 ◽  
Vol 115 (3) ◽  
pp. 183-189 ◽  
Author(s):  
A. V. Madanahalli ◽  
S. R. Gollahalli
Keyword(s):  
Liquid Fuel ◽  
Orientation Angle ◽  
Combustion Products ◽  
Flame Length ◽  
Radiation Emission ◽  
Spray Flames ◽  
Air Stream ◽  
Air Streams ◽  
Nozzle Orientation ◽  
Fuel Stream

An experimental study of the effects of the orientation of the liquid fuel stream relative to the air stream from a twin fluid atomizer located in an open-jet wind tunnel is presented. The orientation angle was set at 0 (concurrent), 45, 90, 135, and 180 deg (directly opposed). At 45 and 90 deg, the flame length, the radiation emission, and the concentrations of carbon monoxide, carbon dioxide, nitric oxide, and soot are higher than those at co-flow conditions. At 135 deg, all these quantities decrease markedly from their values at 90 deg and again increase when the fuel and air streams are directly opposed (180 deg). These changes are discussed in terms of the influx of air and recirculation of combustion products into the salient zones of the flame.

Effects of Air Temperature on Combustion Characteristics of LPG Diffusion Flame

2020 ◽  
Vol 1008 ◽  
pp. 128-138
Author(s):  
Ahmed M. Salman ◽  
Ibrahim A. Ibrahim ◽  
Hamada M. Gad ◽  
Tharwat M. Farag
Keyword(s):  
Air Temperature ◽  
Diffusion Flame ◽  
Nitrogen Addition ◽  
Flame Length ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Low Oxygen ◽  
Air Temperatures ◽  
Air Stream ◽  
Wide Range

In the present study, the combustion characteristics of LPG gaseous fuel diffusion flame at elevated air temperatures were experimentally investigated. An experimental test rig was manufactured to examine a wide range of operating conditions. The investigated parameters are the air temperatures of 300, 350, 400, 450, and 500 K with constant percentage of nitrogen addition in combustion air stream of 5 % to give low oxygen concentration of 18.3 % by mass at constant air swirl number, air to fuel mass ratio, and thermal load of 1.5, 30, and 23 kW, respectively. The gaseous combustion characteristics were represented as axial and radial temperatures distributions, temperatures gradient, visible flame length and species concentrations. The results indicated that as the air temperature increased, the chemical reaction rate increased and flame volume decreased, the combustion time reduced leading to a reduction in flame length. The NO concentration reaches its maximum values near the location of the maximum centerline axial temperature. Increasing the combustion air temperature by 200 K, the NO consequently O2 concentrations are increased by about % 355 and 20 % respectively, while CO2 and CO concentrations are decreased by about % 21 and 99 % respectively, at the combustor end.

scholarly journals A new argument against cooling by convective air eddies formed above sunlit zebra stripes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ádám Pereszlényi ◽  
Dénes Száz ◽  
Imre M. Jánosi ◽  
Gábor Horváth
Keyword(s):  
The Body ◽  
Schlieren Imaging ◽  
Air Stream ◽  
Stream Drift ◽  
Calm Weather ◽  
Air Streams ◽  
Stream Formation

AbstractThere is a long-lasting debate about the possible functions of zebra stripes. According to one hypothesis, periodical convective air eddies form over sunlit zebra stripes which cool the body. However, the formation of such eddies has not been experimentally studied. Using schlieren imaging in the laboratory, we found: downwelling air streams do not form above the white stripes of light-heated smooth or hairy striped surfaces. The influence of stripes on the air stream formation (facilitating upwelling streams and hindering horizontal stream drift) is negligible higher than 1–2 cm above the surface. In calm weather, upwelling air streams might form above sunlit zebra stripes, however they are blown off by the weakest wind, or even by the slowest movement of the zebra. These results forcefully contradict the thermoregulation hypothesis involving air eddies.

Second Law Analysis of Solid Desiccant Rotary Dehumidifiers

1988 ◽  
Vol 110 (1) ◽  
pp. 2-9 ◽  
Author(s):  
E. Van den Bulck ◽  
S. A. Klein ◽  
J. W. Mitchell
Keyword(s):  
Local Maximum ◽  
Operating Conditions ◽  
Second Law ◽  
Transfer Coefficients ◽  
Adiabatic Flow ◽  
Transfer Processes ◽  
Air Stream ◽  
Second Law Analysis ◽  
Pass Through ◽  
Air Streams

This paper presents a second law analysis of solid desiccant rotary dehumidifiers. The equations for entropy generation for adiabatic flow of humid air over a solid desiccant are developed. The generation of entropy during operation of a rotary dehumidifier with infinite transfer coefficients is investigated and the various sources of irreversibility are identified and quantified. As they pass through the dehumidifier, both the process and regeneration air streams acquire nonuniform outlet states, and mixing both of these air streams to deliver homogeneous outlet streams is irreversible. Transfer of mass and energy between the regeneration air stream and the desiccant matrix occurs across finite differences in vapor pressure and temperature and these transfer processes generate entropy. The second law efficiency of the dehumidifier is given as a function of operating conditions and the effect of finite transfer coefficients for an actual dehumidifier is discussed. It is shown that operating the rotary dehumidifier at conditions that minimize regeneration energy also yields a local maximum for the second law efficiency.

Diffusion Driven Desalination for Simultaneous Fresh Water Production and Desulfurization

2010 ◽  
Vol 2 (3) ◽  
Author(s):  
Jameel R. Khan ◽  
James F. Klausner ◽  
Donald P. Ziegler ◽  
Srinivas S. Garimella
Keyword(s):  
Fresh Water ◽  
Fluid Transport ◽  
Transport Model ◽  
Waste Heat ◽  
Feed Water ◽  
Low Grade ◽  
Water Production ◽  
Air Stream ◽  
Mass Transport Model ◽  
Air Streams

The diffusion driven desalination (DDD) process has been previously introduced as a process for distilling water using low-grade waste heat. Here, a configuration of the DDD process is introduced for simultaneously distilling water and scrubbing sulfur dioxide (SO2) out of heated air streams, which is also known as flue gas desulfurization (FGD). This novel DDD/FGD process utilizes the low-grade waste heat carried in industrial discharge air streams. There are many applications, where the industrial air discharge also contains SO2, and in order to utilize the waste heat for the DDD process, the SO2 must be scrubbed out of the air stream. The two major components of the DDD process are the diffusion tower and the direct contact condenser. In the present work, a thermal fluid transport model for the DDD/FGD process, that includes SO2 scrubbing, is developed. It is an extension of the heat and mass transport model previously reported for the DDD process. An existing laboratory scale DDD facility was modified and tested with SO2 in the air stream and with seawater as the feed water to the diffusion tower. The experimental investigation has been completed to evaluate the fresh water production and SO2 scrubbing potential for the DDD/FGD process. The experimental results compare favorably with the model predictions. Chemical analysis on the condenser water demonstrates the capability of the DDD/FGD process to produce high quality fresh water using seawater as the input feed water to the process.

scholarly journals Effects of liquid fuel/wall interaction on thermoacoustic instabilities in swirling spray flames

2020 ◽  
Vol 219 ◽  
pp. 86-101 ◽  
Author(s):  
E. Lo Schiavo ◽  
D. Laera ◽  
E. Riber ◽  
L. Gicquel ◽  
T. Poinsot
Keyword(s):  
Liquid Fuel ◽  
Thermoacoustic Instabilities ◽  
Spray Flames ◽  
Wall Interaction

Flue-Gas Versus Fuel-Injection Recirculation: Effects on Structure and Pollutant Emissions

2005 ◽  
Author(s):  
Ala R. Qubbaj
Keyword(s):  
Flue Gas ◽  
Fuel Injection ◽  
No Reduction ◽  
The Other ◽  
Pollutant Emissions ◽  
Air Stream ◽  
Baseline Case ◽  
Co Reduction ◽  
Air Diffusion ◽  
Fuel Stream

In this study, a co-flow methane/air diffusion flame at Reynolds number of 6000 was numerically simulated. The co-flow air and fuel streams were diluted with Nitrogen in the range of 0% to 20%. The thermal and composition fields in the far-burner reaction zone (close to the exhaust) were computed, and the effects of diluent’s addition to the air stream (simulating FGR) and to the fuel stream (simulating FIR) were investigated. The results show that air-side dilution is very effective up to 5% diluent’s addition. For which, 95% and 65% drops in NO and CO emissions, respectively, along with a 16% increase in temperature, are predicted compared to the baseline case (0% dilution). However, beyond 5% dilution, no effect (reaction) has been predicted. On the other hand, the fuel-side dilution has shown an effect for all simulated diluent’s addition (i.e. 0%–20%). However, that effect is not systematic neither on temperature, CO or NO concentrations. For a similar 5% dilution to the fuel-side, a 14% increase in NO and a 97% decrease in CO are predicted, along with a 5.6% increase in temperature. The simulated results revealed that air-side dilution (simulating FGR) has a dramatic greater effectiveness in NO reduction, whereas, fuel-side dilution (simulating FIR) has a greater effectiveness in CO reduction. Besides, the results suggest an important role for Prompt-NO Fenimore mechanism.

Biological odour control by diffusion into activated sludge basins

2000 ◽  
Vol 41 (6) ◽  
pp. 127-132 ◽  
Author(s):  
R. P. Bowker
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
High Strength ◽  
Air Stream ◽  
Fine Bubble ◽  
Treatment Facilities ◽  
Odour Control ◽  
Odour Emissions ◽  
Air Streams

Diffusion of odourous air into activated sludge basins is an effective and economical approach for odour control at wastewater treatment plants. Over 30 facilities in North America practice this technique. Most of these applications are for dilute or moderate strength air streams with relatively low hydrogen sulfide (H2S) levels. Unfortunately, the lack of data documenting the effectiveness of the process and concerns for blower corrosion have limited its acceptance as a method for controlling odour emissions. This paper presents a compilation and review of wastewater treatment facilities that are currently using activated sludge diffusion. Performance data are tabulated, and information on operation and maintenance of the blower/diffuser systems are summarized. New data are presented that compare the effectiveness of coarse vs. fine bubble diffusers for treatment of a high strength, high-H2S air stream from sludge holding tanks at Concord, NH. Designand performance information is presented on a dedicated odour control system installed at Phoenixville, Pennsylvania in 1996 that collects high-H2S air streams from an influent chamber and primary clarifiers and diffuses it into a mechanically-aerated activated sludge basin. A cost-effectiveness analysis is presented for a blower/diffuser system installed exclusively for odour control. Methods used to overcome initial operational problems are discussed.

The Aerodynamic Approach to Furnace Design

1959 ◽  
Vol 81 (4) ◽  
pp. 361-369 ◽  
Author(s):  
J. H. Chesters
Keyword(s):  
Open Hearth ◽  
Open Hearth Furnace ◽  
Hearth Furnace ◽  
Low Velocity ◽  
Droplet Dynamics ◽  
Free Jets ◽  
Free Jet ◽  
Side Walls ◽  
Air Streams ◽  
Fuel Stream

Flow patterns and mixing in actual furnaces can be best appreciated by starting with free jets and proceeding via jets in simple envelopes to jets (cold or alight) fed with surrounding air streams and impacting on surfaces. The fuel stream in an open-hearth furnace behaves initially as a free jet, entraining the relatively low velocity air around it, but on hitting the bath it splashes and runs forward and up the side walls. The gases reaching the roof eject flux droplets and then divide, part recirculating to meet the oncoming air and part joining the main flow to the exit. Future progress requires more knowledge of droplet dynamics, and demands more symmetrical flow, control of recirculation, or radical changes.

The temperature distribution along a radiating gas stream in which heat is being liberated by a chemical reaction

1951 ◽  
Vol 208 (1093) ◽  
pp. 247-262
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Sink ◽  
Flame Temperature ◽  
Convection Heat Transfer ◽  
Combustion Products ◽  
Distance Curve ◽  
Fuel Jet ◽  
Initial Fuel ◽  
Fuel Stream

As a first approximation, to calculate the variation of flame temperature ( Y ) with distance ( X ) along a slowly burning flame, the flame is taken to consist of a central stream or jet of fuel which enters at the temperature ( T ) of the heat sink and entrains combustion air at a rate constant with respect to X . This entrained air is assumed to react rapidly with the fuel stream and the products of the reactions remain in the fuel stream, so that the temperature ( Y ) of the latter rises at a rate dY/dX which falls off as the heat capacity of this stream increases. When there is no heat loss from the fuel jet the temperature-distance curve is shown to be a rectangular hyperbola. The curvature at any point of the hyperbola increases as ( q ), the ratio of the heat capacity of the initial fuel stream to that of the final combustion products, decreases. In other cases heat transfer is supposed to take place by convection (α [ Y ─ T ]) orradiation (α [ Y 4 ─ T 4 ]) between the fuel jet and the heat sink with a heat-transfer coefficient which is assumed to be constant for a cylindrical flame and proportional to distance from the inlet for a conical flame. It is shown that in the case of the cylindrical flame the flame temperature must increase monotonically until combustion is complete, whereas the temperature in the conical flame can begin to fall off at an earlier stage. In the case of convection-heat transfer the shape of the temperature-distance curve is dependent only on ( q ) and on the ratio L/L 0 (where L ═ length for all combustion air to be entrained and L 0 ═ length in which all the combustion energy would be transferred to the surroundings if the flame remained at the adiabatic combustion temperature T a ). With radiative heat transfer the shape of the curves depends on ( q ) and L/L 0 but also on the ratio T/T a .

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