A Liquid-Pool Simulation of Droplet Combustion in a Swirl Flow

1993 ◽  
Vol 115 (3) ◽  
pp. 175-182 ◽  
Author(s):  
S.-S. Hou ◽  
T.-H. Lin
Keyword(s):  
Angular Velocity ◽  
Evaporation Rate ◽  
Recirculation Zone ◽  
Flame Temperature ◽  
Ethanol Vapor ◽  
Swirl Flow ◽  
Liquid Pool ◽  
Flame Extinction ◽  
Droplet Combustion ◽  
Air Jet

The influence of flow rotation on droplet combustion and evaporation are experimentally studied by using a burning liquid-pool system, and numerically investigated by considering a nonreactive, rotating, stagnation-point flow, respectively. The experiment involves measurements of flame temperature, flame position and evaporation rate of the liquid pool, observations of the recirculation zone and the soot layer, and identification of flame extinction. A finite-volume method is employed to numerically solve the corresponding transport equations. Calculated results show that in the vicinity of the liquid surface, both convection and diffusion transports are weakened by the flow rotation, resulting in the suppression of the evaporation strength of liquid; the recirculation zone can be identified and compared with experimental observation. For the steady burning of an ethanol pool in a swirling air jet, it is found that as the angular velocity increases, the diffusion flame shifts closer to the upper burner, has a larger flame thickness, experiences a smaller flame stretch, but suffers from the reduction of mass diffusion of ethanol vapor to the flame. However, the evaporation rate of ethanol is usually decreased with increasing angular velocity. In the flame extinction experiment, the critical volumetric oxygen concentration at extinction first decreases to a minimum value and then increases with angular velocity. It is generally concluded that flow rotation reduces the rates of both droplet combustion and evaporation.

scholarly journals A Liquid Pool Simulation on Droplet Combustion in a Swirl Flow

1992 ◽  
Author(s):  
Shuhn-Shyurng Hou ◽  
Ta-Hui Lin
Keyword(s):  
Angular Velocity ◽  
Evaporation Rate ◽  
Recirculation Zone ◽  
Flame Temperature ◽  
Swirl Flow ◽  
Liquid Pool ◽  
Flame Extinction ◽  
Droplet Combustion ◽  
Flow Vorticity ◽  
Air Jet

The influence of flow vorticity on droplet combustion and evaporation are experimentally simulated by using a burning liquid-pool system, and numerically investigated by considering a nonreactive, rotating, stagnation-point flow, respectively. The experiment involves measurements of flame temperature, flame position and evaporation rate of the liquid pool, observations of the recirculation zone and the soot layer, and identification of flame extinction. A finite-volume method is employed to numerically solve the corresponding transport equations. Calculated results show that in the vicinity of the liquid surface, both convection and diffusion transports are weakened by the flow vorticity resulting in the suppression of the evaporation strength of liquid; the recirculation zone can be identified and compared with experimental observation. For the steady burning of an ethanol pool in a swirl air jet, it is found that as the angular velocity increases, the diffusion flame shifts closer to the upper burner, has a larger flame thickness, experiences a smaller flame stretch but suffers from the reduction of mass diffusion of ethanol vapor to the flame. However, the evaporation rate of ethanol is usually decreased with increasing the angular velocity. In the flame extinction experiment, the critical volumetric oxygen concentration at extinction first decreases to a minimum value and then increases with angular velocity. It is generally concluded that the flow vorticity has a negative effect on both droplet combustion and evaporation.

Experimental Investigation Into the High Altitude Relight of a Three-Cup Combustor Sector

2018 ◽  
Author(s):  
Michael J. Denton ◽  
Samir B. Tambe ◽  
San-Mou Jeng
Keyword(s):  
Pressure Drop ◽  
High Altitude ◽  
High Speed ◽  
Development Process ◽  
Recirculation Zone ◽  
Operating Conditions ◽  
Pressure Drops ◽  
High Speed Video ◽  
Air Jet ◽  
Flame Development

The altitude relight of a gas turbine combustor is an FAA and EASA regulation which dictates the successful re-ignition of an engine and its proper spool-up after an in-flight shutdown. Combustor pressure loss, ambient pressure, ambient temperature, and equivalence ratio were all studied on a full-scale, 3-cup, single-annular aviation combustor sector to create an ignition map. The flame development process was studied through the implementation of high-speed video. Testing was conducted by placing the sector horizontally upstream of an air jet ejector in a high altitude relight testing facility. Air was maintained at room temperature for varying pressure, and then the cryogenic heat exchanger was fed with liquid nitrogen to chill the air down to a limit of −50 deg F, corresponding with an altitude of 30,000 feet. Fuel was injected at constant equivalence ratios across multiple operating conditions, giving insight into the ignition map of the combustor sector. Results of testing indicated difficulty in achieving ignition at high altitudes for pressure drops greater than 2%, while low pressure drops show adequate performance. Introducing low temperatures to simulate the ambient conditions yielded a worse outcome, with all conditions having poor results except for 1%. High-speed video of the flame development process during the relight conditions across all altitudes yielded a substantial effect of the pressure drop on ignitability of the combustor. An increase in pressure drop was associated with a decrease in the likelihood of ignition success, especially at increasing altitudes. The introduction of the reduced temperature effect exacerbated this effect, further hurting ignition. High velocity regions in the combustor were detrimental to the ignition, and high area, low velocity regions aided greatly. The flame tended to settle into the corner recirculation zone and recirculate back into the center-toroidal recirculation zone (CTRZ), spreading downstream and likewise into adjacent swirl cups. These tests demonstrate the need for new combustor designs to consider adding large recirculation zones for combustor flame stability that will aid in relight requirements.

Numerical simulation of airflow characteristics in the spinning zone at starting time of air-jet spinning machine

2018 ◽  
Vol 89 (12) ◽  
pp. 2342-2352
Author(s):  
Thi Viet Bac Phung ◽  
Akihiro Yoshida ◽  
Yoshiyuki Iemoto ◽  
Hideyuki Uematsu ◽  
Shuichi Tanoue
Keyword(s):  
Fiber Bundle ◽  
High Speed ◽  
Three Dimensional ◽  
Swirl Flow ◽  
Air Pressure ◽  
Suction Force ◽  
Starting Time ◽  
Air Jet ◽  
Spinning Process ◽  
Center Axis

To clarify the formation mechanism of a source of yarn and to discuss the effects of supplied air pressure and exhaust air pressure on the fiber suction force and twist torque at the starting time of the spinning process in an air-jet spinning machine, we simulated, numerically, the three-dimensional airflow pattern without fibers in the spinning zone. Results obtained are as follows: High-speed air jetted through the starting nozzles into the yarn duct in the circumferential direction causes a swirl flow in the yarn duct and a negative pressure region near the center axis of the yarn duct. Hence, air and fibers at the fiber inlet are sucked through the processing duct into the yarn duct. A fiber bundle sucked into the yarn duct rotates, owing to the action of the swirl airflow, and twists the fiber bundle in the processing duct, hence generating a source of yarn. The fiber suction force takes a distribution with a peak against the supplied air pressure and is independent of the exhaust air pressure. The fiber twist torque increases monotonously with supplied air pressure.

Combustion Efficiency of a Premixed Continuous Flow Combustor

1985 ◽  
Vol 107 (3) ◽  
pp. 695-705 ◽  
Author(s):  
M. S. Anand ◽  
F. C. Gouldin
Keyword(s):  
Recirculation Zone ◽  
Thin Sheet ◽  
Turbulent Flame ◽  
Combustion Efficiency ◽  
Combustion Mechanism ◽  
Mean Flow ◽  
Outer Flow ◽  
Flow Swirl ◽  
Air Jet ◽  
Radial Profiles

Experimental data in the form of radial profiles of mean temperature, gas composition and velocity at the combustor exit and combustion efficiency are reported and discussed for a swirling flow, continuous combustor. The combustor is composed of two confined, concentric independently swirling jets: an outer, annular air jet and a central premixed fuel-air jet, the fuel being propane or methane. Combustion is stabilized by a swirl-generated central recirculation zone. The primary objective of this research is to determine the effect of fuel substitution and of changes in outer flow swirl conditions on combustor performance. Results are very similar for both methane and propane. Changes in outer flow swirl cause significant changes in exit profiles, but, surprisingly, combustion efficiency is relatively unchanged. A combustion mechanism is proposed which qualitatively explains the results and identifies important flow characteristics and physical processes determining combustion efficiency. It is hypothesized that combustion occurs in a thin sheet, similar in structure to a premixed turbulent flame, anchored on the combustor centerline just upstream of the recirculation zone and swept downstream with the flow. Combustion efficiency depends on the extent of the radial propagation, across mean flow streamtubes, of this reaction sheet. It is concluded that, in general, this propagation and hence efficiency are extremely sensitive to flow conditions.

Resolving Large- and Small-Scale Structures in the Swirl Flow of a Typical Land-Based Gas Turbine Combustor Single Nozzle Rig

2014 ◽  
Author(s):  
R. K. R. Katreddy ◽  
S. R. Chakravarthy
Keyword(s):  
Velocity Field ◽  
Gas Turbine ◽  
Large Scale ◽  
Recirculation Zone ◽  
Laser Diagnostics ◽  
Swirl Flow ◽  
Sudden Expansion ◽  
Small Scale ◽  
Gas Turbine Combustor ◽  
Scale Structures

The present study focuses on identifying and resolving large-scale energy containing structures and turbulent eddies in a typical gas turbine combustor single nozzle rig, using particle image velocimetry in cold flow. A generic fuel-air nozzle through a swirler is integrated with a sudden expansion square duct with optical access to perform laser diagnostics. Experiments are conducted to analyze the swirl flow field under starting and operating flow conditions. Three-component velocities are obtained in cross-sectional planes of Z/D = 0, 1.25, and 2.5 (normalized by the nozzle diameter), and two-component velocities are obtained in the mid-plane along the longitudinal (Z-) axis from Z/D = 0 to 2.5D. Velocity splitting is performed using spatial Gaussian smoothing with a kernel with filter width equal to integral scale is performed over the velocity fields to resolve the field of large-scale energy containing eddies. Proper orthogonal decomposition is performed over the large-scale velocity field, and the modes obtained indicate the existence of the precessing vortex core (PVC), formation of small scales Kelvin-Helmholtz (K-H) vortices for Z/D < 1.25D, and large-scale growing K-H structures in 1.25D < Z/D < 2.5D. Turbulent kinetic energy (TKE) is obtained from the turbulent velocity fluctuations below the integral length scale and is observed to be higher at the interface of the corner recirculation zone (CRZ) and central toroidal recirculation zone (CTRZ). Resolving the swirl velocity field obtained in the above manner into large-scale structures formed by the PVC, CTRZ, K-H vortices, CRZ, and small-scale turbulence field, indicates the clear distinction in rapid mixing zones and unsteady convective zones. The length-scales and zones of these structures within the swirl combustor are identified.

Gas Turbine Combustor Liner Wall Heat Load Characterization for Different Gaseous Fuels

2019 ◽  
Author(s):  
Kishore Ranganath Ramakrishnan ◽  
Shoaib Ahmed ◽  
Benjamin Wahls ◽  
Prashant Singh ◽  
Maria A. Aleman ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Load ◽  
Recirculation Zone ◽  
Flame Temperature ◽  
Conduction Model ◽  
Steady State Condition ◽  
Gaseous Fuels ◽  
Peak Heat Flux ◽  
Combustor Liner

Abstract The knowledge of detailed distribution of heat load on swirl stabilized combustor liner wall is imperative in the development of liner-specific cooling arrangements, aimed towards maintaining uniform liner wall temperatures for reduced thermal stress levels. Heat transfer and fluid flow experiments have been conducted on a swirl stabilized lean premixed combustor to understand the behavior of Methane-, Propane-, and Butane-based flames. These fuels were compared at different equivalence ratios for a matching adiabatic flame temperature of Methane at 0.65 equivalence ratio. Above experiments were carried out a fixed Reynolds number (based on the combustor diameter) of 12000, where the pre-heated air temperature was approximately 373K. Combustor liner in this setup was made from 4 mm thick quartz tube. An infrared camera was used to record the inner and outer temperatures of liner wall, and two-dimensional heat conduction model was used to find the wall heat flux at a quasi-steady state condition. Flow field in the combustor was measured through Particle Image Velocimetry. The variation of peak heat flux on the liner wall, position of peak heat flux and heat transfer, and position of impingement of flame on the liner have been presented in this study. For all three gaseous fuels studied, the major swirl stabilized flame features such as corner recirculation zone, central recirculation zone and shear layers have been observed to be similar. Liner wall and exhaust temperature for Butane was highest among the fuel tested in this study which was expected as the heat released from combustion of Butane is higher than that of Methane and Propane.

scholarly journals The dilution effect on the extinction of wall diffusion flame

2014 ◽  
Vol 35 (4) ◽  
pp. 43-54
Author(s):  
Nadjib Ghiti
Keyword(s):  
Dilution Rate ◽  
Diffusion Flame ◽  
Flame Temperature ◽  
Dilution Effect ◽  
Lateral Wall ◽  
Flame Extinction ◽  
Jet Flame ◽  
Extinction Process ◽  
Nitrogen Dilution ◽  
Flame Response

Abstract The dynamic process of the interaction between a turbulent jet diffusion methane flame and a lateral wall was experimentally studied. The evolution of the flame temperature field with the Nitrogen dilution of the methane jet flame was examined. The interaction between the diffusion flame and the lateral wall was investigated for different distance between the wall and the central axes of the jet flame. The dilution is found to play the central role in the flame extinction process. The flame response as the lateral wall approaches from infinity and the increasing of the dilution rate make the flame extinction more rapid than the flame without dilution, when the nitrogen dilution rate increase the flame temperature decrease.

Numerical Analysis of Distribution of Ion Concentration Affected by Flame Temperature behind a V-Gutter Flameholder

2014 ◽  
Vol 672-674 ◽  
pp. 1454-1458
Author(s):  
Xue Jiao Luo ◽  
Wei Jun Fan
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Recirculation Zone ◽  
Flame Temperature ◽  
Ion Current ◽  
Ion Concentration ◽  
Outlet Section ◽  
Turbulent Model ◽  
Combustion Condition ◽  
Good Agreement

To obtain evident ion current signals which reflect combustion condition in afterburner, areas of high ion concentration need to be identified. Using C12H23as the fuel species, H3O+, CHO+, COH+, O-and OH-as main ions, total ion concentration and temperature in flame behind a V-gutter flameholder are numerically simulated by realizable κ-ε turbulent model and non-premixed equilibrium chemistry model. Outlet section temperature is in good agreement with experimental data. The results show that distributions of ion concentration and temperature are consistent. There are two areas of high ion concentration: regions of the highest temperature in recirculation zone; regions close to upper and lower edges of flameholder. Peaks of each area appear near the injection holes.

On Effect of the Flare Angle on the Behaviour of the Flow Field of Twin-Radial Swirlers/High Shear Injector

2019 ◽  
Author(s):  
Sonu Kumar ◽  
Swetaprovo Chaudhuri ◽  
Saptarshi Basu
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
High Speed ◽  
Recirculation Zone ◽  
Swirl Flow ◽  
High Shear ◽  
Gas Turbine Combustor ◽  
Flow Topology ◽  
Mean Velocity ◽  
And Performance

Abstract The swirl flow in gas turbine combustor plays a major role in flame stabilisation and performance of engine. Since the swirl flow is very complex and boundary sensitive phenomena, it is difficult to interpret it properly. High shear injector is being used now a days in modern gas turbine combustor to generate the swirl flow and achieve better fuel atomisation in the combustion chamber. High shear injector accommodates a series of swirlers (primary and secondary) with a diverging flare at the exit and fuel nozzle mounted at the centre of the swirler. In the present study it is tried to understand the influence of the flare angle on the non-reactive flow behaviour of the swirling spray flow-field generated through counter-rotating high shear injector. To perceive the influence of flare angle on the flow topology of the spray flow-field generated by a high shear injector, seven different flare half angles (β): 40°, 45°, 50°, 55°, 60°, 65° and 70° respectively were selected as a geometrical parameter to conduct the experiments. High-Speed Particle Image Velocimetry (HSPIV) technique was employed to perceive the topological structure of the spray flow field, mean and instantaneous behaviour of the velocity fields respectively. For all the cases mass flow of air and liquid (water) were kept constant. It was observed that with change in flare angle the size of the CTRZ, mean velocity and turbulent behaviour were also changing. Here the size of CTRZ is represented in terms of nondimensional radial width (W/Df) and height (H/Df) of the recirculation zone. The experiment was conducted without flare, initially and then subsequently with flares. It was found that both the radial width and the height of the recirculation zone were smallest for without flare case. With increase in flare angle the radial width and height of the CTRZ increases initially up to 60° flare angle and afterward decreased. The experiments made clear that flare angle has strong effect on the spray flow-field.

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