Liquid Fuel Placement and Mixing of Generic Aeroengine Premix Module at Different Operating Conditions

Fuel placement and air-fuel mixing in a generic aeroengine premix module employing plain jet liquid fuel injection into a counter-swirling double-annular crossflow were investigated at different values of air inlet pressure (6 bar, 700 K and 12 bar, 700 K) and liquid-to-air momentum flux ratio, both parameters being a function of engine power. Kerosene Jet A-1 was used as liquid fuel. Measurement techniques included LDA for investigation of the airflow and Mie-scattering laser light sheets and PDA for investigation of the two-phase flow. Measurements were taken at various axial distances from the fuel nozzle equivalent to mean residence times of up to 0.47 ms. It was found that the initial fuel placement reacts very sensitively to a variation of liquid-to-air momentum flux ratio. Susceptibility of the spray to dispersion due to centrifugal forces and to turbulent mixing is primarily a function of the fuel droplet diameters, which in turn depend on operating pressure. The data are interpreted by evaluation of the corresponding Stokes numbers.

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Liquid Jets in Subsonic Air Crossflow at Elevated Pressure

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4028565 ◽

2014 ◽

Vol 137 (4) ◽

Cited By ~ 22

Author(s):

Jinkwan Song ◽

Charles Cary Cain ◽

Jong Guen Lee

Keyword(s):

Weber Number ◽

Momentum Flux ◽

Drop Size ◽

Density Ratio ◽

Flux Ratio ◽

Mie Scattering ◽

Air Pressure ◽

Scattering Intensity ◽

Nozzle Orifice ◽

Momentum Flux Ratio

The breakup, penetration, droplet size, and size distribution of a Jet A-1 fuel in air crossflow has been investigated with focus given to the impact of surrounding air pressure. Data have been collected by particle Doppler phased analyzer (PDPA), Mie-scattering with high speed photography augmented by laser sheet, and Mie-scattering with intensified charge-coupled device (ICCD) camera augmented by nanopulse lamp. Nozzle orifice diameter, do, was 0.508 mm and nozzle orifice length to diameter ratio, lo/do, was 5.5. Air crossflow velocities ranged from 29.57 to 137.15 m/s, air pressures from 2.07 to 9.65 bar, and temperature held constant at 294.26 K. Fuel flow provides a range of fuel/air momentum flux ratio (q) from 5 to 25 and Weber number from 250 to 1000. From the results, adjusted correlation of the mean drop size has been proposed using drop size data measured by PDPA as follows: (D0/D32)=0.267Wea0.44q0.08(ρl/ρa)0.30(μl/μa)-0.16. This correlation agrees well and shows roles of aerodynamic Weber number, Wea, momentum flux ratio, q, and density ratio, ρl/ρa. Change of the breakup regime map with respect to surrounding air pressure has been observed and revealed that the boundary between each breakup modes can be predicted by a transformed correlation obtained from above correlation. In addition, the spray trajectory for the maximum Mie-scattering intensity at each axial location downstream of injector is extracted from averaged Mie-scattering images. From these results, correlations with the relevant parameters including q, x/do, density ratio, viscosity ratio, and Weber number are made over a range of conditions. According to spray trajectory at the maximum Mie-scattering intensity, the effect of surrounding air pressure becomes more important in the farfield. On the other hand, effect of aerodynamic Weber number is more important in the nearfield.

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Experimental Investigation of a RQL Burner With Jet in Cross Flow Fuel Injection: Characterization of the Reacting Flow Field at Realistic Operating Conditions

Volume 4B: Combustion, Fuels, and Emissions ◽

10.1115/gt2019-91244 ◽

2019 ◽

Author(s):

T. Soworka ◽

T. Behrendt ◽

C. Hassa ◽

J. Heinze ◽

E. Magens ◽

...

Keyword(s):

Flow Field ◽

Fuel Injection ◽

Measurement Techniques ◽

Cross Flow ◽

Mie Scattering ◽

Operating Conditions ◽

Reacting Flow ◽

Axial Location ◽

Primary Zone ◽

Jet In Cross Flow

Abstract Future rich-burn/quick-quench/lean-burn (RQL) burners for aero engines face the challenge to further reduce the emission of soot. Alternative ways of fuel injection are therefore in the focus of modern RQL combustion systems. This contribution aims to investigate experimentally the influence of fuel injection on the reacting flow field, with the emphasis on soot production in the primary zone. For the test, a Rolls-Royce prototype burner was used in two different configurations which differ only in the axial location of jet in cross flow fuel injection and thereby provoke different ways of fuel atomization. In the upstream configuration the burner features characteristics of a pre-filming airblast atomizer. Whereas with the fuel tip in downstream position solely Jet-in-Cross-Flow fuel atomisation is expected. The burner was tested at realistic aero engine combustor conditions (p30 = 9.28 bar, T30 = 603 K, AFR = 7.6). Several optical measurement techniques were used to characterise the reacting flow field. Their difficult application in a rich burn environment is described briefly. The structure of the reacting flow field is illustrated by Particle-Image-Velocimetry (PIV). Planar Mie scattering and Planar Laser-Induced Fluorescence (PLIF) are used to characterise the placement of liquid and gaseous fuel respectively. The location and structure of heat release zones are captured in terms of OH* and CO2* chemiluminescence. Finally Laser-Induced-Incandescence (LII) is used to obtain three dimensional soot distributions in the primary zone. On this basis 20% less soot was measured for the upstream configuration at the axial location of maximal soot concentration. This remarkable difference could be attributed to the different placement of liquid fuel and the resulting better mixing.

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Characterization of Spray Formed by Liquid Jet Injected Into Oscillating Air Crossflow

Volume 4B: Combustion, Fuels and Emissions ◽

10.1115/gt2015-43726 ◽

2015 ◽

Cited By ~ 1

Author(s):

Jinkwan Song ◽

Jong Guen Lee

Keyword(s):

Weber Number ◽

Momentum Flux ◽

Drop Size ◽

Flux Ratio ◽

Mie Scattering ◽

Liquid Jet ◽

Velocity Modulation ◽

Momentum Flux Ratio ◽

Crossflow Velocity ◽

Modulation Level

This paper presents experimental results on the characteristics of spray formed by a liquid (Jet-A) jet injected into an oscillating air crossflow. Ambient air pressure is raised up to 15.86 bar, and the corresponding aerodynamic Weber number and liquid-air momentum flux ratio are up to 1000 and 25, respectively. The level of modulated crossflow velocity is kept up to 20% of its mean value. For limited cases, the air crossflow is preheated. Planar Mie-scattering measurements are utilized to visualize changes of the spray penetration and cross-sectional spray area in the oscillating air crossflow, and PDPA measurements are used to measure the mean drop size and drop size distribution. Phase-synchronized PDPA measurement of droplet size under the modulation of crossflow shows that the modulating crossflow results in preferentially larger amount of smaller and bigger droplets than average-sized droplets. Global spray response of spray to modulating crossflow is characterized by using proper orthogonal decomposition (POD) analysis of Mie-scattering images and collecting (and hence determining gain of) Mie-scattering intensity of droplets at a fixed downstream distance. It is found that the dominant behavior of the spray is convective oscillation in the axial direction and the change of vertical penetration of the spray is almost negligible for the level of crossflow velocity modulation up to 20%. The gain of Mie-scattering intensity with respect to crossflow velocity modulation level gradually decreases as liquid-air momentum flux ratio increases. Also, per given momentum flux ratio and Weber number, the gain hardly varies with respect to crossflow modulation level, suggesting the response of spray increases in proportion to crossflow velocity modulation level.

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Effects of Swirl on the Stabilization of Non-Premixed Oxygen Enriched Flames Above Coaxial Injectors

Volume 4B: Combustion, Fuels, and Emissions ◽

10.1115/gt2019-91516 ◽

2019 ◽

Author(s):

A. Degeneve ◽

C. Mirat ◽

J. Caudal ◽

R. Vicquelin ◽

T. Schuller

Keyword(s):

Oxygen Concentration ◽

Momentum Flux ◽

Flame Structure ◽

Flux Ratio ◽

Operating Conditions ◽

Momentum Flux Ratio ◽

Annular Jet ◽

Finite Distance ◽

The Mean ◽

Lift Off

Abstract An experimental study is carried out to analyze effects of swirl on the structure and stabilization of methane non-premixed oxygen-enriched flames above a co-axial injector in which the two streams are eventually swirled. The mean position of the flame and the liftoff height above the injector lips are investigated with OH* chemiluminescence images. The oxygen enrichement, the momentum flux ratio between the two co-flows, the swirl level inside the central jet and the swirl level in the annular jet are varied over a large range of operating conditions. It is found that, in the absence of swirl in the central stream, the flame is always attached to the lips of the internal injection tube. As the inner swirl level increases, the flame front located at the lips of the internal injection tube disappears. When the annular swirl level is high enough to create a central recirculating bubble, the flame detaches from the nozzle rim and remains lifted at a finite distance above the injector. Increasing the oxygen concentration shifts this transition to smaller momentum flux ratios and smaller annular swirl levels. The lift-off distance can be finely tuned and depends on the inner and outer swirl levels, and on the momentum flux ratio between the two coaxial streams. It is shown that this feature neither depends on the confinement of the injector nor on the thermal stress exerted by the hot burnt gases on the injector back plane. About 1000 configurations were investigated that could be classified into only four distinct stabilization modes, in which the flame structure was shown to follow a similar pathway when the momentum flux ratio between the two streams, the swirl level in the central and external streams and the quarl angle of the annular stream are varied. It is finally shown how these limits are altered when the oxygen concentration in the annular oxidizer stream is varied from air to oxygen-enriched operation.

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Experimental and Numerical Investigation of Confined Jets in Hot Co-Flow

Volume 4A: Combustion, Fuels and Emissions ◽

10.1115/gt2014-25843 ◽

2014 ◽

Cited By ~ 1

Author(s):

G. Tautschnig ◽

E.-M. Haner ◽

C. Hirsch ◽

T. Sattelmayer

Keyword(s):

Gas Turbines ◽

Momentum Flux ◽

Measurement Techniques ◽

Water Channel ◽

Combustion Process ◽

Computational Cost ◽

Flux Ratio ◽

Flow Measurements ◽

Auto Ignition ◽

Tabulated Chemistry

Sequential staged combustion with an expansion turbine between both stages is an efficient way of extending the low emission regime of gas turbines towards very low loads. The dominating combustion regime in the second stage is auto-ignition. A confined natural gas jet in hot vitiated co-flow is investigated to obtain deeper insights in the parameters effecting auto-ignition. A generic pressurized combustion experiment is presented. Optical measurement techniques are applied to determine lift-off height and air excess ratio of the flame in the ignition region. Oxygen content of the co-flow, momentum flux ratio and pressure are varied in the experiments. Cold flow measurements are used to analyze the mixing behavior for different momentum flux ratios. Tendencies observed in the experiments are successfully simulated by a numerical method wherein the flow-, mixture- and temperature-fields are acquired using a non-reacting Realizable k-ε RANS simulation in Fluent. Mixture-PDFs obtained from water-channel measurements are used to take mixture-fluctuations into account. In a post-processing step the combustion-process is calculated with unsteady flamelet equations evaluated in Matlab. By using a progress variable approach with tabulated chemistry only two partial differential equations need to be solved. Hence the computational cost is low. With this study a low-cost numerical model for auto-ignition is demonstrated and the effect of temperature gradients in the co-flow on self-ignition is highlighted.

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CFD Modeling of the Atomization of Plain Liquid Jets in Cross Flow for Gas Turbine Applications

Volume 1: Turbo Expo 2004 ◽

10.1115/gt2004-54269 ◽

2004 ◽

Cited By ~ 8

Author(s):

Sachin Khosla ◽

D. Scott Crocker

Keyword(s):

Momentum Flux ◽

Drop Size ◽

Fuel Injection ◽

Cross Flow ◽

Flux Ratio ◽

Wake Flow ◽

Cfd Modeling ◽

Liquid Jets ◽

Momentum Flux Ratio ◽

Primary Breakup

A numerical model for liquid jet atomization in a subsonic gas cross flow has been developed and incorporated into a CFD code. The model is designed primarily for the shear breakup regime, which is appropriate for many fuel injection applications. The model considers Weber number and momentum flux ratio ranges that are dominated by either jet surface breakup or column breakup. A boundary layer stripping model has been modified to account for both shearing from the column and shear primary breakup of large drops. Further secondary breakup was modeled with the Rayleigh-Taylor model. The effect of drop distortion on the drag is also considered. Results of the model have been compared with experimental data for jet-A liquid jets in air cross flows with varying pressure, air velocity, and liquid-to-gas momentum flux ratio. Comparisons were made for drop volume flux and drop size as a function of distance from the injector wall. Trends were captured for liquid penetration associated with varying momentum flux ratio, and for drop size as a function distance from the wall. In general, agreement between measurements and CFD predictions were quite good. Areas of disagreement could be reasonably explained by the model’s inherent inability to capture the wake flow behind the liquid column.

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Sprays in Cross Flow: Dependence on Weber Number

Volume 2: Turbo Expo 2007 ◽

10.1115/gt2007-27645 ◽

2007 ◽

Cited By ~ 1

Author(s):

Eugene Lubarsky ◽

Jonathan R. Reichel ◽

Ben T. Zinn ◽

Rob McAmis

Keyword(s):

Weber Number ◽

Momentum Flux ◽

Fuel Injection ◽

Flow Direction ◽

Air Flow ◽

Cross Flow ◽

Flux Ratio ◽

Elevated Pressure ◽

Momentum Flux Ratio ◽

Breakup Mechanism

This paper describes an experimental investigation of the spray created by Jet A fuel injection from a plate containing sharp edged orifice 0.018 inches (457 μm) in diameter and L/D ratio of 10 into the crossflow of preheated air (555 K) at elevated pressure in the test section (4 ata) and liquid to air momentum-flux ratio of 40. A 2 component Phase Doppler Particle Analyzer used for measuring the characteristics of the spray. The Weber number of the spray in crossflow was varied between 33 and 2020 and the effect of Weber number on spray properties was investigated. It was seen that shear breakup mechanism dominates at Weber number greater than about 100. Droplets’ diameters were found to be in the range of 15-30 microns for higher values of Weber numbers, while larger droplets (100-200 microns) were observed at Weber number of 33. Larger droplets were observed at the periphery of the spray. The droplet velocities and diameters were measured in a plane 30mm downstream of the orifice along the centerline of the spray at an incoming air flow Mach number of 0.2 and liquid to air momentum-flux ratio of 40. The droplets reach a maximum of 90% of the flow velocity at this location. The velocity of droplets in the directions perpendicular to the air flow direction is higher at the periphery of the spray possibly due to the presence of larger droplets. The RMS values of the droplet velocities are highest slightly off center of the centerline of the spray showing the presence of strong vortices formed due to the liquid jet in crossflow. The data presented here could serve as benchmark data for CFD code validation.

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Liquid Jets in Subsonic Air Crossflow at Elevated Pressure

Volume 4B: Combustion, Fuels and Emissions ◽

10.1115/gt2014-26162 ◽

2014 ◽

Author(s):

Jinkwan Song ◽

Charles Cary Cain ◽

Jong Guen Lee

Keyword(s):

Weber Number ◽

Momentum Flux ◽

Drop Size ◽

Density Ratio ◽

Flux Ratio ◽

Mie Scattering ◽

Air Pressure ◽

Scattering Intensity ◽

Nozzle Orifice ◽

Momentum Flux Ratio

The breakup, penetration, droplet size and size distribution of a Jet A-1 fuel in air crossflow has been investigated with focus given to the impact of surrounding air pressure. Data has been collected by Particle Doppler Phased Analyzer (PDPA), Mie-Scattering with high speed photography augmented by laser sheet, and Mie-Scattering with ICCD Camera augmented by nano-pulse lamp. Nozzle orifice diameter, do, was 0.508 mm and nozzle orifice length to diameter ratio, lo/do, was 5.5. Air crossflow velocities ranged from 29.57 to 137.15 m/s, air pressures from 2.07 to 9.65 bar and temperature held constant at 294.26 K. Fuel flow was governed to provide a range of fuel/air momentum flux ratio q from 5 to 25 and Weber number from 250 to 1000. From the results, adjusted correlation of the mean drop size has been suggested using drop size data measured by PDPA as follows; (1)D0D32=0.267Wea0.44q0.08ρlρa0.30μlμa-0.16This correlation agrees well and shows roles of aerodynamic Weber number, Wea, momentum flux ratio, q, and density ratio, ρl/ρa. Change of the breakup regime map with respect with surrounding air pressure has been observed and revealed that the boundary between each breakup modes can be predicted by a transformed correlation induced from above correlation. In addition, the spray trajectory for the maximum Mie-scattering intensity at each axial location downstream of injector was extracted from averaged Mie-scattering images. From these results correlations with the relevant parameters including q, x/do, density ratio, viscosity ratio, and Weber number are made over a range of conditions. According to spray trajectory at the maximum Mie-scattering intensity, the effect of surrounding air pressure becomes more important in the farfield. On the other hand, effect of aerodynamic Weber number is more important in the nearfield.

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Flow and Temperature Characteristics of a 15° Backward-Inclined Jet Flame in Crossflow

Energies ◽

10.3390/en12010132 ◽

2018 ◽

Vol 12 (1) ◽

pp. 132

Author(s):

Ching Min Hsu ◽

Dickson Bwana Mosiria ◽

Wei Chih Jhan

Keyword(s):

Momentum Flux ◽

Symmetry Plane ◽

Flow Characteristics ◽

Flux Ratio ◽

Mie Scattering ◽

Temperature Fields ◽

Wake Region ◽

Jet Flame ◽

Momentum Flux Ratio ◽

Blue Flame

The flow and flame characteristics of a 15° backward-inclined jet flame in crossflow were investigated in a wind tunnel. The flow structures, flame behaviors, and temperature fields were measured. The jet-to-crossflow momentum flux ratio was less than 7.0. The flow patterns were investigated using photography and Mie-scattering techniques. Meanwhile, the velocity fields were observed using particle image velocimetry techniques, whereas the flame behaviors were studied using photographic techniques. The flame temperatures were probed using a fine-wire R-type thermocouple. Three flame modes were identified: crossflow dominated flames, which were characterized by a blue flame connected to a down-washed yellow recirculation flame; transitional flames identified by a yellow recirculation flame and an elongated yellow tail flame; and detached jet dominated flames denoted by a blue flame base connected to a yellow tail flame. The effect of the flow characteristics on the combustion performance in different flame regimes is presented and discussed. The upwind shear layer of the bent jet exhibited different coherent structures as the jet-to-crossflow momentum flux ratio increased. The transitional flames and detached jet dominated flames presented a double peak temperature distribution in the symmetry plane at x/d = 60. The time-averaged velocity field of the crossflow dominated flames displayed a standing vortex in the wake region, whereas that of the detached jet dominated flames displayed a jet-wake vortex and a wake region source point.

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