Liquid Jets in Subsonic Air Crossflow at Elevated Pressure

2014 ◽  
Vol 137 (4) ◽  
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.

Liquid Jets in Subsonic Air Crossflow at Elevated Pressure

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.

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

2015 ◽  
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.

Response of Liquid Jet to Modulated Crossflow

2013 ◽  
Author(s):  
Jinkwan Song ◽  
Chandrasekar Ramasubramanian ◽  
Jong Guen Lee
Keyword(s):  
Weber Number ◽  
Momentum Flux ◽  
Flux Ratio ◽  
Mie Scattering ◽  
Liquid Jet ◽  
Atomization Process ◽  
Pixel Intensity ◽  
Spray Transfer ◽  
Momentum Flux Ratio ◽  
Image Velocimetry

Experimental results on the response of spray formed by the liquid (Jet-A) jet injection into a crossflow (Air) is presented with a special emphasis on its response to the modulating crossflow. The pressure of the chamber is up to 3.5 atm and the corresponding Weber number is up to 510. The spray of a liquid jet for steady and oscillating crossflow is characterized. The flow field at the injector location in the crossflow direction is determined using PIV (Particle Image Velocimetry) for oscillating as well as steady crossflow case. Planar Mie-scattering measurement is used to characterize the response of spray formed under oscillating crossflow and supplementary phase-averaged PDPA measurements are used to understand the response behavior. The global response of spray to the oscillating crossflow is characterized using the planar Mie-scattering imaging. It shows that there exist very little differences in the heights of the maximum-pixel intensity trajectory for the non-oscillating and oscillating crossflow conditions and the trajectory under oscillating crossflow is lower than that of steady crossflow, suggesting the oscillating crossflow affects the atomization (i.e. the oscillating crossflow enhances atomization process, results in smaller droplets and penetrates less transversely). The response of spray to the oscillating crossflow characterized in terms of the spray transfer function (STF) shows that the gain of the STF increases linearly (at least monotonically) as the liquid-air momentum flux ratio increases but does not change as much with respect to the change of the Weber number for a fixed liquid-air momentum flux ratio. This also indicates that the liquid jet atomization under oscillating crossflow is enhanced much more with the increase of liquid-air momentum flux ratio than with the increase of Weber number. The phase-averaged PDPA measurements confirm that the oscillating crossflow indeed enhances the atomization process in that the oscillating crossflow results in relatively greater number of smaller droplets and the mean droplet size.

scholarly journals Drop Size Characteristics of Forward Angled Injectors in Subsonic Cross Flows

2013 ◽  
Author(s):  
Venkat S. Iyengar ◽  
Sathiyamoorthy Kumarasamy ◽  
Srinivas Jangam ◽  
Manjunath Pulumathi
Keyword(s):  
Gas Turbine ◽  
Test Section ◽  
Momentum Flux ◽  
Drop Size ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Axial Distance ◽  
Momentum Flux Ratio ◽  
Spray Plume

Cross flow fuel injection is a widely used approach for injecting liquid fuel in gas turbine combustors and afterburners due to the higher penetration and rapid mixing of fuel and the cross flowing airstream. Because of the very limited residence time available in these combustors it is essential to ensure that smaller drop sizes are generated within a short axial distance from the injector in order to promote effective mixing. This requirement calls for detailed investigations into spray characteristics of different injector configurations in a cross-flow environment for identifying promising configurations. The drop size characteristics of a liquid jet issuing from a forward angled injector into a cross-flow of air were investigated experimentally at conditions relevant to gas turbine afterburners. A rig was designed and fabricated to investigate the injection of liquid jet in subsonic cross-flow with a rectangular test section of cross section measuring 50 mm by 70 mm. Experiments were done with a 10 degree forward angled 0.8 mm diameter plain orifice nozzle which was flush mounted on the bottom plate of test section. Laser diffraction using Malvern Spraytec particle analyzer was used to measure drops size and distributions in the near field of the spray. Measurements were performed at a distance of 70 mm from the injector at various locations along the height of the spray plume for a reasonable range of liquid flow rates as in practical devices. The sprays were characterized using the non dimensional parameters such as the Weber number and the momentum flux ratio and drop sizes were measured at three locations along the height of the spray from the bottom wall. The momentum flux ratio was varied from 5 to 25. Results indicate that with increase in momentum flux ratio the SMD reduced at the specific locations and an higher overall SMD was observed as one goes from the bottom to the top of the spray plume. This was accompanied by a narrowing of the drop size distribution.

scholarly journals Theory of Non-Dimensional Groups in Film Effectiveness Studies

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Francesco Ornano ◽  
Thomas Povey
Keyword(s):  
Heat Capacity ◽  
Physical Interpretation ◽  
Film Cooling ◽  
Gas Turbines ◽  
Momentum Flux ◽  
Density Ratio ◽  
Flux Ratio ◽  
Cooling Performance ◽  
Momentum Flux Ratio ◽  
Blowing Ratio

Abstract The desire to improve gas turbines has led to a significant body of research concerning film cooling optimization. The open literature contains many studies considering the impact on film cooling performance of both geometrical factors (hole shape, hole separation, hole inclination, row separation, etc.) and physical influences (effect of density ratio (DR), momentum flux ratio, etc.). Film cooling performance (typically film effectiveness, under either adiabatic or diabatic conditions) is almost universally presented as a function of one or more of three commonly used non-dimensional groups: blowing—or local mass flux—ratio, density ratio, and momentum flux ratio. Despite the abundance of papers in this field, there is some confusion in the literature about the best way of presenting such data. Indeed, the very existence of a discussion on this topic points to lack of clarity. In fact, the three non-dimensional groups in common use (blowing ratio (BR), density ratio, and momentum flux ratio) are not entirely independent of each other making aspects of this discussion rather meaningless, and there is at least one further independent group of significance that is rarely discussed in the literature (specific heat capacity flux ratio). The purpose of this paper is to bring clarity to this issue of correct scaling of film cooling data. We show that the film effectiveness is a function of 11 (additional) non-dimensional groups. Of these, seven can be regarded as boundary conditions for the main flow path and should be matched where complete similarity is required. The remaining four non-dimensional groups relate specifically to the introduction of film cooling. These can be cast in numerous ways, but we show that the following forms allow clear physical interpretation: the momentum flux ratio, the blowing ratio, the temperature ratio (TR), and the heat capacity flux ratio. Two of these parameters are in common use, a third is rarely discussed, and the fourth is not discussed in the literature. To understand the physical mechanisms that lead to each of these groups being independently important for scaling, we isolate the contribution of each to the overall thermal field with a parametric numerical study using 3D Reynolds-averaged Navier–Stokes (RANS) and large eddy simulations (LES). The results and physical interpretation are discussed.

Computational Fluid Dynamics Evaluations of Film Cooling Flow Scaling Between Engine and Experimental Conditions

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
James L. Rutledge ◽  
Marc D. Polanka ◽  
Nathan J. Greiner
Keyword(s):  
Low Temperature ◽  
Film Cooling ◽  
Momentum Flux ◽  
Room Temperature ◽  
Density Ratio ◽  
Flux Ratio ◽  
Experimental Conditions ◽  
Cold Air ◽  
Momentum Flux Ratio ◽  
Adiabatic Effectiveness

The hostile turbine environment requires testing film cooling designs in wind tunnels that allow for appropriate instrumentation and optical access, but at temperatures much lower than in the hot section of an engine. Low-temperature experimental techniques may involve methods to elevate the coolant to freestream density ratio to match or approximately match engine conditions. These methods include the use of CO2 or cold air for the coolant while room temperature air is used for the freestream. However, the density is not the only fluid property to differ between typical wind tunnel experiments so uncertainty remains regarding which of these methods best provide scaled film cooling performance. Furthermore, matching of both the freestream and coolant Reynolds numbers is generally impossible when either mass flux ratio or momentum flux ratio is matched. A computational simulation of a film cooled leading edge geometry at high-temperature engine conditions was conducted to establish a baseline condition to be matched at simulated low-temperature experimental conditions with a 10× scale model. Matching was performed with three common coolants used in low-temperature film cooling experiments—room temperature air, CO2, and cold air. Results indicate that matched momentum flux ratio is the most appropriate for approximating adiabatic effectiveness for the case of room temperature air coolant, but matching the density ratio through either CO2 or cold coolant also has utility. Cold air was particularly beneficial, surpassing the ability of CO2 to match adiabatic effectiveness at the engine condition, even when CO2 perfectly matches the density ratio.

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

2003 ◽  
Vol 125 (4) ◽  
pp. 901-908 ◽  
Author(s):  
J. Becker ◽  
C. Hassa
Keyword(s):  
Momentum Flux ◽  
Liquid Fuel ◽  
Fuel Injection ◽  
Measurement Techniques ◽  
Flux Ratio ◽  
Mie Scattering ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Flow Measurements ◽  
Momentum Flux Ratio

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.

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

2002 ◽  
Author(s):  
Julian Becker ◽  
Christoph Hassa
Keyword(s):  
Momentum Flux ◽  
Liquid Fuel ◽  
Fuel Injection ◽  
Measurement Techniques ◽  
Flux Ratio ◽  
Mie Scattering ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Flow Measurements ◽  
Momentum Flux Ratio

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.

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

2004 ◽  
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.

Sprays in Cross Flow: Dependence on Weber Number

2007 ◽  
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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