CRITICAL EVALUATION OF MOMENTUM FLUX RATIO RELATIVE TO A LIQUID JET IN CROSSFLOW

2018 ◽  
Vol 28 (7) ◽  
pp. 599-620 ◽  
Author(s):  
Scott B. Leask ◽  
Vincent G. McDonell ◽  
Scott Samuelsen
Keyword(s):  
Momentum Flux ◽  
Critical Evaluation ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Momentum Flux Ratio ◽  
Jet In Crossflow

Volumetric Velocimetry Measurements of Film Cooling Jets

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Artur Joao Carvalho Figueiredo ◽  
Robin Jones ◽  
Oliver J. Pountney ◽  
James A. Scobie ◽  
Gary D. Lock ◽  
...  
Keyword(s):  
Film Cooling ◽  
Momentum Flux ◽  
Three Dimensional ◽  
Flux Ratio ◽  
Quality Data ◽  
Data Set ◽  
Momentum Flux Ratio ◽  
Jet In Crossflow ◽  
Lift Off ◽  
Induced Velocity

This paper presents volumetric velocimetry (VV) measurements for a jet in crossflow that is representative of film cooling. VV employs particle tracking to nonintrusively extract all three components of velocity in a three-dimensional volume. This is its first use in a film-cooling context. The primary research objective was to develop this novel measurement technique for turbomachinery applications, while collecting a high-quality data set that can improve the understanding of the flow structure of the cooling jet. A new facility was designed and manufactured for this study with emphasis on optical access and controlled boundary conditions. For a range of momentum flux ratios from 0.65 to 6.5, the measurements clearly show the penetration of the cooling jet into the freestream, the formation of kidney-shaped vortices, and entrainment of main flow into the jet. The results are compared to published studies using different experimental techniques, with good agreement. Further quantitative analysis of the location of the kidney vortices demonstrates their lift off from the wall and increasing lateral separation with increasing momentum flux ratio. The lateral divergence correlates very well with the self-induced velocity created by the wall–vortex interaction. Circulation measurements quantify the initial roll up and decay of the kidney vortices and show that the point of maximum circulation moves downstream with increasing momentum flux ratio. The potential for nonintrusive VV measurements in turbomachinery flow has been clearly demonstrated.

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.

Optimization of Multiple Jets Mixing With a Confined Crossflow

1997 ◽  
Vol 119 (2) ◽  
pp. 315-321 ◽  
Author(s):  
Th. Doerr ◽  
M. Blomeyer ◽  
D. K. Hennecke
Keyword(s):  
Temperature Distribution ◽  
Momentum Flux ◽  
Flux Ratio ◽  
Mixing Process ◽  
Mixing Rate ◽  
Mixing Processes ◽  
Jet Mixing ◽  
Momentum Flux Ratio ◽  
Jet In Crossflow ◽  
Geometric Conditions

An experimental investigation of a nonreacting multiple jet mixing with a confined crossflow has been conducted. Flow and geometric conditions were varied in order to examine favorable parameters for mixing. The requirement for a rapid and intense mixing process originates from combustion applications, especially the RQL-combustion concept. Thus, the jets were perpendicularly injected out of one opposed row of circular orifices into a heated crossflow in a rectangular duct. Spacing and hole size were varied within the ranges referring to combustor applications. The results presented are restricted to an in-line orientation of opposed jet axis. Temperature distribution, mixing rate, and standard deviation were determined at discrete downstream locations. Best, i.e., uniform mixing can be observed strongly depending on momentum flux ratio. For all geometries investigated, an optimum momentum flux ratio yields to a homogeneous temperature distribution in the flow field downstream of the injection plane. Overly high ratios deteriorate the mixing process due to the mutual impact of the opposed entraining jets along with a thermal stratification of the flowfield. Correlations are introduced describing the dependency of optimum momentum flux ratio on mixing hole geometry. They allow the optimization of jet-in-crossflow mixing processes in respect to uniform mixing.

Optimization of Multiple Jets Mixing With a Confined Crossflow

1995 ◽  
Author(s):  
Th. Doerr ◽  
M. Blomeyer ◽  
D. K. Hennecke
Keyword(s):  
Temperature Distribution ◽  
Momentum Flux ◽  
Flux Ratio ◽  
Mixing Process ◽  
Mixing Rate ◽  
Mixing Processes ◽  
Jet Mixing ◽  
Momentum Flux Ratio ◽  
Jet In Crossflow ◽  
Geometric Conditions

An experimental investigation of a non-reacting multiple jet mixing with a confined crossflow has been conducted. Flow and geometric conditions were varied in order to examine favourable parameters for mixing. The requirement for a rapid and intense mixing process originates from combustion applications, especially the RQL-combustion concept. Thus, the jets were perpendicularly injected out of one opposed row of circular orifices into a heated crossflow in a rectangular duct. Spacing and hole size were varied within the ranges referring to combustor applications. The results presented are restricted to an inline orientation of opposed jet axis. Temperature distribution, mixing rate and standard deviation were determined at discrete downstream locations. Best i.e. uniform mixing can be observed strongly depending on momentum flux ratio. For all geometries investigated an optimum momentum flux ratio yields to a homogeneous temperature distribution in the flowfield downstream of the injection plane. Too high ratios deteriorate the mixing process due to the mutual impact of the opposed entraining jets along with a thermal stratification of the flowfield. Correlations are introduced describing the dependency of optimum momentum flux ratio on mixing hole geometry. They allow the optimization of jet-in-crossflow mixing processes in respect to uniform mixing.

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.

Volumetric Velocimetry Measurements of Film Cooling Jets

2018 ◽  
Author(s):  
Artur Joao Carvalho Figueiredo ◽  
Robin Jones ◽  
Oliver J. Pountney ◽  
James A. Scobie ◽  
Gary D. Lock ◽  
...  
Keyword(s):  
Film Cooling ◽  
Momentum Flux ◽  
Three Dimensional ◽  
Flux Ratio ◽  
Quality Data ◽  
Data Set ◽  
Momentum Flux Ratio ◽  
Jet In Crossflow ◽  
Lift Off ◽  
Induced Velocity

This paper presents Volumetric Velocimetry (VV) measurements for a jet in crossflow that is representative of film cooling. Volumetric velocimetry employs particle tracking to non-intrusively extract all three components of velocity in a three-dimensional volume. This is its first use in a film-cooling context. The primary research objective was to develop this novel measurement technique for turbomachinery applications, whilst collecting a high-quality data set that can improve the understanding of the flow structure of the cooling jet. A new facility was designed and manufactured for this study with emphasis on optical access and controlled boundary conditions. For a range of momentum flux ratios from 0.65 to 6.5 the measurements clearly show the penetration of the cooling jet into the freestream, the formation of kidney-shaped vortices and entrainment of main flow into the jet. The results are compared to published studies using different experimental techniques, with good agreement. Further quantitative analysis of the location of the kidney vortices demonstrates their lift off from the wall and increasing lateral separation with increasing momentum flux ratio. The lateral divergence correlates very well with the self-induced velocity created by the wall-vortex interaction. Circulation measurements quantify the initial roll up and decay of the kidney vortices and show that the point of maximum circulation moves downstream with increasing momentum flux ratio. The potential for non-intrusive volumetric velocimetry measurements in turbomachinery flow has been clearly demonstrated.

Trajectory of a Liquid Jet in a High Temperature and Pressure Gaseous Cross Flow

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Amirreza Amighi ◽  
Nasser Ashgriz
Keyword(s):  
Momentum Flux ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Momentum Flux Ratio ◽  
Flow Parameters ◽  
System A ◽  
Air Temperatures ◽  
Jet Trajectory ◽  
Temperature And Pressure

An experimental study of liquid jet injection into subsonic air crossflow is presented. The aim of this study was to relate the jet trajectory to flow parameters, including jet and air velocities, pressure and temperature, as well as a set of nondimensional variables. For this purpose, an experimental setup was developed, which could withstand high temperatures and pressures. Images were captured using a laser-based shadowgraphy system. A total of 209 different conditions were tested and over 72,000 images were captured and processed. The crossflow air temperatures were 25 °C, 200 °C, and 300 °C; absolute crossflow air pressures were 2.1, 3.8, and 5.2 bars, and various liquid and gas velocities were tested for each given temperature and pressure. The results indicate that the trajectory and atomization change when the air and jet velocities are changed while keeping the momentum flux ratio constant. Therefore, it is beneficial to describe the trajectory based on air and jet Weber numbers or momentum flux ratio in combination with one of the Weber numbers. Also, examples are given where both Weber numbers are kept constant but the atomization is changed, and therefore, other terms beyond inertia terms are required to describe the spray behavior. It is also shown that the gas viscosity has to be considered when developing correlations. The correlations that include this term are generally better in predicting the trajectory. Therefore, Ohnesorge numbers in combination with the Weber numbers is used in the present correlations to describe the trajectories.

Liquid Jet in Crossflow: Effect of Momentum Flux Ratio on Spray and Vaporization Characteristics

2019 ◽  
Author(s):  
Manu Kamin ◽  
Prashant Khare
Keyword(s):  
Gas Phase ◽  
Momentum Flux ◽  
High Speed ◽  
Bluff Body ◽  
Elevated Temperatures ◽  
Three Dimensional ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Momentum Flux Ratio ◽  
Droplet Distribution

Abstract A comprehensive study is conducted to identify the effects of momentum flux ratio on the spray and vaporization characteristics of liquid jet injected in air crossflow at elevated temperatures, a configuration relevant to high-speed propulsion systems, such as ramjets and afterburners. The physical setup consists of a straight chamber with a triangular bluff body down-stream of the liquid injection location. The numerical simulations are based on an Eulerian-Lagrangian framework, where the gas phase flow behaviors such as recirculation zones, turbulence statistics, mixing of vaporized liquid and gas streams are resolved by solving the complete set of three-dimensional conservation equations of mass, momentum, energy and species, and the liquid phase is treated using the blob approach and tracked in a Lagrangian coordinate system. Turbulence closure is achieved using Large Eddy Simulation (LES) technique. Primary breakup of the liquid jet is simulated using the K-H wave breakup model, and the Taylor Analogy Breakup (TAB) model is used for secondary breakup. Two-way coupling between the liquid and gas phases is implemented in the LES framework to systematically model the exchange of mass, momentum and energy between the two phases. The formulation is validated against experimental measurements of liquid jet penetration and sauter mean diameter for a Weber number of 68 and momentum flux ratio of 9 at two temperatures, 298K and 573K. Results show excellent agreement with measurements for both cases. Next, simulations are conducted for a range of momentum flux ratios from 10–140 to identify the detailed gas and spray fields for vaporizing flow cases. This study helps to estimate the penetration of the liquid jet, droplet distribution, and then, location of the core of evaporated liquid in the gas-phase are quantitatively identified.

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.

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