Numerical and Experimental Study on Jet Trajectories and Mixing Behavior of Venturi-Jet Mixer

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
S. Sundararaj ◽  
V. Selladurai
Keyword(s):  
Cross Flow ◽  
Mixing Efficiency ◽  
Axial Distance ◽  
Injection Angle ◽  
Jet Mixing ◽  
Initial Injection ◽  
Negative Root ◽  
Mixing Behavior ◽  
Mean Concentration ◽  
Insight Into

An investigation of the jet trajectories and mixing behavior of venturi-jet mixers, in which turbulent jet injects fluid at an arbitrary angle to mix incompressible fluids, is described in this paper. Numerical results of an incompressible cross flow-jet mixing in venturi-jet mixers are presented and validated against experimental results. Jet trajectories, concentration decay of tracer jet, spatial unmixedness, and mixing length are computed for a range of injection angles (45 deg≤θo≤135 deg). Twenty-five cases are studied with five different initial injection angles, each with five different jet momentum ratios. As an example of practical insights that can be gained from such detailed analysis, the resulting flow field is used to obtain an equation for trajectory and tracer concentration in the mixer. The penetration of jet scales with the third root of the jet-to-mainstream momentum ratio and that of with square root of downstream distance. The decay of mean concentration scales with the inverse of axial distance and with the negative root of injection angle. The results show a consistency in the experimental data and simulation has provided a good insight into the flow details and has paved the way in optimization of the geometry based on jet injection angle to get a good mixing efficiency.

Vortex modeling of single and multiple dilution jet mixing in a cross flow

1986 ◽  
Vol 2 (4) ◽  
pp. 354-360 ◽  
Author(s):  
A. R. Karagozian ◽  
T. T. Nguyen ◽  
C. N. Kim
Keyword(s):  
Cross Flow ◽  
Jet Mixing

Investigation of Circular and Shaped Effusion Cooling Arrays for Combustor Liner Application—Part 2: Numerical Analysis

2009 ◽  
Author(s):  
A. Andreini ◽  
C. Bianchini ◽  
A. Ceccherini ◽  
B. Facchini ◽  
L. Mangani ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Cross Flow ◽  
Lateral Spreading ◽  
Elliptical Cross ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Combustor Liner ◽  
Effectiveness Data ◽  
Overall Effectiveness ◽  
Good Agreement

A numerical analysis of two different effusion cooled plates, with a feasible arrangement for combustor liner application, is presented in this paper. Though having the same porosity and very shallow injection angle (17°), the first configuration presents a “conventional” circular drilling, while the other has “shaped” holes with such an elliptical cross-section that leads to a circular imprint on the cooled surface. Either geometries were the object of an experimental survey in which both adiabatic and overall effectiveness were measured. In order to compensate for the lack of detailed aerodynamic measurements, 3D CFD computations were performed for the two geometries. Steady state RANS calculations were carried out using a k–ε Two Layer turbulence model, both in the standard isotropic and in an algebraically corrected non isotropic version specifically tuned to better predict the lateral spreading of jets in a cross flow. Flow characteristic reproduce typical effusion cooled combustor liner conditions with blowing ratio of 5 and coolant jet Reynolds number of 12500. Even though good agreement could not be obtained comparing thermal adiabatic effectiveness with experiments, the findings of the experiments regarding the rating of the cooling efficiency of the two configurations were confirmed. Additionally, conjugate simulations were performed for the circular hole geometry in order to quantify heat transfer effects and to directly compare them with raw experimental overall effectiveness data.

Estimation of the Time Delay Associated With Damping Controlled Fluidelastic Instability in a Normal Triangular Tube Array

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
John Mahon ◽  
Craig Meskell
Keyword(s):  
Time Delay ◽  
Cross Flow ◽  
Fluid Forces ◽  
Fluidelastic Instability ◽  
Order Of Magnitude ◽  
Sample Frequency ◽  
Pitch Ratio ◽  
Parameterized Model ◽  
Semi Empirical ◽  
Insight Into

Fluidelastic instability (FEI) produces large amplitude self-excited vibrations close to the natural frequency of the structure. For fluidelastic instability caused by the damping controlled mechanism, there is a time delay between tube motion and the resulting fluid forces but magnitude and physical cause of this is unclear. This study measures the time delay between tube motion and the resulting fluid forces in a normal triangular tube array with a pitch ratio of 1.32 subject to air cross-flow. The instrumented cylinder was forced to oscillate in the lift direction at three excitation frequencies for a range of flow velocities. Unsteady surface pressures were monitored with a sample frequency of 2 kHz at the mid plane of the instrumented cylinder. The instantaneous fluid forces were obtained by integrating the surface pressure data. A time delay between the tube motion and resulting fluid forces was obtained. The nondimensionalized time delay was of the same order of magnitude assumed in the semi-empirical quasi-steady model (i.e., τ2 = 0.29 d/U). Although, further work is required to provide a parameterized model of the time delay which can be embedded in a model of damping controlled fluidelastic forces, the data already provides some insight into the physical mechanism responsible.

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.

Investigation of the Magnus Effect of a Generic Projectile at Mach 3 Up to 16 Degrees Angle of Attack

2013 ◽  
Vol 80 (3) ◽  
Author(s):  
D. Klatt ◽  
R. Hruschka ◽  
F. Leopold
Keyword(s):  
Angle Of Attack ◽  
Cross Flow ◽  
Primary Source ◽  
Nonlinear Dependence ◽  
Navier Stokes ◽  
Side Force ◽  
Magnus Effect ◽  
Mach 3 ◽  
Secondary Vortices ◽  
Insight Into

The Magnus effect on a generic 6.37 diameter long tangential-ogive-cylinder type projectile was studied by means of 3D Reynolds-averaged Navier–Stokes (RANS) simulations and wind tunnel measurements. The nominal Mach number was 3 and the Reynolds number, based on the model length, was 1.09 × 107. The simulations provided a profound insight into the flow structure and revealed a shift of the cross-flow separation lines as a consequence of the spin. This was shown to be the primary source of the Magnus side force for the higher angles of attack in the investigated range. The nonlinear dependence of the Magnus side force on the angle of attack was analyzed and reached a maximum value between 10 and 15 deg before decreasing again. The occurrence of secondary vortices in this range of angles of attack is presented as an explanation for a locally negative Magnus side force portion acting on the model.

scholarly journals Static and Dynamic Experimental Analysis of the Galloping Stability of Porous H-Section Beams

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
F. Gandia ◽  
J. Meseguer ◽  
A. Sanz-Andrés
Keyword(s):  
Cross Flow ◽  
Industrial Applications ◽  
Geometrical Parameters ◽  
Smoke Visualization ◽  
Surface Pressure Distribution ◽  
Prismatic Beam ◽  
Visualization Techniques ◽  
Limiting Case ◽  
Static Criterion ◽  
Insight Into

The phenomenon of self-induced vibrations of prismatic beams in a cross-flow has been studied for decades, but it is still of great interest due to their important effects in many different industrial applications. This paper presents the experimental study developed on a prismatic beam with H-section. The aim of this analysis is to add some additional insight into the behaviour of the flow around this type of bodies, in order to reduce galloping and even to avoid it. The influence of some relevant geometrical parameters that define the H-section on the translational galloping behaviour of these beams has been analysed. Wind loads coefficients have been measured through static wind tunnel tests and the Den Hartog criterion applied to elucidate the influence of geometrical parameters on the galloping properties of the bodies under consideration. These results have been completed with surface pressure distribution measurements and, besides, dynamic tests have been also performed to verify the static criterion. Finally, the morphology of the flow past the tested bodies has been visualised by using smoke visualization techniques. Since the rectangular section beam is a limiting case of the H-section configuration, the results here obtained are compared with the ones published in the literature concerning rectangular configurations; the agreement is satisfactory.

scholarly journals Conjugate Heat Transfer CFD Predictions of Impingement Jet Array Flat Wall Cooling Aerodynamics With Single Sided Flow Exit

2013 ◽  
Author(s):  
Abubakar M. El-Jummah ◽  
Gordon E. Andrews ◽  
John E. J. Staggs
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Conjugate Heat Transfer ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Significant Feature ◽  
Axial Distance ◽  
Impingement Jet ◽  
The Cross

Conjugate heat transfer CFD studies were undertaken on impingement square jet arrays with self induced crossflow in the impingement gap with a single sided exit. The aim was to understand the aerodynamic interactions that result in the deterioration of heat transfer with axial distance, whereas the addition of duct flow heat transfer would be expected to lead to an increase in heat transfer with axial distance. A square array of impingement holes was investigated for a common geometry investigated experimentally, pitch to diameter ratio X/D of 5 and impingement gap to diameter ratio Z/D of 3.3 for 11 rows of holes in the crossflow direction. A metal duct wall was used as the impingement surface with an applied heat flux of 100kW/m2, which for a gas turbine combustor cooling application operating at steady state with a temperature difference of ∼450K corresponds to a convective heat transfer coefficient of ∼200 W/m2K. A key feature of the predicted aerodynamics was recirculation in the plane of the impingement jets normal to the cross-flow, which produced heating of the impingement jet wall. This reverse flow jet was deflected by the cross flow which had its peak velocity in the plane between the high velocity impingement jets. The cross-flow interaction with the impingement jets reduced the interaction between the jets on the surface, with lower surface turbulence as a result and this reduced the surface convective heat transfer. A significant feature of the predictions was the interaction of the cross-flow aerodynamics with the impingement jet wall and associated heat transfer to that wall. The results showed that the deterioration in heat transfer with axial distance was well predicted, together with predictions of the impingement wall surface temperature gradients.

Structure of Turbulent Flow in Subchannel of Rod Bundle Downstream of Spacer Grid With Hybrid Flow Mixing Device

2002 ◽  
Author(s):  
Dong Seok Oh ◽  
Wang Kee In ◽  
Tae Hyun Chun
Keyword(s):  
Rectangular Channel ◽  
Cross Flow ◽  
Mixing Efficiency ◽  
Lateral Velocity ◽  
Spacer Grid ◽  
Turbulent Diffusion Coefficient ◽  
Rod Bundle ◽  
Flow Mixing ◽  
A Cell ◽  
Rod Array

An experiment was performed in a wind tunnel to investigate the flow structure in a rod bundle with a hybrid vane grid. The hybrid vane is a flow-mixing device, which consists of two pairs of primary and secondary vanes in a cell. The test section is a rectangular channel (300 mm × 300 mm × 2400 mm) including 3 × 3 rod (75 mm diameter) array with a spacer grid. The pitch to diameter ratio of the rod array is 1.33. The flow structures downstream the grid are measured at Reynolds number of 1.2 × 105 for 35-degree deflecting angle of the hybrid flow-mixing vane. The data are obtained for the distributions of the time mean axial velocity, lateral velocity, and turbulent intensities in 3 component directions over a center subchannel along axial locations and compared with the previous results of split vane grid that has two vanes in a cell. The results show that the mixing efficiency of the hybrid vane grid could be similar with that of the split vane grid because swirl factor of the hybrid vane grid is higher than that of split vane grid and the magnitude of axial turbulent intensity, turbulent diffusion coefficient, and cross flow factor is similar to each other in spite of differences of the vane numbers and shape in a cell between hybrid and split vane grids.

Inclined Injection of Under Expanded Supersonic Gas Jet

2019 ◽  
Author(s):  
A. M. Sheridan ◽  
S. Srivastava ◽  
M. Henneke ◽  
M. S. Raza ◽  
K. A. Sallam
Keyword(s):  
Interaction Mechanism ◽  
Ambient Air ◽  
Industrial Applications ◽  
Gas Jet ◽  
Injection Angle ◽  
Jet Mixing ◽  
Flow Vorticity ◽  
Nd:Yag Lasers ◽  
Image Velocimetry ◽  
Oxide Particles

Abstract The injection of choked gaseous jets into the still air is investigated experimentally motivated by many industrial applications including flares and burners. The objective is to study the effect of injection angle on the jet mixing with ambient air. The experimental methods consist of particle image velocimetry (PIV) using pulsed Nd:YAG lasers of a choked gas jet, seeded with aluminum oxide particles, injected into still air, seeded with water fog. The computational methods consisted of 7.7 million cells simulation using Star CCM+. The test conditions include injection angles of 0°, 15°, and 30°. The results including mean and fluctuating velocities and the flow vorticity are presented. The flow field is not symmetric along the injection axis due to the asymmetric triggering of expansion fans at the jet exit due to the inclined injection plane. Moreover, the numerical simulation reveals the complex interaction mechanism of the expansion fans and shockwaves within the injection port.

Modulation of a Liquid-Fuel Jet in an Unsteady Cross-Flow

2001 ◽  
Author(s):  
Torger J. Anderson ◽  
William Proscia ◽  
Jeffrey M. Cohen
Keyword(s):  
Cross Flow ◽  
Flow Modulation ◽  
Jet Mixing ◽  
Physical Mechanisms ◽  
Fuel Flow ◽  
Fuel Jet ◽  
Spray Density ◽  
Jet Behavior ◽  
Unique Method ◽  
Spray Distribution

This paper describes an experimental study of a fuel jet in an unsteady cross flow as part of a program to evaluate active control of combustion instabilities that involve acoustic / spray coupling. The results provide insights into the different physical mechanisms through which the jet and cross flow interact and the degree to which acoustic velocity fluctuations modulate liquid jet mixing, penetration and spray distribution. They also provide a means of evaluating the effectiveness of fuel flow modulation for controlling fuel jet behavior, demonstrating that fluctuations in the downstream spray distribution can be significantly reduced by phased fuel flow modulation. The paper describes a unique method for modulating the fuel and a relatively simple diagnostic for evaluating the fuel spray density and uniformity.

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