scholarly journals Mixing of Multiple Jets With a Confined Subsonic Crossflow in a Cylindrical Duct

1996 ◽  
Author(s):  
James D. Holdeman ◽  
David S. Liscinsky ◽  
G. Scott Samuelsen ◽  
Victor L. Oechsle ◽  
Clifford E. Smith
Keyword(s):  
Mass Flow ◽  
Momentum Flux ◽  
Flux Ratio ◽  
Reacting Flow ◽  
Wall Region ◽  
Ratio Distribution ◽  
Momentum Flux Ratio ◽  
Jet Penetration ◽  
Subsonic Crossflow ◽  
Cylindrical Duct

This paper summarizes NASA-supported experimental and computational results on the mixing of a row of jets with a confined subsonic crossflow in a cylindrical duct. The studies from which these results were excerpted investigated flow and geometric variations typical of the complex 3-D flowfield in the combustion chambers in gas turbine engines. The principal observations were that the momentum-flux ratio and the number of orifices were significant variables. Jet penetration was critical, and jet penetration decreased as either the number of orifices increased or the momentum-flux ratio decreased. It also appeared that jet penetration remained similar with variations in orifice size, shape, spacing, and momentum-flux ratio when the number of orifices was proportional to the square-root of the momentum-flux ratio. In the cylindrical geometry, planar variances are very sensitive to events in the near-wall region, so planar averages must be considered in context with the distributions. The mass-flow ratios and orifices investigated were often very large (mass-flow ratio >1 and ratio of orifice area-to-mainstream cross-sectional area up to 0.5), and the axial planes of interest were sometimes near the orifice trailing edge. Three-dimensional flow was a key part of efficient mixing and was observed for all configurations. The results shown also seem to indicate that non-reacting dimensionless scalar profiles can emulate the reacting flow equivalence ratio distribution reasonably well. The results cited suggest that further study may not necessarily lead to a universal “rule of thumb” for mixer design for lowest emissions, because optimization will likely require an assessment for a specific application.

Mixing of Multiple Jets With a Confined Subsonic Crossflow: Part I—Cylindrical Duct

1997 ◽  
Vol 119 (4) ◽  
pp. 852-862 ◽  
Author(s):  
J. D. Holdeman ◽  
D. S. Liscinsky ◽  
V. L. Oechsle ◽  
G. S. Samuelsen ◽  
C. E. Smith
Keyword(s):  
Mass Flow ◽  
Momentum Flux ◽  
Three Dimensional ◽  
Flux Ratio ◽  
Reacting Flow ◽  
Wall Region ◽  
Momentum Flux Ratio ◽  
Jet Penetration ◽  
Subsonic Crossflow ◽  
Cylindrical Duct

This paper summarizes NASA-supported experimental and computational results on the mixing of a row of jets with a confined subsonic crossflow in a cylindrical duct. The studies from which these results were excerpted investigated flow and geometric variations typical of the complex three-dimensional flowfield in the combustion chambers in gas turbine engines. The principal observations were that the momentum-flux ratio and the number of orifices were significant variables. Jet penetration was critical, and jet penetration decreased as either the number of orifices increased or the momentum-flux ratio decreased. It also appeared that jet penetration remained similar with variations in orifice size, shape, spacing, and momentum-flux ratio when the number of orifices was proportional to the square root of the momentum-flux ratio. In the cylindrical geometry, planar variances are very sensitive to events in the near-wall region, so planar averages must be considered in context with the distributions. The mass-flow ratios and orifices investigated were often very large (mass-flow ratio >1 and ratio of orifice area-to-mainstream cross-sectional area up to 0.5), and the axial planes of interest were sometimes near the orifice trailing edge. Three-dimensional flow was a key part of efficient mixing and was observed for all configurations. The results shown also seem to indicate that nonreacting dimensionless scalar profiles can emulate the reacting flow equivalence ratio distribution reasonably well. The results cited suggest that further study may not necessarily lead to a universal “rule of thumb” for mixer design for lowest emissions, because optimization will likely require an assessment for a specific application.

scholarly journals Mixing of Multiple Jets With a Confined Subsonic Crossflow: Part II — Opposed Rows of Orifices in Rectangular Ducts

1997 ◽  
Author(s):  
James D. Holdeman ◽  
David S. Liscinsky ◽  
Daniel B. Bain
Keyword(s):  
Mass Flow ◽  
Momentum Flux ◽  
Three Dimensional ◽  
Flux Ratio ◽  
Combustion Chambers ◽  
Cross Sectional ◽  
Momentum Flux Ratio ◽  
Jet Penetration ◽  
Geometric Variables ◽  
Subsonic Crossflow

This paper summarizes experimental and computational results on the mixing of opposed rows of jets with a confined subsonic crossflow in rectangular ducts. The studies from which these results were excerpted investigated flow and geometric variations typical of the complex 3-D flowfield in the combustion chambers in gas turbine engines. The principal observation was that the momentum-flux ratio, J, and the orifice spacing, S/H, were the most significant flow and geometric variables. Jet penetration was critical, and penetration decreased as either momentum-flux ratio or orifice spacing decreased. It also appeared that jet penetration remained similar with variations in orifice size, shape, spacing, and momentum-flux ratio when the orifice spacing was inversely proportional to the square-root of the momentum-flux ratio. It was also seen that planar averages must be considered in context with the distributions. Note also that the mass-flow ratios and the orifices investigated were often very large (jet-to-mainstream mass-flow ratio >1 and the ratio of orifices-area-to-mainstream-cross-sectional-area up to 0.5 respectively), and the axial planes of interest were often just downstream of the orifice trailing edge. Three-dimensional flow was a key part of efficient mixing and was observed for all configurations.

Mixing of Multiple Jets With a Confined Subsonic Crossflow: Part II—Opposed Rows of Orifices in Rectangular Ducts

1999 ◽  
Vol 121 (3) ◽  
pp. 551-562 ◽  
Author(s):  
J. D. Holdeman ◽  
D. S. Liscinsky ◽  
D. B. Bain
Keyword(s):  
Mass Flow ◽  
Momentum Flux ◽  
Three Dimensional ◽  
Flux Ratio ◽  
Combustion Chambers ◽  
Cross Sectional ◽  
Momentum Flux Ratio ◽  
Jet Penetration ◽  
Geometric Variables ◽  
Subsonic Crossflow

This paper summarizes experimental and computational results on the mixing of opposed rows of jets with a confined subsonic crossflow in rectangular ducts. The studies from which these results were excerpted investigated flow and geometric variations typical of the complex three-dimensional flowfield in the combustion chambers in gas turbine engines. The principal observation was that the momentum-flux ratio, J, and the orifice spacing, S/H, were the most significant flow and geometric variables. Jet penetration was critical, and penetration decreased as either momentum-flux ratio or orifice spacing decreased. It also appeared that jet penetration remained similar with variations in orifice size, shape, spacing, and momentum-flux ratio when the orifice spacing was inversely proportional to the square-root of the momentum-flux ratio. It was also seen that planar averages must be considered in context with the distributions. Note also that the mass-flow ratios and the orifices investigated were often very large (jet-to-mainstream mass-flow ratio > 1 and the ratio of orifices-area-to-mainstream-cross-sectional-area up to 0.5, respectively), and the axial planes of interest were often just downstream of the orifice trailing edge. Three-dimensional flow was a key part of efficient mixing and was observed for all configurations.

Numerical Study of Turbulent Flow in a Tangentially Injected Swirl Generator

2007 ◽  
Author(s):  
Sandeep Mogili ◽  
Jie Cui
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Momentum Flux ◽  
Numerical Study ◽  
Fixed Ratio ◽  
Flux Ratio ◽  
Reacting Flow ◽  
Momentum Flux Ratio ◽  
Swirl Generator ◽  
Swirl Intensity

The swirl effects in inert and reacting flow systems have been studied for many years. Some processes have appreciated the presence of swirl while some have entitled to curtail the swirl. The swirl intensity is an important parameter in characterizing flows with swirl. In this study, the turbulent flow in a tangentially injected swirl generator was analyzed using commercial CFD software Fluent. The Reynolds numbers considered were 12,500, 15,300, and 30,600 for a fixed ratio of tangential to total momentum flux of 7.84. At Reynolds number 12,500, several cases with various injector configuration and momentum flux ratio were also studied. The numerical results were validated with available experimental data. The results showed that the flow in the generator can be classified into two regions, core and annulus. Reversed flow region was observed in all these cases. The swirl intensity was found to decay exponentially along the axial lengths. The simulations also showed that the swirl intensity was significantly affected by the momentum flux ratio and the Reynolds number.

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.

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