LES of Jets and Sprays Injected into Crossflow
(2006) Abstract
 The objective of this thesis is to numerically simulate a fluid jet injected into a crossflow of the same or another fluid, respectively. Such flows are encountered in many engineering applications in which cooling or mixing plays an important role, e.g. gas turbine combustors. The jet in crossflow (JICF) is used both for cooling and for injecting liquid fuel into the air stream prior to combustion. The numerical simulations regard three space dimensions and track also the flow dynamics by integrating the governing equations in time. The spatial and the temporal resolution are such that the largescale flow structures are resolved. Such an approach is referred to as large eddy simulations (LES). The motion of the fuel droplets is treated... (More)
 The objective of this thesis is to numerically simulate a fluid jet injected into a crossflow of the same or another fluid, respectively. Such flows are encountered in many engineering applications in which cooling or mixing plays an important role, e.g. gas turbine combustors. The jet in crossflow (JICF) is used both for cooling and for injecting liquid fuel into the air stream prior to combustion. The numerical simulations regard three space dimensions and track also the flow dynamics by integrating the governing equations in time. The spatial and the temporal resolution are such that the largescale flow structures are resolved. Such an approach is referred to as large eddy simulations (LES). The motion of the fuel droplets is treated by Lagrangian particle tracking (LPT) with the stochastic parcel method, along with submodels for evaporation, collision, breakup, and a novel submodel for aerodynamic fourway coupling: The particle drag is corrected depending on relative positions of the particles. Mixture fraction and temperature transport equations are solved to enable the modeling of droplet evaporation and the mixing of the gaseous fuel with ambient air.
In the simulations of multiphase JICF, several computed results are shown to be inconsistent with the underlying assumptions of the LPT approach: The magnitude of the Weber numbers indicates that droplets are not spherical in large portions of the flow field in wide ranges of parameters which are relevant for gas turbine operation. The magnitude of the droplet spacing suggests that aerodynamic interaction (indirect fourway coupling) among droplets may be important. The LES with aerodynamic fourway coupling reveals significant effects compared to twoway coupling for monodisperse particles in a dense multiphase flow.
For singlephase JICF, the impact of nozzle shape on the largescale coherent structures and the mixing is studied. Effects of circular, square, and elliptic nozzles and their orientation are considered. It is demonstrated that square and elliptic nozzles with blunt orientation raise turbulence levels significantly. The scalar distribution in a crosssectional plane is found to be singlepeaked for these nozzles whereas circular and the nozzles with pointed orientation show doublepeaked scalar distribution. It is the nozzles with a singlepeaked distribution which are the better mixers.
The differences and similarities of single and multiphase JICF are compared, and it is demonstrated that the flow field solution for multiphase flow approaches the flow field solution of singlephase flow in the limit of small Stokes numbers. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/547458
 author
 Salewski, Mirko ^{LU}
 supervisor

 Laszlo Fuchs ^{LU}
 opponent

 Prof. Dr.Ing. habil. Sommerfeld, Martin, MartinLutherUniversity HalleWittenberg, Germany
 organization
 publishing date
 2006
 type
 Thesis
 publication status
 published
 subject
 keywords
 Gaser, fluid dynamics, large eddy simulation, spray, plasmas, Gases, lagrangian particle tracking, jet in crossflow, fluiddynamik, plasma
 pages
 100 pages
 publisher
 Lund Institute of Technology
 defense location
 Room M:E, Mbuilding, Ole Römers väg 1, Lund Institute of Technology
 defense date
 20061128 10:15:00
 external identifiers

 other:ISRN:LUTMDN/TMHP06/1046SE
 ISBN
 9789162869670
 language
 English
 LU publication?
 yes
 id
 55048c64f515465883ce81f79da3354e (old id 547458)
 date added to LUP
 20160401 15:23:45
 date last changed
 20181121 20:34:13
@phdthesis{55048c64f515465883ce81f79da3354e, abstract = {The objective of this thesis is to numerically simulate a fluid jet injected into a crossflow of the same or another fluid, respectively. Such flows are encountered in many engineering applications in which cooling or mixing plays an important role, e.g. gas turbine combustors. The jet in crossflow (JICF) is used both for cooling and for injecting liquid fuel into the air stream prior to combustion. The numerical simulations regard three space dimensions and track also the flow dynamics by integrating the governing equations in time. The spatial and the temporal resolution are such that the largescale flow structures are resolved. Such an approach is referred to as large eddy simulations (LES). The motion of the fuel droplets is treated by Lagrangian particle tracking (LPT) with the stochastic parcel method, along with submodels for evaporation, collision, breakup, and a novel submodel for aerodynamic fourway coupling: The particle drag is corrected depending on relative positions of the particles. Mixture fraction and temperature transport equations are solved to enable the modeling of droplet evaporation and the mixing of the gaseous fuel with ambient air.<br/><br> <br/><br> In the simulations of multiphase JICF, several computed results are shown to be inconsistent with the underlying assumptions of the LPT approach: The magnitude of the Weber numbers indicates that droplets are not spherical in large portions of the flow field in wide ranges of parameters which are relevant for gas turbine operation. The magnitude of the droplet spacing suggests that aerodynamic interaction (indirect fourway coupling) among droplets may be important. The LES with aerodynamic fourway coupling reveals significant effects compared to twoway coupling for monodisperse particles in a dense multiphase flow.<br/><br> <br/><br> For singlephase JICF, the impact of nozzle shape on the largescale coherent structures and the mixing is studied. Effects of circular, square, and elliptic nozzles and their orientation are considered. It is demonstrated that square and elliptic nozzles with blunt orientation raise turbulence levels significantly. The scalar distribution in a crosssectional plane is found to be singlepeaked for these nozzles whereas circular and the nozzles with pointed orientation show doublepeaked scalar distribution. It is the nozzles with a singlepeaked distribution which are the better mixers.<br/><br> <br/><br> The differences and similarities of single and multiphase JICF are compared, and it is demonstrated that the flow field solution for multiphase flow approaches the flow field solution of singlephase flow in the limit of small Stokes numbers.}, author = {Salewski, Mirko}, isbn = {9789162869670}, language = {eng}, publisher = {Lund Institute of Technology}, school = {Lund University}, title = {LES of Jets and Sprays Injected into Crossflow}, url = {https://lup.lub.lu.se/search/files/4383045/547459.pdf}, year = {2006}, }