Turbulent mixing flow characteristics of solid-cone type diesel spray

2002 ◽  
Vol 16 (8) ◽  
pp. 1135-1143 ◽  
Author(s):  
Jeekuen Lee ◽  
Shinjae Kang ◽  
Byoungjoon Rho
Keyword(s):  
Turbulent Mixing ◽  
Flow Characteristics ◽  
Diesel Spray ◽  
Solid Cone ◽  
Cone Type

A Computational Study on the Effect of Angles of Attack on a Double-Cone Type Supersonic Inlet With Bleeding System

2010 ◽  
Author(s):  
Kyung Jin Ryu ◽  
Seol Lim ◽  
Sang Dug Kim ◽  
Dong Joo Song
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Computational Study ◽  
Angle Of Attack ◽  
Flow Characteristics ◽  
Uniform Flow ◽  
Double Cone ◽  
Interface Plane ◽  
Supersonic Inlet ◽  
Cone Type

The flow characteristics on a supersonic inlet with bleeding system at various angles of attack are studied by using computational 3D turbulent flow analysis. A turbulent CSCM compressible upwind flux difference splitting Navier-Stokes method with k-w turbulence model is used to compute the inlet flowfields. MPICH-2.0 library and PC-cluster system are used to reduce computational times. Distortion and average of total pressure recovery at the AIP (aerodynamic interface plane) are used as evaluation criteria of inlet performance. The flow characteristics at zero of angle of attack of double-cone type supersonic inlet without and with bleeding system have been compared. Without bleeding system inlet with the strong SBLI (shock/boundary-layer interaction) induces slow flow recovery near the throat and produces very thick boundary layer downstream. But the bleeding system successfully removes the low energy flow from the boundary layer near the throat. As the angle of attack at the AIP because large, we can see more non-uniform flow field, and the non-uniform flow field is the major aggravating factor of inlet performance.

scholarly journals Fluid Flow Characteristics of a Co-Flow Fluidic Slot Jet Thrust Augmentation Propulsion System

2020 ◽  
Author(s):  
Brian Garrett ◽  
Kareem Ahmed
Keyword(s):  
Fluid Flow ◽  
Turbulent Mixing ◽  
High Speed ◽  
High Performance ◽  
Flow Characteristics ◽  
Propulsion System ◽  
Secondary Flows ◽  
High Momentum ◽  
Cross Sectional ◽  
Bulk Fluid

Abstract The UAV industry is booming with investments in research and development on improving UAV systems. Current UAV machines are developed according to the quadcopter design which consists of a rotary propulsion system providing lift needed for flight. This design has some flaws; namely safety concerns and noise/vibration production both of which come stem from the rotary propulsion system. As such, a novel propulsion system using slip stream air passed through high performance slot jets is proposed and an analysis of the fluid characteristics is presented in this report. The test section for the experiment is developed using 3D printed ABS plastic airfoils modified with internal cavities where pressurized air is introduced and then expelled through slot jets on the pressure side of the airfoils. Entrainment processes develop in the system through high momentum fluid introduction into a sedentary secondary fluid. Entrainment is governed by pressure gradients and turbulent mixing and so turbulent quantities that measure these processes are extracted and analyzed according to the independent variable’s effects on these quantities. Pitot probe testing extracted one dimensional fluid information and PIV analysis is used to characterize the two-dimensional flow aspects. High slot jet velocities are seen to develop flows dominated by convection pushing momentum mixing downstream reducing the mixing in the system while low slot jet speeds exhibit higher mass fluxes and thrust development. Confinement spacing is seen to cause a decrease in flow velocity and thrust as the spacing is decreased for high speed runs. The most constricted cross sectional runs showed high momentum mixing and developed combined self-similar flow through higher boundary layer interactions and pressures, but this also hurts thrust development by minimizing secondary flows. The Angle of Attack of the assembly proved to be the most important variable. Outward angling showed the influence of coanda effects but also demonstrated the highest bulk fluid flow with turbulence driven momentum mixing. Inward angling created combined fluid flow downstream with high momentum mixing upstream driven by pressure. Minimal mixing is seen when the airfoils are not angled, and high recirculation zones occur along the boundaries. The optimal setup is seen when the airfoils are angled outwards where the highest thrust and bulk fluid movement is developed driven by the turbulent mixing induced by the increasing cross sectional area of the system.

scholarly journals Turbulent mixing and reacting flow characteristics of axisymmetric bluff-body stabilized propane-air flames, under inlet mixture stratification and preheat

2019 ◽  
Author(s):  
Κωνσταντίνος Σούφλας
Keyword(s):  
Turbulent Mixing ◽  
Bluff Body ◽  
Flow Characteristics ◽  
Reacting Flow ◽  
Ft Ir

Στην παρούσα εργασία μελετήθηκαν και αναλύθηκαν τα ισόθερμα και αντιδρώντα, χρονικά μέσα και διακυμαινόμενα, πεδία ροής καθώς και τα χαρακτηρίστηκα ανάμειξης στην περιοχή κατάντη ενός προ-αναμείκτη καυστήρα, για μια σειρά μειγμάτων καυσίμου-αέρα και επίπεδων προθέρμανσης των αντιδρώντων. Ο καυστήρας αποτελείται από τρείς ομοαξονικούς δίσκους οι οποίοι δημιουργούν δύο κοιλότητες. Το καύσιμο (προπάνιο) παροχετεύεται στην πρώτη κοιλότητα και αναμειγνύεται μερικώς με τον αέρα, καταλήγοντας σε μια διαστρωματωμένη κατανομή σχετικού λόγου καυσίμου αέρα στην είσοδο της περιοχής σταθεροποίησης. Μελετήθηκαν τέσσερα επίπεδα προθέρμανσης των αντιδρώντων τα οποία κυμαίνονται από 300 έως 743Κ, για πτωχά και υπέρ-πτωχα μείγματα. Ο συγκεκριμένος καυστήρας, προθέρμανσης και διαστρωμάτωσης των αντιδρώντων, επιτρέπει τη σταθεροποίηση φλόγας για πολύ πτωχά μείγματα, διευρύνοντας τα πτωχά όρια απόσβεσης και προωθώντας την σταθεροποίηση σε ολικούς σχετικούς λόγους καυσίμου αέρα της τάξης του Φ=0.13 στους 743Κ. Βασικό κίνητρο για την συγκεκριμένη μελέτη ήταν ότι τα χαρακτηριστικά σταθεροποίησης φλογών, σε σταθεροποιητικό σώμα, υπό την επίδραση διαστρωμάτωσης και προθέρμανσης των αντιδρώντων δεν έχουν, ακόμη, εκτενώς καταγραφεί. Για τις ισόθερμες (μη-αντιδρώσες) περιπτώσεις, πραγματοποιήθηκαν μετρήσεις Απεικόνισης Ταχυμετρίας Σωματιδίων (PIV) και Φασματοσκοπίας Υπέρυθρου με Μετασχηματισμό Fourier (FT-IR) για την αξιολόγηση των πεδίων ροής και ανάμειξης που αναπτύσσονται στην περιοχή της κατάντη ανακυκλοφορίας. Επίσης μελετήθηκε η επίδραση της προθέρμανσης του αντιδρώντος μείγματος στα χαρακτηριστικά ανάμειξης και αξιολογήθηκαν τα χαρακτηριστικά λειτουργείας του καυστήρα. Επιπλέον η παρούσα μελέτη βοήθησε στο να διευκρινιστεί η επίδραση της διαστρωμάτωσης του μείγματος, μόνη της ή σε συνδυασμό με την προθέρμανση, στα χαρακτηριστικά απόδοσης του φλογοσταθεροποιητή, καθώς και να αναγνωριστούν παράμετροι ελέγχου της τοπολογίας του μείγματος στην περιοχή της ανακυκλοφορίας.Για τις αντιδρώσες περιπτώσεις, πραγματοποιήθηκαν επίσης μετρήσεις Απεικόνισης Ταχυμετρίας Σωματιδίων (PIV) για το μέσο και διακυμαινόμενο πεδίο ταχυτήτων, μετρήσεις εκπομπών χημειοφωταυγαζώντων ριζικών OH* καθώς και μετρήσεις των εκπεμπόμενων ρύπων με σκοπό να αξιολογηθεί η επίδραση της προθέρμανσης των αντιδρώντων στην τοπολογία της φλόγας, στις εκπομπές ρύπων και στην απόδοση της καύσης. Επιπλέον, εκτιμήθηκαν και αναλύθηκαν ιδιότητες της φλόγας όπως οι διδιάστατες αεροδυναμικές τάσεις που επιδρούν σε αυτήν, οι αριθμοί Damköhler και Karlovitz, το μέσο πάχος του τυρβώδους μετώπου της φλόγας και οι ταχύτητα διάδοσης του τυρβώδους μετώπου, σε διάφορες θέσεις πάνω στο μέτωπο της φλόγας, με σκοπό να διευκρινιστεί η επίδραση της τύρβης καθώς και της προθέρμανσης και σύστασης του μείγματος στην δομή της φλόγας και στα χαρακτηριστικά σταθεροποίησής της.

Subchannel Analysis on Two-Phase Flow Characteristics Through Narrow Gaps in a Tight-Lattice Rod Bundle

2004 ◽  
Author(s):  
Hidesada Tamai ◽  
Akira Ohnuki ◽  
Hajime Akimoto
Keyword(s):  
Liquid Phase ◽  
Turbulent Mixing ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Rod Bundle ◽  
Tight Lattice ◽  
Narrow Gaps

Evaluation of a critical heat flux is one of the most important issues for design of an advanced water-cooled reactor core. Since it becomes difficult to perform full-scale experiments due to a larger scale of the advanced reactor cores, an analytical approach has been widely noticed in the core design. To predict the critical heat flux in high accuracy, it is required to correctly understand a horizontal distribution of a two-phase flow in the rod bundles. In this study, the two-phase flow characteristics through narrow gaps in the tight-lattice 37-rod bundle experiment at JAERI were investigated using the subchannel analysis code, NASCA. At the center of the bundle, liquid flowed toward the periphery due to the diversion cross-flow at the elevation where boiling started and the turbulent mixing and the void drift were not influential as they can be neglected. On the periphery of the bundle, the flow mixings due to the diversion cross flow, turbulent mixing and void drift were almost the same order. Gas flowed in the same way with the liquid phase due to the diversion cross-flow, and the turbulent mixing and the void drift moved the gas in the opposite way of the liquid phase migration. An amount of the diversion cross-flow for the liquid phase increased in proportion to the square of the mass velocity. The characteristics of cross flow were almost the same in the different local power peaking and in the different gap widths in the present model.

3-D Simulation of Rotary Atomized Nozzle Flow Characteristics at Low Pressure

2002 ◽  
Author(s):  
Jingyu Ran ◽  
Li Zhang ◽  
Mingdao Xin ◽  
Lin Yang
Keyword(s):  
Energy Loss ◽  
Flow Characteristics ◽  
Initial Pressure ◽  
Low Pressure ◽  
Combustion Efficiency ◽  
Nozzle Flow ◽  
Solid Cone ◽  
Simple Method ◽  
Physics Model ◽  
Fluid Characteristics

In order to realize liquid (oil etc.) atomized and to improve the combustion efficiency, the atomization or adding moisture is required by atomized nozzle in the oil burner and some power driven thrusters. Based on physics model and some suitable hypothesizes, the 3-D mathematical models for rotary atomized nozzle with micro-expanded tangent channel at low pressure are presented, and the same time, the various simulation tests are taken with the k-ε/RNG models and SIMPLE method, the tests results shown: The angle (θ) of the micro-expanded tangent channel plays an important role for the fluid characteristics, if θ<0, the circumfluence at the exit of the nozzle is obviously, and θ>0, the solid cone in nozzle are formed easily, but its energy loss is bigger. While the initial pressure p0 = 0.3Mpa, Ux,0 = 0, Uy,0 = 0, Uz,0 = −0.2m/s, the circumfluence at the exit of the nozzle isn’t exactly formed with θ = 5.8°, and the energy loss is reduced and the atomized angle can get 80°. The nozzle can be widely adequate to the medium atomized instrument about the oil burner and some power driven thrusters.

Predicting the Two-Phase Flow Patterns Implementing the Froude Number Correlation

2008 ◽  
Author(s):  
Mohammad A. Rahman ◽  
Ted Heidrick ◽  
Brian A. Fleck
Keyword(s):  
Froude Number ◽  
Flow Pattern ◽  
Turbulent Mixing ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Design Flow ◽  
Phase Flow ◽  
The Novel ◽  
Liquid Content ◽  
Two Phase

In this study, two-phase air/water horizontal flow characteristics with different conduit geometries were investigated. After mixing in a horizontal feeding conduit (100 cm long and 2.54 cm ID) the two-phase, air/water fluid passes through an industrial nozzle, which generates spray. Three different novel geometries were investigated in this study along with the existing design. Flow stability and different flow regimes (dispersed, intermittent and slug) for these three types of geometries were investigated. It is observed that when the input liquid content (εL) decreased to 0.5 (high ALR), the two-phase flow became unstable. It is concluded that the novel geometries are capable of producing more stable and dispersed two-phase flow pattern and spray in an industrial nozzle due to enhanced turbulent mixing.

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