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Modeling Of The Internal Two Phase Flow In A Gas Centered Swirl Coaxial Fuel Injector
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Book Synopsis Modeling of the Internal Two-Phase Flow in a Gas-Centered Swirl Coaxial Fuel Injector by :
Download or read book Modeling of the Internal Two-Phase Flow in a Gas-Centered Swirl Coaxial Fuel Injector written by and published by . This book was released on 2009 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Predicting the liquid film dynamics inside the injector cup of gas-centered swirl coaxial fuel injectors requires a general two-phase approach that is appropriate for all liquid volume fractions, high Weber number, and complex geometries. The rapid exchange of momentum at the highly convoluted interface requires tight numerical coupling between the gas and liquid phases. An Eulerian two-phase model is implemented to represent the liquid and gas interactions in the injector as well as the atomization processes at the rough interface. The model, originally proposed by Vallet et al, assumes that in the limit of infinite Reynolds and Weber number, features of the atomization process acting at large length scales are separable from small scale mechanisms. A transport equation for the liquid volume fraction represents the dispersion of the liquid into the gas via a traditional turbulent diffusion hypothesis. A model for the growth of mean interfacial surface area is then used to characterize the growth of instability at the interface, allowing a characterization of Sauter mean diameter. The model shows promise as a computationally inexpensive tool for characterizing spray quality in regions where optical experimental data are difficult to obtain and two-phase direct numerical simulation methods are too demanding.
Book Synopsis Swirl Coaxial Injector Development, Part II: CFD Modeling by :
Download or read book Swirl Coaxial Injector Development, Part II: CFD Modeling written by and published by . This book was released on 2002 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Injector design is critical to obtaining the dual goals of long engine life as well as providing high energy release efficiency in the main combustion chamber. Introducing a swirl component in the injector flow can enhance the propellant mixing and thus improve engine performance. A combined experimental and computational effort is underway to examine the properties of GOX-centered, swirl coaxial injectors to examine their performance and lifetime characteristics. These injectors can be easily manufactured and can be designed to maintain a low face temperature, which will improve engine life. Therefore, swirl coaxial injectors, which swirl liquid fuel around a gaseous oxygen core, show promise for the next generation of high performance staged combustion rocket engines utilizing hydrocarbon fuels. The purpose of this work is to not only examine the properties of these injectors, but also to develop a design methodology, utilizing a combination of high-pressure cold-flow testing, uni-element hot- fire testing, and computations to create a high performing, long life swirl coaxial injector for multi-element combustor use.
Book Synopsis Fuel Injector: Air Swirl Characterization Aerothermal Modeling, Phase 2, Volume 1 by :
Download or read book Fuel Injector: Air Swirl Characterization Aerothermal Modeling, Phase 2, Volume 1 written by and published by . This book was released on 1993 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Issues in Aerospace and Defense Research and Application: 2013 Edition by :
Download or read book Issues in Aerospace and Defense Research and Application: 2013 Edition written by and published by ScholarlyEditions. This book was released on 2013-05-01 with total page 628 pages. Available in PDF, EPUB and Kindle. Book excerpt: Issues in Aerospace and Defense Research and Application: 2013 Edition is a ScholarlyEditions™ book that delivers timely, authoritative, and comprehensive information about Aerospace Research. The editors have built Issues in Aerospace and Defense Research and Application: 2013 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Aerospace Research in this book to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Aerospace and Defense Research and Application: 2013 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
Book Synopsis Fuel Injector: Air Swirl Characterization Aerothermal Modeling, Phase 2, Volume 2 by :
Download or read book Fuel Injector: Air Swirl Characterization Aerothermal Modeling, Phase 2, Volume 2 written by and published by . This book was released on 1993 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Simulation of the Internal Two-Phase Flow Within an Aerated-Liquid Injector and Its Injection Into the Corresopnding High-speed Crossflows by :
Download or read book Numerical Simulation of the Internal Two-Phase Flow Within an Aerated-Liquid Injector and Its Injection Into the Corresopnding High-speed Crossflows written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerated-liquid atomization, which is produced by the introduction of gas directly into a liquid flow immediately upstream of the injector exit orifice to generate a two-phase flow, has been shown to produce well-atomized sprays in a quiescent environment with only a small amount of aerating gas at relatively low injection pressures. A time-derivative preconditioning method using the Low-Diffusion Flux-Splitting Scheme (LDFSS) has been extended to a 'mixture' model of two-phase flow and applied to simulate the structure of internal two-phase flow for aerated-liquid injectors, with each phase governed by its own equation of state. The Continuum Surface Force (CSF) model of Brackbill, et al. is adapted to model compressible fluid flow influenced by interfacial surface tension. A sub-iterative time integration method based on a planar Gauss-Seidel partitioning of the system matrix is used with implicit source terms as a means of solving the three-dimensional, time-dependent form of the governing equations. The calculations are parallelized using domain-decomposition and Message-Passing Interface (MPI) methods, and are optimized for operation on the 720 processor IBM SP-2 at the North Carolina Supercomputing Center (NCSC). Simulation results for 2-D aerated-liquid injector flowfields at gas-to-liquid (GLR) mass ratios of 0.08% and 2.45% are discussed. In accord with experimental visualization data, the results for GLR = 0.08% indicate a combination of slugging and core-annular two-phase flow in the injector. Results at GLR = 2.45% indicate that a core-annular flow mode dominates, again in agreement with experimental results. The effects of the choice of reference velocity and the level of surface tension on the injector flowfield solutions are also examined.
Book Synopsis Numerical Simulation of the Internal Two-Phase Flow Within an Aerated-Liquid Injector and Its Injection Into the Corresponding High-speed Crossflows by :
Download or read book Numerical Simulation of the Internal Two-Phase Flow Within an Aerated-Liquid Injector and Its Injection Into the Corresponding High-speed Crossflows written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The current study investigates the flow structures within an aerated-liquid (barbotage) injector, which is designed to facilitate the rapid breakup of a hydrocarbon fuel jet prior to its entering a scramjet combustor, and the spray structures in the corresponding crossflow. Simulations of the transient, three-dimensional, two-phase flow within the "out-in" injector operating at different gas-to-liquid (GLR) mass ratios and in the corresponding crossflow domain have been performed, and the results compared with experimental pressure measurements of the injector and shadowgraph images of the crossflow. The numerical method solves a "mixture" model of two-phase flow using a preconditioning strategy. High-order spatial accuracy and good interface-capturing properties are facilitated by the use of shock-capturing schemes combined with second order TVD methods. Also, an immersed boundary method is used to investigate the probe effects, and a droplet transport model is used in the crossflow simulations to get more details about effect of droplet size. The injector simulation results highlight the effects of mesh refinement and turbulence model on the predicted solutions. The pressure drop across the injector is predicted reasonably well by the computational methodology, and the trend of increasing injector pressure with increasing GLR is captured properly. Predictions of the absolute pressure level within the injector show some discrepancies in comparison with experimental data but agree well with theoretical estimates. The results of the injector simulations with plenum included are consistent with the results of the discharge tube cases. If the centerline pressure is close to the experimental data, the gas mass flow rate at outlet will approach a value below the experimental data. If the gas mass flow rate at outlet approaches the experimental data, then the centerline pressure will be higher than the experimental data, but agrees well with theoretical analyses. The intr.
Book Synopsis The Development of a Methodology to Scale Between Cold-Flow and Hot-Fire Evaluations of Gas-Centered Swirl Coaxial Injectors by :
Download or read book The Development of a Methodology to Scale Between Cold-Flow and Hot-Fire Evaluations of Gas-Centered Swirl Coaxial Injectors written by and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Uni-element cold flow and hot fire evaluations were performed on a variety of gas-centered swirl coaxial injectors. Gaseous oxygen and various liquid hydrocarbons were used in the combustion evaluations, while water and gaseous nitrogen were the simulants for the cold flow experiments. The connections between the two sets of data were examined. The cold flow experiments demonstrated that the mixing efficiency of the various injector designs was highly sensitive to the internal geometry of the injector as well as the scaling methodology used to simulate the hot-fire conditions. When the proper scaling methodology was employed, a correlation which captures the general trend of injector geometry and c ̂performance between the measured cold-flow mixing efficiency and hot-fire c ̂performance was observed. This semi-empirical correlation was developed based on a film stripping mechanism that relates the measured c ̂efficiency of these injectors to the injector geometry and fuel properties. The effects of injector geometry on the injector internal flowfield were ascertained with a combination of cold-flow CFD simulations and experimental measurements. The correlation also implies that fuel properties are secondary to injector geometry effects in determining the performance of various injector configurations. Hot-fire testing of several common hydrocarbon fuels including RP-1, Butane, JP-10, JP-7 and JP-8 confirmed that injector geometric effects dominated performance and demonstrated that c ̂efficiency in excess of 95% is achievable with all of these fuels. However, the effect of fuel properties does appear to be within the measurement limits of the experiments and a correlating parameter which captures these effects was found.
Book Synopsis Atomization in Gas-Centered Swirl-Coaxial Injectors (PREPRINT). by :
Download or read book Atomization in Gas-Centered Swirl-Coaxial Injectors (PREPRINT). written by and published by . This book was released on 2006 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A preliminary study of atomization mechanisms in gas-centered swirl-coaxial injectors for use in rocket engines has been undertaken. Gas-centered swirl-coaxial injectors differ from other injectors in that atomization occurs from a wall-bounded liquid. Few studies of atomization mechanisms in wall-bounded flows exist; some probable atomization processes have been determined, however. These mechanisms include liquid turbulence, aerodynamic stripping and a process driven by gas-phase structures. The likely character of the gas and film undergoing these atomization processes is presented. Relevant nondimensional groupings based on simplified theoretical descriptions of select mechanisms are outlined. Preliminary experimental and numerical results taken at atmospheric pressure are qualitatively compared to the likely mechanisms and each other.
Book Synopsis LES of Atomization and Cavitation for Fuel Injectors by : Aqeel Ahmed
Download or read book LES of Atomization and Cavitation for Fuel Injectors written by Aqeel Ahmed and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents Large Eddy Simulation (LES) of fuel injection, atomization and cavitation inside the fuel injector for applications related to internal combustion engines. For atomization modeling, Eulerian Lagrangian Spray Atomization (ELSA) model is used. The model solves for volume fraction of liquid fuel as well as liquid-gas interface surface density to describe the complete atomization process. In this thesis, flow inside the injector is also considered for subsequent study of atomization. The study presents the application of ELSA model to a typical diesel injector, both in the context of RANS and LES. The model is validated with the help of experimental data available from Engine Combustion Network (ECN). The ELSA model which is normally designed for diffused (unresolved) interfaces, where the exact location of the liquid-gas interface is not considered, is extended to work with Volume of Fluid (VOF) type formulation of two phase flow, where interface is explicitly resolved. The coupling is achieved with the help of Interface Resolution Quality (IRQ) criteria, that takes into account both the interface curvature and modeled amount of interface surface. ELSA model is developed first considering both phases as incompressible, the extension to compressible phase is also briefly studied in this thesis, resulting in compressible ELSA formulation that takes into account varying density in each phase. In collaboration with Imperial College London, the Probability Density Function (PDF) formulation with Stochastic Fields is also explored to study atomization. In modern fuel injection systems, quite oftenthe local pressure inside the injector falls below the vapor saturation pressure of the fuel, resulting in cavitation. Cavitation effects the external flow and spray formulation. Thus, a procedure is required to study the phase change as well as jet formulation using a single and consistent numerical setup. A method is developed in this thesis that couples the phase change inside the injector to the external jet atomization. This is achieved using the volume of fluid formulation where the interface is considered between liquid and gas; gas consists of both the vapor and non condensible ambient air.
Book Synopsis The Investigation on Dynamic Spray Characteristics of Gas-centered Swirl Coaxial Injector by : York Tzuyu Lin
Download or read book The Investigation on Dynamic Spray Characteristics of Gas-centered Swirl Coaxial Injector written by York Tzuyu Lin and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the popularity in space exploration, the importance of liquid propellant rocket engines (LPRE) has increased. Gas-centered swirl coaxial (GCSC) injectors are widely implemented in gas-generation cycled LPREs. Thus, GCSC injectors has been a popular subject these years. The aims of this thesis were to establish a design process of LPRE and GCSC injector, and gain deeper understanding of the behavior of GCSC injector under large amplitude flowrate variation by conducting dynamic cold flow experiment using self-developed flowrate excitation ball valve. The LPRE and GCSC injector were firstly designed by theoretical formulae, and the detailed design were done with key geometric parameters acquired for future ground static test and cold flow experiments. After that, full-bridge gate driver and microcontroller chips were used to developed a DC motor controller. Angular position controller was realized by LabView, incremental encoder, DC motor and DC motor controller mentioned above. Finally, both steady and dynamic cold flow experiments were conducted with self-constructed backlight illumination observation system, fluid supply system, flowrate excitation ball valve, and GCSC injectors. After analyzing the results of cold flow experiment with self-developed computer program, four major conclusions were made: 1. The design of changing gas nozzle length to change recess ratio was found to be weakening the swirl strength. 2. The pressure oscillation in liquid manifold would create addition perturbation to liquid film, leading to the shortening of breakup length. 3. Large intact liquid films were more sensitive to change in gas momentum. 4. Momentum ratio was found to be a dominant factor determining the general breakup of liquid film based on the fact that spray cone structure was independent of phase difference in pressure oscillation.
Book Synopsis Atomization Rate of Gas-Centered Swirl-Coaxial Injectors (Preprint). by :
Download or read book Atomization Rate of Gas-Centered Swirl-Coaxial Injectors (Preprint). written by and published by . This book was released on 2008 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas-centered swirl-coaxial injectors are garnering much interest in the area of liquid hydrocarbon rocket development. However, robust design criteria and scaling of these injectors remains unclear. Here an examination of primary atomization has been undertaken through the study of a gas-centered swirl-coaxial injector. Film length is measured experimentally over a range of operating conditions and injector geometries. Experiments are performed at atmospheric pressure using water and nitrogen as working fluids. The atomization rate, reflected in the length of the intact liquid film, is related to the momentum flux ratio. Using the characteristic dimensions for determining the bulk velocities of the fluids, the film lengths of various injector geometries may be collapsed onto a single curve of nondimensionalized length versus momentum flux ratio. The injectors tested have a geometry which produces separated gas flow just prior to contact with the liquid. The effect of this recirculation zone on initial film height is discussed.
Book Synopsis Swirl Coaxial Injector Development, Part I: Test Results by :
Download or read book Swirl Coaxial Injector Development, Part I: Test Results written by and published by . This book was released on 2002 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sierra Engineering, in conjunction with the Air Force Research Laboratory Propulsion Directorate, has undertaken a program to develop a gas-centered, swirl coaxial injector. This injector design will be used in the multi-element Advanced Fuels Tester (AFT) engine to test a variety of hydrocarbon propellants. As part of this program, a design methodology is being developed which will be applicable to future injector design efforts. The methodology combines cold flow data, acquired in the AFRL High Pressure Injector Flow facility, uni-element hot fire data, collected in AFRL Test Cell EC-1, and a computational effort conducted at University of Alabama-Birmingham, to identify key design features and sensitivities. Results from the computational effort will be presented in the Part II companion paper (9). Three different gas-centered swirl coaxial element concepts were studied: a converging design, a diverging design, and a pre-filming design. The cold flow experiments demonstrated that all three classes of elements produced an extremely dense, solid cone spray, with the highest mass density in the center. The atomization of all of these injectors was excellent, producing mean drop sizes 1/3 to 1/4 of that typically measured for shear coaxial elements operating under similar conditions. Uni-element hot fire testing of these elements has begun, but the elements have not yet been tested at the design operating conditions. Preliminary low chamber pressure test results show the converging design performs better than the pre-filming and diverging design. Uni-element C* efficiencies in excess of 90% have been measured over a wide-range of mixture ratios.
Book Synopsis Coarse Grained Simulation and Turbulent Mixing by : Fenando F. Grinstein
Download or read book Coarse Grained Simulation and Turbulent Mixing written by Fenando F. Grinstein and published by Cambridge University Press. This book was released on 2016-06-30 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reviews our current understanding of the subject. For graduate students and researchers in computational fluid dynamics and turbulence.
Book Synopsis A Numerical Simulation of Internal Two-phase Flow for Aerated-liquid Injectors by : Ming Tian
Download or read book A Numerical Simulation of Internal Two-phase Flow for Aerated-liquid Injectors written by Ming Tian and published by . This book was released on 2002 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: two-phase flow, aerated-liquid injector, CFD.
Book Synopsis Atomization Performance Predictions of Gas-Centered Swirl-Coaxial Injectors by :
Download or read book Atomization Performance Predictions of Gas-Centered Swirl-Coaxial Injectors written by and published by . This book was released on 2007 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability to predict injector performance can reduce the cost of rocket engine development. This paper details a new theory to predict the atomization efficiency and droplet diameter from the atomization of wall-bounded films with strong gas-phase influences. In this theory atomization occurs when a disturbance is created on the film surface then breaks down into droplets via stripping. The theory relates the mass of film lost via atomization to the mass of liquid introduced into the atomizer to predict atomization efficiency and offers some estimations of primary droplet diameter. A specific example involving a gas-centered swirl coaxial injector is discussed. The results of experiments and simulations are used to support assumptions and are successfully compared to some simple predictions from the theory. Despite the application to a specific injector efforts are made to keep the theory as general as possible so that it applies to many types of injectors and a wide range of operating conditions.
Book Synopsis Comprehensive Study of Internal Flow Field and Linear and Nonlinear Instability of an Annular Liquid Sheet Emanating from an Atomizer by : Ashraf Ibrahim
Download or read book Comprehensive Study of Internal Flow Field and Linear and Nonlinear Instability of an Annular Liquid Sheet Emanating from an Atomizer written by Ashraf Ibrahim and published by . This book was released on 2006 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Performance of fuel injectors affects the combustion efficiency, pollutant emissions and combustion instability in gas turbine engines, internal combustion engines and industrial furnaces. In these combustion systems, either pressure swirl (simplex) atomizers, or prefilming airblast atomizers, or plain orifice pressure atomizers are used for fuel atomization. In this dissertation, a comprehensive model for pressure-swirl atomization is developed that includes computational treatment of the internal flow field and the nonlinear liquid sheet instability analysis for primary breakup. For a prefilming airblast atomizer and a plain orifice atomizer, nonlinear breakup processes for an annular liquid sheet and a liquid jet are analyzed using a perturbation method. Two-dimensional axi-symmetric numerical simulations have been carried out to study the unsteady, turbulent, swirling two-phase flow field inside pressure swirl atomizers with the volume of fluid (VOF) method. Internal flow field simulation results are validated using available experimental data for velocity measurements inside a large-scale prototype atomizer, the film thickness at orifice exit, the spray angle, and the discharge coefficient. The effect of air pressure and liquid viscosity on flow field inside the atomizer is investigated. The relationship between the internal flow characteristics and discharge parameters confirms that the internal flow structure plays a very important role in determining the atomizer performance. Linear and nonlinear asymmetric instability analyses are carried out to study the primary atomization of annular liquid sheets and liquid jets emanating from the pressure swirl (simplex) atomizer, prefilming airblast atomizer, and plain orifice pressure atomizer using a perturbation method with the initial amplitude of the disturbance as the perturbation parameter. For a coaxial liquid jet subjected to a swirling gas stream, the axisymmetric disturbance mode (n = 0) is the most dominant only when the gas swirl number is very small. However at higher swirl strength the helical (asymmetric) disturbance modes (n> 0) become dominant compared to the axisymmetric mode. The liquid jet breaks up over a shorter distance at higher gas swirl number. The gas swirl number for transition to a highly asymmetric breakup with a high circumferential wave number (n = 5) is found to vary as the inverse of the square root of the gas-to-liquid momentum ratio when the gas-to-liquid momentum ratio is less than 1. For annular liquid sheets, the breakup length is reduced by an increase in the liquid Weber number, initial disturbance amplitude and the inner and outer gas-liquid velocity ratios. The inner gas stream is found to be more effective in disintegrating and enhancing the instability of annular liquid sheets than the outer gas stream. Air swirl not only promotes the instability of the annular liquid sheet, but also switches the dominant mode from the axisymmetric mode to a helical mode (n> 0). As outer air swirl strength increases, the circumferential wave number (n) increases and the ligament shapes at the breakup time become highly asymmetric. Using the atomizer exit conditions as input, a non-linear sheet instability and breakup analysis has been carried out to predict the breakup length and the primary breakup for a simplex atomizer. The predictions of breakup length are compared with available experimental measurements which show good agreement. The coupled internal flow simulation and nonlinear sheet instability analysis provides a comprehensive approach to modeling atomization from a pressure-swirl atomizer.
