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Atomization Performance Predictions Of Gas Centered Swirl Coaxial Injectors
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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 A Method to Predict Atomization Performance in Gas-Centered Swirl-Coaxial Injectors by :
Download or read book A Method to Predict Atomization Performance in Gas-Centered Swirl-Coaxial Injectors written by and published by . This book was released on 2007 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability to predict atomizer performance can reduce the cost of system development in many areas. This paper investigates the atomization efficiency and droplet distribution from films with strong gas-phase influences. A prediction of atomization efficiency based on a general theory of the droplet creation process is given. In this process a disturbance is created on the film surface then broken 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 given to illustrate how the theory would be applied; however, efforts are made to keep the model as general as possible so that it applies to many types of atomizers and a wide range of operating conditions.
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 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 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 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 0 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 Swirl Effects on Coaxial Injector Atomization by :
Download or read book Swirl Effects on Coaxial Injector Atomization written by and published by . This book was released on 1996 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: The focus of this AASERT grant was the investigation of atomization processes for swirl coaxial gas/liquid spray injection for rocket combustor applications. The work has included review and analysis of atomization literature for swirled and non-swirled gas/liquid sprays, design and fabrication of a rocket-scale swirl coaxial injector for research, and cold-flow and hot-fire characterizations of atomization and combustion with the designed injector. Two significant findings have emerged from the present studies; (1) our experiments in a windowed research combustor were the first to demonstrate that swirl coaxial injection allows for highly efficient propellant combustion (liquid oxygen/gaseous hydrogen) over a wide range of oxidizer-to-fuel ratios from 3 to 175. The result was of interest to industry in conceptual design of a novel rocket-engine cycle, for RLV application, relying upon very high oxidizer-to-fuel ratio combustion in a liquid oxygen preburner, and (2) optical diagnostics were applied to demonstrate a methodology for scaling spray drop size/velocity results based on liquid Weber number. This is of intrinsic value to the spray community, and of direct impact within the rocket-injector design community, where the scaling approach can be incorporated into injector sizing activities.
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 Swirl Coaxial Injector Development by :
Download or read book Swirl Coaxial Injector Development written by and published by . This book was released on 2002 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sierra Engineering and the Air Force Research Laboratory Propulsion Directorate, have undertaken a program to develop gas-centered, swirl coaxial injectors. 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. Only results from the experimental effort will be presented in this work. Three different gas-centered swirl coaxial element concepts are being 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 has found that the converging designs produce C* efficiencies in excess of 90% over a wide-range of mixture ratios and pressure conditions. Near the design pressure, efficiencies exceeding 96% have been measured. In the diverging designs, a chamber oscillation of near 200 Hz has been noted. The cause of this oscillation is under investigation.
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 Numerical Analysis on Combustion Characterization of Gas Centered Swirl Coaxial Injector by : 許庫瑪
Download or read book Numerical Analysis on Combustion Characterization of Gas Centered Swirl Coaxial Injector written by 許庫瑪 and published by . This book was released on 2018 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Cup Length on Film Profiles in Gas-Centered Swirl-Coaxial Injectors by :
Download or read book Effect of Cup Length on Film Profiles in Gas-Centered Swirl-Coaxial Injectors written by and published by . This book was released on 2009 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent interest in LOX-hydrocarbon rocket engines has resulted in the need for design criteria and scaling laws for injectors which work well in such an environment. One injector type that has been shown to work well in LOX-hydrocarbon engines is a Gas-Centered Swirl-Coaxial (GCSC) Injector. While earlier work has focused on a number of the important parameters, one that has been left unexplored is the injector cup length. In this study the effect of the injector cup length on the atomizing film in GCSC injectors is explored. The length of the atomizing film is used as reference parameter for the overall spray quality. Using laser-sheet illuminations along with water and nitrogen as the working fluid, film lengths and were determined in six unique injector geometries and over a number of flow conditions. Each injector geometry and flow condition was tested with two injector cup lengths. Results will show that the injector cup length has little effect on the films for test conditions with momentum-flux ratios greater than 400 as long as the film is completely broken up within the cup.
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 21 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 Theory and Practice of Swirl Atomizers by : Yuriy I Khavkin
Download or read book Theory and Practice of Swirl Atomizers written by Yuriy I Khavkin and published by CRC Press. This book was released on 2003-10-28 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, prominent Russian scientist Yuriy I. Khavkin shows that the droplet sizes in swirl atomizers depend only on the specific energy of the liquid drops and on viscosity. The new theory based only on two parameters is shown to be far simpler and in better agreement with experimental data than any previous presentations. The following topics are included in the book: · The solution of the Navier-Stokes equation for a liquid rotating flow · Atomizers for gas turbine combustion chambers · Atomizers for high capacity steam boilers · Atomizers for liquid-propellant rocket engines · Quality of liquid atomization by non-swirl atomizers · A unique table of experimental data of 232 atomizers, enables the reader to find an atomizer with the flow rate from 5 kg/h to 15,000 kg/h Readers will also learn: · To create an atomizer with the given mean droplet size · To create an atomizer with the given droplet size distribution · To create an atomizer with the given limits of flow rate control. The book is intended for the design engineer, as well as the theoretical scientist.
Book Synopsis Atomization and Mixing Characteristics of Gas/liquid Coaxial Injector Elements by : R. J. Burick
Download or read book Atomization and Mixing Characteristics of Gas/liquid Coaxial Injector Elements written by R. J. Burick and published by . This book was released on 1971 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Computational Simulation of Flow Inside Pressure-swirl Atomizers by :
Download or read book Computational Simulation of Flow Inside Pressure-swirl Atomizers written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Simplex atomizers (pressure-swirl atomizers) are widely used in air-breathing gas turbine engines as they have good atomization characteristics and are relatively simple and inexpensive to manufacture. To reduce emissions, it is critical to design fuel atomizers that can produce spray with a predetermined droplet size distribution at the desired combustor location (small mean droplet diameters and uniform local air/fuel ratios). Manufacturing methods are now available where complex atomizer geometries can be easily obtained. However to use such methods, the influence of atomizer geometry on its performance must be well understood. In this dissertation, a two-dimensional axisymmetric computational fluid dynamics (CFD) model based on the Arbitrary-Lagrangian-Eulerian (ALE) method to predict the flow in pressure-swirl atomizers was developed. The Arbitrary-Lagrangian-Eulerian method was applied so that the free interface between gas and liquid could be tracked sharply and accurately. The developed code was validated by comparison of predictions with experimental data for large scale prototype and with semi-empirical correlations at small scale. The computational predictions agreed well with experimental data for the film thickness at the exit, spray cone angle, and the pressure drop across the atomizer as well as velocity field in the swirl chamber. Using the validated code, a comprehensive parametric study on simplex atomizer performance was conducted. The geometric parameters of atomizer covered in this study include: atomizer constant, the ratio of length to diameter in swirl chamber, the ratio of length to diameter in orifice, the swirl chamber to orifice diameter ratio, inlet slot angle, trumpet angle, trumpet length, and swirl chamber convergent angle. The effects of these geometric parameters on the atomizer performance were studied for a fixed mass flow rate through the atomizer as well as for a fixed pressure drop across the atomizer. The atomizer performance was described in term of dimensionless film thickness at the exit, discharge coefficient and spray cone half angle. To address applications in pharmaceutical and food processing industry, flow of non-Newtonian power-law fluids through pressure-swirl atomizers was considered. Detailed flow patterns inside the atomizer for shear-thinning, Newtonian and shear-thickening fluids were investigated. A range of power-law index from 0.7 to 1.3 was considered. With a fixed flow rate through the atomizer, the shear-thickening fluids exhibited higher film thickness at exit, lower spray angle, and higher discharge coefficient compared to Newtonian fluids. For the range of power-law index considered in this study, the atomizer performance parameters for shear-thinning fluids showed small change from Newtonian fluids. The variation of atomizer performance with the atomizer constant was delineated for different power-law index.
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.
