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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 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 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 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 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 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 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 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 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.
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781723540226 Total Pages :202 pages Book Rating :4.5/5 (42 download)
Book Synopsis Coaxial Airblast Atomizers by : National Aeronautics and Space Administration (NASA)
Download or read book Coaxial Airblast Atomizers written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-23 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation was performed to quantify the characteristics of the sprays of coaxial injectors with particular emphasis on those aspects relevant to the performance of rocket engines. Measurements for coaxial air blast atomizers were obtained using air to represent the gaseous stream and water to represent the liquid stream. A wide range of flow conditions were examined for sprays with and without swirl for gaseous streams. The parameters varied include Weber number, gas flow rate, liquid flow rate, swirl, and nozzle geometry. Measurements were made with a phase Doppler velocimeter. Major conclusions of the study focused upon droplet size as a function of Weber number, effect of gas flow rate on atomization and spray spread, effect of nozzle geometry on atomization and spread, effect of swirl on atomization, spread, jet recirculation and breakup, and secondary atomization. Hardalupas, Y. and Whitelaw, J. H. Unspecified Center NASA-CR-193845, NAS 1.26:193845, SRA-R93-9083-F NAS8-38872...
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 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 Numerical Cold Flow and Combustion Characterization of Swirl Coaxial Injectors by :
Download or read book Numerical Cold Flow and Combustion Characterization of Swirl Coaxial Injectors written by and published by . This book was released on 2002 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Air Force and its partners are developing and validating an injector design methodology that utilizes both high-pressure cold-flow testing and uni-element hot-fire testing, to create a high performing, long life swirl coaxial injector. Several gas-centered swirl coax injector configurations have been tested under cold- flow and hot-fire test conditions in a single element research engine. The methodology uses computational fluid dynamics (CFD) analyses to provide insight into the flowfield and guide the evolution of injector designs. Both cold-flow and hot-fire analyses were completed, with cold flow results compared with test data. The companion paper will discuss the experimental results.
Book Synopsis Experimental and Computational Study on Liquid Atomization by Slinger Injector by : Carmen Sescu
Download or read book Experimental and Computational Study on Liquid Atomization by Slinger Injector written by Carmen Sescu and published by . This book was released on 2011 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this research work the flow characteristics of a type of rotary atomizer, referred to as slinger injector, were experimentally and numerically investigated at relatively low rotational speeds. Although slinger injectors provide a good level of atomization at high rotational speeds where they are intended to operate (30,000 rpm or higher), a critical aspect in small gas turbines is related to the start-up phase, which typically takes place at speeds around 10,000 rpm. The quality of atomization is very important, especially at these low speeds where smaller mean fuel droplet diameters are desirable. The current work focused on the study of atomization provided by slinger injectors at rotational speed related pertinent to the start-up phase (up to 15,000 rpm). An optical measurement system was implemented to investigate the liquid atomization provided by the slinger injector. The qualitative behavior of fuel emerging from the slinger was evaluated to determine whether a satisfactory atomization was provided within a distance compatible with the size of a small gas turbine engine combustion chamber. The size of the droplets was measured using the Global Sizing Velocimetry (GSV) system. Visualization of the primary liquid breakup process, determination of breakup lengths, and measurement of droplet size were performed by varying rotational speed, liquid flow rate, injector hole shape, size and orientation, and number of holes. Photographs of the liquid breakup, various mean and representative diameters, droplet size histograms and cumulative volume distribution are presented. The findings of this thesis show that droplet size decrease with an increase in rotational speed, as expected. Moreover, hole diameter, hole shape and flow rates affect the slinger atomization. For a given flow rate and a given rotational speed, the experimental data show that the droplet sizes decrease by increasing the hole diameter. The droplets increase in size when the flow rates is increased for a given hole size. The atomization was found to be characteristically different for a slit compared to a circular hole injector. However, the orientation of the emerging jet relative to the axis of rotation insignificantly influenced the slinger atomization for the cases studied. A correlation equation was obtained for a slinger with circular hole, estimating the Sauter mean diameter as a function of the rotational speed of the slinger, the hole diameter, the liquid flow rate and the liquid properties. Two-dimensional and three-dimensional numerical simulations of the internal flow and the external near-field flow for a slinger atomizer were conducted. The simulations were carried out using the commercial Computational Fluid Dynamics code FLUENT, wherein the Volume of Fluid model was used to track the interface between the two phases. A User Defined Function was developed to take into account the centrifugal and Coriolis forces needed for FLUENT computations. The numerical simulations focused on the study of formation of the liquid film along the channel injector wall, and on the upstream characteristics of the liquid jet near the exit of the atomizer. The numerical simulations were in qualitative agreement with the experiment, showing that an annular jet exiting from the channel collapses and the liquid breaks up into droplets a short distance from the exist. The results show that the Volume of Fluid model is appropriate for developing simulation models of the working of a slinger atomizer.
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.
