Download or read book Numerical Simulation of Steady and Pulsed Flows Through Thrust Augmenting Ejectors written by Emmanuel Chima Okpara and published by . This book was released on 2008 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Simple Model of Pulsed Ejector Thrust Augmentation written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-29 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: A simple model of thrust augmentation from a pulsed source is described. In the model it is assumed that the flow into the ejector is quasi-steady, and can be calculated using potential flow techniques. The velocity of the flow is related to the speed of the starting vortex ring formed by the jet. The vortex ring properties are obtained from the slug model, knowing the jet diameter, speed and slug length. The model, when combined with experimental results, predicts an optimum ejector radius for thrust augmentation. Data on pulsed ejector performance for comparison with the model was obtained using a shrouded Hartmann-Sprenger tube as the pulsed jet source. A statistical experiment, in which ejector length, diameter, and nose radius were independent parameters, was performed at four different frequencies. These frequencies corresponded to four different slug length to diameter ratios, two below cut-off, and two above. Comparison of the model with the experimental data showed reasonable agreement. Maximum pulsed thrust augmentation is shown to occur for a pulsed source with slug length to diameter ratio equal to the cut-off value.Wilson, Jack and Deloof, Richard L. (Technical Monitor)Glenn Research CenterTHRUST AUGMENTATION; MATHEMATICAL MODELS; FLOW VELOCITY; HARTMANN-SPRENGER TUBES; VORTEX RINGS; PULSED JET ENGINES; EJECTORS...

Download or read book Workshop on Thrust Augmenting Ejectors written by and published by . This book was released on 1979 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Control Volume Method for Analysis of Unsteady Thrust Augmenting Ejector Flows written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-11-21 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: A method for predicting transient thrust augmenting ejector characteristics is presented. The analysis blends classic self-similar turbulent jet descriptions with a control volume mixing region discretization to solicit transient effects in a new way. Division of the ejector into an inlet, diffuser, and mixing region corresponds with the assumption of viscous-dominated phenomenon in the latter. Inlet and diffuser analyses are simplified by a quasi-steady analysis, justified by the assumptions that pressure is the forcing function in those regions. Details of the theoretical foundation, the solution algorithm, and sample calculations are given. Drummond, Colin K. COMPUTATIONAL FLUID DYNAMICS; COMPUTERIZED SIMULATION; EJECTORS; FINITE VOLUME METHOD; MATHEMATICAL MODELS; THRUST AUGMENTATION; TURBULENT JETS; UNSTEADY FLOW; ALGORITHMS; INLET FLOW; PREDICTION ANALYSIS TECHNIQUES; REAL TIME OPERATION...

Download or read book Development of a Numerical Tool to Study the Mixing Phenomenon Occuring During Mode One Operation of a Multi mode Ejector augmented Plused Detonation Rocket Engine written by Joshua Dawson and published by . This book was released on 2016 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: A novel multi-mode implementation of a pulsed detonation engine, put forth by Wilson et al. [2], consists of four modes; each specifically designed to capitalize on flow features unique to the various flow regimes. This design enables the propulsion system to generate thrust through the entire flow regime. The multi-mode ejectoraugmented pulsed detonation rocket engine operates in mode one during take-o_ conditions through the acceleration to supersonic speeds. Once the mixing chamber internal flow exceeds supersonic speed, the propulsion system transitions to mode two. While operating in mode two, supersonic air is compressed in the mixing chamber by an upstream propagating detonation wave and then exhausted through the convergent-divergent nozzle. Once the velocity of the air flow within the mixing chamber exceeds the Chapman-Jouguet Mach number, the upstream propagating detonation wave no longer has sufficient energy to propagate upstream and consequently the propulsive system shifts to mode three. As a result of the inability of the detonation wave to propagate upstream, a steady oblique shock system is established just upstream of the convergent-divergent nozzle to initiate combustion. And finally, the propulsion system progresses on to mode four operation, consisting purely of a pulsed detonation rocket for high Mach number flight and use in the upper atmosphere as is needed for orbital insertion. Modes three and four appear to be a fairly significant challenge to implement, while the challenge of implementing modes one and two may prove to be a more practical goal in the near future. A vast number of potential applications exist for a propulsion system that would utilize modes one and two, namely a high Mach number hypersonic cruise vehicle. There is particular interest in the dynamics of mode one operation, which is the subject of this study. Several advantages can be obtained by use of this technology. Geometrically, the propulsion system is fairly simple and the rapid combustion process results in an engine cycle which is more efficient compared to its combined-cycle counterparts. The flow path geometry consists of an inlet system, followed just downstream by a mixing chamber where an ejector structure is placed within the flow path. Downstream of the ejector structure is a duct leading to a convergent-divergent nozzle. During mode one operation and within the ejector, products from the detonation of a stoichiometric hydrogen/air mixture are exhausted directly into the surrounding secondary air stream. Mixing then occurs between both the primary and secondary flow streams, at which point the air mass containing the high pressure, high temperature reaction products is convected downstream towards the nozzle. The engine cycle is engineered to a specific number of detonations per second, creating the pulsating characteristic of the primary flow. The pulsing nature of the primary flow serves as a momentum augmentation, enhancing the thrust and specific impulse at low speeds. Consequently, it is necessary to understand the transient mixing process between the primary and secondary flow streams occurring during mode one operation. Using OPENFOAM®, a numerical tool is developed to simulate the dynamics of the turbulent detonation process along with detailed chemistry in order to understand the physics involved with the stream interactions. The computational code has been developed within the framework of OPENFOAM®, an open-source alternative to commercial CFD software. A conservative formulation of the Farve averaged Navier-Stokes equations are used to facilitate programming and numerical stability. Time discretization is accomplished by using the Crank-Nicolson method, achieving second-order convergence in time. Species mass fraction transport equations are implemented and a Seulex ODE solver was used to resolve the system of ordinary differential equations describing the hydrogen-air reaction mechanism detailed in Appendix A. The Seulex ODE solution algorithm is an extrapolation method based on the linearly implicit Euler method with step size control. A second-order total variation diminishing method with a modified Sweby ux limiter was used for space discretization. And finally the use of operator splitting (PISO algorithm, and chemical kinetics) is essential due to the significant differences in characteristic time scales evolving simultaneously in turbulent reactive flow. Capturing the turbulent nature of the combustion process was done using the k-w-SST turbulence model, as formulated by, [1]. Mentor's formulation is well suited to resolve the boundary layer while remaining relatively insensitive to freestream conditions, blending the merits of both the k-w and k-E models. Further developement of the tool is possible, most notably with the Numerical Propulsion System Simulation application. NPSS allows the user to take advantage of a zooming functionality in which high-fidelity models of engine components can be integrated into NPSS models, allowing for a more robust propulsion system simulation. A more comprehensive understanding of the multi-mode ejector-augmented pulsed detonation rocket engine can be achieved with a systematic study of the impact pulsed flow has on thrust production. Although a significant increase in computational requirements, adding nozzle geometry to this study would illuminate any problems associated with pulsed flow through a nozzle. Additionally, a study including nozzle geometry would bring more clarity in regards to the efficiency of the propulsion design.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1572 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Simple Model of Pulsed Ejector Thrust Augmentation written by and published by . This book was released on 2003 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multiple Cycle Simulation of a Pulse Detonation Engine Ejector written by S. Yungster and published by . This book was released on 2002 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Steady Flow Ejector Research Program written by Lockheed-Georgia Company and published by . This book was released on 1961 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation was conducted to determine the jet thrust augmentation under static conditions for rectangular parallel-divergent wall ejector configurations with multiple primary nozzles. The effect of various geometrical and flow parameters were investigated in order to provide design information. Parameters investigated included the ratio of the ejector exit area to the primary nozzle area, the diffuser angle, the mixing section length, the primary nozzle position, the entrance radius, the number of primary nozzle rows, and the primary nozzle pressure ratio and temperature ratio. The test results are generalized to obtain curves relating the augmentation factor to ejector geometry and flow parameters over a wide range of ejector exit to primary nozzle area ratios. (Author).

Download or read book Thrust Augmentation Study of High Performance Ejectors written by John E. Minardi and published by . This book was released on 1983 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: A technique is developed for determining a representative value of the maximum efficiency that can be achieved with high performance ejectors when operating on the supersonic solution branch of an ejector. These efficiencies are used to calculate thrust augmentation for an ejector over a wide range of parameters including operation with a hypothetical engine. Reasonable values of thrust augmentation can be achieved at low subsonic flight mach numbers. However, at flight Mach numbers near one, little or not thrust augmentation was found. At supersonic flight Mach numbers, thrust augmentation was achieved. Basic studies indicated that the effects of temperature was opposite at subsonic and supersonic flight Mach numbers. Thrust augmentation decreased with increasing temperature at subsonic Mach number sand increased with increasing temperature at supersonic Mach numbers.

Download or read book Performance of Thrust Augmenting Ejectors written by Paul Allen Van and published by . This book was released on 1971 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Experimental Study of a Pulsed Jet Ejector written by Isaac M. Choutapalli and published by . This book was released on 2007 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first objective was addressed by carrying out direct thrust measurements on the free steady jet, free pulsed jet and the pulsed jet ejector configurations. Within the range of parameters investigated, it has been demonstrated conclusively that for an incompressible pulsed jet (Mj = 0.30) operating at a Strouhal number of around 0.1, thrust augmentation values as high as 1.9 can be obtained with a compact ejector (L/ D ≈ 3) at an area ratio (ejector inlet area/primary nozzle exit area) of about 11.0.

Download or read book Parametric Investigation of Thrust Augmentation by Ejectors on a Pulsed Detonation Tube written by Jack Wilson and published by BiblioGov. This book was released on 2013-08 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: A parametric investigation has been made of thrust augmentation of a 1 in. diameter pulsed detonation tube by ejectors. A set of ejectors was used which permitted variation of the ejector length, diameter, and nose radius, according to a statistical design of experiment scheme. The maximum augmentation ratios for each ejector were fitted using a polynomial response surface, from which the optimum ratios of ejector diameter to detonation tube diameter, and ejector length and nose radius to ejector diameter, were found. Thrust augmentation ratios above a factor of 2 were measured. In these tests, the pulsed detonation device was run on approximately stoichiometric air-hydrogen mixtures, at a frequency of 20 Hz. Later measurements at a frequency of 40 Hz gave lower values of thrust augmentation. Measurements of thrust augmentation as a function of ejector entrance to detonation tube exit distance showed two maxima, one with the ejector entrance upstream, and one downstream, of the detonation tube exit. A thrust augmentation of 2.5 was observed using a tapered ejector.

Download or read book Applicability of Thrust Augmenting Ejectors in a Supersonic Cruise Configuration written by Wendell S. Hertzelle and published by . This book was released on 1997-04-01 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thrust augmenting ejectors were analyzed by the author in an attempt to see if they could be used to provide a significant thrust increase over the baseline thrust of a primary core. This was done for the purpose of determining if leaving the ejectors open in the cruise configuration of the High Speed Civil Transport would lead to a thrust increase that would at least offset the weight of the ejectors themselves. If this was found to be true then the fuel economy of the HSCT might be improved by leaving them open and not closing them during cruise. In analyzing the ejectors, no assumptions were made regarding inlet nor outlet configurations, so an attempt was made to find the point of optimal thrust augmentation by varying secondary stream bypass Mach number and the amount of flow entrainment. Two solutions were found to each mixing scenario, one subsonic and the other supersonic. These two solutions were each analyzed and ones not satisfying the Second Law of Thermodynamics were eliminated. Analytic diffuser and bleed losses were also explored in the analysis of the ejector flow. Within the limitations of the assumptions discussed in this paper, appreciable thrust augmentations have been discovered over a large range of bypass Mach numbers and entrained mass flows. This lead the author to the conclusion that ejectors warrant further research beyond a first order analysis, and serious thought should be put into leaving them open in cruise.

Download or read book An Experimental Investigation of Two Dimensional Thrust Augmenting Ejectors written by L. Bernal and published by . This book was released on 1984 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments were performed with subsonic and underexpanded choked two-dimensional primary nozzle ejector flow systems without diffusion to evaluate the role of entrainment and mixing in thrust augmentation. Two-component Laser Doppler velocity measurements (mean and fluctuating values), thrust measurements, ejector shroud surface pressure measurements and flow visualization were used to determine the evolution of the velocity profiles and their relationship to the ejector performance. Key findings include: (1) Primary jet growth is significantly altered by the ejector shroud. (2) Primary jet turbulent characteristics when normalized with the local mean centerline velocity are in agreement with those for the free-jet. (3) In the neighborhood of the ejector shroud the flow field can be classified into two regions--the potential flow region and the region close to the ejector exit which is dominated by the turbulent transport. (4) Pressure recovery is very sharp in the first region and is more gradual in the region close to the ejector exit. The investigation is continuing toward the near-term objectives of obtaining measurements within diffused flow and with heated primary air. This volume emphasizes the laser doppler velocimetry developed especially for this program. Part II (AD-A154 083) presents detailed cold flow measurements along with preliminary primary hot flow data.

Download or read book An Experimental Study of a Three Dimensional Thrust Augmenting Ejector Using Laser Doppler Velocimetry written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-11-17 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow field measurements were obtained in a three-dimensional thrust augmenting ejector using laser Doppler velocimetry and hot wire anemometry. The primary nozzle, segmented into twelve slots of aspect ratio 3.0, was tested at a pressure ratio of 1.15. Results are presented on the mean velocity, turbulence intensity, and Reynolds stress progressions in the mixing chamber of the constant area ejector. The segmented nozzle was found to produce streamwise vortices that may increase the mixing efficiency of the ejector flow field. Compared to free jet results, the jet development is reduced by the presence of the ejector walls. The resulting thrust augmentation ratio of this ejector was also calculated to be 1.34. Storms, Bruce Lowell Unspecified Center EJECTORS; FLOW MEASUREMENT; LASER DOPPLER VELOCIMETERS; REYNOLDS STRESS; THREE DIMENSIONAL FLOW; THRUST AUGMENTATION; TURBULENCE EFFECTS; VORTICES; ASPECT RATIO; EXHAUST VELOCITY; HOT-WIRE ANEMOMETERS; NOZZLE DESIGN; PRESSURE RATIO; V/STOL AIRCRAFT...

Download or read book Numerical Analysis of an Axisymmetric Thrust Augmenting Ejector written by Kenneth R. Gage and published by . This book was released on 1990 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Use of an ejector is an effective way to increase the thrust produced by a jet. In this thesis project an axisymmetric ejector concept which had been previously explored by experiment was numerically modeled. An existing axisymmetric, internal flow code based on the explicit MacCormack method was modified to incorporate primary nozzle structure and flow injection within the flowfield. Results were compared qualitatively and quantitatively with experimental results to verify the validity of the model. Internal flow structure, difficult to obtain in experiment, is easily examined. This code may be used for parametric analysis of such ejector performance parameters as primary nozzle location, flow injection angle, diffuser area ratio, and inlet geometry to optimize future hardware configurations.