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Journal ArticleDOI

Experimental parametric studies on the performance and mixing characteristics of a low area ratio rectangular supersonic gaseous ejector by varying the secondary flow rate

15 Oct 2018-Energy (Pergamon)-Vol. 161, pp 832-845
TL;DR: In this article, a low area ratio rectangular supersonic gaseous ejector is subjected to parametric evaluation to calculate the performance parameters like stagnation pressure ratio, compression ratio, entrainment ratio and the mixing parameter known as non-mixed length.
About: This article is published in Energy.The article was published on 2018-10-15. It has received 28 citations till now. The article focuses on the topics: Stagnation pressure & Mach number.
Citations
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Journal ArticleDOI
TL;DR: The objective of this work is to provide a literature survey on the research attempts made in the field of ejector refrigeration systems and the studies made on the ejector as a component.

202 citations

Journal ArticleDOI
15 Jul 2020-Energy
TL;DR: In this paper, the role of the step condition on the mixing efficiency of the multi-jets within the scramjet was investigated, and the impact of step conditions on fuel mixing in region of the fuel injection was analyzed.

79 citations

Journal ArticleDOI
06 Mar 2019
TL;DR: A review of the main developments in ejectors over the last few years can be found in this article, where the main findings and trends in the area of heat-driven ejectors and ejector-based machines using low boiling point working fluids are summarized.
Abstract: Ejectors used in refrigeration systems as entrainment and compression components or expanders, alone or in combination with other equipment devices, have gained renewed interest from the scientific community as a means of low temperature heat recovery and more efficient energy use. This paper summarizes the main findings and trends, in the area of heat-driven ejectors and ejector-based machines, using low boiling point working fluids, which were reported in the literature for a number of promising applications. An overall view of such systems is provided by discussing the ejector physics principles, as well as a review of the main developments in ejectors over the last few years. Recent achievements on thermally activated ejectors for single-phase compressible fluids are the main focus in this part of the review. Aspects related to their design, operation, theoretical and experimental approaches employed, analysis of the complex interacting phenomena taking place within the device, and performance are highlighted. Conventional and improved ejector refrigeration cycles are discussed. Some cycles of interest employing ejectors alone or boosted combinations are presented and their potential applications are indicated.

70 citations

Journal ArticleDOI
01 Mar 2019-Energy
TL;DR: In this paper, a critical discussion with an outlook for the future research of ejector technology is proposed, which is grounded on the multi-scale relationship between the local-scale and component-scale performances.

68 citations

Journal ArticleDOI
TL;DR: In this paper, the impinging shock of varying strengths on the free shear layer in a confined supersonic cavity flow is studied numerically using the detached-eddy simulation, and the resulting spatiotemporal variations are analyzed between the different cases using unsteady statistics, spectral analysis, and modal decomposition.
Abstract: The impinging shock of varying strengths on the free shear layer in a confined supersonic cavity flow is studied numerically using the detached-eddy simulation. The resulting spatiotemporal variations are analyzed between the different cases using unsteady statistics, $x-t$ diagrams, spectral analysis, and modal decomposition. A cavity of length to depth ratio $[L/D]=2$ at a freestream Mach number of $M_\infty = 1.71$ is considered to be in a confined passage. Impinging shock strength is controlled by changing the ramp angle ($\theta$) on the top-wall. The static pressure ratio across the impinging shock ($p_2/p_1$) is used to quantify the impinging shock strength. Five different impinging shock strengths are studied by changing the pressure ratio: $1.0,1.2,1.5,1.7$ and $2.0$. As the pressure ratio increases from 1.0 to 2.0, the cavity wall experiences a maximum pressure of 25% due to shock loading. At [$p_2/p_1]=1.5$, fundamental fluidic mode or Rossiter's frequency corresponding to $n=1$ mode vanishes whereas frequencies correspond to higher modes ($n=2$ and $4$) resonate. Wavefronts interaction from the longitudinal reflections inside the cavity with the transverse disturbances from the shock-shear layer interactions is identified to drive the strong resonant behavior. Due to Mach-reflections inside the confined passage at $[p_2/p_1]=2.0$, shock-cavity resonance is lost. Based on the present findings, an idea to use a shock-laden confined cavity flow in an enclosed supersonic wall-jet configuration as passive flow control or a fluidic device is also demonstrated.

21 citations

References
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Journal ArticleDOI
TL;DR: The size specifications for suitable tracer particles for particle image velocimetry (PIV), particularly with respect to their flow tracking capability, are discussed and quantified for several examples.
Abstract: The size specifications for suitable tracer particles for particle image velocimetry (PIV), particularly with respect to their flow tracking capability, are discussed and quantified for several examples. A review of a wide variety of tracer materials used in recent PIV experiments in liquids and gases indicates that appropriately sized particles have normally been used. With emphasis on gas flows, methods of generating seeding particles and for introducing the particles into the flow are described and their advantages are discussed.

1,122 citations

Reference BookDOI
01 Jan 2007
TL;DR: A central organizing theme of this handbook is that 'experimental fluid mechanics" can be understood as a parallel activity to that described above, in which basic expressions are combined to analyze a given problem and to derive new information and insight from the resulting mathematical steps of the analysis.
Abstract: Introduction The expression: "analytical work", often connotes an effort in which basic expressions are combined to analyze a given problem and to derive new information and insight from the resulting mathematical steps of the analysis. Specifically, having started with the appropriate relationships and bringing appropriate mathematical manipulations to the task, the analyst is able to create new information to address the motivating question(s). A central organizing theme of this handbook is that 'experimental fluid mechanics" can be understood as a parallel activity to that described above. The motivating questions will set the context for the experiment. The experiment will be established as a boundary value problem in which the experimentalist will address all aspects of the boundary conditions that will influence the "solution." If a transient or an evolving solution is sought, the appropriate initial conditions will similarly be addressed. Having established these conditions, the solution to the boundary value problem will be revealed in the experimental data that will - ideally - not be contaminated by unintended or unknown perturbing effects and that will be fully converged if statistical average values are sought. Part A Experiments in Fluid Mechanics The objective of Part A is to establish the fundamental concepts and equations that undergird experimental fluid mechanics. The first chapter: addresses both the governing equations and the constitutive equations for Newtonian and non-Newtonian fluids. Chapter 2 provides the systematic bases for model testing and the scaling of experimental results. Sections 2.1 through 2.7 derive similitude parameters (Reynolds number, Froude number, etc.) from the governing equations and the boundary conditions. Dimensional analysis (Sect. 2.2) provides a rational approach for the organization and interpretation of experimental data Sect. 2.3, self-similarity, documents known flow fields that exhibit this condition and it provides guidance on what other flows may exhibit this behavior. The encyclopedic presentation of examples will allow the reader to comprehend the universal features of both complete and incomplete self-similarity. Chap. 1 The Experiment as a Boundary-Value Problem Chap. 2 Nondimensional Representation of the Boundary-Value Problem Part B Measurement of Primary Quantities The objective of Part B is to provide specific information to the reader on the following primary quantities: material properties (Chap. 3), flow field properties (Chap. 4 - pressure, Chap. 5 - velocity, vorticity, Mach number, Chap. 6 - spatial density variations and Chap. 7 - temperature and heat flux) and forces and moments (Chap. 8). Chapter 3 is focused on providing quantitative information for the material properties, the sources of this information and the associated confidence levels for the given data. Chapters 4 through 8 provide comprehensive guidance to the reader on: i) the objectives, ii) the available equipment, iii) the utilization techniques, and iv) the post-processing of the primitive information for the stated quantities. Chap. 3 Material Properties: Measurement and Data Chap. 4 Pressure Measurement Systems Chap. 5 Velocity, Vorticity and Mach Number Chap. 6 Spatial Density Variations Chap. 7 Temperature, Concentration and Heat Flux Chap. 8 Forces and Moments Part C Specific Experimental Approaches Building on the previous two parts of this Springer Handbook, which have dealt with the fundamental concepts and equations that undergrid experimental fluid mechanics and the measurement of primary quantities, respectively, Part C addresses experimental fluid mechanics from an application point of view. According to application, often unique and specific forms of equipment, experimental procedure, or analysis and interpretation of results have been developed. It is the purpose of Part C to elucidate a selection of such application areas, in particular measurements of non-Newtonian flows, turbulence, flow visualization, wall-bounded flows, surface topology, turbomachines, hydraulics, aerodynamics, atmospheric and oceanographic measurements, combustion diagnostics and electrohydrodynamic systems. Chap. 9 Non-Newtonian Flows Chap. 10 Measurement of Turbulent Flows Chap. 11 Flow Visualization Chap. 12 Wall-Bounded Flows Chap. 13 Surface Topology Chap. 14 Turbomachines Chap. 15 Hydraulics Chap. 16 Aerodynamics Chap. 17 Atmospheric Measurements Chap. 18 Oceanographic Measurements Chap. 19 The No-Slip Boundary Condition Chap. 20 Combustion Diagnostics Chap. 21 Electrohydrodynamic Systems Part D Analyses and Post-Processing of Data This final part of the Springer Handbook is actually meant to be a reference source about single and data processing techniques commonly encountered in fluid mechanics. These topics have been complemented by a section discussing data acquisition by imaging detectors, a topic becoming increasingly important for optical measurement techniques. These are all subjects, which in their development are not naturally associated with fluid mechanics hence Part D attempts to collect information from many diverse sources and present them conveniently to the fluid mechanic researcher. Topics covered in this part include fundamental topics of signal and data processing transforms (Fourier, Hilbert, wavelet), proper orthogonal decomposition and stochastic estimation. This is followed by a discussion of estimator expectation and variance and the influence of noise on these quantities. The Cramer-Rao Lower Bound (CRLB) is introduced and developed for several common signal processing examples from fluid mechanics. Imaging detectors and measures of their performance are then discussed in detail before closing with a chapter on image processing and motion analysis, two topics especially relevant for the Particle Image Velocity (PIV) measurement technique. Chap. 22 Review of Some Fundamentals Chap. 23 Fundamentals of Data Processing Chap. 24 Data Acquisition Chap. 25 Data Analyses About the Authors Subject Index

1,065 citations

Journal ArticleDOI

548 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive literature review on ejector refrigeration systems and working fluids is presented, which deeply analyzes ejector technology and behavior, refrigerant properties and their influence over ejector performance.
Abstract: The increasing need for thermal comfort has led to a rapid increase in the use of cooling systems and, consequently, electricity demand for air-conditioning systems in buildings. Heat-driven ejector refrigeration systems appear to be a promising alternative to the traditional compressor-based refrigeration technologies for energy consumption reduction. This paper presents a comprehensive literature review on ejector refrigeration systems and working fluids. It deeply analyzes ejector technology and behavior, refrigerant properties and their influence over ejector performance and all of the ejector refrigeration technologies, with a focus on past, present and future trends. The review is structured in four parts. In the first part, ejector technology is described. In the second part, a detailed description of the refrigerant properties and their influence over ejector performance is presented. In the third part, a review focused on the main jet refrigeration cycles is proposed, and the ejector refrigeration systems are reported and categorized. Finally, an overview over all ejector technologies, the relationship among the working fluids and the ejector performance, with a focus on past, present and future trends, is presented.

359 citations

Journal ArticleDOI
TL;DR: A literature review on ejectors and their applications in refrigeration can be found in this article, where a number of studies are grouped and discussed in several topics, i.e. background and theory of ejector and jet refrigeration cycle, performance characteristics, working fluid and improvement of jet refrigerator.
Abstract: This paper provides a literature review on ejectors and their applications in refrigeration. A number of studies are grouped and discussed in several topics, i.e. background and theory of ejector and jet refrigeration cycle, performance characteristics, working fluid and improvement of jet refrigerator. Moreover, other applications of an ejector in other types of refrigeration system are also described.

339 citations