Download or read book Simulation of Primary Fuel Atomization Processes at Subcritical Pressures written by and published by . This book was released on 2013 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report documents results from an LDRD project for the first-principles simulation of the early stages of spray formation (primary atomization). The first part describes a Cartesian embedded-wall method for the calculation of flow internal to a real injector in a fully coupled primary calculation. The second part describes the extension to an all-velocity formulation by introducing a momentum-conservative semi-Lagrangian advection and by adding a compressible term in the Poisson's equation. Accompanying the description of the new algorithms are verification tests for simple two-phase problems in the presence of a solid interface; a validation study for a scaled-up multi-hole Diesel injector; and demonstration calculations for the closing and opening transients of a single-hole injector and for the high-pressure injection of liquid fuel at supersonic velocity.

Download or read book Computational Exploration of Flash boiling Internal Flow and Near nozzle Spray written by Sampath K. Rachakonda and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Gasoline engines operating under the principle of direct injection are susceptible to flash-boiling due to superheated nature of the fuel and the sub-atmospheric in-cylinder pressures during injection. A review of the literature on flash-boiling sprays shows that a majority of the studies have focused on the far-field regions of the spray, with limited attention given to understanding the influences of the injector geometry and the near-nozzle regions of the spray. Modeling the internal nozzle flow and the primary atomization, on which the far-field spray depends, is a challenge. This thesis, therefore, is aimed at understanding the complex flow through a fuel injector nozzle and the nature of the spray in the near-nozzle region, with the help of computer simulations under flash-boiling and non-flash-boiling conditions. In the current study, the simulations were performed using an in-house Eulerian CFD solver called HRMFoam. Improvements to the solver's near-nozzle spray modeling capability are discussed. These improvements include the implementation of a liquid-gas interface-area-density transport equation to model the primary atomization process. The simulations of direct injection of gasoline and gasoline-like sprays were performed on single-hole and multi-hole injectors, for a wide range of operating conditions. Spray characteristics such as the nozzle's coefficient of discharge and the mean droplet diameter in the dense region of the spray were seen to be captured adequately well with the help of a 2D axi-symmetry assumption in the case of single-hole injectors. A novel approach to identify the near-nozzle spray plume boundary in CFD simulations is presented and validated against experimental measurements for a single-hole asymmetric injector. Case studies on single-hole asymmetric injectors revealed a direct correlation between the drill angle of the nozzle and near-nozzle spray plume angle. A hypothesis of the similarity between a stepped-hole two-phase nozzle and a conventional single-phase converging-diverging nozzle is presented. Furthermore, it was observed that flash-boiling jets behave as underexpanded jets, and therefore, are wider. Whereas, non-flash-boiling behave as overexpanded jets, and thus are narrower. Through the case studies on multi-hole injectors, the collapse of the spray or lack thereof was qualitatively and quantitatively characterized. In this process, a resemblance between the experimentally and computationally identified spray collapse mechanism was established. The application of LES modeling to internal and near-nozzle GDI sprays was explored in a pilot study, and the results were qualitatively validated against the experimentally available near-nozzle X-ray radiography measurements. Finally, in another pilot study, an attempt to model the interphase slip velocity is discussed.

Download or read book Modeling Primary Atomization Processes written by Stephen Heister and published by . This book was released on 1999 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: The contributions of atomization processes to combustion instabilities in liquid rocket engines has been assessed via a series of analytic/numerical models. Simulations of high-speed injection of a viscous jet have revealed a jet "swelling" phenomenon for the first time. Modeling of F-1 fuel injectors reveals a potential instability of the fuel columns to transverse acoustic modes in injector designs which showed large instabilities. Limited experimental work relevant to hybrid rocket injection has also been accomplished under the subject program. A new consumable, catalytic igniter has shown to provide reliable, reproducible ignition in hydrogen peroxide/polyethylene hybrid engines. Currently, a complete dense spray simulation tool is under development to assess spray dynamics under time-varying chamber conditions.

Download or read book A Stable and Conservative Framework for Detailed Numerical Simulation of Primary Atomization written by Vincent Henri Marie Le Chenadec and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Energy conversion devices often rely on the combustion of high energy-density liquid fuel to meet weight and volume restrictions. The efficiency of the conversion and the emission of harmful pollutants depend directly on the mixing of the fuel and oxidizer, which itself results from a cascade of mechanisms initiated by the atomization of a coherent liquid stream. Despite existing investigations, the effects of nozzle design, surface tension, turbulence, and cavitation on atomizer performance are still poorly understood. The challenges found in experimental studies caused by the multi-scale and multi-physics aspects of such flows have motivated the development of numerical strategies to simulate the atomization process. In the direct numerical simulation approach considered in this work, the physics of the flow are all solved for directly. In the presence of complex topologies, the underlying equations are stiff, and, therefore, the development and improvement of numerical methods has been an area of active research. Among algorithms that have emerged, sharp interface methods including Volume-of-Fluid and Level Set have been shown to give reasonable performance. Applications of these methods to study primary atomization of turbulent jets have been documented, but the rare convergence studies available show strong grid dependence, suggesting the need for further developments. The present work focuses on two novel developments: an unsplit Volume-of-Fluid interface capturing algorithm designed to improve conservation on arbitrary grids, and a robust flow solver for incompressible Navier-Stokes equations in two-phase flows involving large density ratios. The resulting approach is shown to be stable and second order accurate. The framework is then assessed in a set of validation cases. In particular, the effect of mesh resolution is studied, and the ability of the method to accurately retain under-resolved structures is shown. Finally, computations of a large scale atomizer for varying operating conditions are presented. The excellent computational efficiency of the algorithm motivates the use of such a framework for simulating industrially relevant configurations.

Download or read book Simulations and Optical Diagnostics for Internal Combustion Engines written by Akhilendra Pratap Singh and published by Springer Nature. This book was released on 2019-10-11 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on combustion simulations and optical diagnostics techniques, which are currently used in internal combustion engines. The book covers a variety of simulation techniques, including in-cylinder combustion, numerical investigations of fuel spray, and effects of different fuels and engine technologies. The book includes chapters focused on alternative fuels such as DEE, biomass, alcohols, etc. It provides valuable information about alternative fuel utilization in IC engines. Use of combustion simulations and optical techniques in advanced techniques such as microwave-assisted plasma ignition, laser ignition, etc. are few other important aspects of this book. The book will serve as a valuable resource for academic researchers and professional automotive engineers alike.

Download or read book Large Eddy Simulation of Fuel Injection at Subcritical and Supercritical Conditions written by Amir Žilić and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advancement of Numerical Methods for Simulating Primary Atomization written by Robert Michael Chiodi and published by . This book was released on 2020 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiphase flows are ubiquitous in natural and engineered systems and occur over scales ranging many orders of magnitude, from the movement of the ocean to the flow of blood through a capillary. In each case, the interface between the phases plays a key role in the dynamics of the flow. In this dissertation, I will detail the development of novel numerical methods for accurately and efficiently tracking the interface in simulations of multiphase flows, specifically focusing on flow configurations involving large density ratios, high shear at the interface, and liquid structures that span orders of magnitude in size. One specific instance where this occurs is during primary atomization, where a large liquid structure breaks up into smaller, more stable structures. This important class of flows is present in many different industries that currently employ over 2.5 million people. Enabling more accurate simulation of primary atomization is a central motivation of my work. To this end, I present significant improvements to the state-of-the-art for both level-set and volume of fluid methods. First, in the context of the conservative level-set method, the solution of the reinitialization equation is improved to drastically reduce the amount of error introduced. This reduction in error also leads to better volume conservation properties, especially for the under-resolved structures commonly created during atomization simulations. I then go on to detail improvements to geometric volume of fluid methods, which are capable of discretely conserving phase volumes at any level of resolution. For advecting the phase volumes, I provide a systematic approach to geometric advection on unstructured meshes that leads to significant gains in speed with no sacrifice in solution accuracy. On the topic of interface reconstruction, a novel multi-plane strategy capable of capturing arbitrarily-thin sub-grid scale films is given. To improve the performance of these methods, a general, robust, and efficient polyhedron intersection algorithm has also been developed and will be discussed in detail. In all cases, the work is placed in the context of the current state-of-the-art through direct comparison to published results. A major portion of my work has also involved creating the open-source Interface Reconstruction Library, which provides implementations of modern algorithms used in volume of fluid methods, including those presented in this dissertation. This library, along with the presented methods, has been applied to simulate large-scale, complicated, and realistic atomizing flows. In particular, they have driven the near-field simulation capabilities for an Office of Naval Research Multidisciplinary Research Initiative (MURI) on active spray control, been used to study the dynamics of a compressible liquid jet in cross-flow configuration for the Air Force Research Laboratory, and been employed by Los Alamos National Laboratory to simulate the injection of liquid metal in metal casting simulations.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Supercritical Fluid Technology for Energy and Environmental Applications written by Vladimir Anikeev and published by Newnes. This book was released on 2013-12-21 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supercritical Fluid Technology for Energy and Environmental Applications covers the fundamental principles involved in the preparation and characterization of supercritical fluids (SCFs) used in the energy production and other environmental applications. Energy production from diversified resources — including renewable materials — using clean processes can be accomplished using technologies like SCFs. This book is focused on critical issues scientists and engineers face in applying SCFs to energy production and environmental protection, the innovative solutions they have found, and the challenges they need to overcome. The book also covers the basics of sub- and supercritical fluids, like the thermodynamics of phase and chemical equilibria, mathematical modeling, and process calculations.A supercritical fluid is any substance at a temperature and pressure above its critical point where distinct liquid and gas phases do not exist. At this state the compound demonstrates unique properties, which can be "fine-tuned," making them suitable as organic solvents in a range of industrial and laboratory processes.This volume enables readers to select the most appropriate medium for a specific situation. It helps instructors prepare course material for graduate and postgraduate courses in the area of chemistry, chemical engineering, and environmental engineering. And it helps professional engineers learn supercritical fluid-based technologies and use them in solving the increasingly challenging environmental issues. - Relates theory, chemical characteristics, and properties of the particular supercritical fluid to its various applications - Covers the fundamentals of supercritical fluids, like thermodynamics of phase and chemical equilibria, mathematical modeling, and process calculations - Includes the most recent applications of supercritical fluids, including energy generation, materials synthesis, and environmental protection

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1997 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Two Phase Flow for Automotive and Power Generation Sectors written by Kaushik Saha and published by Springer. This book was released on 2018-11-03 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the two-phase flow problems relevant in the automotive and power generation sectors. It includes fundamental studies on liquid–gas two-phase interactions, nucleate and film boiling, condensation, cavitation, suspension flows as well as the latest developments in the field of two-phase problems pertaining to power generation systems. It also discusses the latest analytical, numerical and experimental techniques for investigating the role of two-phase flows in performance analysis of devices like combustion engines, gas turbines, nuclear reactors and fuel cells. The wide scope of applications of this topic makes this book of interest to researchers and professionals alike.

Download or read book 40th AIAA ASME SAE ASEE Joint Propulsion Conference Exhibit July 11 14 2004 Fort Lauderdale FL 04 3350 04 3399 written by and published by . This book was released on 2004 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Recent Advances In Spray Combustion written by Kenneth K. Kuo and published by AIAA. This book was released on 1996 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handbook of Atomization and Sprays written by Nasser Ashgriz and published by Springer Science & Business Media. This book was released on 2011-02-18 with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomization and sprays are used in a wide range of industries: mechanical, chemical, aerospace, and civil engineering; material science and metallurgy; food; pharmaceutical, forestry, environmental protection; medicine; agriculture; meteorology and others. Some specific applications are spray combustion in furnaces, gas turbines and rockets, spray drying and cooling, air conditioning, powdered metallurgy, spray painting and coating, inhalation therapy, and many others. The Handbook of Atomization and Sprays will bring together the fundamental and applied material from all fields into one comprehensive source. Subject areas included in the reference are droplets, theoretical models and numerical simulations, phase Doppler particle analysis, applications, devices and more.

Download or read book ICLASS 2000 Proceedings written by and published by . This book was released on 2000 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: All contributed papers, except for invited papers and the plenary paper, and all abstracts for work-in-progress posters, appear on this CD-ROM in Adobe PDF format. The accompanying book of abstracts contains abstracts for all contributed papers and work-in-progress posters.

Download or read book On the Continuity of the Gaseous and Liquid States written by J. D. Van Der Waals and published by Courier Corporation. This book was released on 2004-01-01 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: This much-cited thesis by J. D. van der Waals, the recipient of the 1910 Nobel Prize in physics, is accompanied by an introductory essay by J. S. Rowlinson and another work by van der Waals on the theory of liquid mixtures. 1988 edition.

Download or read book 40th AIAA Aerospace Sciences Meeting Exhibit written by and published by . This book was released on 2002 with total page 624 pages. Available in PDF, EPUB and Kindle. Book excerpt: