Modeling of Air Assisted and Flash Boiling Sprays in Gasoline Direct Injection Engines PDF Download

Author: Dar-Lon Chang
Publisher:
ISBN:
Category :
Languages : en
Pages : 412

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Author: Kshitij Neroorkar
Publisher:
ISBN:
Category : Ethanol
Languages : en
Pages : 117

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Flash boiling may be defined as the finite-rate mechanism that governs phase change in a high temperature liquid that is depressurized below its vapor pressure. This is a transient and complicated phenomenon which has applications in many industries. The main focus of the current work is on modeling flash boiling in injectors used in engines operating on the principle of gasoline direct injection (GDI). These engines are prone to flash boiling due to the transfer of thermal energy to the fuel, combined with the sub-atmospheric pressures present in the cylinder during injection. Unlike cavitation, there is little tendency for the fuel vapor to condense as it moves downstream because the fuel vapor pressure exceeds the downstream cylinder pressure, especially in the homogeneous charge mode. In the current work, a pseudo-fluid approach is employed to model the flow, and the non-equilibrium nature of flash boiling is captured through the use of an empirical time scale. This time scale represents the deviation from thermal equilibrium conditions. The fuel composition plays an important role in flash boiling and hence, any modeling of this phenomenon must account for the type of fuel being used. In the current work, standard, NIST codes are used to model single component fluids like n-octane, n-hexane, and water, and a multi-component surrogate for JP8. Additionally, gasoline-ethanol blends are also considered. These mixtures are azeotropic in nature, generating vapor pressures that are higher than those of either pure component. To obtain the properties of these fuels, two mixing models are proposed that capture this non-ideal behavior. Flash boiling simulations in a number of two and three dimensional nozzles are presented, and the flow behavior and phase change inside the nozzles is analyzed in detail. Comparison with experimental data is performed in cases where data are available. The results of these studies indicate that flash boiling significantly affects the characteristics of the nozzle spray, like the spray cone angle and liquid penetration into the cylinder. A parametric study is also presented that can help understand how the two different time scales, namely the residence time in the nozzle and the vaporization time scale, interact and affect the phenomenon of flash boiling.

Author: Sampath K. Rachakonda
Publisher:
ISBN:
Category :
Languages : en
Pages :

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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.

Author: André Marques Gomes
Publisher:
ISBN:
Category :
Languages : en
Pages : 372

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Author: Muzammil Mohamad Alias
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 58

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The project is to study the spray breakup and mixture in Gasoline Direct Injection (GDI) The spray breakup and fuel air mixture in the injector system really important to improve the fuel efficiency of Gasoline Direct Injection (GDI) Engine. Engine by using simulation. By using the ANSYS Design Modeler, the design of the injector with different inlet size and combustion chamber has been done. Then, by using Computational Fluid Dynamic (CFD), ANSYS Fluent the flow simulation has been run. The results extracted from the simulation are spray cone angle and penetration length. The simulation is done based on different size of nozzle which are 0.2, 0.3, 0.4 and 0.5 mm. While for another variable is injection pressure which are 3, 6, 10, 15 and 20 Mpa. From the result, the spray cone angle is decreasing as the pressure increase which means the spray cone angle is inversely proportional to the injection pressure. While for another results, the penetration length is directly proportional to the injection pressure. The penetration length is increase as the injection pressure is increase. But, as the nozzle diameterincrease with the same pressure, the penetration length is decreases.

Author: Kshitij Neroorkar
Publisher: LAP Lambert Academic Publishing
ISBN: 9783845442686
Category :
Languages : en
Pages : 128

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Book Description
The flow behavior of liquid fuel through injectors greatly affects its atomization and combustion efficiency inside an engine. A computational fluid dynamics (CFD) model is developed using the open source CFD library OpenFOAM to predict the fuel flow in injectors that are used in the gasoline direct injection systems (GDI). Additionally, a method is formulated to couple this model with fluids that represent the physical properties of gasoline-ethanol blends like E85.

Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 772

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Author: John H Johnson
Publisher: SAE International
ISBN: 1468602098
Category : Technology & Engineering
Languages : en
Pages : 700

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Book Description
Emission and fuel economy regulations and standards are compelling manufacturers to build ultra-low emission vehicles. As a result, engineers must develop spark-ignition engines with integrated emission control systems that use reformulated low-sulfur fuel. Emission Control and Fuel Economy for Port and Direct Injected SI Engines is a collection of SAE technical papers that covers the fundamentals of gasoline direct injection (DI) engine emissions and fuel economy, design variable effects on HC emissions, and advanced emission control technology and modeling approaches. All papers contained in this book were selected by an accomplished expert as the best in the field; reprinted in their entirety, they present a pathway to integrated emission control systems that meet 2004-2009 EPA standards for light-duty vehicles.

Author: Saptarshi Basu
Publisher: Springer
ISBN: 9811074496
Category : Technology & Engineering
Languages : en
Pages : 433

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Book Description
This book focuses on droplets and sprays relevant to combustion and propulsion applications. The book includes fundamental studies on the heating, evaporation and combustion of individual droplets and basic mechanisms of spray formation. The contents also extend to the latest analytical, numerical and experimental techniques for investigating the behavior of sprays in devices like combustion engines and gas turbines. In addition, the book explores several emerging areas like interactions between sprays and flames and the dynamic characteristics of spray combustion systems on the fundamental side, as well as the development of novel fuel injectors for specific devices on the application side. Given its breadth of coverage, the book will benefit researchers and professionals alike.

Author: Fuquan Zhao
Publisher: SAE International
ISBN: 0768008824
Category : Technology & Engineering
Languages : en
Pages : 372

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Book Description
This book covers the latest global technical initiatives in the rapidly progressing area of gasoline direct injection (GDI), spark-ignited gasoline engines and examines the contribution of each process and sub-system to the efficiency of the overall system. Including discussions, data, and figures from many technical papers and proceedings that are not available in the English language, Automotive Gasoline Direct Injection Systems will prove to be an invaluable desk reference for any GDI subject or direct-injection subsystem that is being developed worldwide.