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Modeling of Flash Boiling Flows in Injectors with Gasoline-Ethanol Fuel Blends

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Modeling of Flash Boiling Flows in Injectors with Gasoline-Ethanol Fuel Blends University of Massachusetts Amherst ScholarWorks@UMass Amherst Open Access Dissertations 2-2011 Modeling of Flash Boiling Flows in Injectors with Gasoline-Ethanol Fuel Blends Kshitij Deepak Neroorkar University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/open_access_dissertations Part of the Mechanical Engineering Commons Recommended Citation Neroorkar, Kshitij Deepak, "Modeling of Flash Boiling Flows in Injectors with Gasoline-Ethanol Fuel Blends" (2011). Open Access Dissertations. 338. https://scholarworks.umass.edu/open_access_dissertations/338 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Open Access Dissertations by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. MODELING OF FLASH BOILING FLOWS IN INJECTORS WITH GASOLINE-ETHANOL FUEL BLENDS A Dissertation Presented by KSHITIJ NEROORKAR Submitted to the Graduate School of the University of Massachusetts Amherst in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY February 2011 Mechanical and Industrial Engineering c Copyright by Kshitij Neroorkar 2011 All Rights Reserved MODELING OF FLASH BOILING FLOWS IN INJECTORS WITH GASOLINE-ETHANOL FUEL BLENDS A Dissertation Presented by KSHITIJ NEROORKAR Approved as to style and content by: David P. Schmidt, Chair Stephen de Bruyn Kops, Member Michael Henson, Member Ronald O. Grover, Jr., Member Donald Fisher, Department Head Mechanical and Industrial Engineering To my lovely family ACKNOWLEDGMENTS I would like to thank my advisor Prof. David Schmidt for his guidance and support during the course of this PhD. He has always given the highest priority to the development of his students’ careers, for which I will always be grateful. I wish to express my gratitude to Dr. Ronald Grover Jr., whose in-depth knowledge of fuel injectors and engine design has been extremely beneficial for me. I would like to thank Prof. Michael Henson for his help with the development of the fuel property models without which I would probably have taken twice as long to complete this work. Thanks to Prof. Stephen de Bruyn Kops for serving on all my committees from my qualifier to my final defense. I truly appreciate his comments and suggestions. I acknowledge the financial support provided by the General Motors Research and Development Center and NASA for this work. I would like to thank my loving wife Sneha and my family, who have stood by me and encouraged me throughout the course of my student years. Special thanks to Shiva for being such a great friend and mentor. I would also like to thank my colleagues Sandeep, Martell, Partha, Dnyanesh, Raghu, Colarossi, Tim, Kyle, Tom, Nat, Kaus, Brad, Ali, and Chris for their help, and for being such amazing friends. Finally, a lot of people have influenced and impacted my life in different ways over the years. The list would be too long to mention here and so I will just say thanks everyone. v ABSTRACT MODELING OF FLASH BOILING FLOWS IN INJECTORS WITH GASOLINE-ETHANOL FUEL BLENDS FEBRUARY 2011 KSHITIJ NEROORKAR B.E., MUMBAI UNIVERSITY M.S., UNIVERSITY OF ALABAMA AT BIRMINGHAM Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor David P. Schmidt 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 in- dustries. 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 pres- sure, 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 boil- vi ing 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. vii TABLE OF CONTENTS Page ACKNOWLEDGMENTS ............................................. v ABSTRACT ................................................... ....... vi LIST OF TABLES ................................................... xi LIST OF FIGURES.................................................. xii CHAPTER 1. INTRODUCTION ................................................. 1 1.1 FlashBoiling .................................... ................1 1.1.1 Physics of Flash Boiling......................... ............3 1.2 Modeling of the Two-Phase Region Inside the Nozzle . .............8 1.3 Gasoline Direct Injection (GDI) .................... ...............17 1.4 Ethanol as Transportation Fuel..................... ...............20 1.5 Multicomponent Fuel Simulations . ...............21 2. METHODOLOGY ................................................ 26 2.1 Modeling of the Flashing Process . ..............26 2.1.1 Governing Equations ............................ ..........26 2.1.2 Flash Boiling Model ............................. ..........28 2.1.3 Numerical Method ............................... .........30 2.2 Modeling of Gasoline-Ethanol Fuel . ...............33 2.2.1 VaporPressure ................................. ..........33 2.2.2 Enthalpy of Vaporization........................ ...........35 2.2.3 Saturated Liquid and Vapor Densities . ..........36 2.2.4 Mole Fractionof Vapor ........................... .........40 viii 2.2.5 Final Setup of GEFlash Model ...................... ........42 2.2.6 Aspen Plus for Gasoline-Ethanol Fuel Blends . .........44 2.2.6.1 ModelforWater ............................... ...45 2.2.6.2 Model for Gasoline-Ethanol Fuel . ....48 2.2.6.3 Surrogate for Gasoline ........................ .....49 3. RESULTS ................................................... ..... 52 3.1 Gasoline-Ethanol Fuel Modeling Results . ...............52 3.1.1 VaporPressure ................................. ..........52 3.1.2 Enthalpy of Vaporization........................ ...........53 3.1.3 Saturated Liquid Density........................ ...........54 3.1.4 Mole Fractionof Vapor ........................... .........57 3.2 Simulations with n-Hexane......................... ...............60 3.2.1 Geometry and Test Conditions ..................... .........60 3.2.2 Results and Discussions ......................... ...........61 3.3 Simulations with Multi-Component JP8 . .............66 3.3.1 Geometry and Test Conditions ..................... .........66 3.3.2 Results and Discussion.......................... ...........68 3.4 Simulations with Gasoline-Ethanol Blends . ...............80 3.5 ParametricStudy................................. ...............87 3.5.1 SectionI: ..................................... ...........91 3.5.2 SectionII: .................................... ...........92 3.5.3 SectionIII: ................................... ...........93 4. CONCLUSIONS .................................................. 98 4.1 Multi-Component Fuel Model ........................ .............98 4.2 Flash Boiling Simulations......................... ...............100 4.3 Contributions of the Current Work................... .............103 5. FUTURE WORK ................................................ 105 APPENDIX: INPUT FILES FOR GEFlash AND OUTPUT FORMAT ................................................... 108 ix BIBLIOGRAPHY .................................................. 110 x LIST OF TABLES Table Page 2.1 Parameters for five cubic EOS........................ .............37 2.2 Formulation of gasoline surrogates [20] ............. ................49 3.1 Test cases simulated for JP8 ........................ ..............68 3.2 Test cases for parametric study using water as working fluid...........88 3.3 Test cases for parametric study using n-hexane as working fluid........88 3.4 Test cases for parametric study using octane as working
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