A STUDY ON THE EMISSIONS OF BUTANOL USING A SPARK IGNITION ENGINE AND THEIR REDUCTION USING ELECTROSTATICALLY ASSISTED INJECTION BY BENJAMIN R. WIGG THESIS Submitted in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering in the Graduate College of the University of Illinois at Urbana-Champaign, 2011 Urbana, Illinois Adviser: Professor Dimitrios C. Kyritsis Abstract Butanol is a potential alternative to ethanol and offers many benefits including a much higher heating value and lower latent heat of vaporization. It also has a higher cetane number than ethanol and improved miscibility in diesel fuel. Additionally, butanol is less corrosive and less prone to water absorption than ethanol, which allows it to be transported using the existing fuel supply pipelines. However, while some previous research on the emissions of butanol-gasoline blends is available, little research exists on the emissions of neat butanol. This thesis focuses on two areas of study. The first area relates to on the comparison of UHC, NOx, and CO emissions of several butanol-gasoline and ethanol-gasoline blended fuels during combustion in an SI engine. The objective was to compare the emissions of butanol combustion to the ones of ethanol and gasoline. The second part of the study relates to the use of electrostatically assisted injection as a means of reducing the UHC emissions of butanol by decreasing the fuel droplet size using a charge electrode and extraction ring designed for a port fuel injector. Emissions measurements taken with and without a charge applied to the injector were used to determine the effect of applying a voltage to the fuel spray on engine emissions. It was established that the UHC emissions of neat butanol were approximately double the UHC emissions of gasoline and were appreciably higher than ethanol. CO emissions decreased and NOx emissions increased as the amount of butanol in gasoline was increased. Additionally, the CO emissions of butanol were lower than ethanol while it was not clear whether butanol had increased or decreased NOx emissions. It was also established that addition of 25% ethanol to butanol resulted in UHC emissions that were approximately 33% higher than those of neat butanol despite ethanol producing approximately 33% less UHC emissions than butanol. The results of the electrostatically assisted injection tests showed that, at certain engine operating conditions, application of 2000 V to the fuel spray resulted in a 10% increase in peak cylinder pressure, 4% reduction in UHC emissions, a 13.5% increase in NOx emissions, and a 13.5% reduction in CO emissions, which is consistent with the hypothesis that the voltage increased fuel atomization. However, tests at lower engine loads showed results contradictory to those at the higher engine load which suggested that the fuel droplet size may vary depending on engine operating conditions. ii Acknowledgements I would like to start by offering my sincerest thanks to Dr. Dimitrios C. Kyritsis not only for giving me the opportunity to work in the Combustion Physics group for the past two years but also for guiding me through the work contained herein. The path leading to the completion of this thesis was a long and certainly frustrating one and your patience during this process was invaluable. I’ve learned so much during my stay at Illinois including many Greek proverbs. My predecessor, Eric K. Anderson, also deserves credit for setting up the test engine and guiding me through the process of using it in addition to helping me troubleshoot several of the seemingly thousands of issues that arose during my time at Illinois. I would also like to thank Bob Coverdill for funding me during the summer months of my stay at Illinois and putting up with the seemingly continuous string of equipment failures that plagued them and Mike Leick for helping me solve countless issues with both test engines. My assistant, Carol Regalbuto, also deserves thanks for helping me in the lab in addition to pointing me towards the Combustion Physics group. I would also like to thank several of my friends for helping me to maintain my sanity and providing me with several great memories during my stay at Illinois including David Schmidt, David Joyce, Lance Hibbeler, Scott Daigle, Phil Poission, Albert Cheng, and countless others. My family also deserves a mention as their unending love and support, (mental, emotional, and financial) through my entire college career has been extremely helpful and without them I wouldn’t be where I am today. Finally, I would like to extend a special thanks to Kevin Hines. Had it not been for you and your red Honda Civic, I probably wouldn’t have ever developed my interest in cars that led me to where I am today. The spontaneous drives in the middle of winter, the autocrosses, and the endless breakdowns of our Integras (mainly mine) have given me many great memories which I’ll cherish for the rest of my life. iii Table of Contents Page Chapter 1 Introduction .......................................................................................................................... 1 1.1 Butanol in Internal Combustion Engines ...................................................................................... 1 1.2 Previous Studies of Butanol combustion and use in Spark Ignition Engines ............................... 4 1.3 Electrostatically Assisted Sprays in Spark Ignition Engines ........................................................ 8 1.4 Electrostatically Assisted Sprays using Butanol ......................................................................... 12 1.5 Electrosprays of Low Conductivity Fluids ................................................................................. 17 1.6 Objectives and Structure of the Thesis ....................................................................................... 20 Chapter 2 Experimental Methodology ............................................................................................... 22 2.1 Overview of Experimental Strategy ........................................................................................... 22 2.2 Test Engine Setup and Specifications ......................................................................................... 22 2.3 Measurement Devices ................................................................................................................. 26 2.3.1 In-cylinder Pressure Measurement ................................................................................ 26 2.3.2 NOx and Lambda Measurement .................................................................................... 27 2.3.3 UHC and CO Measurement ........................................................................................... 28 2.4 Engine Setup Modifications ........................................................................................................ 29 2.4.1 Oil System...................................................................................................................... 30 2.4.2 Fuel Injection System .................................................................................................... 31 2.5 Modifications for Electrostatically Assisted Injection ................................................................ 32 2.6 Test Fuels .................................................................................................................................... 34 2.7 Test Conditions ........................................................................................................................... 35 Chapter 3 Emissions Characteristics of Butanol-blended Fuels ...................................................... 38 3.1 Gasoline Fuel Characterization ................................................................................................... 38 3.2 Emissions of Butanol-Gasoline Blended Fuels ........................................................................... 42 3.3 Comparison to the Emissions of Ethanol-Gasoline Blended Fuels ............................................ 51 3.4 Emissions of Blends of Butanol Ethanol, and Isooctane on a Heating Value basis ................... 62 Chapter 4 Electrostatically Assisted Injection of Butanol ................................................................ 70 4.1 High load (90 kPa), Lean operation ............................................................................................ 70 4.2 Low load (70 kPa), Lean operation ............................................................................................. 76 4.3 Low load (70 kPa), Rich operation ............................................................................................. 82 Chapter 5 Conclusions and Recommendations for Future Work ................................................... 88 5.1 Summary and Conclusions ......................................................................................................... 88 5.1.1 Emissions of Butanol-blended fuels .............................................................................. 88 5.1.2 Electrostatically Assisted Injection of Butanol .............................................................. 91 5.2 Recommendations for Future Research ...................................................................................... 94 References ............................................................................................................................................... 97