Effects of Ethanol and Volatility Parameters on Exhaust Emissions
Final Report Effects of Ethanol and Volatility Parameters on Exhaust Emissions CRC Project No. E-67 Prepared for: Coordinating Research Council, Inc. 3650 Mansell Road, Suite 140 Alpharetta, GA 30022 Submitted: January 30, 2006
Thomas D. Durbin, Principal Investigator J. Wayne Miller, Co-Investigator Theodore Younglove Tao Huai Kathalena Cocker College of Engineering-Center for Environmental Research and Technology University of California Riverside, CA 92521 (951) 781-5797 (951) 781-5790 fax
06-VE-59596-E67
University of California, Riverside, CE-CERT
CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
Table of Contents Executive Summary ......................................................................................................... vi 1. 2.
3.
4. 5. 6. 7. 8.
Introduction............................................................................................................1 Experimental Procedures......................................................................................2 2.1 Test Vehicles................................................................................................2 2.2 Fuels.............................................................................................................2 2.3 Catalyst and Oxygen Sensor Aging .............................................................5 2.4 Test Sequence Randomization.....................................................................6 2.5 Test Protocol ................................................................................................6 2.6 Vehicle Emissions Measurements ...............................................................9 2.7 Statistical Analysis.....................................................................................10 Results ...................................................................................................................11 3.1 FTP Regulated Emissions Results .............................................................11 3.2 NMOG and Toxic Emissions Results ........................................................31 Comparisons with Previous Studies ..............................................................47 Driveability Index..............................................................................................49 Summary and Conclusions ..............................................................................51 Acknowledgments ................................................................................................54 References.............................................................................................................55
Appendices Appendix A. Appendix B. Appendix C. Appendix D.
Properties of the Test Fuels Results for Testing of Vinyl Acetate Fuel Effects Description of Catalyst Aging Detailed Description of Statistical Analysis
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
List of Figures Figure 1. CRC E-67 Fuel Cube Design ..........................................................................................3 Figure 2. Fuel Square for Fuels D, E, K, and L .............................................................................5 Figure 3. Flow Chart for CRC Project No. E-67 Vehicle Testing..................................................8 Figure 4. Composite NMHC Balanced Average by T50 - Fleet Average and Individual Vehicles ...12 Figure 5a. Composite NMHC Balanced Average by EtOH x T90 - Fleet Average ......................13 Figure 5b. Composite NMHC Balanced Average by T90 x EtOH - Fleet Average ......................13 Figure 6a. Bag 1 NMHC Balanced Average by EtOH x T50 – Fleet Average .............................15 Figure 6b. Bag 1 NMHC Balanced Average by T50 x EtOH - Fleet Average..............................15 Figure 7a. Bag 1 NMHC Balanced Average by EtOH x T90 – Fleet Average .............................16 Figure 7b. Bag 1 NMHC Balanced Average by T90 x EtOH - Fleet Average..............................16 Figure 8a. Composite CO Balanced Average by EtOH x T90 - Fleet Average.............................18 Figure 8b. Composite CO Balanced Average by T50 x EtOH - Fleet Average ............................18 Figure 9. Composite CO Balanced Average by T90 - Fleet Average and Individual Vehicles.....19 Figure 10a. Bag 1 CO Balanced Average by EtOH x T50 – Fleet Average..................................20 Figure 10b. Bag 1 CO Balanced Average by T50 x EtOH - Fleet Average ..................................20 Figure 11. Bag 1 CO Balanced Average by T90 – Fleet Average and Individual Vehicles..........21 Figure 12a. Composite NOx Balanced Average by EtOH x T50 – Fleet Average ........................23 Figure 12b. Composite NOx Balanced Average by T50 x EtOH - Fleet Average.........................23 Figure 13. Bag 1 NOx Balanced Average by EtOH - Fleet Average and Individual Vehicles.....24 Figure 14. Bag 1 NOx Balanced Average by T50 – Fleet Average and Individual Vehicles........25 Figure 15. Fuel Consumption Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................27 Figure 16. Fuel Consumption Balanced Average by T50 - Fleet Average and Individual Vehicles.................................................................................................................................27 Figure 17. Fuel Consumption Balanced Average by T90 - Fleet Average and Individual Vehicles ................................................................................................................................28 Figure 18. Bag 1 Fuel Consumption Balanced Average by EtOH – Fleet Average and Individual Vehicles.................................................................................................................................29 Figure 19. Bag 1 Fuel Consumption Balanced Average by T50 – Fleet Average and Individual Vehicles.................................................................................................................................29 Figure 20. Bag 1 Fuel Consumption Balanced Average by T90 - Fleet Average and Individual Vehicles ................................................................................................................................30 Figure 21. NMOG Balanced Average by EtOH - Fleet Average and Individual Vehicles ..........33 Figure 22. NMOG Balanced Average by T50 - Fleet Average and Individual Vehicles ..............33
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
Figure 23. Composite Formaldehyde Balanced Average by T50 - Fleet Average and Individual Vehicles ................................................................................................................................35 Figure 24. Bag 1 Formaldehyde Balanced Average by EtOH - Fleet Average and Individual Vehicles ................................................................................................................................36 Figure 25. Bag 1 Formaldehyde Balanced Average by T50 - Fleet Average and Individual Vehicles ................................................................................................................................36 Figure 26. Composite Acetaldehyde Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................38 Figure 27. Bag 1 Acetaldehyde Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................39 Figure 28. Composite Benzene Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................40 Figure 29. Composite Benzene Balanced Average by T50 - Fleet Average and Individual Vehicles.................................................................................................................................41 Figure 30. Bag 1 Benzene Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................42 Figure 31. Bag 1 Benzene Balanced Average by T50 - Fleet Average and Individual Vehicles ..42 Figure 32. Composite 1,3-Butadiene Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................44 Figure 33. Composite 1,3-Butadience Balanced Average by T50 - Fleet Average and Individual Vehicles.................................................................................................................................44 Figure 34. Bag 1 1,3-Butadiene Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................45 Figure 35. Bag 1 1,3-Butadience Balanced Average by T50 - Fleet Average and Individual Vehicles.................................................................................................................................46 Figure 36. DI Model Results.........................................................................................................50
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
List of Tables Table 1. Description of Test Vehicles ........................................................................................... 2 Table 2. Summary of Target and Actual Fuel Properties ...............................................................4 Table 3. Description of General Fuel Properties ...........................................................................4 Table 4. Fuel Randomization Matrix .............................................................................................6 Table 5. Mixed Model Summary for NMHC ..............................................................................11 Table 6. Mixed Model Summary for CO .....................................................................................17 Table 7. Mixed Model Summary for NOx ...................................................................................22 Table 8. Mixed Model Summary for Fuel Consumption*1000 ...................................................26 Table 9. Mixed Model Summary for NMOG ...............................................................................31 Table 10. Four Fuel Mixed Model Summary for NMHC.............................................................31 Table 11. Mixed Model Summary for Formaldehyde ..................................................................34 Table 12. Mixed Model Summary for Acetaldehyde ...................................................................37 Table 13. Mixed Model Summary for Benzene ..........................................................................39 Table 14. Mixed Model Summary for 1,3-Butadiene...................................................................43
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
Disclaimer This report was prepared by the University of California-Riverside, College of EngineeringCenter for Environmental Research and Technology (CE-CERT) as an account of work sponsored by the Coordinating Research Council (CRC). Neither the CRC, members of the CRC, CE-CERT, nor any person acting on their behalf: (1) makes any warranty, expressed or implied, with respect to the use of any information, apparatus, method, or process disclosed in this report, or (2) assumes any liabilities with respect to use of, inability to use, or damages resulting from the use or inability to use, any information, apparatus, method, or process disclosed in this report.
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
Executive Summary Regulations on the composition of gasoline for environmental and other initiatives continue to play an important role in the production of gasoline. Predictions of the effects of changes in fuel properties on vehicle emissions are incorporated in the Environmental Protection Agency’s (EPA’s) Complex Model and the California Air Resources Board’s (CARB’s) Predictive Model. Oxygenate content and fuel volatility (distillation) variables are important parameters when determining the emission reduction potential of new fuels and these properties are included in the models used by EPA and CARB. Although the effects of fuel volatility and oxygenates on emissions have been extensively studied in the past, data on the effects of these fuel properties on the latest-technology vehicles – those certified to California’s Low-Emission Vehicle (LEV), Ultra-Low-Emission Vehicle (ULEV), and Super-Ultra-Low-Emission Vehicle (SULEV) standards – are quite limited. The goal of the present project is to expand the database of information available on the impacts of gasoline volatility parameters and ethanol content on exhaust emissions. This program includes a test fleet with the newest technology vehicles and a comprehensive set of test fuels with varying ethanol content and mid-range and back-end volatility. For this study, 12 California-certified LEV to SULEV vehicles, with an even split between passenger cars and light-duty trucks, were tested on a 12 fuel test matrix. The 12 fuels were designed with independently varying levels of ethanol concentration (0 volume %, 5.7 volume %, and 10 volume %), T50 (195°F, 215°F, and 235°F), and T90 (295°F, 330°F, and 355°F). The fuel matrix was designed to represent both non-oxygenated and oxygenated fuels available in California and the rest of the US. Vehicles were tested with catalysts that were bench-aged to an equivalent of 100,000 miles. Measurements included regulated exhaust emissions (non-methane hydrocarbons (NMHC), carbon monoxide (CO), and oxides of nitrogen (NOx)), fuel consumption, as well as detailed non-methane organic gas (NMOG) speciation for a subset of four fuels. Complete randomization of the fuels testing order resulted in a more statistically-robust dataset for analysis. The final analysis of project data estimated regression coefficients for the fuel effects, with the levels of ethanol, T50, and T90 used as continuous variables. Models predicting emissions and fuel consumption from first order effects, second order effects, and interactions of the fuel parameters were derived. Key findings are as follows: Regulated Emissions and Fuel Consumption •
NMHC: o There was a statistically significant interaction between ethanol and T90. The interaction showed that NMHC emissions increased with increasing ethanol content at the mid-point and high level of T90, but were unaffected at the low T90 level. Looked at another way, NMHC emissions increased with increasing T90 at
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
the mid-point and high level of ethanol, but were unaffected by T90 at the zero level of ethanol. o NMHC emissions increased with increasing T50. The percentage increases in NMHC emissions in going from the low and mid-point level for T50 to the high T50 level were 36 and 25%, respectively. •
CO: o There was a statistically significant interaction between ethanol and T50. The interaction showed that CO emissions decreased as ethanol content was increased from the low to the mid-point level for all levels of T50. However, increasing ethanol content from the mid-point to the high level produced little to no change in CO for the low and mid-point levels of T50, and increased CO at the high level of T50. Looked at another way, CO emissions increased with increasing T50 at the mid-point and high levels of ethanol, but were unaffected by T50 at the zero level of ethanol. o CO emissions decreased with increasing T90. The percentage decreases in CO emissions in going from the low and mid-point level for T90 to the high T90 level were 24% and 7%, respectively.
•
•
NOx:
o There was a statistically significant interaction between ethanol and T50. The interaction showed that NOx emissions increase with increasing ethanol content at the low level of T50. At the mid-point level of T50, NOx emissions are largely unaffected as ethanol content is increased from the zero to the mid-point level, but increase as ethanol is increased to the high level. At the high level of T50, NOx emissions are largely unaffected by ethanol content. Looked at another way, NOx emissions decreased with increasing T50 at the high level of ethanol, but were largely unaffected by T50 at the zero and mid-point levels of ethanol.
Fuel Consumption: o Fleet average fuel consumption increased by 1.4% when ethanol content was increased from the zero to the high level. o Fleet average fuel consumption decreased by 1.2% when T50 was increased from the low to the high level. o Fleet average fuel consumption decreased by 0.6% when T90 was increased from the low to the high level.
In the fuel set used in this work, 10% ethanol tended to decrease volumetric heat content by 2.2%. NMOG and Toxics Emissions Detailed speciation measurements were performed for a subset of four fuels with target T90 = 355°F in order to evaluate the fuel effects of ethanol and T50 on NMOG and the four mobile source air toxics: benzene, 1,3-butadiene, formaldehyde and acetaldehyde. Key findings are as follows:
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
•
NMOG: o NMOG emissions increased by 14% when ethanol content was increased from the zero to the high level. o NMOG emissions increased by 35% when T50 was increased from the low to the high level.
•
Formaldehyde: o Formaldehyde emissions increased by 23% when T50 was increased from the low to the high level.
•
Acetaldehyde: o Acetaldehyde emissions increased by 73% when ethanol content was increased from the zero level to the high level.
•
Benzene: o Benzene emissions increased by 18% when ethanol content was increased from the zero to the high level. o Benzene emissions increased by 38% when T50 was increased from the low to the high level.
•
1,3-butadiene: o 1,3-butadiene emissions increased by 22% when ethanol content was increased from the zero to the high level. o 1,3-butadiene emissions increased by 56% when T50 was increased from the low to the high level.
The effects of ethanol and T50 on NMOG and mobile source toxics described above were only observed for the subset of fuels having the high level of T90. The results of this study do not permit any conclusions as to what effects ethanol or T50 might have had on NMOG or toxics emissions for fuels having low or mid-point T90 levels.
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1. Introduction As vehicle and fuel technologies continue to meet more stringent emission standards, it is useful to understand the effects of fuel properties on the emissions and performance of vehicles. Over the years, the impact of fuel properties on vehicle emissions has been the subject of numerous studies and programs. Data from these earlier programs have been used in the development of regulations for fuel properties. These data also have been incorporated into the Environmental Protection Agency’s (EPA’s) Complex Model and the California Air Resources Board’s (CARB’s) Predictive Model to estimate the effects of changes in fuel properties on vehicle emissions. Although the database on the emissions impact of fuel properties is large, data on the effects of fuel properties on the latest technology vehicles – those certified to California’s LowEmission Vehicle (LEV), Ultra-Low-Emission Vehicle (ULEV), and Super-Ultra-Low-Emission Vehicle (SULEV) standards – is more limited. In the future, these vehicle technologies will account for an increasing share of the emissions of the in-use vehicle fleet. Today, regulatory agencies continue to consider changes in gasoline composition regulations in response to environmental and other initiatives. Oxygenate content and fuel volatility are two parameters that are considered to be important in determining the emission reduction potential of new fuels. Both properties are included in the models used by EPA and CARB. Many states have banned methyl t-butyl ether (MTBE), leading to greater use of ethanol (EtOH). The Renewable Fuel Standard (RFS) adopted as part of the federal Energy Policy Act of 2005 requires significant and increasing volumes of renewables to blended into the transportation fuel pool between 2006 and 2012, much of which is likely to be ethanol. The effects of fuel volatility and ethanol/oxygenates on emissions have been investigated extensively in past studies [1-12]. These studies have shown some general trends of how these properties affect emissions. The reduction of T50 and T90 and the corresponding reduction of heavy fuel hydrocarbon compounds have generally been found to reduce exhaust hydrocarbon emissions [2,3,5,8]. Ethanol and other oxygenates typically have been found to reduce total hydrocarbon (THC) and carbon monoxide (CO) emissions [1,2,7-9,11,12]. Increases in oxides of nitrogen (NOx) have been observed for oxygenates in some studies, although this observation is not consistent over all test fleets [1,2,7-9,11,12]. While these studies provide important information, there is relatively limited data on how these fuel parameters will affect emissions in advanced technology vehicles. Some of the more recent studies also include some contradictory data, including a recent study in which slightly higher NOx emissions were found for a fuel with no oxygenates in comparison with the oxygenated fuels [1]. The goal of this project is to expand the database of information available on the impacts of gasoline volatility parameters and ethanol content on exhaust emissions. This program includes a comprehensive set of test fuels with varying ethanol content and mid- and back-end volatility, and a test fleet with the newest technology vehicles. Measurements include detailed non-methane organic gas (NMOG) speciation for a subset of fuels. The information obtained from this study is valuable in better understanding and predicting the implications of changes in fuel properties for regulatory or other reasons.
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
2. Experimental Procedures 2.1 Test Vehicles Twelve vehicles were recruited for testing. The vehicles included present day technologies with California low-emission vehicle (LEV), ultra-low emission vehicle (ULEV), and super-ultralow-emission vehicle (SULEV) certification. The test fleet was evenly split between passenger cars and light-duty trucks. Within each general certification category, e.g., LEV, the passenger cars and trucks are certified to different standards, and as such represent different emissions categories. Vehicles were obtained from a combination of sources including rental agencies, private parties, and corporate sponsors. All vehicles had accumulated at least 10,000 miles. Prior to entering the program, all vehicles were inspected using a standard checklist to ensure that they were in sound mechanical and operational condition. The vehicles were fitted with catalysts that had been bench-aged to the equivalent of 100,000 miles for testing. The specific details of the vehicles used in this project are listed in Table 1. Table 1. Description of Test Vehicles # MY 1 2 3 4 5 6 7 8 9 10 11 12
OEM
Model
California Type Certification 2002 Ford Taurus LEV PC 2003 Chevrolet Cavalier LEV PC 2003 Ford F-150 LEV LDT 2003 Dodge Caravan LEV LDT 2003 Ford Explorer LEV LDT 2003 Chevrolet Trailblazer LEV LDT 2002 Toyota Camry ULEV PC 2003 Buick LeSabre ULEV PC 2001 VW Jetta ULEV PC 2003 Ford Windstar ULEV LDT 2003 Chevrolet Silverado ULEV LDT 2003 Honda Accord SULEV PC
Engine Size 3.0 L 2.2 L 4.6 L 3.3 L 4.0 L 4.2 L 2.4 L 3.8 L 2.0 L 3.8 L 5.3 L 2.4 L
Mileage Engine Family 19,414 28,728 13,856 18,342 16,445 13,141 14,731 10,364 28,761 20,523 10,298 12,432
1FMXV03.0VF4 1GMXV02.2025 3FMXT05.4PFB 3CRXT03.32DR 3FMXT04.02FB 3GMXT04.2185 1TYXV02.4JJA 3GMXV03.8044 1VWXV02.0223 3FMXT03.82HA 3GMXT05.3176 3HNXV02.4KCP
PC = passenger car; LDT = light-duty truck; vehicles equipped with catalysts aged to 100,000 miles for testing
2.2 Fuels Twelve fuels were prepared and provided for testing for this project. These 12 fuels were designed to encompass three levels of ethanol content (0%, 5.7% and 10%), three levels of T50 (195°F, 215°F and 235°F), and three levels of T90 (295°F, 330°F, and 355°F). The values for ethanol represent typical ethanol concentrations found in California (5.7%) and the rest of the US (10%). The ranges for both T50 and T90 span the 10th and 90th percentile values based on summer fuel surveys during/through calendar year 2002. Previous studies had shown that in addition to the main effects of ethanol, T50, and T90, curvature effects for each of these factors and interactions between ethanol and each of T50 and T90 might be important. From a full factorial design matrix of 27 fuels obtained from the three fuel factors each at three levels, statistical optimality criteria combined with practical concerns about what fuels could be blended 2
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
from refinery streams led to the selection of 12 fuels as best for estimating the possible fuel effects. The fuel design matrix is shown graphically in Figure 1. A summary of the design and actual values of the fuel properties is provided in Table 2. The actual fuel property values shown in Table 2 represent averages of measurements from four or five laboratories, depending on the specific property. Driveability Index (DI) was calculated for each fuel using the equation recently balloted by ASTM. A more detailed listing of the fuel properties is provided in Appendix A. The fuels were blended from refinery streams with the general properties targeted to be constant for all fuels in order to reduce or eliminate any potential confounding effect of these properties with the design parameters. The target values for the general fuel properties are provided in Table 3. The general fuel properties are intended to be representative of fuels that are available in the commercial marketplace, but are not necessarily representative of all commercial fuels. The fuels were blended by Haltermann Products, Channelview, TX. The lubricant used for this study was a zero-sulfur, synthetic base lubricant containing ashless, zero-sulfur antiwear and anti-oxidant additives. This is the same lubricant that was used in two other recent vehicle emissions test programs [13, 14].
Figure 1. CRC E-67 Fuel Cube Design
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
Table 2. Summary of Target and Actual Fuel Properties. Target Properties for Actual Values Design Variables Fuel T50,°F T90,°F Ethanol, T50,°F T90,°F Ethanol, E200, E300, Driveability % % % % Index (DI)* A 195 295 0 195 294 0.0 54 91 1082 B 195 295 5.7 191 290 5.6 58 92 1076 C 195 330 10 193 329 10.4 52 84 1128 D 195 355 0 199 355 0.0 51 84 1153 E 195 355 10 198 352 10.3 51 80 1165 F 215 295 0 217 295 0.0 40 91 1148 G 215 295 10 212 291 10.1 47 80 1151 H 215 330 0 216 327 0.1 42 85 1177 I 215 355 5.7 216 354 5.9 43 78 1211 J 235 330 5.7 237 329 5.9 35 78 1255 K 235 355 0 236 355 0.0 38 75 1258 L 235 355 10 233 349 10.5 39 78 1282 * DI = 1.5*T10 + 3.0*T50 + 1.0*T90 + 2.4*vol% Ethanol (Equation recently balloted by ASTM)
Table 3. Description of General Fuel Properties. Property RVP FBP RON MON (R+M)/2 Aromatics
Limits 7.5-7.8 psi
Thomas D. Durbin, Principal Investigator J. Wayne Miller, Co-Investigator Theodore Younglove Tao Huai Kathalena Cocker College of Engineering-Center for Environmental Research and Technology University of California Riverside, CA 92521 (951) 781-5797 (951) 781-5790 fax
06-VE-59596-E67
University of California, Riverside, CE-CERT
CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
Table of Contents Executive Summary ......................................................................................................... vi 1. 2.
3.
4. 5. 6. 7. 8.
Introduction............................................................................................................1 Experimental Procedures......................................................................................2 2.1 Test Vehicles................................................................................................2 2.2 Fuels.............................................................................................................2 2.3 Catalyst and Oxygen Sensor Aging .............................................................5 2.4 Test Sequence Randomization.....................................................................6 2.5 Test Protocol ................................................................................................6 2.6 Vehicle Emissions Measurements ...............................................................9 2.7 Statistical Analysis.....................................................................................10 Results ...................................................................................................................11 3.1 FTP Regulated Emissions Results .............................................................11 3.2 NMOG and Toxic Emissions Results ........................................................31 Comparisons with Previous Studies ..............................................................47 Driveability Index..............................................................................................49 Summary and Conclusions ..............................................................................51 Acknowledgments ................................................................................................54 References.............................................................................................................55
Appendices Appendix A. Appendix B. Appendix C. Appendix D.
Properties of the Test Fuels Results for Testing of Vinyl Acetate Fuel Effects Description of Catalyst Aging Detailed Description of Statistical Analysis
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
List of Figures Figure 1. CRC E-67 Fuel Cube Design ..........................................................................................3 Figure 2. Fuel Square for Fuels D, E, K, and L .............................................................................5 Figure 3. Flow Chart for CRC Project No. E-67 Vehicle Testing..................................................8 Figure 4. Composite NMHC Balanced Average by T50 - Fleet Average and Individual Vehicles ...12 Figure 5a. Composite NMHC Balanced Average by EtOH x T90 - Fleet Average ......................13 Figure 5b. Composite NMHC Balanced Average by T90 x EtOH - Fleet Average ......................13 Figure 6a. Bag 1 NMHC Balanced Average by EtOH x T50 – Fleet Average .............................15 Figure 6b. Bag 1 NMHC Balanced Average by T50 x EtOH - Fleet Average..............................15 Figure 7a. Bag 1 NMHC Balanced Average by EtOH x T90 – Fleet Average .............................16 Figure 7b. Bag 1 NMHC Balanced Average by T90 x EtOH - Fleet Average..............................16 Figure 8a. Composite CO Balanced Average by EtOH x T90 - Fleet Average.............................18 Figure 8b. Composite CO Balanced Average by T50 x EtOH - Fleet Average ............................18 Figure 9. Composite CO Balanced Average by T90 - Fleet Average and Individual Vehicles.....19 Figure 10a. Bag 1 CO Balanced Average by EtOH x T50 – Fleet Average..................................20 Figure 10b. Bag 1 CO Balanced Average by T50 x EtOH - Fleet Average ..................................20 Figure 11. Bag 1 CO Balanced Average by T90 – Fleet Average and Individual Vehicles..........21 Figure 12a. Composite NOx Balanced Average by EtOH x T50 – Fleet Average ........................23 Figure 12b. Composite NOx Balanced Average by T50 x EtOH - Fleet Average.........................23 Figure 13. Bag 1 NOx Balanced Average by EtOH - Fleet Average and Individual Vehicles.....24 Figure 14. Bag 1 NOx Balanced Average by T50 – Fleet Average and Individual Vehicles........25 Figure 15. Fuel Consumption Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................27 Figure 16. Fuel Consumption Balanced Average by T50 - Fleet Average and Individual Vehicles.................................................................................................................................27 Figure 17. Fuel Consumption Balanced Average by T90 - Fleet Average and Individual Vehicles ................................................................................................................................28 Figure 18. Bag 1 Fuel Consumption Balanced Average by EtOH – Fleet Average and Individual Vehicles.................................................................................................................................29 Figure 19. Bag 1 Fuel Consumption Balanced Average by T50 – Fleet Average and Individual Vehicles.................................................................................................................................29 Figure 20. Bag 1 Fuel Consumption Balanced Average by T90 - Fleet Average and Individual Vehicles ................................................................................................................................30 Figure 21. NMOG Balanced Average by EtOH - Fleet Average and Individual Vehicles ..........33 Figure 22. NMOG Balanced Average by T50 - Fleet Average and Individual Vehicles ..............33
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Figure 23. Composite Formaldehyde Balanced Average by T50 - Fleet Average and Individual Vehicles ................................................................................................................................35 Figure 24. Bag 1 Formaldehyde Balanced Average by EtOH - Fleet Average and Individual Vehicles ................................................................................................................................36 Figure 25. Bag 1 Formaldehyde Balanced Average by T50 - Fleet Average and Individual Vehicles ................................................................................................................................36 Figure 26. Composite Acetaldehyde Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................38 Figure 27. Bag 1 Acetaldehyde Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................39 Figure 28. Composite Benzene Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................40 Figure 29. Composite Benzene Balanced Average by T50 - Fleet Average and Individual Vehicles.................................................................................................................................41 Figure 30. Bag 1 Benzene Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................42 Figure 31. Bag 1 Benzene Balanced Average by T50 - Fleet Average and Individual Vehicles ..42 Figure 32. Composite 1,3-Butadiene Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................44 Figure 33. Composite 1,3-Butadience Balanced Average by T50 - Fleet Average and Individual Vehicles.................................................................................................................................44 Figure 34. Bag 1 1,3-Butadiene Balanced Average by EtOH - Fleet Average and Individual Vehicles.................................................................................................................................45 Figure 35. Bag 1 1,3-Butadience Balanced Average by T50 - Fleet Average and Individual Vehicles.................................................................................................................................46 Figure 36. DI Model Results.........................................................................................................50
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List of Tables Table 1. Description of Test Vehicles ........................................................................................... 2 Table 2. Summary of Target and Actual Fuel Properties ...............................................................4 Table 3. Description of General Fuel Properties ...........................................................................4 Table 4. Fuel Randomization Matrix .............................................................................................6 Table 5. Mixed Model Summary for NMHC ..............................................................................11 Table 6. Mixed Model Summary for CO .....................................................................................17 Table 7. Mixed Model Summary for NOx ...................................................................................22 Table 8. Mixed Model Summary for Fuel Consumption*1000 ...................................................26 Table 9. Mixed Model Summary for NMOG ...............................................................................31 Table 10. Four Fuel Mixed Model Summary for NMHC.............................................................31 Table 11. Mixed Model Summary for Formaldehyde ..................................................................34 Table 12. Mixed Model Summary for Acetaldehyde ...................................................................37 Table 13. Mixed Model Summary for Benzene ..........................................................................39 Table 14. Mixed Model Summary for 1,3-Butadiene...................................................................43
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CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
Disclaimer This report was prepared by the University of California-Riverside, College of EngineeringCenter for Environmental Research and Technology (CE-CERT) as an account of work sponsored by the Coordinating Research Council (CRC). Neither the CRC, members of the CRC, CE-CERT, nor any person acting on their behalf: (1) makes any warranty, expressed or implied, with respect to the use of any information, apparatus, method, or process disclosed in this report, or (2) assumes any liabilities with respect to use of, inability to use, or damages resulting from the use or inability to use, any information, apparatus, method, or process disclosed in this report.
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University of California, Riverside, CE-CERT
CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
Executive Summary Regulations on the composition of gasoline for environmental and other initiatives continue to play an important role in the production of gasoline. Predictions of the effects of changes in fuel properties on vehicle emissions are incorporated in the Environmental Protection Agency’s (EPA’s) Complex Model and the California Air Resources Board’s (CARB’s) Predictive Model. Oxygenate content and fuel volatility (distillation) variables are important parameters when determining the emission reduction potential of new fuels and these properties are included in the models used by EPA and CARB. Although the effects of fuel volatility and oxygenates on emissions have been extensively studied in the past, data on the effects of these fuel properties on the latest-technology vehicles – those certified to California’s Low-Emission Vehicle (LEV), Ultra-Low-Emission Vehicle (ULEV), and Super-Ultra-Low-Emission Vehicle (SULEV) standards – are quite limited. The goal of the present project is to expand the database of information available on the impacts of gasoline volatility parameters and ethanol content on exhaust emissions. This program includes a test fleet with the newest technology vehicles and a comprehensive set of test fuels with varying ethanol content and mid-range and back-end volatility. For this study, 12 California-certified LEV to SULEV vehicles, with an even split between passenger cars and light-duty trucks, were tested on a 12 fuel test matrix. The 12 fuels were designed with independently varying levels of ethanol concentration (0 volume %, 5.7 volume %, and 10 volume %), T50 (195°F, 215°F, and 235°F), and T90 (295°F, 330°F, and 355°F). The fuel matrix was designed to represent both non-oxygenated and oxygenated fuels available in California and the rest of the US. Vehicles were tested with catalysts that were bench-aged to an equivalent of 100,000 miles. Measurements included regulated exhaust emissions (non-methane hydrocarbons (NMHC), carbon monoxide (CO), and oxides of nitrogen (NOx)), fuel consumption, as well as detailed non-methane organic gas (NMOG) speciation for a subset of four fuels. Complete randomization of the fuels testing order resulted in a more statistically-robust dataset for analysis. The final analysis of project data estimated regression coefficients for the fuel effects, with the levels of ethanol, T50, and T90 used as continuous variables. Models predicting emissions and fuel consumption from first order effects, second order effects, and interactions of the fuel parameters were derived. Key findings are as follows: Regulated Emissions and Fuel Consumption •
NMHC: o There was a statistically significant interaction between ethanol and T90. The interaction showed that NMHC emissions increased with increasing ethanol content at the mid-point and high level of T90, but were unaffected at the low T90 level. Looked at another way, NMHC emissions increased with increasing T90 at
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University of California, Riverside, CE-CERT
CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
the mid-point and high level of ethanol, but were unaffected by T90 at the zero level of ethanol. o NMHC emissions increased with increasing T50. The percentage increases in NMHC emissions in going from the low and mid-point level for T50 to the high T50 level were 36 and 25%, respectively. •
CO: o There was a statistically significant interaction between ethanol and T50. The interaction showed that CO emissions decreased as ethanol content was increased from the low to the mid-point level for all levels of T50. However, increasing ethanol content from the mid-point to the high level produced little to no change in CO for the low and mid-point levels of T50, and increased CO at the high level of T50. Looked at another way, CO emissions increased with increasing T50 at the mid-point and high levels of ethanol, but were unaffected by T50 at the zero level of ethanol. o CO emissions decreased with increasing T90. The percentage decreases in CO emissions in going from the low and mid-point level for T90 to the high T90 level were 24% and 7%, respectively.
•
•
NOx:
o There was a statistically significant interaction between ethanol and T50. The interaction showed that NOx emissions increase with increasing ethanol content at the low level of T50. At the mid-point level of T50, NOx emissions are largely unaffected as ethanol content is increased from the zero to the mid-point level, but increase as ethanol is increased to the high level. At the high level of T50, NOx emissions are largely unaffected by ethanol content. Looked at another way, NOx emissions decreased with increasing T50 at the high level of ethanol, but were largely unaffected by T50 at the zero and mid-point levels of ethanol.
Fuel Consumption: o Fleet average fuel consumption increased by 1.4% when ethanol content was increased from the zero to the high level. o Fleet average fuel consumption decreased by 1.2% when T50 was increased from the low to the high level. o Fleet average fuel consumption decreased by 0.6% when T90 was increased from the low to the high level.
In the fuel set used in this work, 10% ethanol tended to decrease volumetric heat content by 2.2%. NMOG and Toxics Emissions Detailed speciation measurements were performed for a subset of four fuels with target T90 = 355°F in order to evaluate the fuel effects of ethanol and T50 on NMOG and the four mobile source air toxics: benzene, 1,3-butadiene, formaldehyde and acetaldehyde. Key findings are as follows:
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University of California, Riverside, CE-CERT
CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
•
NMOG: o NMOG emissions increased by 14% when ethanol content was increased from the zero to the high level. o NMOG emissions increased by 35% when T50 was increased from the low to the high level.
•
Formaldehyde: o Formaldehyde emissions increased by 23% when T50 was increased from the low to the high level.
•
Acetaldehyde: o Acetaldehyde emissions increased by 73% when ethanol content was increased from the zero level to the high level.
•
Benzene: o Benzene emissions increased by 18% when ethanol content was increased from the zero to the high level. o Benzene emissions increased by 38% when T50 was increased from the low to the high level.
•
1,3-butadiene: o 1,3-butadiene emissions increased by 22% when ethanol content was increased from the zero to the high level. o 1,3-butadiene emissions increased by 56% when T50 was increased from the low to the high level.
The effects of ethanol and T50 on NMOG and mobile source toxics described above were only observed for the subset of fuels having the high level of T90. The results of this study do not permit any conclusions as to what effects ethanol or T50 might have had on NMOG or toxics emissions for fuels having low or mid-point T90 levels.
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University of California, Riverside, CE-CERT
CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
1. Introduction As vehicle and fuel technologies continue to meet more stringent emission standards, it is useful to understand the effects of fuel properties on the emissions and performance of vehicles. Over the years, the impact of fuel properties on vehicle emissions has been the subject of numerous studies and programs. Data from these earlier programs have been used in the development of regulations for fuel properties. These data also have been incorporated into the Environmental Protection Agency’s (EPA’s) Complex Model and the California Air Resources Board’s (CARB’s) Predictive Model to estimate the effects of changes in fuel properties on vehicle emissions. Although the database on the emissions impact of fuel properties is large, data on the effects of fuel properties on the latest technology vehicles – those certified to California’s LowEmission Vehicle (LEV), Ultra-Low-Emission Vehicle (ULEV), and Super-Ultra-Low-Emission Vehicle (SULEV) standards – is more limited. In the future, these vehicle technologies will account for an increasing share of the emissions of the in-use vehicle fleet. Today, regulatory agencies continue to consider changes in gasoline composition regulations in response to environmental and other initiatives. Oxygenate content and fuel volatility are two parameters that are considered to be important in determining the emission reduction potential of new fuels. Both properties are included in the models used by EPA and CARB. Many states have banned methyl t-butyl ether (MTBE), leading to greater use of ethanol (EtOH). The Renewable Fuel Standard (RFS) adopted as part of the federal Energy Policy Act of 2005 requires significant and increasing volumes of renewables to blended into the transportation fuel pool between 2006 and 2012, much of which is likely to be ethanol. The effects of fuel volatility and ethanol/oxygenates on emissions have been investigated extensively in past studies [1-12]. These studies have shown some general trends of how these properties affect emissions. The reduction of T50 and T90 and the corresponding reduction of heavy fuel hydrocarbon compounds have generally been found to reduce exhaust hydrocarbon emissions [2,3,5,8]. Ethanol and other oxygenates typically have been found to reduce total hydrocarbon (THC) and carbon monoxide (CO) emissions [1,2,7-9,11,12]. Increases in oxides of nitrogen (NOx) have been observed for oxygenates in some studies, although this observation is not consistent over all test fleets [1,2,7-9,11,12]. While these studies provide important information, there is relatively limited data on how these fuel parameters will affect emissions in advanced technology vehicles. Some of the more recent studies also include some contradictory data, including a recent study in which slightly higher NOx emissions were found for a fuel with no oxygenates in comparison with the oxygenated fuels [1]. The goal of this project is to expand the database of information available on the impacts of gasoline volatility parameters and ethanol content on exhaust emissions. This program includes a comprehensive set of test fuels with varying ethanol content and mid- and back-end volatility, and a test fleet with the newest technology vehicles. Measurements include detailed non-methane organic gas (NMOG) speciation for a subset of fuels. The information obtained from this study is valuable in better understanding and predicting the implications of changes in fuel properties for regulatory or other reasons.
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University of California, Riverside, CE-CERT
CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
2. Experimental Procedures 2.1 Test Vehicles Twelve vehicles were recruited for testing. The vehicles included present day technologies with California low-emission vehicle (LEV), ultra-low emission vehicle (ULEV), and super-ultralow-emission vehicle (SULEV) certification. The test fleet was evenly split between passenger cars and light-duty trucks. Within each general certification category, e.g., LEV, the passenger cars and trucks are certified to different standards, and as such represent different emissions categories. Vehicles were obtained from a combination of sources including rental agencies, private parties, and corporate sponsors. All vehicles had accumulated at least 10,000 miles. Prior to entering the program, all vehicles were inspected using a standard checklist to ensure that they were in sound mechanical and operational condition. The vehicles were fitted with catalysts that had been bench-aged to the equivalent of 100,000 miles for testing. The specific details of the vehicles used in this project are listed in Table 1. Table 1. Description of Test Vehicles # MY 1 2 3 4 5 6 7 8 9 10 11 12
OEM
Model
California Type Certification 2002 Ford Taurus LEV PC 2003 Chevrolet Cavalier LEV PC 2003 Ford F-150 LEV LDT 2003 Dodge Caravan LEV LDT 2003 Ford Explorer LEV LDT 2003 Chevrolet Trailblazer LEV LDT 2002 Toyota Camry ULEV PC 2003 Buick LeSabre ULEV PC 2001 VW Jetta ULEV PC 2003 Ford Windstar ULEV LDT 2003 Chevrolet Silverado ULEV LDT 2003 Honda Accord SULEV PC
Engine Size 3.0 L 2.2 L 4.6 L 3.3 L 4.0 L 4.2 L 2.4 L 3.8 L 2.0 L 3.8 L 5.3 L 2.4 L
Mileage Engine Family 19,414 28,728 13,856 18,342 16,445 13,141 14,731 10,364 28,761 20,523 10,298 12,432
1FMXV03.0VF4 1GMXV02.2025 3FMXT05.4PFB 3CRXT03.32DR 3FMXT04.02FB 3GMXT04.2185 1TYXV02.4JJA 3GMXV03.8044 1VWXV02.0223 3FMXT03.82HA 3GMXT05.3176 3HNXV02.4KCP
PC = passenger car; LDT = light-duty truck; vehicles equipped with catalysts aged to 100,000 miles for testing
2.2 Fuels Twelve fuels were prepared and provided for testing for this project. These 12 fuels were designed to encompass three levels of ethanol content (0%, 5.7% and 10%), three levels of T50 (195°F, 215°F and 235°F), and three levels of T90 (295°F, 330°F, and 355°F). The values for ethanol represent typical ethanol concentrations found in California (5.7%) and the rest of the US (10%). The ranges for both T50 and T90 span the 10th and 90th percentile values based on summer fuel surveys during/through calendar year 2002. Previous studies had shown that in addition to the main effects of ethanol, T50, and T90, curvature effects for each of these factors and interactions between ethanol and each of T50 and T90 might be important. From a full factorial design matrix of 27 fuels obtained from the three fuel factors each at three levels, statistical optimality criteria combined with practical concerns about what fuels could be blended 2
University of California, Riverside, CE-CERT
CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
from refinery streams led to the selection of 12 fuels as best for estimating the possible fuel effects. The fuel design matrix is shown graphically in Figure 1. A summary of the design and actual values of the fuel properties is provided in Table 2. The actual fuel property values shown in Table 2 represent averages of measurements from four or five laboratories, depending on the specific property. Driveability Index (DI) was calculated for each fuel using the equation recently balloted by ASTM. A more detailed listing of the fuel properties is provided in Appendix A. The fuels were blended from refinery streams with the general properties targeted to be constant for all fuels in order to reduce or eliminate any potential confounding effect of these properties with the design parameters. The target values for the general fuel properties are provided in Table 3. The general fuel properties are intended to be representative of fuels that are available in the commercial marketplace, but are not necessarily representative of all commercial fuels. The fuels were blended by Haltermann Products, Channelview, TX. The lubricant used for this study was a zero-sulfur, synthetic base lubricant containing ashless, zero-sulfur antiwear and anti-oxidant additives. This is the same lubricant that was used in two other recent vehicle emissions test programs [13, 14].
Figure 1. CRC E-67 Fuel Cube Design
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University of California, Riverside, CE-CERT
CRC E-67: Effects of Ethanol and Volatility on Exhaust Emissions
Table 2. Summary of Target and Actual Fuel Properties. Target Properties for Actual Values Design Variables Fuel T50,°F T90,°F Ethanol, T50,°F T90,°F Ethanol, E200, E300, Driveability % % % % Index (DI)* A 195 295 0 195 294 0.0 54 91 1082 B 195 295 5.7 191 290 5.6 58 92 1076 C 195 330 10 193 329 10.4 52 84 1128 D 195 355 0 199 355 0.0 51 84 1153 E 195 355 10 198 352 10.3 51 80 1165 F 215 295 0 217 295 0.0 40 91 1148 G 215 295 10 212 291 10.1 47 80 1151 H 215 330 0 216 327 0.1 42 85 1177 I 215 355 5.7 216 354 5.9 43 78 1211 J 235 330 5.7 237 329 5.9 35 78 1255 K 235 355 0 236 355 0.0 38 75 1258 L 235 355 10 233 349 10.5 39 78 1282 * DI = 1.5*T10 + 3.0*T50 + 1.0*T90 + 2.4*vol% Ethanol (Equation recently balloted by ASTM)
Table 3. Description of General Fuel Properties. Property RVP FBP RON MON (R+M)/2 Aromatics
Limits 7.5-7.8 psi
