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Title: Analytical Examination of the Relationship between Fuel Properties, Engine Efficiency, and R Factor Values

Abstract

The variability in gasoline energy content, though most frequently not a consumer concern, is an issue of concern for vehicle manufacturers in demonstrating compliance with regulatory requirements. Advancements in both vehicle technology, test methodology, and fuel formulations have increased the level of visibility and concern with regard to the energy content of fuels used for regulatory testing.The R factor was introduced into fuel economy calculations for vehicle certification in the late 1980s as a means of addressing batch-to-batch variations in the heating value of certification fuels and the resulting variations in fuel economy results. While previous studies have investigated values of the R factor for modern vehicles through experimentation, subsequent engine studies have made clear that it is difficult to distinguish between the confounding factors that influence engine efficiency when R is being studied experimentally.The proposed study focuses on an analytical approach to examining the heating value effects so that R values can be studied without the influence of confounding effects of other fuel properties. Data previously published for a 1.6-liter naturally-aspirated engine are used as a case study to explore the relationship between fuel properties, engine efficiency, and R factor values. The results demonstrate that engine efficiency does varymore » as a result of differences in heating value among fuels, although other factors that are variant among fuels also impact efficiency. R factor values depend not only on the difference in heating value between two fuels, but also on the directionality of the change and on engine operating loads. The latter is integral because the reference engine efficiency point is itself a function of the engine operating condition. R factor values asymptotically approach unity as engine operating load increases. Increasing engine efficiency causes R values for a given test fuel to increase. A method is presented for which the test data from only one fuel is required to establish R factor values for individual vehicles and test cycles. An alternative method of establishing Indolene fuel economy equivalency for certification tests is also discussed.« less

Authors:
ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
OSTI Identifier:
1506803
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Society of Automotive Engineers Technical Paper Series
Additional Journal Information:
Journal Volume: 1; Journal Issue: 01
Country of Publication:
United States
Language:
English
Subject:
33 ADVANCED PROPULSION SYSTEMS

Citation Formats

Sluder, C. Scott. Analytical Examination of the Relationship between Fuel Properties, Engine Efficiency, and R Factor Values. United States: N. p., 2019. Web. doi:10.4271/2019-01-0309.
Sluder, C. Scott. Analytical Examination of the Relationship between Fuel Properties, Engine Efficiency, and R Factor Values. United States. doi:10.4271/2019-01-0309.
Sluder, C. Scott. Tue . "Analytical Examination of the Relationship between Fuel Properties, Engine Efficiency, and R Factor Values". United States. doi:10.4271/2019-01-0309.
@article{osti_1506803,
title = {Analytical Examination of the Relationship between Fuel Properties, Engine Efficiency, and R Factor Values},
author = {Sluder, C. Scott},
abstractNote = {The variability in gasoline energy content, though most frequently not a consumer concern, is an issue of concern for vehicle manufacturers in demonstrating compliance with regulatory requirements. Advancements in both vehicle technology, test methodology, and fuel formulations have increased the level of visibility and concern with regard to the energy content of fuels used for regulatory testing.The R factor was introduced into fuel economy calculations for vehicle certification in the late 1980s as a means of addressing batch-to-batch variations in the heating value of certification fuels and the resulting variations in fuel economy results. While previous studies have investigated values of the R factor for modern vehicles through experimentation, subsequent engine studies have made clear that it is difficult to distinguish between the confounding factors that influence engine efficiency when R is being studied experimentally.The proposed study focuses on an analytical approach to examining the heating value effects so that R values can be studied without the influence of confounding effects of other fuel properties. Data previously published for a 1.6-liter naturally-aspirated engine are used as a case study to explore the relationship between fuel properties, engine efficiency, and R factor values. The results demonstrate that engine efficiency does vary as a result of differences in heating value among fuels, although other factors that are variant among fuels also impact efficiency. R factor values depend not only on the difference in heating value between two fuels, but also on the directionality of the change and on engine operating loads. The latter is integral because the reference engine efficiency point is itself a function of the engine operating condition. R factor values asymptotically approach unity as engine operating load increases. Increasing engine efficiency causes R values for a given test fuel to increase. A method is presented for which the test data from only one fuel is required to establish R factor values for individual vehicles and test cycles. An alternative method of establishing Indolene fuel economy equivalency for certification tests is also discussed.},
doi = {10.4271/2019-01-0309},
journal = {Society of Automotive Engineers Technical Paper Series},
number = 01,
volume = 1,
place = {United States},
year = {2019},
month = {4}
}

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This content will become publicly available on April 2, 2020
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