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Title: Effects of Heat of Vaporization and Octane Sensitivity on Knock-Limited Spark Ignition Engine Performance

Abstract

Knock-limited loads for a set of surrogate gasolines all having nominal 100 research octane number (RON), approximately 11 octane sensitivity (S), and a heat of vaporization (HOV) range of 390 to 595 kJ/kg at 25 degrees C were investigated. A single-cylinder spark-ignition engine derived from a General Motors Ecotec direct injection (DI) engine was used to perform load sweeps at a fixed intake air temperature (IAT) of 50 degrees C, as well as knock-limited load measurements across a range of IATs up to 90 degrees C. Both DI and pre-vaporized fuel (supplied by a fuel injector mounted far upstream of the intake valves and heated intake runner walls) experiments were performed to separate the chemical and thermal effects of the fuels' knock resistance. The DI load sweeps at 50 degrees C intake air temperature showed no effect of HOV on the knock-limited performance. The data suggest that HOV acts as a thermal contributor to S under the conditions studied. Measurement of knock-limited loads from the IAT sweeps for DI at late combustion phasing showed that a 40 vol% ethanol (E40) blend provided additional knock resistance at the highest temperatures, compared to a 20 vol% ethanol blend and hydrocarbon fuel withmore » similar RON and S. Using the pre-vaporized fuel system, all the high S fuels produced nearly identical knock-limited loads at each temperature across the range of IATs studied. For these fuels RON ranged from 99.2 to 101.1 and S ranged from 9.4 to 12.2, with E40 having the lowest RON and highest S. The higher knock-limited loads for E40 at the highest IATs examined were consistent with the slightly higher S for this fuel, and the lower engine operating condition K values arising from use of this fuel. The study highlights how fuel HOV can affect the temperature at intake valve closing, and consequently the pressure-temperature history of the end gas leading to more negative values of K, thereby enhancing the effect of S on knock resistance.« less

Authors:
 [1];  [1];  [1]; ORCiD logo [1];  [1];  [1]
  1. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B)
OSTI Identifier:
1433471
Report Number(s):
NREL/CP-5400-70443
DOE Contract Number:
AC36-08GO28308
Resource Type:
Conference
Resource Relation:
Conference: Presented at WCX 18: SAE World Congress Experience, 10-12 April 2018, Detroit, Michigan
Country of Publication:
United States
Language:
English
Subject:
33 ADVANCED PROPULSION SYSTEMS; knock; engine performance; spark ignition

Citation Formats

Ratcliff, Matthew A, Burton, Jonathan L, Sindler, Petr, McCormick, Robert L, Christensen, Earl D, and Fouts, Lisa A. Effects of Heat of Vaporization and Octane Sensitivity on Knock-Limited Spark Ignition Engine Performance. United States: N. p., 2018. Web. doi:10.4271/2018-01-0218.
Ratcliff, Matthew A, Burton, Jonathan L, Sindler, Petr, McCormick, Robert L, Christensen, Earl D, & Fouts, Lisa A. Effects of Heat of Vaporization and Octane Sensitivity on Knock-Limited Spark Ignition Engine Performance. United States. doi:10.4271/2018-01-0218.
Ratcliff, Matthew A, Burton, Jonathan L, Sindler, Petr, McCormick, Robert L, Christensen, Earl D, and Fouts, Lisa A. Tue . "Effects of Heat of Vaporization and Octane Sensitivity on Knock-Limited Spark Ignition Engine Performance". United States. doi:10.4271/2018-01-0218. https://www.osti.gov/servlets/purl/1433471.
@article{osti_1433471,
title = {Effects of Heat of Vaporization and Octane Sensitivity on Knock-Limited Spark Ignition Engine Performance},
author = {Ratcliff, Matthew A and Burton, Jonathan L and Sindler, Petr and McCormick, Robert L and Christensen, Earl D and Fouts, Lisa A},
abstractNote = {Knock-limited loads for a set of surrogate gasolines all having nominal 100 research octane number (RON), approximately 11 octane sensitivity (S), and a heat of vaporization (HOV) range of 390 to 595 kJ/kg at 25 degrees C were investigated. A single-cylinder spark-ignition engine derived from a General Motors Ecotec direct injection (DI) engine was used to perform load sweeps at a fixed intake air temperature (IAT) of 50 degrees C, as well as knock-limited load measurements across a range of IATs up to 90 degrees C. Both DI and pre-vaporized fuel (supplied by a fuel injector mounted far upstream of the intake valves and heated intake runner walls) experiments were performed to separate the chemical and thermal effects of the fuels' knock resistance. The DI load sweeps at 50 degrees C intake air temperature showed no effect of HOV on the knock-limited performance. The data suggest that HOV acts as a thermal contributor to S under the conditions studied. Measurement of knock-limited loads from the IAT sweeps for DI at late combustion phasing showed that a 40 vol% ethanol (E40) blend provided additional knock resistance at the highest temperatures, compared to a 20 vol% ethanol blend and hydrocarbon fuel with similar RON and S. Using the pre-vaporized fuel system, all the high S fuels produced nearly identical knock-limited loads at each temperature across the range of IATs studied. For these fuels RON ranged from 99.2 to 101.1 and S ranged from 9.4 to 12.2, with E40 having the lowest RON and highest S. The higher knock-limited loads for E40 at the highest IATs examined were consistent with the slightly higher S for this fuel, and the lower engine operating condition K values arising from use of this fuel. The study highlights how fuel HOV can affect the temperature at intake valve closing, and consequently the pressure-temperature history of the end gas leading to more negative values of K, thereby enhancing the effect of S on knock resistance.},
doi = {10.4271/2018-01-0218},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Apr 03 00:00:00 EDT 2018},
month = {Tue Apr 03 00:00:00 EDT 2018}
}

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