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Title: Premixed ignition behavior of C{sub 9} fatty acid esters: A motored engine study

An experimental study on the premixed ignition behavior of C{sub 9} fatty acid esters has been conducted in a motored CFR engine. For each test fuel, the engine compression ratio was gradually increased from the lowest point (4.43) to the point where significant high temperature heat release (HTHR) was observed. The engine exhaust was sampled and analyzed through GC-FID/TCD and GC-MS. Combustion analysis showed that the four C{sub 9} fatty acid esters tested in this study exhibited evidently different ignition behavior. The magnitude of low temperature heat release (LTHR) follows the order, ethyl nonanoate > methyl nonanoate >> methyl 2-nonenoate > methyl 3-nonenoate. The lower oxidation reactivity for the unsaturated fatty acid esters in the low temperature regime can be explained by the reduced amount of six- or seven-membered transition state rings formed during the oxidation of the unsaturated esters due to the presence of a double bond in the aliphatic chain of the esters. The inhibition effect of the double bond on the low temperature oxidation reactivity of fatty acid esters becomes more pronounced as the double bond moves toward the central position of the aliphatic chain. GC-MS analysis of exhaust condensate collected under the engine conditions where onlymore » LTHR occurred showed that the alkyl chain of the saturated fatty acid esters participated in typical paraffin-like low temperature oxidation sequences. In contrast, for unsaturated fatty acid esters, the autoignition can undergo olefin ignition pathways. For all test compounds, the ester functional group remains largely intact during the early stage of oxidation. (author)« less
Authors:
; ;  [1]
  1. EMS Energy Institute, The Pennsylvania State University, University Park, PA 16802 (United States)
Publication Date:
OSTI Identifier:
21177445
Resource Type:
Journal Article
Resource Relation:
Journal Name: Combustion and Flame; Journal Volume: 156; Journal Issue: 6; Other Information: Elsevier Ltd. All rights reserved
Country of Publication:
United States
Language:
English
Subject:
33 ADVANCED PROPULSION SYSTEMS; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CARBOXYLIC ACID ESTERS; COMBUSTION; DIESEL FUELS; PRESSURE RANGE KILO PA; AUTOIGNITION; HEAT; ENGINES; TEMPERATURE RANGE 0400-1000 K; BIOFUELS; QUANTITATIVE CHEMICAL ANALYSIS; COMBUSTION PROPERTIES; COMPRESSION RATIO; ACTIVATION ENERGY; INHIBITION Low-temperature heat release; High- temperature heat release; Low-temperature oxidation; Motored engine