The NOx and N2O emission characteristics of an HCCI engine operated with n-Heptane

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Journal titleJournal of Energy Resources Technology
SubjectHCCI engine; n-heptane; NOx emissions; N2O emissions; Combustion efficiency; Combustion phasing
AbstractThis paper presents the oxides of nitrogen (NOx ) and nitrous oxide (N2 O) emission characteristics of a Cooperative Fuel Research (CFR) engine modified to operate in homogeneous charge compression ignition (HCCI) combustion mode. N-heptane was used as the fuel in this research. Several parameters were varied, including intake air temperature and pressure, air/fuel ratio (AFR), compression ratio (CR), and exhaust gas recirculation (EGR) rate, to alter the HCCI combustion phasing from an overly advanced condition where knocking occurred to an overly retarded condition where incomplete combustion occurred with excessive emissions of unburned hydrocarbons (UHC) and carbon monoxide (CO). NOx emissions below 5 ppm were obtained over a fairly wide range of operating conditions, except when knocking or incomplete combustion occurred. The NOx emissions were relatively constant when the combustion phasing was within the acceptable range. NOx emissions increased substantially when the HCCI combustion phasing was retarded beyond the optimal phasing even though lower combustion temperatures were expected. The increased N2 O and UHC emissions observed with retarded combustion phasing may contribute to this unexpected increase in NOx emissions. N2 O emissions were generally less than 0.5 ppm; however, they increased substantially with excessively retarded and incomplete combustion. The highest measured N2 O emissions were 1.7 ppm, which occurred when the combustion efficiency was approximately 70%.
Publication date
AffiliationNational Research Council Canada; NRC Institute for Chemical Process and Environmental Technology
Peer reviewedYes
NRC number53039
NPARC number21268475
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Record identifier276127f7-0354-4ec7-baea-810b682b02d2
Record created2013-07-26
Record modified2016-05-09
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