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Propane as an engine fuel for clean air requirements.

Fleming RD; Allsup JR; Franch TR; Eccleston DE
JAPCA 1972 Jun; 22(6):451-458
Air pollutants in exhaust gas produced from lp-gas (propane) were studied using both laboratory engines and vehicles. The objective of the study was both to evaluate propane as a low-pollution fuel and to provide information on adjustment of engine parameters for advantageous use of propane as a low-pollution fuel. Variables in the study were air-fuel ratio (a/f), ignition timing schedule, and ambient temperature. Data comparable to that for propane relating a/f and ambient temperature to emissions are shown for natural gas and for gasoline. Results showed that engines using propane as compared with gasoline can operate over a wider range of a/f with minimum carbon monoxide and hydrocarbon emissions. Propane and natural gas emission levels were similar. No significant difference in nitrogen oxides was found for the three fuels. In simulated typical city driving using propane as a fuel, emissions were markedly reduced by retarding ignition timing with a/f increased to approach the lean misfire limit. However, serious power loss accompanied engine adjustment for minimum emissions. In addition to favorable lean-limit characteristics, propane offers two other advantages as low-pollution fuel: (1) mixture enrichment during starting and during warmup is avoided. In addition, carbon monoxide and hydrocarbon emissions with propane are unaffected by ambient temperature--in contrast to highly significant increases in emissions at low ambients with gasoline. (2) The photochemical reactivity of hydrocarbon emissions from propane, although higher than those from natural gas,
Publication Date
Document Type
OP; Journal Article
Fiscal Year
Identifying No.
OP 117-72
Issue of Publication
NIOSH Division
Source Name
Journal of Air Pollution Control Association
Page last reviewed: December 23, 2021
Content source: National Institute for Occupational Safety and Health Education and Information Division