CARBONYL-COMPOUNDS AND PAH EMISSIONS FROM CNG HEAVY-DUTY ENGINE

Previous works carried out in Istituto Motori laboratories have shown that natural gas is a suitable fuel for general means of transportatio n. This is because of its favorable effects on engine performance and pollutant emissions. The natural gas fueled engine provided the same p erformance as the diesel engine, met R49 emission standards, and showe d very low smoke levels. On the other hand, it is well known that inte rnal combustion engines emit some components that are harmful for huma n health, such as carbonyl compounds and polycyclic aromatic hydrocarb ons (PAH). This paper shows the results of carbonyl compounds and PAH emissions analysis for a heavy-duty Otto cycle engine fueled with natu ral gas. The engine was tested using the R49 cycle that is used to mea sure the regulated emissions. The test analysis has been compared with an analysis of a diesel engine, tested under the same conditions. Tot al PAH emissions from the CNG engine were about three orders of magnit ude lower than from the diesel engine. Formaldehyde emission from the CNG engine was about ten times as much as from the diesel engine, whil e emissions of other carbonyl compounds were comparable.