Hydrocarbon oxidation in the exhaust port and runner of a spark ignition engine

Abstract

An exhaust gas quenching experiment was conducted to study the evolution of HC emissions and the extent of HC oxidation in the exhaust port and runner of a spark ignition engine. Fuel composition and engine parameter effects were of particular interest. The fuel set consisted of gasoline, several alkanes (methane, ethane, propane, n-butane, iso-octane), an alkene (ethene) and an aromatic (toluene); all fuel composition experiments were completed at a light load condition. The engine parameter set included engine speed, load, spark timing, equivalence ratio and coolant temperature; experiments involved mostly single parameter variations about a light load condition.The cylinder-exit HC emissions varied significantly over the set of fuels tested. There was no significant fuel dependency in the percentage of HC oxidation in the exhaust port/runner system, which ranged from 35 to 45%. A substantial portion of the oxidation occurred in the exhaust port. Speciated HC emissions identified unburned fuel as the major cylinder-exit species. The unburned fuel contribution ranged from 80 to 95% for methane, ethene and toluene and from 40 to 70% for the non-methane alkane fuels.Changes in the species distributions for the non-methane alkane fuels were observed in both the port and runner. Alkenes, the most reactive species in the formation of photochemical smog, were the dominant non-fuel species. Hence, the benefit of HC oxidation was accompanied by an increase in photochemical reactivity.Independent increases in engine speed and load produced decreases in the percentage of HC oxidation in the exhaust port/runner system. Higher temperatures due to spark retard increased HC oxidation from approximately 38% at MBT to approximately 53% at 12 degrees retard. Fuel lean conditions yielded higher oxidation levels (42%) than did fuel rich conditions (27%) due to the 02 availability. There was negligible change in oxidation level over the coolant temperature range tested.

High Ethylene and Propylene in an Area Dominated by Oil Production

“…Hesterberg, et al [70] showed that, compared to uncontrolled diesel-fueled engines, uncontrolled natural gas-fueled engines have higher propylene:ethylene ratios (0.07 versus 0.28). The propylene:ethylene ratio in our measurements, however, was more than three times higher than that reported for natural gas engines by Hesterberg et al Ethylene and propylene can be generated from the combustion of methane or from combustion of NMHC [71], and Kim and Bae [72] showed that propylene emissions (but not ethylene emissions) increased with the NMHC content of fuel (also see Drobot, et al [73]). The raw gas available at Uinta Basin oil wells is richer in propane and other NMHC [26] than the purified natural gas used by Hesterberg et al, possibly explaining the difference between the two studies.…”

Speciated hydrocarbon emissions from a gas-fuelled spark-ignition engine with various operating parameters

“…methane, ethane, propane, i-butane, nbutane, i-pentane and n-pentane) that were found in the exhaust gases. Since non-methane alkane fuels are easily converted to ole®n species by late-cycle burn-up at the exhaust port [12], the fuel components from natural gas are higher than those from LPG. This is con®rmed in the plot of fuel components, where fuel components were distinguished among the exhaust gases, versus exhaust temperature (Fig.…”

Study on Carbonyl Emissions of Diesel Engine Fueled with Biodiesel

“…It can be seen that the detection goal has a reasonable retention time and a better resolution. Saturated aldehyde hydrazones of DNPH have strong absorption at 360 nm [14], so the detection wavelength of UV detector was set at 360 nm.…”