Exploration of the Hysteresis in Speciated Emissions during Transient Gasoline Engine Combustion

Abstract

Emissions of various fuel components (cyclohexane, ethanol, and pentane) and reaction intermediate species (acetylene, ethylene, formaldehyde, and methane) from a multicylinder, port-fuel-injected, spark-ignited gasoline engine undergoing transient loads are measured using Fourier transform infrared (FTIR) spectroscopy. The load profiles explored herein consist of positive and negative load ramps spanning brake mean effective pressures of 2–7 bar lasting 1, 2.5, and 5 s, as well as periodic load ramps of identical magnitudes and durations. Experiments are performed at two constant speed settings of 1500 and 2000 rpm. Fourier transform infrared spectroscopy measurements are processed with a recently developed unscented Kalman filter [WilsonD. Wilson, D. Energy Fuels2017311115611168; WilsonD. Wilson, D. Energy Fuels2018321189911912], which combats the biasing effects of sample recirculation and signal nonstationarity associated with transient FTIR measurements, to improve emission estimations. Emissions during load transients are compared to quasi-steady model predictions and estimated emission stochasticity. Overall, the data shows that transient effects (i.e., load ramp rate, speed/load history, nonstoichiometric equivalence ratio) substantially influence volatile organic compound (VOC) emissions in a deterministic manner, as quasi-steady prediction errors regularly exceed the combined effects of stochasticity and uncertainty. Negative load ramps (from 7 to 2 bar) result in the greatest quasi-steady prediction errors of all load profiles. For the periodic load ramps, the greatest quasi-steady prediction errors of the intermediate and fuel component emissions occur for 1 and 2.5 s load ramps, respectively. In both cases, these errors surpass the 95% confidence interval of statistical significance for each species except cyclohexane. Benzene and toluene emissions are unreported due to low quantities and excessive measurement noise, whereas 1,3-butadiene emissions show minimal relation to engine speed/load. The results of this work suggest that transient and historical effects must be taken into account when predicting VOC engine emissions and that the quasi-steady approach is insufficient.

Adsorption of Volatile Organic Compounds at Medium-High Temperature Conditions by Activated Carbons

“…Their concentrations are much lower than those of other polluting gases discharged from industrial sources; however, coal-fired power plants are still a major anthropogenic source of organic pollutants because a large amount of flue gas is emitted into the atmosphere . Most of the VOCs and SVOCs pose a threat to human health by irritating the eyes, skin, and nervous and respiratory systems; in addition, they represent major contributors to secondary organic aerosols, ozone depletion, and photochemical smog . Therefore, it is important to reduce the emission of organic pollutants from coal-fired power plants to improve environmental quality and maintain human health.…”

“…3 Most of the VOCs and SVOCs pose a threat to human health by irritating the eyes, skin, and nervous and respiratory systems; in addition, they represent major contributors to secondary organic aerosols, ozone depletion, and photochemical smog. 6 Therefore, it is important to reduce the emission of organic pollutants from coal-fired power plants to improve environmental quality and maintain human health.…”