Impact of Exhaust Gas Recirculation on Gaseous Emissions of Turbocharged Spark-Ignition Engines

Abstract

Exhaust gas recirculation is one of the technologies that can be used to improve the efficiency of spark-ignition engines. However, apart from fuel consumption reduction, this technology has a significant impact on exhaust gaseous emissions, inducing a significant reduction in nitrogen oxides and an increase in unburned hydrocarbons and carbon monoxide, which can affect operation of the aftertreatment system. In order to evaluate these effects, data extracted from design of experiments done on a multi-cylinder 1.3 L turbocharged spark-ignition engine with variable valve timing and low-pressure exhaust gas recirculation (EGR) are used. The test campaign covers the area of interest for the engine to be used in new-generation hybrid electric platforms. In general, external EGR provides an approximately linear decrease of nitrogen oxides and deterioration of unburned hydrocarbon emissions due to thermal and flame quenching effects. At low load, the impact on emissions is directly linked to actuation of the variable valve timing system due to the interaction of EGR with internal residuals. For the same external EGR rate, running with high valve overlap increases the amount of internal residuals trapped inside the cylinder, slowing down combustion and increasing Unburnt hydrocarbon (HC) emissions. However, low valve overlap (i.e., low internal residuals) operation implies a decrease in oxygen concentration in the exhaust line for the same air–fuel ratio inside the cylinders. At high load, interaction with the variable valve timing system is reduced, and general trends of HC increase and of oxygen and carbon monoxide decrease appear as EGR is introduced. Finally, a simple stoichiometric model evaluates the potential performance of a catalyst targeted for EGR operation. The results highlight that the decrease of nitrogen oxides and oxygen availability together with the increase of unburned hydrocarbons results in a huge reduction of the margin in oxygen availability to achieve a complete oxidation from a theoretical perspective. This implies the need to rely on the oxygen storage capability of the catalyst or the possibility to control at slightly lean conditions, taking advantage of the nitrogen oxide reduction at engine-out with EGR.

Ammonia Can be Currently Considered as one of the Best Green Energy Ally

“…The recirculation of combustion gases also reduces combustion temperature by returning to the reaction zone inert species, creating a quenching effect and acting as NOx control strategy. Exhaust gas recirculation (EGR) is a common feature of diesel engines and, recently, of new spark ignition engines [98,99]. The different operating concepts in ICEs will need to be adapted based on the combustion characteristics of ammonia.…”

Pengaruh Pemasangan Exhaust Gas Recirculation Terhadap Emisi Gas Buang Honda Supra X 100

“…Gambar 5 dan 6 menunjukkan emisi gas buang CO. CO mengalami penurunan seiring dengan penggunaan EGR eksternal. Hal ini sebagai akibat efek kinetik pada reaksi disosiasi CO2 (Piqueras, dkk., 2020).…”

Numerical Evaluation of the Effect of Fuel Blending with CO2 and H2 on the Very Early Corona-Discharge Behavior in Spark Ignited Engines

“…With regard to Spark Ignition (SI) engines, two of the main limiting factors against the improvement of fuel economy are the pressure losses during throttled operations, and the very high cycle average temperature compared with that of Compression Ignition (CI) engines, which strongly affect the indicating and the thermal efficiency, respectively. A promising solution to approach those issue is using a high amount of Exhaust Gas Recirculation (EGR) in order to dilute the fresh charge, thus allowing for the cylinder empty-filling at low load with reduced throttling at the intake manifold and the reactive gas to cool down (lower heat losses and knock mitigation) [1,2]. One of the main concerns regarding highly diluted operations is the flame stability, together with the risk of incomplete combustion and ignition failure [3,4].…”