Effects of rebreathing exhaust gas strategy on performance behaviors of the hydrogen enriched natural gas spark ignition

Recently, more stringent emission regulations and laws are introduced in the transportation section for further reducing the toxic emissions and carbon dioxide emission. These strict regulations promote the technology advancement of the internal combustion engine through in-cylinder combustion process optimization and out-cylinder exhaust emissions after-treatment system. However, the renewable fuels, such as green hydrogen, are encouraged to employ in the transport sector for achieving near-zero carbon emission. In this paper, the effect of hydrogen energy share on the fuel economy and NOx emissions of the hydrogen enriched natural gas (HENG) spark ignition (SI) engine are experimentally investigated under different loads. Then, the full-size one-dimensional (1D) simulation model of the HENG SI engine is built according to the layout of this test engine. Last, various rebreathing exhaust gas strategies are numerically investigated according to the calibrated and validated 1D simulation model. The results indicated that the combustion efficiency of the HENG SI engine is reduced about 0.7 %, 1.5 %, and 1.8 % with using rebreathing exhaust gas strategy @A to rebreathing exhaust gas strategy @C compared to the original exhaust valve lift (EVL). In addition, the NOx emissions of the HENG SI engine could reduce by 79.7 % with adopting the rebreathing exhaust gas strategy @A compared to the original EVL, while the brake specific fuel consumption of the HENG SI engine is increased by 0.29 %, without sacrificing too much its fuel economy. Thus, the performance and exhaust emissions could be trade-off well in the HENG SI engine with using the optimized rebreathing exhaust gas strategy.