Exploring the effects of compression ratio and initial flame kernel radius on combustion characteristics and fuel economy of a dual-fuel spark ignition engine under oxy-fuel combustion mode

In order to mitigate greenhouse effect and promote carbon neutrality, Oxy-Fuel Combustion (OFC) technology implemented in the Internal Combustion Engine (ICE) has been an effective and promising approach to reduce or even eliminate CO2 emissions from the transportation sector. This research contributes novel insights into the effects of compression ratio (𝛿CR) and initial flame kernel radius (𝑅FK) on combustion characteristics and fuel economy of a Dual-Fuel Spark Ignition (DFSI) engine under OFC mode by a numerical method. The research results show that by increasing 𝛿CR from 8.6 to 13.6, an apparent reduction can be seen in equivalent Brake Specific Fuel Consumption (BSFCE). The corresponding ignition delay (𝜃𝐹) has a reduction of 10 degrees, while combustion duration (𝜃𝐶) are relatively stable. Moreover, the maximum cylinder pressure (𝑃max) has a rise of 8 bar and 20 bar at low load and mid-high load, respectively. By increasing 𝑅FK from 0.2 mm to 1.2 mm, 𝑃max and 𝜑Pmax each presents a monotonic trend of growth and advancement, respectively. The reduction of 𝜃𝐹 at low load and mid-high load is each 28.5 degrees and 34.9 degrees. In the meantime, both BSFCE and in-cylinder temperature show a low level of sensitivity. The research findings could provide valuable insights for enhancing the combustion performance and economy of DFSI engines under OFC mode to mitigate the greenhouse effect.