A Numerical Methodology for the Design of Active Prechambers in Spark-Ignition Engines

Active prechamber spark-ignition engines are a feasible and effective solution in reducing fuel consumption and pollutant emissions for internal combustion engines. However, reliable and low-cost numerical approaches need to be developed to support and speed-up their industrial design, considering their geometric complexity and the involved multiple-flow length scales. In this work, a computational fluid dynamics (CFD) methodology is presented for the design of active prechambers (APCHs) in spark-ignition engines. It consists of two connected steps. First, the fuel injection process inside the APCH is simulated inside a constant-volume domain, including only the APCH geometry and considering the main chamber (MCH) as boundary condition. Then, the power-cycle is simulated on the whole closed-valves domain (APCH and MCH). A flame area evolution model is used to describe the flame propagation process. Experimental data from a research single-cylinder heavy-duty engine are used to assess the proposed methodology. Different operating conditions are considered, to evaluate the effects produced by variations of the nozzles diameter, the MCH air/fuel ratio and the load. Satisfactory results were achieved, demonstrating that the proposed methodology is consistent and reliable.