Thermodynamic analysis of performance and emissions of a microwave-assisted ignition automotive engine: A numerical approach

In response to stringent automotive emission regulations, lean-burn combustion has been adopted. To overcome the ignition challenges and enhance fuel oxidation under these conditions, microwave-assisted ignition (MWI) provides an innovative strategy to enable shorter burn durations and more stable combustion in spark-ignition (SI) engines; during part-load operation, the impact of microwave-assisted ignition (MWI) is particularly significant under lean fuel conditions, enhancing both engine power output and fuel efficiency. This paper presents a numerical analysis of MWI’s impact on SI engine combustion, characterizing the essential parameters such as cylinder temperature, HC emissions, heat release rate, and power output. AVL-Fire commercial software is used to employ the K- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mi>ζ</mml:mi> </mml:mrow> </mml:math> -F turbulence model, extended coherent flame model, and Metghalchi-Keck flame propagation scheme for the simulation incorporated SIMPLE algorithm. This study examines the microwave effects on flame-kernel size and growth; it uses a novel approach to calculate the engine’s performance and emissions, validating the results with previous work. It is demonstrated that the enhancement of the electromagnetic field within the cylinder enlarges the flame kernel, the phenomenon simulated with COMSOL Multiphysics software; consequently, he shape and dimensions of the kernel are compared with experimental data, showing good agreement. This research investigates the effects of MWI on engine performance relative to advanced ignition conditions (AIC), excluding the positive effects of spark timing adjustments considered in experimental work. Results indicate that MWI can increase power output by up to 3.86%, reaction rates by 25.02%, OH radical production by 35.21%, and maximum in-cylinder pressure by 16.91%. Additionally, MWI significantly reduces emissions, particularly HC by approximately 91.52% and CO by up to 14.12%. In summary, MWI demonstrates potential for developing ultra-lean combustion engines that achieve performance comparable to traditional engines.