Exergy analysis of combustion in VGT-modified diesel engine with detailed chemical kinetics mechanism

• Exergy terms were analyzed when bowl displacement and radius modified.
• A new model was developed for irreversibility rate with R2 = 0.994 correspondence.
• The optimum bowl configurations were identified regarding first and second law efficiencies.
• Wall heat flux is attributed to exergetic and irreversibility terms with engine modification.

Altogether eight different configurations were considered regarding the bowl geometry to analyze the exergy terms as well as soot mass fraction distribution. Bowl configuration modification was detected to alter exergy and irreversibility by virtue of (1) spray-wall impingement, (2) HRR (heat release rate) delay and combustion initiation postponement (3) squish pressure flow and air-fuel mixing process. The highest total exergy peak and the second law efficiency are attributed to D4 configuration equal to 342.69 J, 49.93%, respectively. The general trend shows that increasing the bowl displacement led to 17.2% and 39.7% increase in the first and second law efficiency, respectively. Results show that only 6.15% exergy efficiency gain is expected with bowl radius modification. An irreversibility rate correlation was proposed based on the most effective parameters with the coefficient determination factor of 0.993, indicating the total completion of the equation. Based on the modeling equation, the highest impact on irreversibility rate is of heat release rate with impact coefficient of 0.471, while soot mass fraction showed inverse proportion (−0.004379) with irreversibility rate. Higher boost and pressure monitoring of the VGT-modified diesel engine can deliver optimized air/fuel mixing mechanism, which gives way to efficient combustion and exergetic performance.