Shahrood University of Technology Journal of Solid and Fluid Mechanics 2251-9475 15 5 2025 11 22 Effect of Oxygen Enriched Air Combined With EGR on Performance Parameters and Diesel Engine Emissions Effect of Oxygen Enriched Air Combined With EGR on Performance Parameters and Diesel Engine Emissions 427 442 3709 10.22044/jsfm.2025.15841.3950 FA Javad Khadem University of Birjand Moslem Ayubi Rad University of Birjand Ali Asadi Bozorgmehr University of Qaenat, Qaen, Iran. Seyed Iman Poormusavi University of Birjand, Birjand, Iran Journal Article 2025 03 11 In this study, the combined effect of oxygen enrichment and exhaust gas recirculation (EGR) on combustion performance and pollutant formation in a direct-injection diesel engine was investigated. The main objective was to analyze the simultaneous influence of increased oxygen concentration and EGR application on improving the combustion process and reducing exhaust emissions. Numerical simulations were conducted using AVL-FIRE software on an AVL 5402 single-cylinder, four-stroke, direct-injection diesel engine. The Shell ignition model and the Zeldovich NOx model were employed to predict temperature, pressure, soot, and NOx emissions, and the results were validated against experimental in-cylinder pressure data. The results show that the desired NO output is achieved at 1400 rpm using 21.5 to 22.5% oxygen enrichment and 5 to 10 percent EGR, and at 1800 rpm using 21 to 22% oxygen enrichment and 10 to 15% EGR. Also, in the case of using cold exhaust EGR, the desired NO can be achieved under 1400 rpm conditions using 21.5 to 22.5% oxygen enrichment and 10 to 15% EGR, and at 1800 rpm engine speed using 21 to 22% oxygen enrichment and 15 to 20% EGR. In this study, the combined effect of oxygen enrichment and exhaust gas recirculation (EGR) on combustion performance and pollutant formation in a direct-injection diesel engine was investigated. The main objective was to analyze the simultaneous influence of increased oxygen concentration and EGR application on improving the combustion process and reducing exhaust emissions. Numerical simulations were conducted using AVL-FIRE software on an AVL 5402 single-cylinder, four-stroke, direct-injection diesel engine. The Shell ignition model and the Zeldovich NOx model were employed to predict temperature, pressure, soot, and NOx emissions, and the results were validated against experimental in-cylinder pressure data. The results show that the desired NO output is achieved at 1400 rpm using 21.5 to 22.5% oxygen enrichment and 5 to 10 percent EGR, and at 1800 rpm using 21 to 22% oxygen enrichment and 10 to 15% EGR. Also, in the case of using cold exhaust EGR, the desired NO can be achieved under 1400 rpm conditions using 21.5 to 22.5% oxygen enrichment and 10 to 15% EGR, and at 1800 rpm engine speed using 21 to 22% oxygen enrichment and 15 to 20% EGR. https://jsfm.shahroodut.ac.ir/article_3709_3f59d1ab8ba25ed4df45d76d57a7e8d4.pdf