A Comprehensive Review of the Oxygen-Enriched Combustion in Internal Combustion Engines

Abstract

Oxygen-enriched combustion (OEC) has attracted growing attention as a potential approach for improving the efficiency of internal combustion engines (ICEs) while reducing harmful exhaust emissions. This paper presents a comprehensive and critical review of the current state of knowledge on OEC in ICEs. The analysis synthesizes experimental and technological studies addressing oxygen delivery methods, engine performance, and emission characteristics across different engine types and fuels. This paper presents a comprehensive and critical review of the current state of knowledge on OEC in ICEs. The analysis synthesizes experimental and technological studies addressing oxygen delivery methods, engine performance, and emission characteristics across different engine types and fuels. Beyond summarizing the available literature, the review critically evaluates reported findings and highlights inconsistencies in experimental results, particularly regarding the effects of oxygen enrichment on thermal efficiency, fuel consumption, and emission formation. The study compares two principal approaches to oxygen enrichment: supplying additional oxygen through the intake air and introducing oxygenated fuels. Their respective advantages, limitations, and practical implementation challenges are discussed. Special attention is given to technological aspects of oxygen supply, including emerging air separation and oxygen delivery systems and their potential integration with ICEs. Based on a systematic comparison of existing studies, several underexplored research directions are identified, including the limited number of investigations on turbocharged direct injection spark ignition engines and the lack of detailed analyses of integrated oxygen separation systems for onboard applications. By consolidating dispersed knowledge and identifying critical research gaps, this review provides guidance for future investigations and supports the development of practical OEC strategies for modern ICEs.