A Constraint-Governed Framework for High-Efficiency, Low-Emission Diesel Combustion

This work introduces a constraint-governed framework for diesel combustion optimization, termed the Diesel Optimization Trinity, which reframes engine development as a problem of coordinated governance rather than isolated metric maximization. The framework integrates three coupled control domains—combustion geometry, chemical environment, and event-level thermal management—to stabilize the traditional trade-offs between efficiency, nitrogen oxides (NOx), particulate matter (PM), combustion noise, durability, and regulatory robustness. The approach is validated using physics-based three-dimensional CFD simulations with detailed combustion chemistry, correlated against published experimental data. A production-relevant diesel configuration is demonstrated to achieve 45.2% brake thermal efficiency while meeting Euro 6, EPA 2010, China VI, and Tier 4 Final emissions limits under transient operating conditions, without reliance on extreme aftertreatment strategies. Additional metrics including combustion noise, brake-specific fuel consumption, durability projections, and economic impacts are explicitly quantified. Rather than claiming universal optimization, the framework emphasizes viable operating envelopes, boundary identification, and control authority under real-world constraints. The Diesel Optimization Trinity is presented as an open, transferable methodology applicable to conventional diesel engines and as a stable baseline for future extensions to dual-fuel, low-temperature combustion, and alternative fuel systems. This preprint is intended as a methodological and conceptual contribution and does not replace experimental certification.