Experimental set-up and numerical optimization of a heavy-duty single-point SI engine fueled with ethanol for a generator set

• SPI-based retrofit to convert diesel engines to 100% ethanol spark ignition. • Tests on an 8.7 L turbocharged engine achieved 225 kW and 32% efficiency. • GA optimization raised 37.5% efficiency and low NO x with minor hardware upgrades. • W-to-W CO 2 reduced by up to 87% vs. CNG using ethanol from renewable feedstocks. • Scalable solution to decarbonize stationary power via existing diesel platforms. This study presents a novel, cost-effective method for converting heavy-duty diesel engines to 100% ethanol-fueled spark-ignition (SI) engines using an advanced single-point injection (SPI) system. Unlike conventional conversion strategies that rely on direct injection (DI) or port fuel injection (PFI), this work pioneers a modern SPI configuration specifically adapted for high-concentration ethanol operation in stationary applications. The proposed solution requires only minor modifications to the engine head and fuel system, offering an economically viable retrofit option for existing diesel platforms. An experimental campaign was conducted on a turbocharged 8.7-liter six-cylinder engine to assess the feasibility and effectiveness of SPI-based ethanol conversion. Additionally, a validated 1-D numerical model enabled extensive investigations into potential improvements through adjustments to compression ratio, optimized cam phasing (EIVC-LEVO strategy), enhanced cooling, and multi-objective optimization. Using genetic algorithms, optimal lambda and spark timings were determined to maximize thermal efficiency while reducing NO x and HC emissions under wide-open throttle lean-burn conditions. Key findings highlight the proposed SPI system’s stable operation, with peak brake power and thermal efficiency closely matching those of the CNG variant of the same engine. The ethanol configuration delivers 225 kW and 32% thermal efficiency, compared to 227 kW and 39.7% for the CNG version, indicating only marginal differences between the two configurations. Numerical optimization demonstrated that minor hardware enhancements could increase thermal efficiency to 37.5% while maintaining controlled NO x and HC emissions. Additionally, the Well-to-Wheel analysis confirmed significant CO 2 reductions, up to 87%, when utilizing ethanol derived from renewable feedstocks, compared to CNG. Overall, this work offers an innovative pathway for the large-scale decarbonization of stationary power systems, emphasizing a simple, robust, and scalable ethanol-conversion methodology via SPI, a concept largely overlooked in recent literature for modern engine applications.