What question did this study set out to answer?

The study aims to analyze strategies for reducing NOx emissions while optimizing performance in a dual-fuel marine engine.

February 12, 2026Open Access

Integrated Analysis of NOx Reduction and Performance Enhancement in HYUNDAI-HiMSEN 7H35DFP Dual-Fuel Marine Engine

Key Points

The study aims to analyze strategies for reducing NOx emissions while optimizing performance in a dual-fuel marine engine.
Experimental investigation of emissions
Computational fluid dynamics modeling
Development of advanced control algorithms
Multivariate analysis with principal component analysis
Optimization model using MATLAB for urea injection rates
Gas mode operation meets IMO Tier III with emissions of 1.41–2.29 g/kWh across loads
Diesel mode achieves 75–82% NOx reduction with emissions of 1.60–1.96 g/kWh
CFD analysis shows gas mode has lower peak temperature (~2000 K) than diesel mode (>2200 K)
Digital twin framework predicts catalyst degradation and fuel injection performance with 94.2% and 91.8% accuracy respectively
Waste heat recovery could potentially utilize 8.5–15.3% of fuel energy from exhaust

Abstract

This comprehensive study presents an integrated analysis of NOx reduction strategies and operational optimization for the HYUNDAI-HiMSEN 7H35DFP dual-fuel marine engine. The optimization scope focuses on selective catalytic reduction control strategies and operational decision-making (fuel mode selection, load management) rather than engine hardware modifications, ensuring practical applicability within certified marine engine operational envelopes. The research employs a multifaceted approach combining experimental investigation, computational fluid dynamics (CFD) modeling, and advanced control algorithms to address the stringent IMO Tier III emission standards. The 3500 kW, 7-cylinder engine achieves IMO Tier III compliance through dual pathways: (1) gas mode operation meeting the 2.4 g/kWh limit inherently with measured emissions of 1.41–2.29 g/kWh across 25–100% load without aftertreatment, and (2) diesel mode achieving compliance via SCR aftertreatment, reducing Tier II baseline emissions (7.68–10.71 g/kWh) by 75–82% to final values of 1.60–1.96 g/kWh. The research quantifies NOx reduction mechanisms separately for each operating mode and establishes optimal operational strategies for mode selection. A MATLAB v2025a-based SCR optimization model successfully predicts optimal urea injection rates, achieving >75% NOx reduction efficiency across all operating conditions. Multivariate analysis using principal component analysis identifies the following three primary factors explaining 89.3% of dataset variability: combustion intensity (45.2%), fuel mixing characteristics (28.7%), and thermal management (15.4%). CFD analysis reveals that gas mode combustion produces more uniform temperature distributions (peak ~2000 K) compared to diesel operation (>2200 K), directly explaining NOx generation differences. The developed digital twin framework with machine learning algorithms achieves 94.2% accuracy in SCR catalyst degradation prediction and 91.8% in fuel injection system performance prediction. Waste heat recovery analysis indicates 25–30% of fuel energy resides in exhaust gases, with theoretical energy recovery potential of 8.5–15.3%. This integrated approach validates dual-fuel technology’s capability to meet current and future maritime environmental regulations while maintaining operational flexibility.

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