Thermodynamic and Environmental Assessment of Hydrogen-Microalgae RCCI Combustion: A Unified Exergy, Performance, and Emission Analysis

This study evaluates a B20 algal methyl ester (HRF) and hydrogen (LRF) framework across 25–100% loads with hydrogen premixing ratios (PR) up to 55%. The research novelty lies in providing a unified exergy-combustion-performance-emission analysis for this specific fuel pairing, quantifying the "thermodynamic price" of emissions reduction through the Exergy Depletion Factor (EDF).The methodology involved experiments on a single-cylinder diesel engine at a constant 1500 rpm using a 23° CA bTDC pilot injection and port-injected hydrogen.

Thermodynamic assessments were performed against a standard ambient dead state to calculate exergy destruction and entropy generation. Results reveal a load-dependent paradigm shift: at low loads, hydrogen’s auto-ignition resistance retarded peak pressure by 3° CA, whereas at 100% load, its rapid flame velocity advanced combustion by 3° CA. Environmentally, PR50 reduced NO and HC emissions by approximately 75% and 80%, respectively.