1160 consumption, emissions, and operational performance. 2. BACKGROUND / STATE OF THE ART Diesel combustion in compression‑ignition engines is a complex process that produces useful mechanical work but also generates CO₂, NOₓ, particulate matter (PM), and other pollutants. The pursuit of higher efficiency and lower emissions has motivated technologies such as hydrogen supplementation, which can function as a secondary fuel. Hydrogen as a Supplementary Fuel: Hydrogen (H₂) has favorable fuel properties, including high specific energy on a mass basis and a wide flammability range. Since hydrogen contains no carbon, its combustion does not produce CO₂. When introduced into a diesel engine, hydrogen can enhance flame propagation and combustion completeness, potentially reducing diesel consumption and associated CO₂ emissions. However, hydrogen supplementation may affect NOₓ formation due to changes in peak combustion temperatures, which makes precise control and monitoring essential. On‑Board Hydrogen Generation via Electrolysis: Hydrogen can be produced through water electrolysis. Alkaline electrolyzers (ALK) represent a mature and robust technology and may be suitable for on‑board applications due to their simplicity and cost‑effectiveness. Producing hydrogen on demand on the vehicle reduces the need for storing and handling large volumes of hydrogen gas, mitigating logistical and safety challenges. Typical on‑board systems include an electrolyzer, a bubbler for purification and cooling, a desiccant filter for moisture removal, a flame arrestor for safety, and sensors to monitor key parameters. Challenges and Risks: Implementing hydrogen supplementation in diesel engines introduces technical and safety challenges. Safety requires adequate ventilation, leak detection (where applicable), and interlocks. Control must prevent abnormal combustion phenomena (e.g., pre‑ignition, backfire) that could damage engine components. Additionally, the long‑term impact on NOₓ emissions and engine durability must be assessed. On‑board electrolysis also requires deionized water supply logistics, which must be considered for mining environments. 3. MATERIALS AND METHODS Embedded System Prototype: The embedded hydrogen injection system was developed for integration into a mine-haul road truck. The prototype includes: • Alkaline electrolyzer (ALK): hydrogen production at 4.5 L/min, 55 °C, 25 A. • Bubbler: purification and cooling to reduce moisture and impurities. • Desiccant filter: residual moisture removal. • Flame arrestor: flashback protection. • Sensors: pressure, temperature, hydrogen flow; engine operating parameters (RPM, load, exhaust gas temperature). • Control unit: real-time control of hydrogen generation/injection and safety logic. • Data acquisition (SD/RTC): logging of operational data and safety events for traceability. Control and Safety Architecture: Safety was a core design requirement. The control architecture includes interlocks and fail‑safe logic: • Automatic shutdown under abnormal conditions (sensor failure, out‑of‑range pressure/temperature, safety alarms); • Continuous EGT monitoring with hydrogen reduction/cutoff above a defined limit; • Sensor‑failure cutoffs that revert the engine to diesel‑only operation; • Fail‑safe behavior prioritizing safe diesel operation in uncertain states.
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