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UBC Theses and Dissertations

The effect of hydrogen substitution on the real-world CO₂, NOx, and PM emissions of a heavy-duty diesel truck Meiklejohn, Jeffrey Dean


Hydrogen substitution can reduce the diesel consumption and CO₂ output of diesel engines. This thesis investigates its effect on the real-world, on-road emissions of CO₂, NOx and particulate matter (PM) from a heavy-duty diesel truck. Testing was conducted on a Class 8 truck fitted with a 13 L common-rail direct-injection (CDI) engine and a supplemental intake manifold-injection hydrogen fuel system. The peak hydrogen energy substitution rate was 40%, while the observed average was 24%. The truck operated with Gross Combined Vehicle Weights (GCVWs) between 20,000 kg and 60,000 kg. A Portable Emissions Measurement System (PEMS) was built and was used to sample engine-out, pre-aftertreatment exhaust gases. Torque was measured on the driveshaft with a wireless transducer, CO₂ was measured via non-dispersive infrared sensor, NOx was measured with an electrochemical sensor, and PM was measured via light scattering and gravimetric methods. Data was logged at 10 Hz by a data acquisition system (DAQ) that was also connected to the truck’s J1939 communication networks. From this data, detailed emission maps were generated which showed the varied emissions across the engine’s speed/load operating range. For accurate comparison on-road testing was conducted in both hydrogen/diesel and plain diesel fueling modes, totaling over 2500 kilometers logged. Overall CO₂ emissions decreased by 25±1%, which was approximately equal to the hydrogen displacement. Engine-out NOx emissions increased by 10±1% and engine-out PM emissions increased by 2±3%. For PM measurement, high correlation (R2 = 0.9) was found between integration of the instantaneous light scattering and the total gravimetric measurement methods. Overall thermal efficiency was virtually unchanged between the two fueling modes, with small decrease noted at low loads and small increase at high loads. Increased exhaust gas temperature (EGT) was measured while operating in hydrogen/diesel mode and increased in-cylinder temperature is suspected as the cause of the increased NOx emissions. Preliminary analysis of the post-aftertreatment NOx showed a decrease of 36±2% in hydrogen/diesel mode versus the diesel baseline, suggesting that the increased engine-out NOx does not increase tailpipe emissions. Furthermore, the consumption of diesel exhaust fluid (DEF) only increased by 3±3% in hydrogen/diesel mode, suggesting a higher conversion efficiency.

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