Exploring the Emission Spectrum of Pure Hydrogen Combustion in Spark Ignition Engines: A Comprehensive Experimental Study

Hydrogen internal combustion engines (H2ICE) have shown enormous potential for zero-carbon emissions, aligning with the European zero-carbon targets in 2050. Adopting hydrogen as a zero-carbon fuel offers a time- and cost-effective approach to directly replacing carbon-based and fossil fuel-powered ICEs. The study aims to provide comprehensive data on the H2ICE engine during steady-state operations on a single-cylinder spark ignition engine with direct and port-fuel hydrogen injection systems. It focuses on emissions, including carbon monoxide (CO2) and unburnt hydrocarbons (HC), utilizing ultra-fast analyzers close to the exhaust valves to reduce signal delay. Particulate matter (PM) emissions are also measured to evaluate the potential for zero carbon emissions from the H2ICE. Additionally, NO and NO2 emissions are analyzed against air-fuel ratios (AFR) to estimate combustion temperature and NOx mechanisms. Water vapor and oxygen emissions are captured to assess their quantities at different loads and to verify the actual lambda compared to the wide-band O2 sensor. The study's main findings show that by looking at the averaged data, the averaged CO2 and HC emissions were less than 0.02% over mid-load of 10 bar IMEP at 2000 rpm and lambda value of 2.75. However, examining cycle peak values near the exhaust valve opening reveals small spikes under 100 ppm, correlated with PM emissions data to confirm carbon emissions resulting from lubricant induction. These emissions exhibit distinct characteristics, particularly during higher coefficient of variation (COV) periods, and are captured during abnormal combustion events. This suggests increased piston acceleration leads to greater lubricant entry into the combustion chamber. Also, an impressive water vapor peak value of 42.7% volume of the exhaust at lambda 1 shows a great potential to adopt EGR and water injection.