Hydrogen as carbon-free fuel is a very promising candidate for climate-neutral internal combustion engine operation. In comparison to other renewable fuels, hydrogen does obviously not produce CO₂ emissions. In this work, two concepts of hydrogen internal combustion engines (H₂-ICEs) are investigated experimentally. One approach is the modification of a state-of-the-art gasoline passenger car engine using hydrogen direct injection. It targets gasoline-like specific power output by mixture enrichment down to stoichiometric operation. Another approach is to use a heavy-duty diesel engine equipped with spark ignition and hydrogen port fuel injection. Here, a diesel-like indicated efficiency is targeted through constant lean-burn operation. The measurement results show that both approaches are applicable. For the gasoline engine-based concept, stoichiometric operation requires a three-way catalyst or a three-way NO_X storage catalyst as the primary exhaust gas aftertreatment system. For the diesel engine-based concept, state-of-the-art selective catalytic reduction (SCR) catalysts can be used to reduce the NOx emissions, provided the engine calibration ensures sufficient exhaust gas temperature levels. In conclusion, while H₂-ICEs present new challenges for the development of the exhaust gas aftertreatment systems, they are capable to realize zero-impact tailpipe emission operation.

The progression of emission legislation has intensified the efforts of the automotive industry to develop improved exhaust gas after-treatment systems. The requirement to fulfill Euro 6d-TEMP in real-world driving scenarios, the already significant calibration effort for Euro 6d and the Euro 7 emission standards in discussion have significantly increased the work load for calibration engineers and the requirements for testing resources. Many original equipment manufacturers are implementing taskforces in order not to have to discard the planned start of production for their products, and some are even already forced to reduce their product portfolio. This is due to the diverse testing matrix required to cover all possible real driving emissions test scenarios. One big challenge is the extension and possible variation of boundary conditions regarding ambient temperatures, traffic conditions, road gradients and other varying driving resistances. Moreover, the test duration can cause considerable differences in the measured emissions, even if the same route is driven repeatedly. Addressing these challenges makes the application of a dedicated, event-targeted emission calibration mandatory. Since only a few sequences of the time-consuming road tests are relevant for improving the emission calibration, the methodology presented in this article focuses on the exact reproduction of these emission events on an emission chassis dynamometer with the aim of implementing calibratable solutions for these events. This is done using a real driving emission-cycle-generator which creates real driving emission compliant severe test scenarios and which focuses on the statistical relevance related to the typical product specific operation. The underlying generation process accesses a large database with real driving emission measurement results focusing on vehicle- or vehicle-group-specific challenges, using statistical approaches. It will be demonstrated how this procedure reduces test time and how it helps to tackle the substantial real driving emission work-load, while providing a dependable base to achieve real driving emission legislation compliance.

Reducing air pollution caused by emissions from road traffic, especially in urban areas, is an important goal of legislators and the automotive industry. The introduction of so-called “Real Driving Emission” (RDE) tests for the homologation of vehicles with internal combustion engines according to the EU6d legislation was a fundamental milestone for vehicle and powertrain development. Due to the introduction of non-reproducible on-road emission tests with “Portable Emission Measurement Systems” (PEMS) in addition to the standardized emission tests on chassis dynamometers, emission aftertreatment development and validation has become significantly more complex. For explicit proof of compliance with the emission and fuel consumption regulations, the legislators continue to require the “Worldwide Harmonized Light Duty Vehicle Test Cycle” (WLTC) on a chassis dynamometer. For calibration purposes, also various RDE profiles are conducted on the chassis dynamometer. However, the combination of precisely defined driving profiles on the chassis dynamometer and the dynamics-limiting boundary conditions in PEMS tests on the road still lead to discrepancies between the certified test results and the real vehicle behavior. The expected future emissions standards to replace EU6d will therefore force even more realistic RDE tests. This is to be achieved by significantly extending the permissible RDE test boundary conditions, such as giving more weight to the urban section of an RDE test. In addition, the introduction of limit values for previously unregulated pollutants such as nitrogen dioxide (NO₂), nitrous oxide (N₂O), ammonia (NH₃) and formaldehyde (CH₂O) is being considered. Furthermore, the particle number (for diameters of solid particles > 10 nm: PN₁₀), the methane (CH₄) emissions and emissions of non-methane organic gases (NMOG) shall be limited and must be tested. To simplify the test procedure in the long term, the abandonment of predefined chassis dyno emission tests to determine the pollutant emission behavior is under discussion. Against this background, current testing, validation, and development methods are reviewed in this paper. New challenges and necessary adaptations of current approaches are discussed and presented to illustrate the need to consider future regulatory requirements in today’s approaches. Conclusions are drawn and suggestions for a robust RDE validation procedure are formulated.

Filtration of cathode air is one of the challenges in operating proton-exchange membrane (PEM) fuel cells. The poisoning with air contaminants can lead to rapid performance degradation and initiate an aging process of the fuel cell. Various commercially available cathode filters are being tested in a laboratory gas test bench within the research project X-EMU (03B10502B and 03B10502B2). A literature review of harmful gas contaminants in the air used for the oxygen reduction reaction (ORR) on the cathode side was conducted. Experimental investigations took place at 40 °C with synthetic humid air containing low concentration contaminants such as ammonia, nitrogen dioxide, carbon monoxide, sulfur dioxide, hydrogen sulfide, and toluene. Test durations varied from 3 to 24 h depending on the filtration efficiency. Each gas contaminant showed different reactions with the investigated filters. The filters did not let sulfur-containing components pass. However, carbon monoxide could not be filtrated by any of the tested filters. The filtration of nitrogen oxides was not efficient for all tested filters, while additional filter materials were essential for a successful filtration of ammonia. Comparative results lead to a discussion of possible effects on a fuel cell with an outlook on optimization of the filtration behavior.