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.

Upcoming legislations aim to significantly reduce carbon dioxide and hydrocarbon emissions compared to current regulations. Accordingly, options have to be evaluated to not only convert the raw emissions in a catalytic converter, but also to reduce the raw emissions from the combustion process in the first place. Therefore, thermal piston top land coatings, which lead to an oscillating piston surface temperature were investigated on a single cylinder research engine using a gasoline RON95E10 fuel. Measurements were conducted at a compression ratio of 12.2 and a long Miller intake event. In this manuscript the results achieved with yttria stabilized zirconia in comparison to an uncoated piston are displayed. Significant effects of the coatings on the indicated efficiency could be observed mainly at low engine speeds and loads due to the high share of fuel energy in the wall heat losses and incomplete combustion. At these operating points, the reduction of wall heat losses can almost be fully transferred into indicated efficiency, leading to an increase in indicated efficiency of 6.3% by the yttria stabilized zirconia coating. At higher engine speeds and loads, the advantage in indicated efficiency vanishes and a decrease of 0.5% can be observed. Near full load operation the indicated efficiency slightly lower. However, the effects of a thermal swing coating on combustion efficiency and wall heat losses strongly depend on the operation conditions.

Future vehicle powertrain systems with internal combustion engines must achieve higher efficiencies and further reduced pollutant emissions. This will require the application of new advanced technologies. Against this background, this paper presents a holistic approach to reduce temporally the wall heat losses, and hydrocarbon and carbon monoxide emissions with thermal coatings on the combustion chamber walls. For this purpose, an yttria-stabilized zirconia (YSZ) coating is applied and evaluated by different methods. The thin layer in combination with the low thermal effusivity of the material allows the wall temperature to follow the gas temperature and perform a so-called thermal swing. The interaction between an uncoated and a YSZ-coated wall with the flame front as well as partially burned gas was investigated. First, in terms of the coating’s potential to reduce the flame quenching distance using an optical method in a constant volume combustion chamber. Second, regarding its influence on the near-wall gas composition, which was analyzed with in-situ diffuse reflectance infrared Fourier transform spectroscopy measurements and a fast gas sampling technique on a single-cylinder engine. From this, it could be derived that the quenching distance can be reduced by 10% at ambient conditions and by 5% at an elevated temperature of 200 °C by using the coating. These findings also support the results that have been obtained by the near-wall gas composition measurements, where a reduced total hydrocarbon emission was found with the applied coating.

Future internal combustion engines using novel fuels and combustion systems have the potential to achieve ultra-high efficiency and lowest pollutant emissions to comply with future regulatory requirements. Realizing indicated efficiencies over 50% with ultra-lean low temperature combustion face new challenges. To meet this goal, hydrocarbon (HC) and carbon monoxide (CO) emissions need to be reduced significantly further. To do this, knowledge must be gained about how the operation regime of the engine affects the HC and CO emissions. Since these emissions partly originate from areas where flame quenching occurs, an investigation of the gases near the wall is of interest. To this end a fast gas sampling method is being developed to extract and analyze the gas from the combustion chamber. The used fast gas sampling valve from Kistler enables sampling durations of less than 1 ms. Fourier-transform-infrared spectroscopy and a fast mass spectroscopy allow the determination of the sample composition. The valve is positioned inside the cylinder head of a single cylinder engine between intake and exhaust valves. In order to assess the effects of engine operating conditions on the formation of HC and CO at the cylinder walls, the measurement uncertainty of the setup must be evaluated. Since the combustion process is subject to cyclic variations, the evaluation of only a few individual measurements is not meaningful. Therefore, mean values are determined from the evaluation of several measurements not performed consecutively. By examining the mean and standard deviation of these measurements for each species, one can determine a measurement error. In comparison, lean operation with RON95E10 fuel at an IMEP = 12 bar and an engine speed of n = 2000 1/min shows a significant reduction in intermediate hydrocarbon species such as acetylene and a significant increase in fuel species such as ethanol compared to stoichiometric operation.