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As society moves towards climate neutrality, hydrogen fuelled internal combustion engines (H2 ICEs) should be considered as a prime technology. These engines are valued for their robustness, superior lifetimes, manufacturing techniques and characteristics, which are already known from diesel or gasoline engines. Since an H2 ICE is run on hydrogen (H2), carbon-based emissions are only released on a very low level from the lube oil. Nitrogen oxides (NOx) emissions are de facto the only gaseous pollutant that must be processed by the exhaust aftertreatment system (EAS) of such engines. This paper provides an overview of the raw exhaust gas emission behaviour of a 2 l four-cylinder passenger car engine that is run solely on hydrogen. As already mentioned, the main challenge faced by the EAS is to reduce NOx. Thus, the inspected EAS includes a selective catalytic reduction (SCR) catalyst with ammonia (NH3) as a reductant. The species of NOx was reduced under stationary operation conditions at all of the considered engine load points at an efficiency of at least 98%. Strategies that could be applied to conduct a load change of an H2 ICE were experimentally investigated. To perform a load change under high performance conditions, H2 ICEs needed to be run on a richer air-fuel mixture than under stationary operation conditions in order to provide enough exhaust enthalpy for the turbocharger. If a richer air-fuel mixture was used, higher NOx emissions were detected, increasing the necessity of an EAS containing an SCR catalyst for H2 ICEs. A WLTC and two RDE cycles were investigated to determine their raw and tailpipe exhaust gas emissions. By applying a simple AdBlue® dosing strategy, the raw NOx exhaust gas emissions from the WLTC could be reduced from 79.9 mg/km to as low as 7.3 mg/km. Carbon-based and secondary emissions such as NH3 and nitrous oxides (N2O) were measured at levels well below 5 mg/km. [ABSTRACT FROM AUTHOR]

In this research, RDE tests were carried out on a pre-China 6 TGDI vehicle in the two cases of installing or not installing GPF to explore the impacts of GPF on RDE emission behaviors. The results indicated that the GPF can effectively filter PN emissions, especially at low speed, high load engine operating conditions, where the PN emissions can be reduced to about 1/200 of the original emissions. For TGDI vehicles, the installation of GPF can reduce the RDE PN emissions by more than 30 times, which indicates that the GPF is the key post-processing device for TGDI vehicles to meet the China 6 regulation. And in the upgrade process of China 5 vehicles to China 6 vehicles, especially for TGDI vehicles, the engine, the post processor and the turbocharger all needs re-calibrating or re-matching to concur a series of problems the back pressure raise caused by the installation of GPF, which may bring deterioration of engine combustion process, decrease of catalyst temperature and similar conditions that will worsen the vehicle emissions.

Tunnels are widely used in high-grade roads, particularly in mountainous areas; however, tunnel fires often result in severe economic losses and casualties. The fire effluents produced from asphalt pavement have attracted significant research attention. The main objective of this study is to assimilate information on various aspects of bituminous mixture emissions during fires. In this study, the fume emissions of bitumen and bituminous mixtures during combustion are comprehensively reviewed and summarized. First, the test methods for fire effluents produced by bitumen and bituminous mixtures after combustion are summarized. Second, the factors influencing the fume concentration and composition are determined. In addition, different methods to reduce the emission of fire effluents are compared, particularly for the suppression of toxic gas emissions. Then, reasonable suggestions are proposed to reduce the damage caused by hazardous gases to humans and the environment. This review is beneficial for comprehensively understanding the fume emission behaviour and future research on the smoke suppression of highway tunnel asphalt pavements during fires. [ABSTRACT FROM AUTHOR]

The introduction of wood chips into the market for small-scale heating appliances of below 100 kW has become more challenging due to stricter regulations on emission levels for carbon monoxide and particle emission, e.g. in Germany. Therefore, it is important to identify high wood chip qualities that are suitable for failure-free and low-emission combustion. In this investigation, several wood chip assortments produced from stem wood and forest residues were analysed and combusted in up to two different wood chip boilers with a nominal heat capacity of 50 and 99 kW at full load. Some combustion tests were performed at part load (i.e. 30% heat output). Throughout experiments, the emission behaviour was measured (CO, NOX and total particulate matter (TPM)). In total, seven different wood chip assortments were tested in the large boiler, whereas ten wood chip assortments were combusted in the smaller furnace. Wood chips from stem wood are characterized by lower ash contents (0.27-1.05 w%, d.b.), lower nitrogen contents (0.04-0.14 w%, d.b.) and lower aerosol forming elements (379-1075 mg/kg, d.b.) compared to forest residues (A = 0.58-2.05 w%¸ N = 0.13-0.32 w%, aerosols = 728-2199 mg/kg, d.b.). Combustion of stem wood caused lower emissions compared to forest residues at full-load operation. Overall, part-load operation caused higher CO and particle emissions. In addition, increases of fine woody particles lead to increases in CO emissions. The influence of moisture content was more pronounced especially for CO emissions. [ABSTRACT FROM AUTHOR]

A test fleet including 47 gasoline vehicles with 6 different technical types was organized, and the adaptability of these vehicles under China 6 standard was studied. By analyzing the performance of the vehicles tested in laboratory and in real-world, technical types that could simultaneously reconcile emission and fuel consumption performance were proposed. The results show that all vehicles were well performed under laboratory conditions, but in real-world conditions, 50% direct injection vehicles without GPF would fail the RDE test. On the other hand, vehicles with GPF had better performance, all of which passed the RDE tests even if the conformity factor decreased from 2.1 to 1. In addition, it is found that the fuel consumption of the DI vehicles were lower than that of the PFI vehicles. As the DI vehicles with GPF showed better performance on the balance of emission and fuel consumption, indicating that they may have better potentials to deal with the increasing tightened emission and fuel consumption standards at the same time.

A transient emission test bench was designed for simulating the high-speed cranking start process of a port-fuel-injected gasoline engine in a hybrid electric vehicle (HEV) application. The mechanisms of the emissions of both hydrocarbns (HCs) and nitrogen oxides during the stopping-and-restarting process were investigated. The cranking speed, the transient exhaust air-to-fuel equivalence ratio λ, the ignition timing, the idle speed, and the engine coolant temperature (ECT) during hot idle were calibrated. The experimental results showed that an extremely high cranking speed (greater than 1500 r/min) would sharply increase the coefficient of residual gas in the cylinder and lead to incomplete combustion or misfiring. The λ value should be leaner than the theoretical λ value during the cranking period to reduce the HC emission. Retarding the ignition and increasing the idle speed could shorten the light-off time of the three-way catalytic converter (TWC). Engine-off in the idling strategy depended on the ECT. Heat preservation of the TWC (above 300°C) was very important and was highly effective in increasing the conversion efficiency of the TWC so as to reduce the emissions. After calibration, the HEV emission behaviour in the New European Driving Cycle in a drum test was greatly improved. [ABSTRACT FROM AUTHOR]