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CO2 emission constraints taking effect from 2020 lead to further investigations of technologies to lower knock sensitivity of gasoline engines, main limiting factor to increase engine efficiency and thus reduce fuel consumption. Moreover the RDE cycle demands for higher power operation, where fuel enrichment is needed for component protection. To achieve high efficiency, the engine should be run at stoichiometric conditions in order to have better emission control and reduce fuel consumption. Among others, water injection is a promising technology to improve engine combustion efficiency, by mainly reducing knock sensitivity and to keep high conversion rates of the TWC over the whole engine map. The comprehension of multiple thermodynamic effects of water injection through 3D-CFD simulations and their exploitation to enhance the engine combustion efficiency is the main purpose of the analysis.

Two substantially different methods have become popular in building fast computing catalyst models: physico-chemical approaches focusing on dimensionality reduction and machine learning approaches. Data driven models are known to be very fast computing and to achieve high accuracy but they can lack of extrapolation capability. Physico-chemical models are usually slower and less accurate but superior regarding robustness. The robustness can even be reinforced by implementing an extended Kalman filter, which enables the model to adapt its states based on actual sensor values, even if the sensors are drifting. The present study proposes a combination of both approaches into one hybrid model, keeping the robustness of the physico-chemical model in edge cases while also achieving the accuracy of the data based model in well-known regimes. The output of the hybrid model is controlled by an autoencoder, utilizing methods well known from the field of anomaly detection.

The EPEFE study (European Programme on Emissions, Fuels and Engine Technologies), /1/ and other programmes have identified an increase in tailpipe NOx emissions with reduced gasoline aromatics content for modern 3-way controlled catalyst vehicles. This effect occurs with fully warmed-up catalyst under closed-loop operation. In order to understand the reasons for this effect VW and Shell have mechanistically investigated the effects of fuel properties on EMS (engine management system) and catalyst performance. Fuels with independent variation of oxygen, aromatics and mid-range volatility were tested in different VW engines. λ was monitored using sensors located both pre and post catalyst. The results confirmed that reducing gasoline aromatics content reduced engine-out emissions but increased tailpipe NOx emissions. It could be shown that differences in H/C ratio led to differences in the hydrogen content of engine-out emissions which affected the reading of the λ sensor.

An acknowledged consequence of utilising oxygenates such as MTBE as a gasoline component is known to be a lowering of CO exhaust emissions from mature technology vehicles due to the “natural” leaning effect that the inclusion of MTBE can provide. A small decrease in THC is also commonly seen in these circumstances, while the effect of MTBE on NOx emissions is more variable and not usually beneficial. The present paper describes the results of recent studies in the European arena, covering the effects of fuel oxygenates (notably MTBE) on regulated emissions for non-catalyst and catalyst car fleets examined in in-house programmes. It looks at emissions effects according to the broad classification of the onboard vehicle technology employed. It further cites experimental work that has featured MTBE replacement in gasolines by a single saturated hydrocarbon (2,3-dimethyl butane) that is isoelectronic with MTBE. Some related work conducted concurrently on splashblending is also described.

Water vapor is, aside from carbon dioxide, the major fossil fuel combustion by-product. Depending on its concentration in the exhaust gas mixture as well as on the exhaust gas pressure, its condensation temperature can be derived. For typical gasoline engine stoichiometric operating conditions, the water vapor dew point lies at about 53 °C. The exhaust gas mixture does however contain some pollutants coming from the fuel, engine oil, and charge air, which can react with the water vapor and affect the condensation process. For instance, sulfur trioxide present in the exhaust, reacts with water vapor forming sulfuric acid. This acid builds a binary system with water vapor, which presents a dew point often above 100 °C. Exhaust composition after leaving the combustion chamber strongly depends on fuel type, engine concept and operation point. Furthermore, the exhaust undergoes several chemical after treatments.

Europe is currently on the threshold of introduction of unleaded gasoline. However, this will not proceed uniformly, as some countries such as Germany. Austria. Switzerland and now Scandinavia are moving much more quickly than others. In those countries where unleaded fuel is available, registrations of catalyst cars and the build-up of the gasoline retail network and sales volumes are described. Possible future developments in these areas are discussed. The potentials and limitations on the manufacture of unleaded gasoline are discussed together with the role of oxygenates. The development of specifications in various countries is described and on the basis of market surveys actual quality is compared with the minimum requirements of these specifications. Results of road tests are presented showing the effects of both gasoline with maximum lead content and engine oil with a relatively high phosphorous content on deterioration of catalyst efficiency.