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The crude oil depletion, as well as aspects related to environmental pollution and global warming has caused researchers to seek alternative fuels. Biogas is one of the most attractive available fuels. It is of great interest both economically and ecologically. However, it faces problems that may compromise its industrial use. The dual-fuel engines have been investigated as a technique for the recovery of these gases and finding solutions to these problems. In the present work, performance and emissions of a direct injection diesel engine were first evaluated in conventional mode and dual fuel mode. The effect of biogas composition, based on methane content, is then examined. Also, dual fuel operation with regard to knock is investigated. The results show that, up to 95% of engine full load, the brake thermal efficiency (BTE) is lower in dual fuel mode. In terms of the specific consumption, although at high load the gap is much less, it is more significant in case of dual fuel mode.

As emission restrictions become more stringent and conventional fuel supplies become more limited, dual-fuel engines are emerging as a promising solution that offers both environmental and economic benefits. However, the performance of these engines is often hampered by the issue of knocking, which can negatively impact their overall operation, and also by the increase in NOx emissions at high load. This work investigates the use of pilot injection properties by combining the use of emulsified diesel of different water percentages with injection timing to reduce both knock intensity and NOx emission rate. Specifically, a dual fuel operation case at full load with high enrichment of the primary fuel (natural gas) with hydrogen is considered in order to create conditions for high knocking and high NOx emission rates.

In the last decades, waste lubricating oil (WLO) has attracted a great attention due to its strong effect on the environment degradation. Due to the high content of hydrocarbons in the WLO, these huge quantities could be interesting for recovery as a fuel for internal combustion engines. In the present work, an experimental study is conducted on a DI diesel engine operating with a diesel-like fuel (DLF) obtained by converting WLO via a catalytic pyrolysis process. The DLF physicochemical properties have shown a good agreement with those of diesel fuel, except for the viscosity which is slightly higher than that the values recommended by the international standards. For the engine tests, a single cylinder DI diesel engine, operating at a constant speed (1500 rpm) and under various engine load conditions, is fuelled with either DLF or its blends supplemented with various diesel fuel ratios (10, 20 and 30 % by volume).

An approach for turbocharging automotive engines to reach targeted performance was developed in which the environmental and economic aspects during the turbocharger-engine matching process were considered. Three numerical assessment levels based on output performance, exhaust emissions and techno-economic metrics are established to support users during the decision-making of adequate turbochargers that meets targeted data in terms of boosting and emissions. Satisfactory improvements are measured from a 1.5L, three-cylinders, turbocharged Diesel engine, in terms of brake specific fuel consumption, thermal efficiency and NOx concentrations of about 1.73% (decrease in fuel consumption of around 2.22ml/s), 1.76%, and 4.53% (correspond to a diminution of around 217.54ppm), respectively, at the engine’s extreme conditions (full load and rated power).