Compression ignited (CI) engines, commonly known as diesel engines, are widely used power sources in on-road and off-road applications with complex emissions. Determining the impact of diesel exhaust emissions on human health and the environment requires evaluating both regulated and unregulated properties of exhaust gas. In particular, emissions from new fuels have to be examined thoroughly to prevent any impact from increased emissions of harmful substances. In addition, identifying and utilizing new alternative fuels to replace fossil fuels is an important task not only in Germany but also worldwide, now and in the future. Previous research has generally focused on the composition of exhaust gas, analysis of its operating behavior and optimizations to improve operating and emissions parameters but only with neat biofuels. There has been little examination of new alternative fuels and their blends, e.g. ethanol, ethanol-diesel blends and RME-diesel blends (with ratios over 5%), and, in particular, of their use in heavy-duty diesel engines. Furthermore, investigations of alternative fuels combined with other operating conditions such as different exhaust gas recirculation ratios, retarded or earlier injection pump delivery, etc. have not been analyzed. This study investigates the influences of properties of RME 100%, RME-diesel blends of different ratios, ethanol-diesel blends with low amounts of ethanol and gas-to-liquid and its blends on thermodynamic properties and emissions, specifically their impacts on cylinder pressure levels. To this end, different variables are combined, e.g. different alternative fuels and different blend ratios with different EGR rates, EGR temperatures and injection timing. A cylinder pressure sensor, an injection pipe pressure sensor, evaluation software and data processing equipment were used to detect differences in cylinder pressures, heat release rates and spectrums of cylinder pressure in different operating points and under different operating conditions. Moreover, maximum heat release rates and maximum cylinder pressure peaks were calculated and evaluated in order to correctly interpret the effects of the aforementioned variables at different operating points and under different operating conditions and with different parameters, e.g. ignition delay periods, combustion duration and maximum cylinder pressure rises. The results obtained are used to evaluate and optimize the engine’s operating process with exhaust gas recirculation and different alternative fuels and their blends with conventional fuels.
heavy duty Diesel engine, alternative fuels, EGR, exhaust emissions, HC, NOx, FSN