Effects of biofuel and additive usage on the partial load performance and emission characteristics of a dual-fuel diesel engine fueled with natural gas

For reasons such as their high performance, low fuel consumption and costs, interest in vehicles with diesel engines is growing. Besides, the issue of finding alternative fuels for diesel engines has begun to be considered as a result of decrease in oil reserves, rise in oil prices and the significant increase in air pollution caused by motor vehicles. The use of natural gas in diesel engines is considered to be suitable because of its fuel features and low price. Both engine manufacturers and users are being encouraged to use natural gas in motor vehicles as it not only reduces air pollution and reliance on oil but also has adequate reserves. It is stated in the studies considering the use of natural gas in diesel engines that the fuel costs have decreased and that there has been improvement in exhaust emissions. However, it is also stated that under specific operating conditions, some problems related with engine performance characteristics and exhaust emissions originating from the use of natural gas have been observed.In this study, the effects of different pilot fuel use and the application of additives in handling the problems originating from the use of natural gas are evaluated. For this purpose, biodiesel and dglyme, which have high cetane number and oxygen content, were used. Biodiesel was used as pilot fuel instead of diesel fuel, and diglyme was added to natural gas through fumigation method.In the study, firstly, a single-cylinder diesel engine was equipped in order to operate with dual fuel. Under these circumstances, experiments on the application of diesel fuel and dual fuel containing of diesel fuel and natural gas at different rates were carried out. Having taken the data obtained from the experiments carried out under the conditions of full load and part load into consideration, the problematic parts, have been determined and under these circumstances experiments focusing on the use of biodiesel and diglyme as an additive have been carried out. Data obtained from these experiments are presented comparatively through diagrams at the end of this study, and are also discussed within the context of chi-square test by regarding the ANOVA and S/N data.By evaluating the experimental data, it has been determined that at low-medium engine loads, the use of natural gas through dual fuel method in comparison with the use of diesel fuel has resulted in some problems regarding engine performance and exhaust emissions. The use of biodiesel and the application of diglyme as an additive to resolve such problems resulted in improvement in the brake thermal efficiency and specific energy consumption in comparison to the use of natural gas. Moreover, it has been observed that the application of diglyme caused an improvement in HC emissions and the use of biodiesel resulted in improvement in HC and CO emissions. It has also been observed that the use of biodiesel and the application of diglyme as an additive caused a slight increase in NO emissions in comparison to the use of natural gas.