Effect of an ethanol–diesel blend on a common-rail injection system

This research paper presents a comparative experimental study for determining the functionality of a common-rail injection system used in light-duty diesel vehicles. Two Bosch fuel-injection systems were chosen to be tested using a low sulphur diesel fuel and an ethanol–diesel blend (7.7% v/v). Both systems were composed of a high-pressure injection pump Bosch (320 CDI), a common-rail and a Bosch piezoelectric fuel injector, and were tested during an accelerated durability test. In both cases, the injection systems were mounted in an injection test bench and run for 12 hours/day for 600 hours. An injection pressure of 1500 bar, a pump rotation speed of 2500 min−1 and an injection time of 1 ms were selected to simulate critical engine operating conditions. The selected test conditions were equivalent to driving a light-duty vehicle for over 120,000 km. This work employed several analysis equipment and techniques, including a surface tester for surface roughness characterization of the elements, an optical microscope for observation of the workpiece surface microstructure, a shadow comparator for geometrical characterization of elements, an analytical balance for weighing parts and, finally, a scanning electronic microscopy to determine nozzle dimensions. In both cases, the total fuel delivery was determined using an injection test bench. Results show that the use of the ethanol–diesel blend tested produced a similar effect on the durability of the injection pump parts as that produced when using diesel fuel. However, the effect on the injector nozzle was dissimilar.