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 21 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.