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

The present work is focused on a comparative experimental study for determining the effect of fuel properties on the constructive characteristics of some pieces of a current common rail injection system used in light duty diesel vehicles. Two Bosch fuel injection systems, each composed by a high pressure injection pump Bosch (270 CDI), the common rail and a Bosch piezoelectric fuel injector, were selected to be tested with two fuels. The first of the systems was tested with a low sulphur commercial diesel fuel while the second was tested with an ethanol-biodiesel-diesel blend (7.7% v/v ethanol (E), 27.69% v/v biodiesel (B) and 69.61% v/v (diesel) reference diesel fuel) Both systems were tested during an accelerated durability test. In both cases, the injection systems were mounted in an injection test bench and were working during 12 h/day up to 600 h. An injection pressure of 1500 bar, a regime of 2500 min(-1) and an injection time of 1 ms were selected as the most critical engine operating conditions. Test conditions were equivalent to drive a light duty vehicle during more than 120,000 km. Before and after the durability tests with each fuel tested, different pieces of the injection pump were physical characterized. Several techniques such as: a tester for the roughness surface characterization of elements, an optical microscope for the observation of the surface microstructure, an shadow comparator for geometrical characterization of elements, weighed of components by mean of an analytical balance and, finally, the nozzle dimensions were carefully determined from images of a scanning electronic microscope (SEM) of the inner shape obtained by casting silicone. Results show that the use of the ethanol-biodiesel-diesel blend tested produced a similar effect on the durability on the injection pump components studied and on the injector nozzle as that produced by diesel fuel. (C) 2011 Elsevier B.V. All rights reserved.