Abstract
Biofuels are the only non-fossil fuels, which are currently available to reduce emissions of greenhouse gases (1, 2). The oxidation of the fuel and the following formation of deposits is a significant problem (3–6). A potential failure of the fuel pump, the injector or of the entire injection system increases (3–7). The apparent lack of correlation between the formation of insolubles and other stability-related parameters represents the one major disconnect in the biodiesel stability literature (4). The influence of existing deposits and the best way to deal with them is not known (8).
This paper describes the function and the design of a deposit building and assessment gadget. With the test facility it is possible to study fuel deposits. During the test reproducible formation of fuel deposits are built through fatty acid methyl ester (FAME) on a cylindrical surface. The test fixture is similar to the experimental setup for determining the static shear strength of an adhesive bond between a metal bolt and a metal sleeve (9). The emerging bond strength and the impact of deposits on the fuel injection system can be analyzed by this. The real shear stress can be determined at any time by the calculate overlap surface area between two cylindrical surfaces and the tensile force.The use of a cylindrical surface geometry enables a conversion of the measured force and shear stress to other proportions. The effect of fuel deposits can be described by the area independent value the shear stress on all sliding parts with different diameters and operation forces that are used in a fuel injection equipment (FIE). During a force-displacement measurement it comes to multiple holding positions with different holding times. These holding times represent a kind of a tension or relaxation test. With the relaxation and the restart of a force-path-measurement it is possible to conclude to the adhesion and cohesion performance of the deposits.
Keywords: Deposit, Biodiesel, Injector, FAME, Fuel InjectionEquipment