IMPACT OF AVIATION FUEL ON DURABILITY OF DIESEL COMMON RAIL INJECTION SYSTEM

The article presents the experimental test results reflecting the impact of aviation fuel on durability of the main components of the Common Rail Direct Injection (CRDI) system used in light-duty diesel vehicles. The two identical fuel injection systems operating with turbine type Jet-A1 fuel and normal diesel fuel were prepared for the durability tests. The high-pressure fuel supply pump is one of the most overloaded components in the fuel injection system. Durability of the injection system largely depends on the lubricating properties of diesel fuel. The reduced durability of the fuel injection system's components, such as fuel supply pump and injectors, sometimes can be ascribed to a lack of the lubricating quality of diesel fuel. Considering the relatively poor lubricating properties of the Jet-A1 fuel one should remember that the main moving parts of the fuel system are affected by friction while working under the most difficult conditions in the diesel engine. Overall performance of the fuel delivery system and the surface roughness of the moving parts of the pump were evaluated and measured before and after the laboratory tests to determine the Jet-A1 fuel-made effects on durability of the high pressure fuel pump. The tests were carried out at the high injection pressure variable from 10 MPa till 110 MPa (load) during 300 hour durability tests. An optical microscope was used to measure the wear off surfaces and analyse the effect of the aviation fuel on the surface micro structure of the studied parts. The High-Frequency Reciprocating Rig (HFRR) method was used to measure the resulting wear on the ball to evaluate the lubricity properties of Jet-A1 fuel. The values of the wear scar diameter (WSD) obtained with Jet-A1 fuel were compared to the respective values measured with the reference diesel fuel. The microscopic photographs of the wear scar diameters obtained on the test balls for the above mentioned fuels are presented in the paper.