Search Results

Internal deposits formed within the fuel injection system have been widely reported in the literature. Several root causes exist, with many deposits consisting of more than one material. The final chemistry depends on the availability of trace fuel contaminants and additives and to a lesser extent hydrocarbon/FAME stability and operating conditions. The present paper identifies the primary deposit morphologies, along with the typical root cause. Metal carboxylate salts, also known as metal soaps are most widely reported and are easily recreated under controlled conditions using compounds present at trace concentrations in some market fuels. The salting reaction may occur at low temperatures in the fuel supply system. It is proposed that the resulting fuel insoluble salt molecules are transported as reverse micelles, occasionally plugging filters but more commonly passing to the high pressure injection system.

The need for improved emissions and fuel economy are placing increasingly severe performance requirements on compression ignition engines. These are satisfied in part by advanced fuel injection equipment that provide multiple injections and increased injection pressures along with higher operating temperature. Fuel composition is also changing, with increased use of non-traditional feedstocks combined with a range of additive chemistries to restore or enhance fuel quality. Within this environment, a number of worldwide automotive companies have noted a trend towards increased Internal Injector Deposits (IID). Little quantitative information to understand the root cause is available, largely due to difficulty in reproducing the issue under controlled conditions. The present study details the results of an accelerated test methodology, which is used to evaluate the interrelated effects of fuel composition and operating environment.

Current developments in fuels and emissions regulations are resulting in an increasingly severe operating environment for diesel fuel injection systems. The formation of deposits within the holes or on the outside of the injector nozzle can affect the overall system performance. The rate of deposit formation is affected by a number of parameters, including operating conditions and fuel composition. For the work reported here an accelerated test procedure was developed to evaluate the relative importance of some of these parameters in a high pressure common rail fuel injection system. The resulting methodology produced measurable deposits in a custom-made injector nozzle on a single-cylinder engine. The results indicate that fuels containing 30%v/v and 100% Fatty Acid Methyl Ester (FAME) that does not meet EN 14214 produced more deposit than an EN590 petroleum diesel fuel.

An increasing range of conventional and unconventional feed stocks will be used to produce fuel of varying chemical and physical properties for use in compression ignition engines. Fischer-Tropsh (F-T) technology can be used to produce fuels of consistent quality from a wide range of feed stocks. The present study evaluates the performance of F-T fuel in advanced common rail fuel injection systems. Laboratory scale tests are combined with proprietary engine and electrically driven common rail pump hydraulic rig tests to predict long-term performance. The results obtained indicate that the performance of F-T fuel is at least comparable to conventional hydrocarbon fuels and superior in a number of areas. In particular, the lubricity of F-T fuel was improved by addition of lubricity additives or FAME, with minimal wear under a wide range of operating conditions and temperatures.