External fuel reforming for compression-ignition engines

This paper presents the results of a study on the reduction of toxic exhaust gas emissions from compression-ignition engines by applying a fuel pretreatment. This treatment consists of contacting the fuel with a heterogeneous catalyst in the form of a Cu-Ni alloy applied to the nozzle needle in the fuel injector body. In this case, the pre-treatment of the fuel allows the fuel to reform. As determined in laboratory tests, fuel reforming is presented by an increase in the proportion of the olefin group in the atomised fuel and a decrease in the proportion of the paraffin group, which may indicate the occurrence of a fuel dehydrogenation reaction and the release of free hydrogen on contact with the catalyst. To apply the heterogeneous catalyst by electrospray fusion, the passive part of the atomiser needle was used, connecting the needle’s precision surfaces (its guide and firing cone). Laboratory tests of the atomiser modified in this way showed a change in the hydrocarbon groups of the fuel after contact with the catalyst. Results from bench tests of an experimental compression-ignition engine equipped with a pre-treated fuel injector showed a reduction in nitrogen oxide emissions of up to 30 %. Analysis of the engine process indicator diagrams shows that the achievement of such results is related to the reforming of the fuel, which leads to a reduction in the maximum pressure and heat release values, resulting in a reduction in the combustion temperature in the kinetic phase of the combustion process, responsible for the formation of nitrogen oxides in the engine cylinder. The applied electro-spark alloying method for the deposition of Cu-Ni catalysts on the passive part of the injector nozzle’s needle does not cause thermal distortion of the precision pair of the fuel injector and can be recommended for use both in the production process of injection equipment for compression-ignition engines and during their operation.