Newly identified effects of injector nozzle fouling in diesel engines

Abstract

This paper describes newly identified effects of fouled injectors in diesel engines. As well as restricting and disrupting fuel flow into the combustion chamber, injector fouling has wider impacts on the engine, and these form the focus of this work. Injector fouling was induced synthetically through the addition of zinc to two types of Diesel fuel on a 2.2L engine. A new degree of fouling metric was presented that allows for a consistent comparison of fouling at full and part load. The investigation has identified impacts on air and fuel pumping losses and on combustion phasing that deteriorate brake thermal efficiency by up to 3%. The effects were also seen during a transient cycle representative of on-road conditions (WLTC). This is significant because the effects of injector fouling are typically only studied at high loads and under steady state conditions. The WLTC results also demonstrated an increase in NOx (9%–18%) and CO2 (up to 1%) emissions as a result of nozzle deposits. The magnitudes of fouling effects were found to vary both with base fuel type and with test condition. A premium dose rate of performance fuel additive was effective at cleaning up the deposits and restoring normal engine performance.