Characterization of deposits formed on diesel injectors in field test and from thermal oxidative degradation of n-hexadecane in a laboratory reactor

Diesel fuel has a widespread use in engines that vary in size, speed, power output and application. This includes all forms of land and sea transportation, power generation units and machinery for industrial use. The thermal stability of diesel is therefore a critical parameter for the smooth operation of these systems. Filter plugging and solid deposit formation on fuel injector tips are the two problems most commonly encountered among diesel engine operators. The formation of deposits has been attributed to diesel instability during storage and engine operation [1]. These deposits can cause serious malfunction or even failure in extreme cases. One important feature that distinguishes jet fuel and diesel from gasoline is that their chemical composition allows them to be self igniting. The diesel instability problem is worsened by the presence of relatively longer chain paraffins in the fuel.Studies so far have shown that fuel oxidation products, hydroperoxides and alkylperoxy radicals are primarily responsible for the formation of insoluble deposits from diesel and other middle distillates [1,2]. Solid and liquid products formed from the thermal oxidative degradation of jet fuel were characterized in the previous chapter. This study investigates the nature of HPDI deposits obtained from high-pressure fuel injector, comparing these deposits with those formed from jet fuel. Since information on the hydrocarbon and heteroatom composition of the batch of diesel fuel from which these solids were formed was not available, deposits obtained from the stressing of a model compound (n-hexadecane) were characterized and compared in order to glean the thermal history and formation mechanism of the injector deposits.The thermal stressing conditions to which the diesel fuel was subjected in the injectors were not known. The results of the chemical and morphological analysis of these deposits are discussed in this section, along with the results obtained from n-hexadecane stressi