Investigations on Deposit Formation in the Holes of Diesel Injector Nozzles

Abstract

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. Overall, the addition of zinc to the fuel had the biggest effect on deposit formation and resulted in a 12.2% decrease in Indicated Mean Effective Pressure (IMEP). The effects of zinc were unexpectedly reduced when it was added to fuel containing 30%v/v biodiesel. Reducing the common-rail pressure with 30%v/v biodiesel (no added zinc) increased the loss in IMEP. Raising the air and fuel temperatures by 40°C and 30°C respectively showed no bigger loss in IMEP. The results indicate that deposit formation may continue after engine shut down.

Numerical Modelling of the In-Nozzle Flow of a Diesel Injector with Moving Needle during and after the End of a Full Injection Event

“…The implications of such differences in observed in-nozzle phenomena after the end of injection may well be important in the context of HC emissions, as well as mechanisms of deposit formation [46]. Therefore, the flow after the end of injection and during a whole engine cycle needs to be investigated with appropriate temperature predictions and evaporation submodelling coupled to the cavitation simulation methodology described here.…”

A study of factors influencing the formation of harmful deposits in the diesel engine injectors

“…These are usually a mixture of organic and inorganic deposits. Taking into account the fact that the inside diameter of a fuel channel is less than 0.1 mm, the deposits distort the stream of atomized fuel and change its range with an adverse effect on atomization and mixing of fuel with air in combustion chambers as reported by: Birgel et al [3,4], Caprotti et al [5,6], Quigeley et al [10] and Stępień [14]. Uncontrolled changes of excess air number in the fuel-air mixture combined with an insufficient atomization of the fuel streams and mixing with exhaust gases at incorrect proportions by the EGR system leads to incomplete combustion.…”

Evaluation of RME (rapeseed methyl ester) and mineral diesel fuels behaviour in quiescent vessel and EURO 5 engine

“…This has been related to the different density and viscosity of the fluids [10]. Finally, effects of biodiesels on the injection apparatus have been widely investigated to associate the deposit formation in the injector system to the quality and composition of the fuel [11,12]. These sediments have been observed inside the injector body, on the piston, on nozzle needle but, especially, in the spray-holes resulting in a reduced flow and dispersion modification of the injected fuel.…”