Using one-dimensional modeling to analyze the influence of the use of biodiesels on the dynamic behavior of solenoid-operated injectors in common rail systems: Results of the simulations and discussion

Abstract

The influence of using biodiesel fuels on the hydraulic behavior of a solenoid operated common rail injection system has been explored by means of a one-dimensional model. This model has been previously obtained, including a complete characterization of the different components of the injector (mainly the nozzle, the injector holder and the electrovalve), and extensively validated by means of mass flow rate results under different conditions. After that, both single and multiple injection strategies have been analyzed, using a standard diesel fuel and rapeseed methyl ester (RME) as working fluids. Single long injections allowed the characterization of the hydraulic delay of the injector, the needle dynamics and the discharge capability of the couple injector-nozzle for the two fuels considered. Meanwhile, the effect of biodiesel on main plus post injection strategies has been evaluated in several aspects, such as the separation of the two injections or the effect of the main injection on the post injection fueling. Finally, a modification in the injector hardware has been proposed in order to have similar performances using biodiesel as the original injector configuration using standard diesel fuel.

Study of the influence of the needle lift on the internal flow and cavitation phenomenon in diesel injector nozzles by CFD using RANS methods

“…In this sense, it seems clear that the injection process may affect cavitation development [14], [15], [16] since the geometry upstream the orifices changes during the opening and closing of the injector as a consequence of the variable needle lift position.…”

Impact of biodiesel fuel on cold starting of automotive direct injection diesel engines

“…Indeed, the use of such a fuel can cause clogging of the fuel lines and injector coking. Moreover, due to the higher surface tension and viscosity of biodiesel fuels, the hydraulic behaviour of the injector can be affected and consequently an adequate atomization before the combustion process is hardly achieved [17]. As a consequence, on one hand carbon deposits can be promoted and the sticking of piston rings can be produced as well [18,19]; on the other hand, the lack of atomization has a negative impact on the vaporization process, and consequently on the auto-ignition of the fuel.…”

Study of the influence of the needle eccentricity on the internal flow in diesel injector nozzles by computational fluid dynamics calculations

“…This behavior can be explained as a consequence of the cavitation field seen and explained in Figure 2, since the existence of vapor in the upper and lower part of the orifices 4 and 5 strongly reduces the amount of fuel injected. Figure 5 shows the total mass flow (considering all the orifices of the nozzle) and the averaged momentum flux and effective velocity at the nozzle outlet as a function 15 Attending to the mass flow graph, the amount of fuel injected in the combustion chamber for the case where the needle is perfectly placed increases as the backpressure decreases from 9 to 5 MPa. Once the backpressure arrives to 5 MPa, the mass flow remains chocked or collapsed, and despite decreasing the discharge pressure the mass flow remains invariable.…”

“…With regard to the fuel simulated, the properties set in the model belong to a diesel fuel Repsol CEC RF-06-99 at 23 • C. Its properties, obtained experimentally, 15 are a density at liquid phase of 830 kg/m 3 and a viscosity value of 0.0033 kg/ms. However, due to the difficulties to obtain the properties for the vapour phase, they were adjusted using the values given by Karrholm et al [7].…”

“…It is well known that during the opening and closing process of a diesel injector, the fuel characteristics at the nozzle exit change significantly as a consequence of the needle movement [8,14,15]. This change of fluid properties at the exit of the discharge orifices due to the variable position of the needle strongly affects the spray pattern and the air-fuel mixing process, and therefore its subsequent combustion [5,6,10,12,13].…”