Search Results

The pressure swirl injectors that discharge hollow cone sprays are well known in gasoline direct injection applications. As the injector performances strongly depend on the geometry, an important task consists in the nozzle design. This encourages developing a simplified one-dimensional model to allow a quick determination of injector performances in terms of flow rate and cone angle. This paper presents the model and the methodology to take into account designs where the orifice presents an angle with the injector axis. The model was validated by considering 3D simulations and experimental results.

First, this paper presents four models (three zero and a one dimensional model) for predicting injector performances. The theoretical approaches of these four models are presented in details. A critical review of these models has been made possible by using a huge experimental database where more than 3000 injectors have been experimentally tested. In particular, authors show that the one dimensional model allows a very accurate prediction of both static flow rate and cone angle and takes into account more internal dimensions than the zero dimensional models. In a second part of the paper, a coupling between the one dimensional model with a model that predicts the linear stability of conical sheets is proposed. This coupling allows the determination of a theoretical drop diameter that is representative of the large droplets of the spray.

Gasoline direct injection requires that the injection time may be very short in duration, indicating that transient flow effects can have a strong influence on the flow behavior and on the spray properties. Consequently, a computational analysis of the dynamic flow in a high pressure swirl injector was conducted. In order to perform the flow simulation during a complete injection event, movement of the needle that controls the amount of fluid to be discharged has been considered and deduced from experimental data. To validate the computational model, the predicted dynamic flow rate, temporal cone angle and instantaneous mass flow rate were compared to experimental data. The calculated results were found to be consistent with measurements. The dynamic calculations allow a better understanding of the complex transient flow during one injection event and may be divided into four different stages where characteristics of the liquid emerging from the nozzle are completely different.