Search Results

The injection rate modulation and the spray characteristics are determining factors for the quality of mixture formation when applying GDI. Their variation with load and speed is a basic criterion for the adaptability of a type of injection system to an engine with known requirements. The increased interest for the utilization of regenerative fuels - such as methanol obtained from biomass - as well as the success of previous utilization scenarios of variable gasoline/methanol mixture using manifold injection formed the base of the present analysis: the paper describes the results concerning injection performances and spray characteristics when using gasoline/methanol mixtures with different ratios in a direct injection system with high pressure modulation. The results are compared for different parameters of the injection systems as follows: injection volume, injector opening pressure, needle lift, pintle/seat geometry.

This paper presents a complete numerical and experimental characterisation of the transient diesel spray of a modern 5-holes high pressure electronic controlled injector performed in a constant volume pressurised vessel. The experimental analysis has been carried out using a self-developed injection rate measuring device, a visualisation rig based on a Nd-Yag pulsed laser and a synchronized CCD camera to measure spray penetration and spray cone angles and a PDA equipment to measure droplets size and velocity. The numerical analysis has been carried out by statically coupling a 1D model of the common rail injection system to a full 3D computation of both gas and fuel spray dynamics. The 1D injection system model has been developed in the AVL HYDSIM environment and the reliability of the model is demonstrated by comparing the numerical results with the experimental data. The multidimensional numerical simulation tool is a modified version of the KIVA-3V code.

In the present study, a commercial high pressure, common rail injection system for automotive DI diesel engines was fed with a conventional diesel fuel, a bio-derived fuel and a blend of them. The comparison of spray characteristics was carried out in terms of tip penetration and cone angles; the fuel spray, generated by rail pressures ranging from 60 MPa to 120 MPa, developed in an atmospheric chamber. The experimental set-up is based on a laser sheet technique. The radiation scattered by the spray, generated by a Nd-Yag pulsed laser, is collected by a CCD camera and fed to a frame grabber. A suitably set-up automatic image analysis process allows not only to determine the spray average development in terms of its geometric characteristics, but also to analyse in detail its internal structure. In particular, a suitable elaboration allowed the evaluation of the probability of presence in space of spray liquid fractions.