A research on the diesel spray injected into stagnant ambient air in a chamber is reported in this paper. The main objective of the investigation is to carry Out an in-depth analysis on the influence of injection parameters on the spray internal dynamics and spray macroscopic characteristics. As a result of a theoretical approach based on momentum flux conservation along the sprays' axis, a model which predicts the spray axis velocity and spray tip penetration is obtained. Measurements of momentum flux and spray cone angle are needed in order to predict axis velocity and spray penetration. The chamber density is assumed to be constant and equal to the density of the pressurized air inside the chamber. A Gaussian radial profile is assumed for the axial velocity. Experimental results from a conventional common rail injection system with five axisymmetric nozzles tested in a wide range of injection pressure values and density conditions have been used in order to obtain additional information of the model and also for validation purposes. These experimental results include a large number of momentum flux (impact force), spray tip penetration and spray cone angle measurements. (c) 2005 Elsevier Ltd. All rights reserved.