A model for fuel spray penetration

A new model for fuel spray penetration (location of spray tip) is suggested and validated against available experimental data. Simple analytical expre ssions for fuel spray penetration arc derived in two limiting cases: the in itial stage and the two-phase flow regime. At the initial stage, the effect s of droplet drag and entrainment of air are accounted for. In the case of the two-phase flow, it is assumed that the spray droplets have the same vel ocities as the entrained air. The characteristic time of droplet break-up i n the spray is estimated for both bag and stripping break-up mechanisms. Fo r realistic diesel spray parameters, the droplet break-up takes place almos t immediately after the droplets leave the nozzle. This leads to a consider able shortening of the initial stage and a rapid conversion of the flow to the two-phase stage. This allows the analysis to be restricted to the two-p hase flow approximation for this type of spray. The expressions for spray p enetration derived in this paper give more accurate predictions compared wi th those suggested earlier. (C) 2001 Elsevier Science Ltd. All rights reser ved.