Development in diesel spray characterisation and modelling

Experiments into the characteristics of Diesel fuel injection equipment (FIE) and fuel spray formation have been conducted on a high-pressure and temperature rapid compression machine (Proteus) to simulate realistic Diesel engine working conditions. Two multi-hole injectors, of the solenoid type, were used; one with a faster response actuator. A high speed video image acquisition system was used to characterise the liquid spray formation, penetration, cone angle, and general spray structure. The experimental spray penetration data have revealed the onset of spray tip instability (cluster shedding) at the later stages of spray penetration. The instantaneous rate and shape of injection for different operating conditions has been measured using an injection rate-tube technique. The combination of the above techniques has allowed an alternative approach in the use of empirical spray penetration correlation to be modified in order to gain information on breakup length. This was achieved by way of the derivation of a breakup length proportionality constant, where historically, this constant was found experimentally. An approach to the modelling of transient spray penetration based on the momentum conservation of the in-jected fuel mass as a physical body of varying mass under that action of the drag force acting on the whole body. For cases under consideration, this approach allows a better representation of early stage of spray penetration than the traditional modelling of each individual droplet under conventional Lagrangian approach which is widely employed by CFD codes. It is suggested that the method based on the Centre-of-Mass tracking can ac-count better for the collective effects between droplets in a dense spray.