Search Results

Discrete droplet models in which parcels of droplets are tracked in space in a Lagrangian framework have historically dominated the modelling of fuel sprays. These models are computationally expensive, as the chaotic motions of each droplet have to be predicted. A development of a spray model that captures the full polydisperse nature of spray flow without using droplet size classes has been presented in previous publications. In this paper, the model is applied to solid cone diesel sprays. The size information concerning the spray is obtained by calculating three moments of the droplet-size distribution function from transport equations and one moment from a Gamma size distribution function. The predictions from the model are compared with results from experiments, a discrete droplet model, and two moments-based models. These indicate that droplet break-up, collisions, penetration and sizes are successfully modelled.

A concept combustion chamber, in which an electrospray interacts with electrostatic forces applied on the boundaries, is used to simulate the mixture preparation in a Direct Injection Spark Ignition (DISI) engine. The study is made in a 2D axisymmetric enclosure, which reflects a motored engine operating with an electrostatic atomizer previously investigated for application in fuel burners [1]. Using a rewritten version of a research CFD code [2], the transition injection mode has been chosen given that it integrates the two basic modes of operation of DISI engines [3]. Three pulses of 5 mg each are made at crank angles of 80, 150 and 300 °ATDC of the intake, these falling within the intervals for stable combustion of either early or late injection modes of operation of DISI engines. Over the half engine cycle simulated, the effects of charge are qualitatively studied with use of an uncharged spray as the benchmark.