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The transient behaviour of the fuel spray from an air assisted fuel injector has been investigated both numerically and experimentally in a Constant Volume Chamber (CVC) and an optical engine. This two phase injector is difficult to analyse numerically and experimentally because of the strong coupling between the gas and liquid phases. The gas driven atomization of liquid fuel involves liquid film formation, separation and break up and also liquid droplet coalescence, break up, splashing, bouncing, evaporation and collision. Furthermore, the liquid phase is the dominant phase in many regions within the injector. Experimental results are obtained by using Mie scattering, Laser Induced Fluorescence (LIF) and Laser Sheet Drop sizing (LSD) techniques. Computational results are obtained by using a mixed Lagrangian/Eulerian approach in a commercial Computational Fluid Dynamic (CFD) code.

A phenomenological model having modular formulation is presented for combustion in the open chamber diesel engine. The modules for fuel injection, jet penetration and droplet formation have been calibrated outside the engine in a high pressure, fixed volume chamber by high speed photographic and laser analysis of single spray ‘shots’. In the diagnostic mode of operation the chemical components of the combustion reaction are estimated. In the predictive mode of operation the model is used to estimate engines’ pressure diagrams and various other combustion characteristics of the fuels over a wide range of speed and load conditions. Finally, sensitivity analyses of the reaction rate constants of five fuels namely distillate, sunflower oil, rapeseed oil and methyl esters of sunflower and rapeseed oils, to some of the model inputs are presented.