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Probability Density Function (PDF) is often selected to couple chemistry with turbulence for complex reactive flows since complex reactions can be treated without modeling assumptions. This paper describes a preliminary investigation into the use of the particles approximation of this transport equation approach applied to diesel combustion. The model used here is an IEM (Interaction by Exchange with the Mean) model to describe the micromixing. Therefore, the fluid within the combustion chamber is represented by a number of computational particles. Each particle evolves function of the rate of change due to the chemical reaction term and the mixing term. The chemical reaction term is calculated using a reduced mechanism of n-heptane oxidation with 25 species and 26 reactions developed previously. The parametric study with a variation of the number of particles from 50 up to 104 has been investigated for three initial distributions.

A very accurate control of air fuel ratio in port injected spark ignition engines during transient is required to reach the toughest polluant emissions standards. The prediction of air fuel ratio behavior has been made with models for liquid fuel film, droplets and fuel vapor in the intake manifold of single point injected engines [1], where the droplet deposition rate on the manifold was only a parameter. This paper describes a model for droplet deposition rate on the port walls and intake valve in port injected engines. The model described here takes into account the transient character of fuel injection in a real port geometry. The droplet diameter distribution is included with seven different droplet sizes, and varies across the spray, with a multicomponent fuel. The backflow of hot burned gas at valve opening is also taken into account by the model.

In this paper, the fuel excursion and cyclic variation of the fuel/air equivalence ratio have been studied by means of a catalytic hot wire sonic nozzle probe. This probe, developed in our laboratory, is simple to construct and very sensitive to fuel/air equivalence ratio with a time response less than 400 μs. Transient fuel excursions were studied on an engine with multipoint fuel injection during different transient operations (starting, fast throttle opening and closing). The influence of the coolant temperature was also investigated. The measurement of cycle to cycle variation of the fuel/air equivalence ratio was carried out on both a multipoint stoichiometric fuel injection engine and a lean burn SI engine (direct fuel injection). The influences of engine speed, load and injection timing were investigated. The fuel used was unleaded gasoline and all the measurements were carried out without combustion.