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A study about the utilisation of producer gas from gasifiers for obtaining mechanical energy in a SI engine is presented in this work. Therefore, the influence of the gas composition and its thermodynamic properties on the combustion characteristics and on the engine performance are analysed. A home-made chemical equilibrium model which considers 28 chemical species was used to calculate the gas composition as a function of the gasification conditions, and to study the influence of the gas composition on some thermochemical parameters such as adiabatic flame temperature and heat release. The chemical kinetic package CHEMKIN III was also used to study its autoignition behaviour. Finally, a quasi-dimensional two-zone model for SI engines was used to calculate the knock tendency and to analyse the effect of fuel composition on some combustion parameters related to engine performance (IMEP, cylinder pressure, etc.).

A model of atomization and evaporation of a transient spray is presented. This model includes several submodels. The submodel for the primary atomization of the spray core is based on the jet interface instabilities caused by aerodynamic action and includes an intact length model. The droplet secondary atomization is modelled by means of the Taylor analogy. A submodel of droplet evaporation has been developed, in which a heat-up or transient period and a steady state are taken into account, as well as convection effects. Finally a submodel of the droplet deceleration caused by the aerodynamic action due to the air-droplet relative velocity is included. The model is adjusted with the data obtained with a two component Phase-Doppler Anemometer in a test facility with variable air temperature (at atmospheric pressure) in which a Diesel spray is injected.

The present study is aimed to characterize the compact heat exchangers used in automotive air-conditioning systems. Mathematical models of an automotive air-conditioning evaporator and condenser have been developed for the prediction of their performance under operating conditions. The models consider the heat transfer correlations for the fluids inside the evaporator and condensers. Automotive refrigerant heat exchangers are manufactured with different designs, usually containing various flow passages with several fin geometries. In the present work the evaporator is a finned-tube heat exchanger, and there are two types of condensers: finned-tube, called type A and a finned-plate called type B. The models have been validated over a variety of operating conditions, showing good agreement with available experimental data.