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2.2 Radiation/vaporisation interaction

The objective of this experimental programme is to evaluate and quantify the influence of radiation on the vaporization process of fuel liquid droplets.
The radiation transfer from combustion gases, and the interaction between droplet vaporization and radiation is still ignored in most existent models, although there is evidence that such effects are important and can not be neglected in some applications.

The main purpose of the experimental work is to provide data for the validation of modelling work to be carried out. It comprises measurements of droplet vaporisation when exposed to different radiative heat loads. A droplet of liquid fuel (different liquid fuels are to be used) will be exposed to symmetrically arranged radiative intensities.

One of the main results will be the construction of a database for different radiation/convection conditions for fuel droplets (different diameters and fuel are to be studied). The structure and contents of this database is to be performed with a close cooperation with an Industrial partner (Snecma).

A considerable part of the wall heat load of gas turbine stems from radiation caused by high flame temperatures and high pressures. Therefore, detailed knowledge of the radiative heat load is required to determine the amount of cooling air and to predict wall temperatures. Although the radiative heat transfer is not expected to be as important in gas turbine combustion chambers, as it is in, e.g., large furnaces in steel, glass and cement industries and power station boilers, it is still expected to play an important role, when accurate determination of fuel vaporization rates are concerned, in gas turbine combustion chambers, due to the presence of soot, that cannot be overlooked in certain engine regimes. The radiation influences the gas temperature distribution, and the formation of soot and other pollutants, as well as the flame structure.

Hence, there is a need to establish and quantify the contribution of the radiation term in the heat transfer process from the gas to the liquid phase and assess how adequate some vaporisation models are when applied to real sprays.

The ultimate objective is to gather the fundamental understanding of the vaporisation/radiation interaction phenomena, so that a comprehensive analytical model can be produced. This would allow designers to verify the adequate performance of a combustion model before committing to an expensive validation programme.

Informations connexes

Reported by

Instituto Superior Tecnico
Avenida Rovisco Pais
1049 001 LISBOA
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