Average Vaporisation Rate in Turbulent Subcritical Two-Phase Flow

Abstract

This work considers alternative expressions for turbulent evaporation rate used in the framework of an entirely Eulerian model based on a transport equation for the average liquid surface area. Commonly employed expressions for vaporisation rate derived from Spalding-Godsave theory fail to account for vaporisation enhancement induced by turbulence; moreover, they do not describe experimentally observed fact that the pressure affects vaporisation rate differently in a turbulent and a laminar flow. To address these shortcomings, an alternative formula for the vaporisation rate is proposed based on an assumption that the vaporisation rate is governed by a small-scale turbulence. This model is assessed for a range of pressure and temperature conditions, using experiments of Brandt et al. (1997a) performed in a premix duct with a flat-bed atomiser as the test case. Turbulence intensities and scales in the chosen test case are typical for a modern gas-turbine combustion chamber. This new expression results in prediction of evaporation rate and SMD in a good agreement with experimental results.

Keywords:

• Eulerian modelling
• Turbulent two-phase flow
• Vaporisation rate

The authors thank Dr. M. Brandt for kindly providing the paper Brandt et al. (1997b).