Leeds University

Fuel Combustion Modelling

Chain-branching chemistry models reveal the role of intermediate chemical species on flame structure and stability. A novel turbulent two-phase flow model helps to predict droplet evaporation in engine fuel sprays. Work on intrinsic thermal-diffusive (cellular) and hydrodynamic instabilities of premixed flames includes investigation chain branching chemistry models, which predict the stabilizing role of intermediate chemical species such as radicals in the flame structure and stability. Modelling and direct numerical simulation of expanding flames in
combustion vessels are revealing the effects of ignition transients, vessel geometry and thermo-diffusive and acoustic effects on the flame propagation. The results are being used to help interpret the experimental fuel characterisation studies.
The flow field and liquid pattern emerging from a diesel engine injection

Under current development is a model of turbulent two-phase flow that can
be incorporated into existing CFD (Computational Fluid Dynamics) allowing
designers to predict the size and density of droplets, droplet size distribution, rate of evaporation or condensation and rates of heat exchange between gas and spray and the effects that different propellants and nebuliser designs will have on these factors. The model has been used to help predict and control the atomisation and vaporisation of different fluids across a range of environments including gas turbines and diesel engines.

On the topic of vaporisation in turbulent two-phase flow, relevant to droplet combustion for example, a novel formula for the vaporisation rate has been proposed based on the fact that the vaporisation is affected by small-scale turbulence, a concept which is ignored in currently employed models. This new expression results in prediction of evaporation rate in good agreement with
experimental results.

Gary Sharpe

Alexy Burluka