Automation of CFD simulations

In the field of thermo-chemical biomass conversion, CFD models are being successfully applied for the simulation of turbulent reactive flows in furnaces for the design and development of these plants. However, even a skilled user needs a large number of time-consuming simulations during a CFD based design cycle, whereas never a “real” optimum is found due to the complex interactions of the influencing parameters related to furnace geometry, fuel and plant operation.

Therefore, a tool for the automatic performance of CFD-based parameter studies for the optimisation of biomass grate furnaces has been developed at BEST. Automatic parameterisation and optimisation routines were linked with CFD models developed for biomass grate furnaces, e.g. a 2D CFD packed bed model based (for a time-efficient performance of the simulations) and gas phase combustion models. Hence, the plant geometry as well as the operating conditions (e.g. air staging, air pre-heating and fuel related parameters) can be investigated and optimised in order to meet the following requirements:

• High turbulent mixing and homogenisation of the flow across
• Minimisation of furnace volume (investment costs)
• Reduction of excess air and flue gas recirculation ratio (efficiency, operation costs)
• Reduction of CO and NO_x emissions
• Reduction of temperature peaks (fouling and slagging) and flue gas velocity peaks (material stress and erosion)

This innovative approach allows a further reduction of development times and costs.

Example of an automatic optimization of the secondary air nozzles for a 15kW pellet boiler; burner wall temperature [°C] (left) and flue gas temperature [°C] (right) in dependence of the angle of the secondary air nozzles [Shiehnejad A. 2013]