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 BIOENERGY 2020+. 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 NOx 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]