Development of clean and efficient wood stoves through improved batch combustion models and CFD modelling approaches

In modern wood stoves, produced after emission limits for particles from wood stoves was introduced in 1998, the emissions are relatively low compared to old wood stoves. The new stoves have two-stage air addition, which give better combustion conditions, and hence lower emissions.

But this is not enough in the future, we must also improve today's modern wood stoves - they must become even better and smaller and/or release a lower and more stable effect to have a future in modern low energy and passive houses.

To reduce emissions further and improve the heat comfort, better control of both the heat production and heat release to the room is needed. The ideal would be a continuous combustion process, without fluctuations leading to unstable combustion conditions and increased emissions. However, the combustion process in a wood stove is and always will be a batch process, i.e. the wood will change continuously from moist raw wood to charcoal, and finally ash. This is a challenge, with respect to combustion control.

In WoodCFD we will especially focus on combustion chamber design for minimized emissions. CFD combines geometrical details and reactive flows. The result is a detailed picture of the combustion process and its quality. Various parameters can then be varied to improve the combustion process.

For all modelling it is important with correct sub-models for the physical and chemical processes ongoing, together with correct input to the simulations that use these. Combined with experimental work this will contribute to wood stoves with emissions down to pellets stove level and 1 kW effect, which will be released considerably more stable than from today's wood stoves, i.e. well suited for low energy and passive houses.

Result from this project can give considerable environmental benefits and more sustainable heating.

SINTEF Energy Research headed the project and focused on the wood stove modelling and experimental side. NTNU (Norwegian University of Science and Technology) supervised the PhD and Master candidates, lead the room/building modelling activities and participated in additional selected activities.