‘Smokeless’ can-style fire pits present a great use-case for CFD thermal analysis software. The software allows the user to apply various types of thermal simulations to a solid 3D CAD model. After viewing the analysis the design can then be modified and iterated upon in an attempt to optimize the solution of the product.
The images above describe the general concept of a typical smokeless fire pit. Air at ambient temperature is pulled in through air intakes at the base of the unit. The double-wall construction of the fire pit enables a portion of the intake-air to flow up through the wall cavity as the air is heated and rises. The remainder of the intake air enters the burn chamber at the base to supply the primary wood fire with oxygen. The outlets at the top inner rim allow the air that has been heated within the double-wall chamber to escape creating pressurized air jets. This heated and pressurized air creates a ‘second burn’ that incinerates a large portion of the remaining smoke particles as well as other gases.
For the CFD thermal study I built the CAD model shown above. SimScale was used to perform the different simulations. The first step is to optimize the model as well as create an internal volume that represents the ‘air-flow volume’.
The blue model shown here represents the internal air-flow volume. This will be assigned the correct parameters for the air to be used in the simulation. The top surface designated with the gray icon is the outlet and a velocity or pressure is assigned to it. The extending protrusions at the base represent the intake air flows. The spherical central feature will be assigned as the heat source.
The thermal simulation output can be seen in the images above. The vector lines and cross-section colorations in the left view represent the turbulent kinetic energy of the airflow. The right view shows the air velocity through the secondary-burn output ports when viewed through a horizontal cross section.
The output to the left shows relative temperature and direction of the air as it travels through the system (numerical values are not representative).
Image showing the turbulent kinetic energy of the air entering the base inlets.
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