Yale Coflow Diffusion Flames

Steady flame burner

CAD drawings of the burner in different formats are available here.

Parts list - included with burner
*the number in parenthesis refer to the schematics at the bottom of the parts list.

(1) Coflow Housing: bounds the air flow. Made of 6061 aluminum, black anodized. For dimensions, see CAD file.
(2) Bottom Plate: seals bottom of air plenum. Also 6061 aluminum, not anodized. For dimensions, see CAD file.
(3) Fuel Tube: bounds fuel flow. 3/16” OD, 1/64” thick 316 stainless steel, at least 6 inches long.
(4) Honeycomb: defines exit velocity profile of air flow and supports glass beads (2 per burner).
(6) Screen: supports bottom honeycomb that confines glass beads. 304 stainless steel, 0.017” wire diameter, 18 by 18 mesh.
(7) O-Ring: seals Coflow Housing to Bottom Plate. 3 3/8” outer diameter, 1/16” thick, steam-resistant EPDM rubber.
(8) Fuel Tube Support Fitting: holds fuel tube in Bottom Plate. 3/16” OD tube to 1/8” NPT pipe connector, bored-through, stainless steel.

Parts list - non included with burner

(5) Glass Beads: distribute air flow. Solid soda-lime glass beads, 3 mm diameter.
(9) Fuel Tube Connection Fitting: connects fuel tube to fuel supply. Not included since fuel supplies will vary; on fuel tube side, should be 3/16” OD. (Not shown)
(10) Air Connection Fitting (x4): connects air supply to Coflow Housing. Not included since air supplies will vary; on Coflow Housing side, should be 1/8” NPT pipe.
(11) Nuts and Bolts (x4): hold Coflow Housing and Bottom Plate together. (Not shown)

Assembly instruction:

Assembly will take place in three sections: coflow housing, bottom plate, and final assembly. Note: the following pictures show a plastic 3D printed model of the burner. As specified above, the actual burner body will be aluminum.

Coflow housing:

Fig. 1: Coflow housing, as provided.

The coflow air holes are pre-drilled to 11/32.” For 1/8 NPT fittings, tap the holes, wrap the fittings with Teflon tape, and insert the fittings. If you wish to use different fittings, you may need to make the holes larger before tapping.

Fig. 2: Coflow housing with fittings inserted.

After inserting all four fittings, the burner should look like Fig. 2.

Fig. 3: Coflow housing with mesh and bottom honeycomb.

Insert one of the honeycombs into the bottom of the burner until it seats against the machined edge. Place the mesh on top making sure that all coflow air holes are covered (to avoid the possibility of glass beads entering the fittings.)

Bottom Plate:

The hole in the center of the bottom plate is pre-drilled to 0.12.” This allows for the option to press fit the fuel tube through the hole. For this assembly guide, we will instead use a bored-through 1/8” NPT fitting to connect the fuel tube. This fitting is provided in the kit, as shown in Figure 4.

FIg. 4: Bored-through NPT fitting.

Drill the center hole to 11/32” and tap it. Then screw the fitting into the hole, as shown in Figure 5.

Fig. 5: Bottom plate with NPT fitting inserted.

Final Assembly:

Place the provided o-ring over the bottom of the coflow housing as shown in Fig. 6. Note: the model shown does not have an o-ring grove, which will be part of the actual burner.

Fig. 6: O-ring placed over coflow housing.

Sandwich the o-ring between the bottom plate and the coflow housing. Use nuts and bolts to secure the two pieces together, as shown in Fig. 7.

Fig. 7: Coflow housing and bottom plate assembled.

Insert the fuel line through the bored-through NPT fitting.

Fig. 8: Fuel tube inserted through bottom plate.

Fig. 9: Fuel tube made flush with burner top.

Flip the burner onto a flat surface so that the fuel line is flush with the top of the burner. Using 7/16” and ½” wrenches, tighten the nut on the fitting 1.25 turns. This will permanently attach the fitting’s ferrules to the fuel tube, as shown in Figure 10.

Fig. 10: Ferrule attached to the fuel tube.

Next, pour glass beads into the burner until the machined edge is reached.

Fig. 11: Glass beads placed into burner.

Place the second honeycomb in the top slot and the assembly is complete.