The ornamental design for a burnerassembly, as shown and described.
FIG. 1 is a front perspective view of a burner assembly showing our new design;
FIG. 2 is a top view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a front view thereof; and,
FIG. 6 is a rear view thereof.
The unshaded center circular area and the broken line surrounding it are portions of the burner assembly that are not included in the claim. The interiors of the circular ports surrounding the top outer edging of the article depict portions of the burner assembly that form no part of the claimed design. All other broken lines illustrate environmental material that forms no part of the claimed design.