In English, usually just "the Battle of Kursk". Variations I've seen include "of Kursk and Orel" and "of Orel (Kursk)." And, of course, "Orel" can be spelled "Oryol."

The "bulge" is usually called "the Kursk Salient" or the "Orel-Kursk Salient," but you don't have to mention that since it doesn't seem to be in your original.