They don't seem to have one. My guess is that either they were so early in the design phase that it would be added later or they had no clue what kind of funnel those diesel engines would require. I think one of the features of early diesel ships was that they had no funnel (see MS Selandia), so ma...
One of the main things that really get me with your designs are that your turrets don't seem to fit your time period, the look like something you would find on a modern warship rather than a ship from the 1920s.