Well, there are just so many varieties, but den phal are usually not scented and even the scented ones are often very very faintly so. You will have to stick your nose right to the flowers to detect.
Many of the den phal actually have quite a bit of dose of antelope blood, and the more of that blood, the more likely they will have fragrance and the stonger the scent is.
So, if you like those round full flowers on den phal, they are usually not scented or very very mildy scented. The skinny petaled ones are almost always quite strongly scented.
The best thing is to visit a nursery full of these hybrids, only Hawaii and Florida I think as other place need to spend lots of money to keep them warm during the winter and they simply don't grow these.
Also, check out some vendor's website where they have these and ask them which ones are fragrant.
Sometimes plant description says whether or not they are scented but just because they do not indicate does not necessarily mean they are not scented.
Long story short, if you don't mind skinny petaled antelop type hybrid, the strongest fragrance I've ever had was dendrobium Genting Fragrance.
It will be very hard to find because these hybrids are grown as a large mix among many different hybrids in the same greenhouse. hence, my recommendation of visiting a nursery and pick out the ones you can smell and like.
Good luck!