Thank you for your excellent explanation.Hello Kimaunz, yes, you could say "I was able to smell" in the same sense here, though the normal way is with "could". "Be able to" might imply that you were able to do so despite some kind of hindrance to your ability to smell the cooking, as shown in the sentence below in italics. But there's no reason to use it in your context.
I had a heavy cold and couldn't taste my food, but I was able to smell the evening meal cooking.
There are other contexts in which "could" and "was/were able to" are not interchangeable, and there's a useful discussion (too long to reproduce in this thread) about it here (stackexchange.com), and several previous WR threads about it here.
Thank you for the clarification.Usually 'I can see', 'I can hear', 'I can smell' (and their past tenses with 'could') mean nothing more than 'I see', 'I hear', 'I smell' (saw, smelt, etc.). There's no real emphasis on 'can'. But changing it to '(be) able to' returns emphasis to it. There might be some reason why possibly you couldn't smell it, but now you could smell it.
AmE often says simply 'I see/hear/smell it' where BrE usually adds 'can'.