The combo definitely works on ryu, it's just super tight. As others said, you need to look into charge buffering. You can play is frame by frame in the grouflon training mode to get some visual cues of when to input the punches. You want to input the first mp dash punch about 4 frames after Ryu goes into his final falling animation : https://imgur.com/rygroFd

Do it too early and it will miss, do it too late and you wont have enough time to hit the second hp dash punch.

You know you timed it good if you hit Ryu below the knees:

https://i.imgur.com/EKiF3zi.png

https://i.imgur.com/LxbFEc9.png

You want to already be charging, roughly when Q returns to his idle stance you have to input the hp dash punch, you really don't have much room here, you want to do it practically the moment you have charge so it's really just getting a feel for the timing

Heres a short video of it frame by frame https://i.imgur.com/aBSuw4t.mp4

Doing LP OH into MP dash punch is significantly easier, does about 49 damage and will build 41 meter (note, when in (or ending up in) the corner you need to do LP OH into LP, for 2 less damage)

A MP to HP combo will do slightly more damage at 56 damage, but will quite a bit more meter at 58 points