Can i go out of the airport for long layover

hi i'm travelling manila -kunming- manila round trip,
from mnl to kunming i have a long layover in beijing - about 20hrs
from Kunming on my way back to mnl, about the same 20hrs layover in Chengdu
Can i go out of the airport and spend my layovers in Beijing and Chengdu
I have a single entry china visa btw