Can I go out in kunming since I'll be having a 15h layover?

So you will have a domestic to international transfer in Kunming? If so, I'm afraid you have to hold a China visa during your layover. But if your route is an international area - SH - Kunming - Dubai and the total layover is within 24h in the two domestic cities, you can apply for a stay permit in SH. Then you can use it for leaving airport in both cities visa-free.