Is there a need for a Transit Visa for changing flight at Shanghai airport

The flight touches SH and duration at airport is just adequate to change flight. Details are :-

I am flying from Delhi, India to San Francisco,USA via PVG
My Ticket is by United Airlines but the Delhi - Leg flight is by Air India AI 348 which reaches PVG at 8:20 pm and 4 hours later my next flight by United Airlines UA 890 departs for USA.
Do I need your Transit Visa for this change of flight?