is there a bus from chengdu to chongqing airport?

No direct bus is available to the airport. You can take a bus from local Chengbei Bus Station or Wuguiqiao Bus Station to Chongqing Caiyuanba Bus Station in around 4h first and the last bus leaves from Wuguiqiao at 17:30. After arriving, take subway line 3 to Chongqing Airport. Or you can also take a bullet train from CD East Train Station to Chongqing North in 2 h. Upon arrival, you can take the light rail line 3 to the airport directly.