If you get off the train at Taiyuan Railway Station at 9:40 and catch the flight at 11:20, it’s basically enough time if there are no other delays in between. However, considering the possible security check, waiting, boarding, etc., it is recommended that you arrive at the airport at least 1 hour in advance to ensure that you have enough time to complete all procedures. Therefore, it is better to arrive at the airport before 8:40, which is safer.