Gas turbine and gas turbine manufacturing method

A gas turbine manufacturing method comprising:

• a conventional structure deciding step of deciding a structure of a conventional gas turbine having two outlet pipes;
• an outlet pipe number changing step of changing the number of the outlet pipes in the conventional gas turbine decided in the conventional structure deciding step to two in each of a lower half and an upper half of a casing and setting the two outlet pipes in each of the lower half and the upper half of the casing as outlet pipes of a new gas turbine, maintaining an average flow velocity of exhaust gas in the outlet pipes at an average flow velocity of the exhaust gas in the outlet pipes of the conventional gas turbine to set an outside diameter of the outlet pipes of the new gas turbine, and calculating decrement of length of the outside diameter from an outside diameter of the outlet pipes of the conventional gas turbine;
• and
• an inter-bearing distance reducing step of reducing a distance between bearings based on the decrement of length of the outside diameter found in the outlet pipe number changing step.