Inter-turbine ducts with variable area ratios

A turbine section of a gas turbine engine, the turbine section being annular about a longitudinal axis, the turbine section comprising:

• a high pressure turbine with a first inlet and a first outlet;
• a low pressure turbine with a second inlet and a second outlet;
• and
• an inter-turbine duct extending from the first outlet to the second inlet and configured to direct an air flow from the first turbine to the second turbine, the inter-turbine duct having a first station with a first meridional area ratio, a second station with a second meridional area ratio, and a third station with a third meridional area ratio, wherein the first station is upstream of the second station and the second station is upstream of the third station, and wherein the second meridional area ratio is less than or equal to the first meridional area ratio,
• wherein the inter-turbine duct has an axial length and a first portion extending between the first station and the second station, and wherein the first portion extends to about 15%-80% of the axial length, and
• wherein the first meridional area is calculated according to the following Equation:
• AM=2π*RM*hM
• where
• AM is the first meridional area;
• RM is a radius of the duct at the first station;
• and
• hM is a meridional height at the first station.