Gas turbine engine configured for decreased diffuser windage and method of assembling the same

A gas turbine engine having an outer casing, and an axial centerline, comprising:

• a compressor section;
• a turbine section having a turbine first vane assembly module that includes an annular first vane inner radial support (annular FV inner radial support) coupled to a plurality of stator vanes;
• and
• a combustor section having an annular combustor module and a unitary inner diffuser structure module, the annular combustor module having an inner radial flange, and the unitary inner diffuser structure module including a compressor discharge, an inner diffuser case, and a tangential onboard injector (TOBI) inseparably attached to one another, the unitary inner diffuser structure module further including an outer radial flange and a TOBI connection flange;
• wherein the turbine first vane assembly module, the annular combustor module, and the unitary inner diffuser structure module are independent of one another are coupled to one another.

A method of assembling gas turbine engine components, the gas turbine engine having an aft compressor hub and an outer casing, the method comprising:

• providing an annular combustor module having an inner radial flange;
• providing a plurality of fuel nozzles;
• providing a unitary inner diffuser structure module that includes a compressor discharge, an inner diffuser case, and a tangential onboard injector (TOBI) inseparably attached to one another, and an outer radial flange and a TOBI connection flange;
• attaching the unitary inner diffuser structure module to the outer casing;
• attaching the plurality of fuel nozzles to the outer casing;
• and
• inserting the annular combustor module between the outer casing and the unitary inner diffuser structure module such that a portion of each fuel nozzle is engaged with a forward bulkhead of the annular combustor module, and the combustor module inner radial flange is engaged with the TOBI connection flange.