Combustor size rating for a gas turbine engine using hydrogen fuel

A gas turbine engine comprising:

• a hydrogen fuel delivery assembly configured to deliver a hydrogen fuel flow;
• a compressor section configured to compress air flowing therethrough to provide a compressed air flow;
• and
• a combustor configured to operate without diluent, the combustor including a fuel premixer, an inner liner, an outer liner, and a combustion chamber, the combustion chamber characterized by a combustor size rating between one inch and seven inches at a core air flow parameter between two and one half kN and sixty kN, wherein the combustor size rating is a function of the core air flow parameter, and wherein the combustor size rating is defined by:
• L
• 2
• H
• wherein H is a maximum height of the combustion chamber measured by a forward line extending from an inner surface of the outer liner to an inner surface of the inner liner and L is a length of the combustion chamber measured from a midpoint of the forward line to a midpoint of an aft line, the aft line extending from the inner surface of the inner liner to the inner surface of the outer liner at a leading edge of a turbine nozzle,
• and, wherein the core air flow parameter is defined by:
• Thrust
• Bypass
• ⁢
• Ratio
• ;
• and
• the fuel premixer comprising an annular shroud defining an interior with a mixing chamber, a center body located within the interior and having a first fuel nozzle emitting fuel into the mixing chamber, a second fuel nozzle emitting fuel into the mixing chamber, and wherein at least one cooling aperture is included in the annular shroud of the fuel premixer.