Gas turbine engine compression system with core compressor pressure ratio
A gas turbine engine has a compression system radius ratio defined as the ratio of the radius of the tip of a fan blade to the radius of the tip of the most downstream compressor blade in the range of from 5 to 9. This results in an optimum balance between installation benefits, operability, maintenance requirements and engine efficiency when the gas turbine engine is installed on an aircraft.
1. A gas turbine engine for an aircraft, the gas turbine engine comprising:
an engine core comprising a turbine, a compressor, and a combustor;
a fan comprising a plurality of fan blades; and
a gearbox that receives an input from a core shaft that is connected to at least a part of the turbine, the gearbox outputting drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, wherein
a compression system speed ratio, defined as a ratio of a rotational speed of a most downstream compressor blade to a rotational speed of the fan at cruise conditions, is in a range of 6 to 8.1;
a core compressor pressure ratio, defined as a pressure ratio across the compressor at cruise conditions excluding a pressure rise due to the fan, is in a range from 33 to 60; and
a fan pressure ratio, defined as a ratio of a mean total pressure of a flow at a fan exit to a mean total pressure of a flow at a fan inlet, is no greater than 1.45.
2. The gas turbine engine according to claim 1 , wherein the compression system speed ratio is in a range of 6 to 8.
3. The gas turbine engine according to claim 1 , wherein the compression system speed ratio is in a range of 6.5 to 8.1.
4. The gas turbine engine according to claim 1 , wherein a diameter of the fan is in a range of 220 cm to 360 cm.
5. The gas turbine engine according to claim 1 , wherein the core compressor pressure ratio is in the range 34 to 52.
6. The gas turbine engine according to claim 1 , wherein the compression system speed ratio is in a range of 7.1 to 8.1.
7. The gas turbine engine according to claim 1 , wherein, at cruise conditions, a fan tip loading defined as dH/U tip 2 , where dH is an enthalpy rise across the fan and U tip is a velocity of a fan tip at a leading edge of a tip of a fan blade of the plurality of fan blades, is in a range of 0.28 to 0.30.
8. The gas turbine engine according to claim 1 , wherein the compression system speed ratio is in a range of 7.2 to 8.
9. The gas turbine engine according to claim 1 , wherein a compression system radius ratio, defined as a ratio of a radius of a tip of a fan blade of the plurality of fan blades to a radius of a tip of the most downstream compressor blade, is in a range of 5.2 to 8.5.
10. The gas turbine engine according to claim 1 , wherein the fan pressure ratio is in a range of 1.35 to 1.43.
11. The gas turbine engine according to claim 1 , wherein a fan tip pressure ratio, defined as a ratio of a mean total pressure of a flow at the fan exit that subsequently flows through a bypass duct defined radially outside the engine core to the mean total pressure of the flow at the fan inlet, is in a range of 1.30 to 1.45.
12. The gas turbine engine according to claim 1 , wherein the gearbox has a reduction ratio in a range of 3.2 to 3.8, such that a rotational speed of the core shaft is in a range of 3.2 to 3.8 times the rotational speed of the fan.
13. The gas turbine engine according to claim 9 , wherein
a bypass duct is defined radially outside the engine core, with a leading edge of a splitter defining a point at which flow splits into core flow and bypass flow;
an engine core radius ratio is defined as a ratio of a radius of a tip of a most downstream turbine blade in the gas turbine engine to a radius of the leading edge of the splitter; and
the compression system radius ratio divided by the engine core radius ratio is in a range of 5.5 to 10.
14. The gas turbine engine according to claim 9 , wherein
a bypass duct is defined radially outside the engine core, with a leading edge of a splitter defining a point at which flow splits into core flow and bypass flow;
a core compressor aspect ratio is defined as a ratio of an axial distance between the leading edge of the splitter and a leading edge of the tip of the most downstream compressor blade to a radius of the leading edge of the splitter; and
the compression system radius ratio divided by the core compressor aspect ratio is in a range of 1.7 to 4.2.
15. The gas turbine engine according to claim 1 , wherein the core compressor comprises twelve or thirteen rotor stages.
16. The gas turbine engine according to claim 1 , further comprising an intake that extends upstream of the plurality of fan blades, wherein
an intake length L is defined as an axial distance between a leading edge of the intake and a leading edge of a tip of a fan blade of the plurality of fan blades;
a fan diameter D is a diameter of the fan at the leading edge of the tip of the fan blade; and
a ratio L/D is in a range of 0.25 to 0.4.
17. The gas turbine engine according to claim 9 , wherein
a product of the compression system radius ratio and the compression system speed ratio is in a range of 35 to 60.
18. The gas turbine engine according to claim 1 , wherein
a fan root pressure ratio, defined as a ratio of a mean total pressure of a flow at the fan exit that subsequently flows through the engine core to the mean total pressure of the flow at the fan inlet, is no greater than 1.24.
19. The gas turbine engine according to claim 18 , wherein
a fan tip pressure ratio is defined as a ratio of a mean total pressure of a flow at the fan exit that subsequently flows through a bypass duct defined radially outside the engine core to the mean total pressure of the flow at the fan inlet; and
a ratio between the fan root pressure ratio to the fan tip pressure ratio at cruise conditions is in a range of 0.83 to 0.88.
20. The gas turbine engine according to claim 1 , wherein the cruise conditions correspond to
a forward Mach number of 0.85; and
international standard atmospheric conditions at 35000 ft (10668 m).