Compression in a gas turbine engine
A gas turbine engine for an aircraft comprises an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor, wherein a compressor exit temperature is defined as an average temperature of airflow at the exit from the compressor; and a fan located upstream of the engine core, the fan comprising a plurality of fan blades extending from a hub, each fan blade having a leading edge and a trailing edge, wherein a fan rotor entry temperature is defined as an average temperature of airflow across the leading edge of each fan blade at cruise conditions and a fan tip rotor exit temperature is defined as an average temperature of airflow across a radially outer portion of each fan blade at the trailing edge at cruise conditions. A core to fan tip temperature rise ratio is in the range from 2.845 to 3.8.
1 . A gas turbine engine for an aircraft comprising:
an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor, wherein a compressor exit temperature is defined as an average temperature of airflow at the exit from the compressor at cruise conditions and a core entry temperature is defined as an average temperature of airflow entering the engine core at the cruise conditions, and a core compressor temperature rise is defined as:
compressor
exit
temperature
core
entry
temperature
;
and
a fan located upstream of the engine core, the fan comprising a plurality of fan blades extending from a hub, each fan blade having a leading edge and a trailing edge, wherein a fan rotor entry temperature is defined as an average temperature of airflow across the leading edge of each fan blade at the cruise conditions, and a fan root temperature rise is defined as:
core
entry
temperature
fan
rotor
entry
temperature
,
and wherein a product of a core compressor to fan root temperature rise ratio and a bypass ratio at the cruise conditions of:
core
compressor
temperature
rise
fan
root
temperature
rise
×
bypass
ratio
is in the range from 33.12 to 51.25,
wherein the bypass ratio at the cruise conditions is in the range of from 12 to 15, and wherein the cruise conditions means the conditions at mid-cruise of the aircraft to which the gas turbine engine is attached, and the cruise conditions at mid-cruise means the conditions experienced by the aircraft and the gas turbine engine at a point between top of climb and start of descent at which 50% of the total fuel that is burned between the top of climb and the start of descent has been burned.
2 . The gas turbine engine according to claim 1 , wherein the product of the core compressor to fan root temperature rise ratio and the bypass ratio at the cruise conditions is in the range of from 34.50 to 51.25 and the bypass ratio at the cruise conditions is in the range of from 12.5 to 15.
3 . The gas turbine engine according to claim 1 , wherein the product of the core compressor to fan root temperature rise ratio and the bypass ratio at the cruise conditions is in the range of from 33.12 to 49.20.
4 . The gas turbine engine according to claim 3 , wherein the bypass ratio at the cruise conditions is in the range of from 12 to 14.
5 . The gas turbine engine according to claim 4 , wherein the product of the core compressor to fan root temperature rise ratio and the bypass ratio at the cruise conditions is in the range of from 33.12 to 44.80.
6 . The gas turbine engine according to claim 1 , wherein the product of the core compressor to fan root temperature rise ratio and the bypass ratio at the cruise conditions is in the range of from 33.12 to 41.60 and the bypass ratio at the cruise conditions is in the range of from 12 to 13.
7 . The gas turbine engine according to claim 6 , wherein the core compressor to fan root temperature rise ratio is in the range of from 2.76 to 3.2.
8 . The gas turbine of claim 7 , wherein the fan has a fan diameter in the range of from 330 cm to 380 cm and a fan rotational speed at the cruise conditions in the range of from 1200 rpm to 2000 rpm.
9 . The gas turbine of claim 8 , wherein the fan rotational speed at the cruise conditions is in the range of from 1300 rpm to 1800 rpm.
10 . The gas turbine engine according to claim 1 , wherein the product of the core compressor to fan root temperature rise ratio and the bypass ratio at the cruise conditions is in the range of from 38.40 to 51.25 and the core compressor to fan root temperature rise ratio is in the range of from 3.20 to 4.10.
11 . The gas turbine engine according to claim 10 , wherein the bypass ratio at the cruise conditions is in the range of from 12 to 12.5.
12 . The gas turbine engine according to claim 1 , wherein the fan has a fan diameter in the range of from 220 cm to 300 cm and a fan rotational speed at the cruise conditions in the range of from 1700 rpm to 2500 rpm.
13 . The gas turbine of claim 1 , further comprising a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft.
14 . The gas turbine of claim 13 , wherein the gearbox has a gear ratio in the range of from 3.2 to 5.
15 . The gas turbine engine of claim 14 , wherein the curvature of a root portion of the fan blade is between 10% and 60% less than the curvature of a tip portion of the fan blade.
16 . The gas turbine engine according to claim 14 , wherein the fan has a fan tip loading in the range of from 0.29 to 0.32, or in the range of from 0.30 to 0.32.
17 . The gas turbine engine of claim 16 , wherein the curvature of a root portion of the fan blade is between 40% and 60% less than the curvature of a tip portion of the fan blade and an overall pressure ratio is in the range of from 40 to 45.
18 . The gas turbine of claim 13 , wherein the gearbox has a gear ratio in the range of from 3.2 to 4, and the product of the core compressor to fan root temperature rise ratio and the bypass ratio at the cruise conditions is in the range of from 33.12 to 49.20.
19 . The gas turbine engine of claim 18 , wherein the bypass ratio is in the range of from 12 to 14.5.
20 . The gas turbine engine of claim 18 , wherein an overall pressure ratio is in the range of from 45 to 60 at the cruise conditions.