Efficient, low pressure ratio propulsor for gas turbine engines
A gas turbine engine includes a spool, a turbine coupled to drive the spool, and a propulsor that is coupled to be driven by the turbine through the spool. A gear assembly is coupled between the propulsor and the spool such that rotation of the turbine drives the propulsor at a different speed than the spool. The propulsor includes a hub and a row of propulsor blades that extends from the hub. The row includes no more than 20 of the propulsor blades.
1. A gas turbine engine comprising:
a spool;
a turbine coupled to drive the spool;
a propulsor coupled to be driven by said turbine through said spool, said propulsor being located at an inlet of a core flow passage and bypass flow passage having a design pressure ratio that is between 1.3 and 1.4, with regard to an inlet pressure and an outlet pressure of said bypass flow passage, at a design rotational speed of the propulsor, said bypass flow passage defining a bypass ratio of 8.5 to 13.5 with regard to flow through said bypass flow passage and flow through said core flow passage; and
a gear assembly coupled between said propulsor and said spool such that rotation of said spool drives said propulsor at a lower speed than said spool, said propulsor being susceptible at said lower speed to propulsive losses from at least one of flow discontinuities, shocks and turbulence,
wherein said propulsor includes a hub and a row of propulsor blades that extend from said hub, and said row includes a number (N) of said propulsor blades that is no more than 20, and
wherein each of said propulsor blades extends radially between a root and a tip and in a chord direction between a leading edge and a trailing edge at the tip to define a chord dimension (CD), said row of propulsor blades defining a circumferential pitch (CP) with regard to said tips, said row of propulsor blades including a solidity value (R) of CD/CP that is between 1.0 and 1.3 and a ratio of N/R from 9 to 20 to manage said propulsive losses at said lower speed.
2. The gas turbine engine as recited in claim 1 , wherein R is from 1.1 to 1.2.
3. The gas turbine engine as recited in claim 1 , further comprising a low pressure compressor section and a low pressure turbine section that are each coupled to be driven through said spool, and a high pressure compressor section and a high pressure turbine section that are coupled to be driven through another spool.
4. The gas turbine engine as recited in claim 1 , wherein a ratio of N/R is from 9 to 14.
5. The gas turbine engine as recited in claim 1 , wherein the ratio of N/R is 9 to 15.
6. The gas turbine engine as recited in claim 1 , including a variable area nozzle operative to change a cross-sectional area of an outlet of said bypass flow passage.
7. The gas turbine engine as recited in claim 1 , wherein the number (N) is a total number of said propulsor blades, said total number being between 12 and 20 and said propulsor blades all being equally circumferentially spaced.
8. The gas turbine engine as recited in claim 1 , wherein said number (N) of said propulsor blades, said solidity value (R), and said ratio of N/R are in a combination selected from the Table:
Number of Blades (N)
Solidity
Ratio N/R
20
1.3
15.4
18
1.3
13.8
16
1.3
12.3
14
1.3
10.8
12
1.3
9.2
20
1.2
16.7
18
1.2
15.0
16
1.2
13.3
14
1.2
11.7
12
1.2
10.0
20
1.1
18.2
18
1.1
16.4
16
1.1
14.5
14
1.1
12.7
12
1.1
10.9
20
1.0
20.0
18
1.0
18.0
16
1.0
16.0
14
1.0
14.0
12
1.0
12.0.
9. The gas turbine engine as recited in claim 8 , wherein the number (N) of said blades is 20.
10. The gas turbine engine as recited in claim 8 , wherein the number (N) of said blades is 18.
11. The gas turbine engine as recited in claim 8 , wherein the number (N) of said blades is 16, 18, or 20.