Thrust efficient turbofan engine
A disclosed turbofan engine includes a gas generator section for generating a gas stream flow. A speed reduction device is driven by the power turbine. A propulsor section includes a fan driven by the power turbine through the speed reduction device at a second speed lower than the first speed for generating propulsive thrust as a mass flow rate of air through a bypass flow path. The fan includes a tip diameter greater than forty-five (45) inches and an Engine Unit Thrust Parameter (“EUTP”) defined as net engine thrust divided by a product of the mass flow rate of air through the bypass flow path, a tip diameter of the fan and the first rotational speed of the power turbine for cruise, climb and sea level take-off power conditions.
1. A turbofan engine comprising:
a propulsor section including a fan and a core flow path portion, the fan including less than 26 fan blades with each fan blade having a fan tip diameter greater than 50 inches and less than 160 inches, wherein the fan rotates in operation at a fan tip speed less than 1150 ft/sec;
a power turbine including between 3 and 6 stages;
a gas generator section including the core flow path portion of the propulsor, a low pressure compressor, a high pressure compressor, a combustor, a high pressure turbine, and a part of the power turbine, the gas generator having an overall pressure ratio in operation between airflow entering the gas generator and a gas stream exiting from the gas generator that is between 40 and 80; and
a speed reduction device in driving connection to the power turbine and the fan, the speed reduction device including a speed reduction of greater than 2.3, wherein an Engine Unit Thrust Parameter (“EUTP”) defined as net engine thrust divided by a product of the mass flow rate of air through a bypass flow path, a tip diameter of a fan and a first rotational speed of the power turbine in operation is less than 0.30 at a maximum takeoff thrust, wherein the net engine thrust is between 16,000 lbf and 120,000 lbf, the mass flow rate of air through the bypass flow path is between 625 lbm/sec and 80,000 lbm/sec and the first rotational speed is between 6,200 rpm and 12,500 rpm.
2. The turbofan engine as recited in claim 1 , wherein the fan includes less than 20 fan blades.
3. The turbofan engine as recited in claim 2 , wherein the gas generator section includes a two stage high pressure turbine.
4. The turbofan engine as recited in claim 3 , wherein the EUTP in operation at the maximum takeoff thrust is less than 0.25.
5. The turbofan engine as recited in claim 4 , wherein the EUTP in operation at a cruise condition is less than 0.10.
6. The turbofan engine as recited in claim 5 , wherein the EUTP in operation at a climb condition is less than 0.10.
7. The turbofan engine as recited in claim 6 , wherein the EUTP in operation at a climb condition is less than 0.08.
8. The turbofan engine as recited in claim 7 , wherein the EUTP in operation at a cruise condition is less than 0.08.
9. The turbofan engine as recited in claim 6 , further comprising a low fan pressure ratio across the fan alone that is less than 1.45 in operation, and the EUTP in operation at the maximum takeoff thrust is less than 0.10.
10. The turbofan engine as recited in claim 7 , wherein the EUTP in operation at the maximum takeoff thrust is less than 0.15.
11. A turbofan engine comprising:
a propulsor section including a fan and a core flow path portion, the fan including a fan tip diameter greater than 50 inches and less than 160 inches;
a power turbine;
a gas generator section including the core flow path portion of the propulsor, a low pressure compressor, a high pressure compressor, a combustor, a high pressure turbine, and a part of the power turbine, the gas generator having an overall pressure ratio in operation between airflow entering the gas generator and a gas stream exiting from the gas generator that is between 40 and 80; and
a speed reduction device in driving connection to the power turbine and the fan, wherein the speed reduction device includes a speed reduction of greater than 2.3, wherein an Engine Unit Thrust Parameter (“EUTP”) defined as net engine thrust divided by a product of a mass flow rate of air through a bypass flow path, a tip diameter of the fan and a first rotational speed of the power turbine in operation is less than 0.25 at a sea-level takeoff power condition, wherein the net engine thrust is between 16,000 lbf and 120,000 lbf, the mass flow rate of air through the bypass flow path is between 625 lbm/sec and 80,000 lbm/sec and the first rotational speed is between 6,200 rpm and 12,500 rpm.
12. The turbofan engine as recited in claim 11 , wherein the EUTP at the sea-level takeoff power condition is less than 0.20.
13. The turbofan engine as recited in claim 12 , wherein the EUTP in operation at one of a climb condition and a cruise condition is less than 0.10.
14. The turbofan engine as recited in claim 12 , further comprising a low fan pressure ratio across the fan alone that is less than 1.45 in operation.
15. The turbofan engine as recited in claim 12 , wherein a ratio between a number of fan blades and a number of rotors in the power turbine is between 3.3 and 8.6.
16. The turbofan engine as recited in claim 13 , wherein the EUTP in operation at both of a climb condition and a cruise condition is less than 0.08.
17. The turbofan engine as recited in claim 13 , wherein the EUTP in operation at the cruise condition is less than 0.08.
18. The turbofan engine as recited in claim 13 , wherein the EUTP in operation at the sea-level takeoff power condition is less than 0.15.
19. The turbofan engine as recited in claim 10 , wherein a ratio between the number of fan blades and a number of rotors in the power turbine is between 3.3 and 8.6.
20. The turbofan engine as recited in claim 19 , wherein the EUTP in operation at the sea-level takeoff power condition is less than 0.10.
21. The turbofan engine as recited in claim 20 , including a two stage high pressure turbine.
22. The turbofan engine as recited in claim 17 , wherein the fan rotates at a fan tip speed less than about 1150 ft/sec in operation, and the high pressure turbine comprises a two stage high pressure turbine.
23. The turbofan engine as recited in claim 22 , wherein the EUTP in operation at the sea level takeoff power condition is less than 0.10.
24. The turbofan engine as recited in claim 23 , wherein a ratio between a number of fan blades and a number of rotors in the power turbine is between 3.3 and 8.6.
25. The turbofan engine as recited in claim 24 , further comprising a low fan pressure ratio across the fan alone that is less than 1.45 in operation and wherein the number of fan blades is less than 20.
26. The turbofan engine as recited in claim 25 , wherein the speed reduction device is a planetary gear system.