Advance ratio for single unducted rotor engine

Abstract

A method is provided of operating a single unducted rotor engine, the single unducted rotor engine comprising a single stage of unducted rotor blades. The method includes operating the single unducted rotor engine to define a flight speed, V 0 , in a length unit per second and an angular speed, n, in revolutions per second, the single stage of unducted rotor blades defining a diameter, D, in the length unit; wherein operating the single unducted rotor engine comprises operating the single unducted rotor engine to define an advance ratio greater than 3.8 while operating the single unducted rotor engine at a net efficiency of at least 0.8, the advance ratio defined by the equation V 0 /(n×D).

What is claimed: 
     
         1 . A single unducted rotor engine comprising:
 a turbomachine; and   an unducted rotor assembly driven by the turbomachine comprising a single row of a plurality of rotor blades,   wherein the single unducted rotor engine defines a product of advance ratio and solidity of greater than 2.0 and less than 8.5.   
     
     
         2 . The single unducted rotor engine of  claim 1 , wherein the single unducted rotor engine comprises an outlet guide vane assembly including a plurality of outlet guide vanes located relative to the plurality of rotor blades for reducing a swirl in an airflow from the plurality of rotor blades. 
     
     
         3 . The single unducted rotor engine of  claim 1 , wherein the product of advance ratio and solidity is between 1.8 and 3.5. 
     
     
         4 . The single unducted rotor engine of  claim 1 , wherein the product of advance ratio and solidity is between 4 and 5. 
     
     
         5 . The single unducted rotor engine of  claim 1 , further comprising:
 a stage of stationary guide vanes located downstream from the single row of the plurality of rotor blades, wherein a ratio of a number of stationary guide vanes in the stage of stationary guide vanes to the number of unducted rotor blades in the single stage of unducted rotor blades is at least 1:2 and up to 5:2.   
     
     
         6 . The single unducted rotor engine of  claim 1 , wherein the product of advance ratio and solidity is greater than 2.0, and wherein during operation the single unducted rotor engine is configured to define a net efficiency of at least 0.8. 
     
     
         7 . The single unducted rotor engine of  claim 1 , wherein the turbomachine of the single unducted rotor engine comprises a turbine section having a turbine, a shaft rotatable with the turbine, and a reduction gearbox, wherein the unducted rotor assembly is driven by the shaft across the reduction gearbox, and wherein the reduction gearbox defines a gear ratio of at least 7:1. 
     
     
         8 . The single unducted rotor engine of  claim 1 , wherein the single unducted rotor engine defines a product of a number of the rotor blades, advance ratio and solidity of greater than 16 and less than 150. 
     
     
         9 . The single unducted rotor engine of  claim 8 , wherein the product of a number of the rotor blades, advance ratio and solidity is between 16 and 47. 
     
     
         10 . The single unducted rotor engine of  claim 8 , wherein the product of a number of the rotor blades, advance ratio and solidity is between 51 and 92. 
     
     
         11 . The single unducted rotor engine of  claim 8 , wherein the product of a number of the rotor blades, advance ratio and solidity is between 40 and 75. 
     
     
         12 . The single unducted rotor engine of  claim 1 , wherein the single unducted rotor engine comprises an outlet guide vane assembly including a plurality of outlet guide vanes located relative to the plurality of rotor blades for reducing a swirl in an airflow from the plurality of rotor blades. 
     
     
         13 . The single unducted rotor engine of  claim 1 , wherein the single stage of unducted rotor blades define a diameter, D, in the length unit, wherein during operation of the single unducted rotor engine during a flight condition the single unducted rotor engine defines a flight speed, V 0 , in a length unit per second and an angular speed, n, in revolutions per second, and wherein the advance ratio is defined by the equation V/(n×D). 
     
     
         14 . The single unducted rotor engine of  claim 13 , wherein during operation of the single unducted rotor engine during the flight condition, the single unducted rotor engine defines an advance ratio greater than 3.8 and less than 9.0. 
     
     
         15 . The single unducted rotor engine of  claim 14 , wherein during operation of the single unducted rotor engine during the flight condition, the single unducted rotor engine further defines a net efficiency of at least 0.8 and up to 0.95. 
     
     
         16 . A method of operating a single unducted rotor engine, the single unducted rotor engine comprising a single stage of unducted rotor blades, the method comprising:
 operating the single unducted rotor engine to define a flight speed, V 0 , in a length unit per second and an angular speed, n, in revolutions per second, the single stage of unducted rotor blades defining a diameter, D, in the length unit;   wherein operating the single unducted rotor engine comprises operating the single unducted rotor engine to define a product of advance ratio and solidity of greater than 2.0 and less than 8.5, the advance ratio defined by the equation V/(n×D).   
     
     
         17 . The method of  claim 16 , wherein the product of advance ratio and solidity is between 1.8 and 3.5. 
     
     
         18 . The method of  claim 16 , wherein the product of advance ratio and solidity is between 4 and 5. 
     
     
         19 . The method of  claim 16 , wherein the single unducted rotor engine further comprises a stage of stationary guide vanes located downstream from the single row of the plurality of rotor blades, wherein a ratio of a number of stationary guide vanes in the stage of stationary guide vanes to the number of unducted rotor blades in the single stage of unducted rotor blades is at least 1:2 and up to 5:2. 
     
     
         20 . The method of  claim 16 , wherein the product of advance ratio and solidity is greater than 2.0, and wherein during operation the single unducted rotor engine is configured to define a net efficiency of at least 0.8.