Where a blade airfoil is part of a single stage turbine driving a fan or output shaft (i.e. is a low pressure or LP turbine), as opposed to being part of multiple stage LP turbine, the requirements for such an airfoil design are significantly more stringent, as the fan/output shaft relies solely on this airfoil to deliver work, as opposed to work being spread over several turbine stages. Over and above this, the airfoil is subject to flow regimes which lend themselves easily to flow separation. Such a situation tends to limit the amount of work transferred to the fan/output shaft, and hence the total thrust (or power) capability of the engine, as follows. In order to achieve the work requirement out of a single stage LP turbine, it is desirable to flare the gaspath outward as quickly as possible upon leaving the high pressure (HP) turbine located upstream. This creates a situation where the gaspath entering the LP turbine is on a steep outward flaring angle, and the LP turbine must quickly redirect this flow into a more axial direction without any flow separation. Therefore, improvements in airfoil design are sought.
USPTO Backgrounds
USPTO Backgrounds