An Analysis of a Deposition Tolerant Cooling Approach for Nozzle Guide Vanes

The present paper documents a cooling analysis for an innovative cooling approach designed to reduce the potential for particle deposition while effectively and efficiently using cooling air. The design eliminates showerhead cooling in the stagnation region through the use of incremental impingement (Busche et al. [1]) on the pressure surface, stagnation region and near suction surface. The incremental impingement terminates by collecting and discharging the spent cooling air through a slot. An approach called counter cooling (Ames et al. [2]) is used to cool the suction surface. Counter cooling uses cooling air sparingly by matching the heat up of cooling air with the effective use of full coverage film cooling. Finally, the design promotes the use of a covered trailing edge to improve the thermal protection in that region. The vane is designed with a generous leading edge diameter to allow the integration of double wall cooling. The aft loaded pressure distribution helps to minimize the aerodynamic losses associated with film cooling discharge. The heat load analysis incorporates engine relevant inlet turbulence levels (14%) predicting turbulent augmentation using the algebraic turbulence model of Ames et al. (1999) [3] and the transition model of Mayle (1991) [4]. The internal boundary conditions for the incremental impingement and counter cooling sections, including pressure drop, were based on the research of Busche [1] et al. The trailing edge cooling boundary conditions were based on the work of Jaswal and Ames [5]. The film cooling effectiveness levels were interpolated from the database documented by Busche et al [6]. The cooling design results in moderately high levels of overall effectiveness while using cooling air in a very efficient manner. The objective of the finite element cooling analysis is to help advance the readiness of incremental impingement and counter cooling for use in vane cooling designs. The cooling design is expected to be fabricated and tested in a warm cascade experiment to demonstrate potential of the technologies for integration into engine component designs.