Characterization of Cooled Turbine Efficiency for Off-Design Performance Models

<p>Gas turbine performance modeling is essential for predicting engine behavior across design and off-design conditions. Yet the treatment of cooling or service flows remains inconsistent, as these streams interact with the main flow in complex ways and their contribution to turbine work depends on how they are represented in performance models. The challenge is especially present in “black-box” approaches, where only inlet and outlet conditions are known and engineers must decide whether to introduce cooling flows upstream (if performing useful work) or downstream (if not). This thesis examines how different definitions of isentropic power and cooling-flow treatment affect the apparent efficiency of a cooled two-stage axial turbine. A representative numerical model was developed to simulate several service-flow configurations and compare four modeling approaches. Results show that neglecting cooling contributions (Approach A) yields unrealistically high efficiencies, while more refined methods (Approach B, inlet-weighted enthalpy; Approach C, work-potential factors) capture the reduction in available work more accurately. The most rigorous formulation (Approach D, based on Hartsel) applies individual isentropic expansions to each cooling stream and establishes a theoretical lower bound. The study also quantifies the work potential of each cooling stream using literature-based, design-based, and CFD-derived formulations, illustrating how these factors guide the classification of flows as chargeable or non-chargeable in black-box models. Despite the simplified geometry employed, the results offer insight into the sensitivity of turbine efficiency to cooling-flow modeling choices. This work represents a step toward standardized, physically consistent methods for cooled-turbine performance prediction, with future efforts focusing on more realistic geometries, improved mixing models, and integration of the proposed criterion into advanced performance tools.</p>

Name thesis:degree_name

Master of Science in Aerospace Engineering

Level thesis:degree_level

Thesis - Open Access

Discipline thesis:degree_discipline

Aerospace Engineering

Year

2025

Author dc:creator

• Garcia, Alberto

• Gas turbine
• performance
• efficiency
• cooling
• service flows
• Aerospace Engineering
• Propulsion and Power

Repository record dc:identifier

https://commons.erau.edu/edt/941

OAI identifier oai:identifier

oai:commons.erau.edu:edt-1989