Cooled Turbine Tip Design: Aerothermal Optimization for Engine Transients
Abstract
The current doctoral dissertation addresses the optimization of cooled high-pressure turbines during the aircraft mission. To comply with the ambitious targets set by ACARE 2050, the overall propulsive system should be optimized along the trajectory. Hence, a global model of the engine is needed to quantify the overall engine performance and select the optimal turbine along the trajectory, which highlights the interconnection between optimization and engine modeling. The detailed analysis of the turbine components is however vital to analyze the aerothermal phenomena. This thesis presents optimal cooled turbine tip designs that demonstrate a superior performance during an entire engine transient. The improvement of efficiency is obtained by optimizing the shape of the cooled turbine tip, considering all the phenomena associated with clearance variations. Optimal turbine blade tip designs not only enhance the aerodynamic performance, but they also reduce the thermal loads on one of the most vulnerable parts of the gas turbine. A multi-objective optimization was performed using a differential evolution strategy and Computational Fluid Dynamics software to solve Reynolds-Averaged Navier-Stokes equations. The results showed the strong impact of the over-tip coolant flows on the over-tip flow field. A detailed model for the scaling of tip convective heat flux based on Green’s functions was developed to predict the overtip heat flux at various gaps and engine conditions. The turbine aerothermal models integrated with the mathematical model of the entire engine were used to assess the effect of an improved turbine design on the overall gas turbine performance. Finally, this thesis proposes an experimental approach to validate the numerical models of the turbine aerothermal performance. This experimental procedure relies on an extensive computational analysis which resulted in the development of an unprecedented facility. This new facility, built at Purdue University, will be extensively used to evaluate transients with ad-hoc instrumentation designed using CFD. This work proposes a methodology to extrapolate the experimental results to engine conditions, in terms of aerothermal performance focusing on tip flow.
Degree
Ph.D.
Advisors
Paniagua, Purdue University.
Subject Area
Energy|Fluid mechanics|Marketing|Mechanics|Thermodynamics
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