Abstract
In this paper, a calculation procedure is presented to estimate the heat transfer coefficients of a single spool gas turbine designed to generate 5 kN of thrust. These heat transfer coefficients are the boundary conditions which govern the heat interaction between the solid parts and the working fluid in the gas turbine. However, the calculation of these heat transfer coefficients is not a trivial task, since it depends on complex fluid flow conditions. Empirical correlations and assumptions have been used to find convective heat transfer coefficients over most components, including stator vanes, rotor blades, disc faces, and disc platforms. After defining the heat transfer coefficients, the finite element method was used to determine the temperature distribution in one eighth section of the gas turbine making use of the problem cyclic symmetry. Both static and rotating assemblies have been modeled. The results allowed the prediction of the thermal expansion behavior of the whole single spool gas turbine with special attention to the safety margin of clearances. Furthermore, having the temperature distribution defined, it is possible to calculate the thermal stresses in any mechanical component. Additionally, it is possible to specify suitable metallic alloys for achieving appropriate performance in every case. The structural integrity of all components was then assured with the temperature distribution and thermal expansion behavior under knowledge. Thus, the mechanical drawings could be released to manufacturing.
Highlights
During the design process, the computational simulation phase is extremely important, so that no faults occur during operation, avoiding serious losses and accidents
Where, han is the convection heat transfer coefficient, kair and μair are the conductivity and viscosity of the air, Dan is the hydraulic diameter of the annular passage, mair is the air mass flow rate and Aan is the area of the annular passage
The metallic alloys used to manufacture the single spool gas turbine are of paramount importance, since they will be subjected to high structural and thermal loads, and, they will be subjected to several failure modes
Summary
The computational simulation phase is extremely important, so that no faults occur during operation, avoiding serious losses and accidents. The heat transfer analysis presented in this paper simulates the temperature distribution over the main gas turbine components It provides the thermal expansion behavior of the static and rotating assemblies. Structural analyses can be performed taking into account the thermal effects predicted, which makes it possible to assure that problems generated by high temperatures like creep, thermal stresses, reduction in mechanical strength or insufficient clearances do not cause structural collapse or malfunctioning over the studied gas turbine
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