NESTEM is a computer code that is a combination of a heat-transfer-analysis subprogram and a NASA in-house probabilistic-analysis code called "NESSUS" (for Numerical Evaluation of StochasticStructures Under Stress). NESTEM can be used to analyze a complex combustor thermal environment with uncertainties and to assess the effects of the environment and the uncertainties on the overall responses of components. NESTEM is expected to help in the development of a comprehensive probabilistic methodology for reliable and robust design of such major turbine-engine components as compressors, turbines, impellers, and combustors.

Prior to the development of NESTEM, there was no known program that afforded a capability for perturbing such heat-transfer variables as thermal conductivities of materials, convection coefficients, and radiation temperatures. NESTEM enables one to perform a formal assessment of uncertainties in loads, variations in properties of materials, and geometric imperfections on the overall structural behavior (as characterized by stability parameters, frequencies, stresses, and other parameters).

In addition to enabling probabilistic heat-transfer analysis, NESTEM makes it possible to generate mathematical models of components by use of selected modules from the NASA in-house Composite Blade Structural Analyzer (COBSTRAN) computer code. Furthermore, the material-property parameters needed to represent ceramic-matrix composites are obtained by use of the NASA in-house Ceramic Matrix Composite Analyzer (CEMCAN) code.

This work was done by B. M. Patel of Modern Technologies Corp. for Glenn Research Center. LEW-16788


NASA Tech Briefs Magazine

This article first appeared in the November, 1999 issue of NASA Tech Briefs Magazine.

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