Evaluation of applicability of empirical models of turbine performance to aircraft engine

In order to investigate several problems associated with the turbine cooling, an air-cooled two-stage axial flow turbine for an aircraft engine application was designed. Aerodynamic characteristics of the two-stage turbine without coolants were obtained first from the cold air turbine tests, and predictions of the turbine performance with supplying of coolants were made using the test results. Following these experiments, cooling tests of the first stage turbine were conducted in the range of turbine inlet gas temperatures lower than 1360 K by the another test apparatus. The descriptions of the turbine and the two test apparatus and the experimental results of the two test turbines are presented. The performance prediction, coolant effects and Reynolds number effect on the turbine performance are also described.

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High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164337 ◽

1996 ◽

Vol 54 ◽

pp. 374-375

Author(s):

M. Larsen ◽

R.G. Rowe ◽

D.W. Skelly

Keyword(s):

Heat Treatment ◽

Solid Solution ◽

High Temperature ◽

Elevated Temperatures ◽

Aircraft Engine ◽

Lattice Parameter ◽

Microstructural Stability ◽

Elevated Temperature Strength ◽

Cross Sectional ◽

Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

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