Structural durability of a diverter shaft in the exhaust flow
The diverter valve and its shaft draw the exhaust flow of a gas turbine to either a boiler or chimney. Thus, the components are permanently exposed to a hot exhaust stream.
1. Flow simulation to determine thermal loads
Flow inside diverter (boiler closed)
The thermal load of the components in the exhaust gas stream (600-700 °C) mainly depends on the flow pattern. This is dependent on the level of the diverter valve and can be calculated using a CFD simulation.
Heat transfer coefficients
The result of the CFD are:
Heat transfer coefficients on the diverter shaft and the blade
Pressure losses in the channel
Flow loads on the blades
With the results, a detailed construction of the structural durability and the creep behavior of the components can be performed.
2. Calculation of the thermal strains
Thermal calculations can be performed with the help of the CFD results, and the resulting temperature strains can be superimposed with mechanical loads.
Possible calculations are:
stationary calculation of certain operating points for determining the static strength and creep resistance (e.g. Stack Closed, Boiler Closed, Intermediate Position of the Blade)
transient calculation of input and shut-down operations to determine the operational stability
Temperature distribution of 2 points in time
Based on the results, critical points can be identified, and the geometry can be changed so that a safe operation is given. The proof optionally takes place via stresses or strains under consideration of plastification.
In doing so, even standards like the ASME Sec. VIII, Div. 2, ASME Sec. III NH or the KTA can be used.
Everything from one source: flow simulation, strength calculation, and reporting.
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Other examples of components in the exhaust gas stream