12-18-2013, 10:29 AM
The efficiency and power output of a gas turbine increases with higher turbine inlet gas temperature. Modern gas turbine vanes and blades are exposed to gas with temperatures which far exceeds the melting point of the component material.
Thus,the blades and vanes have to be cooled in order to lower the temperature. When cooling the component it is important to know the correct boundary conditions, to avoid creating too large temperature gradients. Large temperature gradients cause thermal stresses and significantly decrease the component life.Both internal and external cooling is used in turbine blades and vanes.The cooling air is extracted from the compressor. The cooling affects the gas turbine in two ways.
First, less mass flow is available for combustion in the combustion chamber.
Second,the trailing edge thickness has to be increased, which creates a larger wake behind the trailing edge which affects the aerodynamics negatively.The extraction of air decreases the efficiency of the turbine, since less air is available for power generation. Maximum cooling with minimum cooling air is therefore desired.
This work concerns internal cooling of turbine vanes and blades 1 and 2 on Siemens Gas Turbines 700 and 800, shortly called SGT -700 and SGT -800.
These components are situated next to the combustor chamber, and are therefore exposed to the highest temperatures. The report is primarily addressed to gas turbine cooling engineers.
Thus,the blades and vanes have to be cooled in order to lower the temperature. When cooling the component it is important to know the correct boundary conditions, to avoid creating too large temperature gradients. Large temperature gradients cause thermal stresses and significantly decrease the component life.Both internal and external cooling is used in turbine blades and vanes.The cooling air is extracted from the compressor. The cooling affects the gas turbine in two ways.
First, less mass flow is available for combustion in the combustion chamber.
Second,the trailing edge thickness has to be increased, which creates a larger wake behind the trailing edge which affects the aerodynamics negatively.The extraction of air decreases the efficiency of the turbine, since less air is available for power generation. Maximum cooling with minimum cooling air is therefore desired.
This work concerns internal cooling of turbine vanes and blades 1 and 2 on Siemens Gas Turbines 700 and 800, shortly called SGT -700 and SGT -800.
These components are situated next to the combustor chamber, and are therefore exposed to the highest temperatures. The report is primarily addressed to gas turbine cooling engineers.
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