Generally, for blades materials that have high thermal conductivity two discuss are expressing:
1- High thermal conductivity reduces turbine gas inlet energy and consequently reduces efficiency.
2- High thermal conductivity decreases stress in one area of the blade and extends blade life.
So that, prefer high thermal conductivity or low thermal conductivity? Or choose a middle limit? In reality which mode is used?
Dear Kourosh Vaferi
First of all, you need to determine that you are looking for a material for rotor blades or the stator ones.
I think the best material (the ideal one) is a material which can stand for the high temperatures with high thermal conductivity.
If the material can stand for high temperatures, there is no need for cooling. and when it has no cooling, high thermal conductivity results in uniform temperature distribution and lower thermal stresses.
The material should also have low coefficient of thermal expansion and high strength.
Dear Kourosh,
Generally nickel-based alloys with chromium and Cobalt are used for aircraft turbine blade construction due to following reasons:-
1) To avoid Creep that is blade strecting at elevated temperature. ( Generally turbine blade are covered with cooling air to withstand the temperature slughty above 1000K. Also the current trend is to apply thermal barrier coating on the blade surface. These coating are generally ceramic material with low thermal conductivity used at surface, such that the Virgin blade material should not withstand very high temperature. In nutshell thermal conductivity of blade material is not the cretiria for blade design.)
Their are other two reasons also (fatigue and corrosion) which governs the turbine blade construction but for question you have asked, full explaination in terms of these two is not that much necessary.
Dear Kourosh
As you know we need high thermal conductivity to use in heat exchangers and the low thermal coductivity in gas turbines.
Dear Kourosh
I think low thermal conductivity material is used in gas turbines because we need to save heat transfer and the high temperature for the better performance of gas turbines.
Dear Kourosh Vaferi
I think this article can help you
DOI: 10.9734/AIR/2015/15769
Dear Sahar Nekahi
As I mentioned in the text, high thermal conductivity has some advantages and disadvantages. When thermal conductivity in the turbine blade is low then thermal stresses in one area of blade become dense and this matter cause of blade damage and decrease blade life.
Dear Sanam Nekahi
Yes, it is true, but on the other hand, we will have a short life for the blades.
Dear Kourosh Vaferi
First of all, you need to determine that you are looking for a material for rotor blades or the stator ones.
I think the best material (the ideal one) is a material which can stand for the high temperatures with high thermal conductivity.
If the material can stand for high temperatures, there is no need for cooling. and when it has no cooling, high thermal conductivity results in uniform temperature distribution and lower thermal stresses.
The material should also have low coefficient of thermal expansion and high strength.
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