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What is the turbine efficiency of a modern jet engine? Just the turbine efficiency only. What percentage of fuel energy the turbine converts into mechanical energy.

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Slide 7 of this presentation (shown above) states the latest technology for a turbine with cooling flow is 89% efficient, while an uncooled turbine is about 90% efficient. The table from this presentation comes from the well renowned book by Jack Mattingly, "Elements of Propulsion: Gas Turbines and Rockets".

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  • $\begingroup$ 89% efficiency surprises me. Do I understand correctly that this turbine converts 89% of fuel energy into mechanical shaft energy? I thought that ICE and jet engines are only 35% thermally efficiency. Someone please clarify this large discrepancy. thanks $\endgroup$ – Neville p Oct 7 '18 at 15:51
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    $\begingroup$ @Nevillep. To clarify completely is beyond the ability of what one can say in the limited text of a comment. But, the 35% you mention is about correct, and is the overall thermal efficiency of gas turbine. It is how efficient the engine is converting the calorific energy of the fuel to thrust. The 89% efficiency is the (isentropic) efficiency of just the turbine section of the engine. It is a measure of how efficiently the turbine extracts energy from the gas flow, for the given pressure drop across the turbine. The overall efficiency is determined by the efficiency of many individual ... $\endgroup$ – Penguin Oct 10 '18 at 9:25
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    $\begingroup$ ...parts. For example if there were 4 parts each with 90% efficiency, the overall efficiency is 0.9 x 0.9 x 0.9 x 0.9 = 0.6561. So, the overall efficiency is low but the efficiency of individual parts is higher. Your question specifically asked for “just the turbine efficiency only”. $\endgroup$ – Penguin Oct 10 '18 at 9:28

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