240212 Theory ECT

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Politecnico di Milano Energy Conversion Technologies prof. Emanuele Martelli - Academic Year 2023-24 page 1 of 1 Written Exam of 12 February 2024 - Theory Time: 45 minutes 1) Books, lecture notes, cell phones are strictly forbidden. Using them or talking with colleagues and/or copying will lead to the immediate invalidation of the exam. 2) Answer clearly ONLY to the questions posed by the problem sets. Even if correct, additional considerations and/or calculations will NOT be considered. 3) The answers must be in English Energy Conversion Technologies Question 1 (17 points) A) Draw the plant scheme of a sub -critical steam cycle using wood (biomass with low Clorine content) as fuel with (4 points): – superheater – one regenerator – Deaerator B) Draw the T -Q diagram of the regenerator showing the key temperature differences ( 4 points) and providing reasonable values for the optimal cost-efficiency trade-off C) Draw the T -Q diagram of the steam generator with the proper sequence of the economizer, evaporator, and superheater tube banks and provide the key reason of such sequence. (5 points) D) Explain why the steam generator of this type of plant is generally equipped with an air pre-heater (4 points) Question 2 (17 points) A) Draw the scheme of a single-shaft heavy duty gas turbine with cooled turbine blades ( 2 points) B) Explain the main techniques adopted for blade cooling with their advantages and disadvantages (6 points) C) Draw the T-s diagram accounting also for the cooled expansion (assuming that only the first stage blades are cooled) (4 points) D) Explain the effect of the pressure ratio on the efficiency of real gas cycles and explain how the pressure ratio of heavy-duty gas turbines is selected (listing the key motivations and providing a reasonable range…