B2373 - Machines and Sustainable Energy Systems

Learning outcomes

The student is able to face the design of modern energy systems (combined groups, cogeneration groups) for the production of electricity and refrigeration cycles (compression, absorption, air). He is also able to deal with the fluid-dynamic design of the compressible turbomachines. Finally, the student acquires the basic knowledge on systems for the production of electricity and heat from renewable sources.

Course contents

ENERGY SISTEMS

-WORLD energy panorama

-COMBINED CYCLE POWER PLANTS (CCPP) or GAS-STEAM CYCLES: Overall performance, 1 pressure level without and with reheating, 2 pressure levels, optimization of the flow rate spilled from the low-pressure liquid separator (steam drum), 3 pressure levels (lay-out only), T-S diagram and heat exchange diagram T-q

-COGENERATION: POWER AND ENERGY EVALUATION INDEXES, Cogeneration: gas turbine, with back pressure steam turbine and with condensing steam turbine. Cogeneration in Combined Cyle Power Plant.

-WIND ENERGY: Betz – Lancaster limit

-SOLAR ENERGY: Thermal (production of hot water for sanitary purposes). Photovoltaic: production of electricity through the use of semiconductors. Thermodynamic: thermal energy is used to evaporate oils/salts, which then expand in a turbine producing electricity.

-GEOTHERMAL ENERGY: Hydrothermal plants. Dominant water cycle: Ambient discharge, Condensation. Dominant steam cyle: Flash steam cycle, Binary cycle. HYBRID geothermal cycles: Gas turbine systems, Steam power systems with spilled steam.

-FUEL CELLS: Introduction, Working principle, PEM

Hydrogen: Energy vector, Properties, Storage. Production: types of hydrogen. Comparison versus methane.

 

FLUID MACHINES

-Isentropic and polytropic compression and expansion efficiencies -FLUID MACHINES:

-Definition

-Classification

-TURBO-MACHINES

-RADIAL flow

-AXIAL flow

-MIXED flow

-STAGE of a TURBO-MACHINE

-NAVIER-STOKES equations for the study of the flow and simplifications

-Fundamental equations for turbo-machines: Perfect gas, Real gas, State functions, Thermodynamic transformations.

-MASS CONSERVATION PRINCIPLE

-ENERGY CONSERVATION PRINCIPLE:  CLOSED system, OPEN system

-WORK ACCORDING TO EULER IN TURBOMACHINES:

-DIRECT formulation: FIXED and MOBILE (RELATIVE) observer, Potential (gravitational, centrifugal) and Potential Energy, Rothalpy

-INDIRECT formulation or WORK to the DIFFERENCE of KINETIC ENERGIES

-GAS DYNAMIC

-MACH number

-Coupling of equations of motion (mass, energy, momentum)

-1D COMPRESSIBLE MOTION IN THE DUCT

-PROPAGATION OF ACOUSTIC WAVES

-Speed of SOUND

-ISENTROPIC FLOW IN A CONSTANT SECTION DUCT: PARAMETRIZATION OF THE EQUATIONS AS A FUNCTION OF THE MACH NUMBER

-TOTAL quantities

-ISENTROPIC FLOW IN A VARIABLE SECTION DUCT: Nozzle and Diffuser

-SOLUTION OF THE ISOENTROPIC FLOW IN A PURELY CONVERGENT DUCT

-CHOKING

-DE LAVAL nozzle (CONVERGENT-DIVERGENT)

-OPERATING MACHINES (COMPRESSORS)

-COMPRESSORS: VOLUMETRIC; TURBO-COMPRESSORS (STAGE=ROTOR + STATOR):

- AXIAL

- CENTRIFUGAL

- COMPARISON BETWEEN AXIAL AND CENTRIFUGAL COMPRESSOR

- DIAGRAMS: h-s for rotor, stator, compression stage

- PERFORMANCE PARAMETERS: TOTAL to TOTAL efficiency; TOTAL to STATIC efficiency; STATIC to STATIC efficiency.

-GEOMETRICAL TOPICS: MERIDIAN component of velocity

-CENTRIFUGAL COMPRESSOR: Backward blades (negative), forward blades (positive), straight blades (radial), Rotor blade lower surface (or blade pressure face – ventre) and rotor blade upper surface (blade back - dorso): pressure trend as a function of the radius qSTALL; PUMPING; Degree of REACTION; Blade loading (blade stress); Rotor; SLIP FACTOR: EMPIRICAL formulation by STANITZ; DIFFUSERS With blades and Without blades

-AXIAL COMPRESSOR: Degree of REACTION; Symmetrical blades

-VOLUMETRIC COMPRESSOR: Reciprocating compressor (Ideal cycle, Real cycle); Rotating compressor (ROOTS); Sliding vane compressor

-DRIVING MACHINES (TURBINES)

-Introduction

-Thermal turbines: Axial-flow turbine, Inward-flow turbine (centripetal or radial), Stage of turbine, Performance parameters 

-INWARD-FLOW TURBINE: Diagram h-s; TOTAL to TOTAL, TOTAL to STATIC, STATIC to STATIC efficiencies; Performance curves; Force fluid flow - blade; Degree of REACTION

-AXIAL-FLOW TURBINE: Rothalpy; Degree of REACTION; Efficiency; Minimum kinetic energy at the discharge; Simplified calculation of a stage; IMPULSE turbine (ACTION): DE LAVAL turbine, Rotor with symmetric blades, Rotor with non-symmetric blades, Real case

REACTION turbine: Ideal case, Optimized case, Comparison bewteen REACTION stage and IMPULSE stage

-RADIAL INWARD-FLOW TURBINE: Some considerations on applications for ICEs

Readings/Bibliography

"Sistemi Energetici e Macchine a Fluido" Vol. 1 (Macchine a Fluido) e 2 (Complementi), G. Negri di Montenegro, M. Bianchi, A. Peretto, Pitagora Editore.

"Fundamentals Of Renewable Energy Processes" – Aldo Vieira Da Rosa, Juan Carlos Ordonez, Academic Press – ISBN 978-0-12-816036-7

"Advanced Power Generation Systems ", Ibrahim Dincer and Calin Zamfirescu, Elsevier

"Sustainable Power Generation (Current Status, Future Challenges, and Perspectives)", Nikolay Belyakov, Academic Press

"Gas-Turbine Power Generation" - 1st Edition - February 24, 2016 - Paul Breeze - ISBN: 9780128040058

"Macchine a Fluido" DOSSENA V.; FERRARI G.; GAETANI P.; MONTENEGRO G.; ONORATI A.; PERSICO G., HOEPLI Editore

"Turbomachinery Flow Physics and Dynamic Performance" Meinhard T. Schobeiri – Springer – 2nd edition

"Gas Turbine Theory" - H.I.H. Saravanamuttoo, G.F.C. Rogers, H. Cohen, Paul Straznicky, A. C. Nix - Ed. Pearson

"Fluid Mechanics and Thermodynamics of Turbomachinery", Dixon S.L., Hall C., Ed. Butterworth-Heinemann

"Principles of turbomachinery in air breathing engines", E.A. Baskharone, Cambridge University press

"Principles of Turbomachinery", Korpela, S. A.

"Principles of Turbomachinery", Shepherd, D.G., Macmillan Publishing Co., Inc., New York, 1956.

 

 

Teaching methods

PLATFORM ‘VIRTUALE’ (https://virtuale.unibo.it/): Lectures and/or presentations uploaded at the end of the lesson.

IT IS STRONGLY RECOMMENDED TO ALWAYS CONSULT THE BOOKS LISTED BEFORE.

The lessons are frontal in the classroom. The teacher, replacing the traditional blackboard, uses a tablet connected to the projector to develop the concepts and to show the supporting teaching material. At the end of the lesson the teacher makes available the material shown in a pdf file, downloadable from platform VIRTUALE. ALL forms of distribution of this material are FORBIDDEN: every ENROLLED STUDENT can download it in AUTONOMY. This material is NOT intended as a DISPENSE but is ONLY a study support system. The teacher DOES NOT provide any DISPENSE, but INVITES the students to use the TEXT BOOKS.

Attendance is strongly recommended for better learning of concepts and notions, but does not affect the final evaluation process.

It is strongly recommended, before entering the course, to review the basics of steam and gas systems for the production of electricity, as well as the basic components that constitute them.

The teaching participates in the University’s educational experimentation project.

Assessment methods

The exam consists of two tests. In the first test, which lasts 15 minutes, students must answer two very short questions designed to assess their basic knowledge. Correct answers to both questions are required to pass the exam. The result of this first test does not contribute to the final grade, but it does determine admission to the second test. The second test consists of an oral exam, during which students are asked to respond in writing to two questions, one for each module, relating to the theoretical part covered in class. Students then discuss their written work with the instructor, who may request further clarification or add additional questions.
The written part lasts approximately an hour and a half, after which the teacher collects their homework and students wait in class to be called for the discussion.
During the exam, regarding fluid machines and energy systems, their components, and functions, the student's ability to:
- use appropriate technical language;
- correctly use thermodynamic tools;
- describe the operation of machines;
- describe the operation of a thermodynamic system and its components;
- theoretically justify their architecture;
- represent the geometry of a machine or energy system with a freehand sketch;

- evaluate their performance;

- to reproduce demonstrations seen in the classroom;

- to connect a system to its thermodynamic diagram and to each single component.

All of these skills are developed and strengthened during classroom lessons. For this reason, attendance is strongly recommended.

The final grade, expressed in thirtieths, will be higher the more the student is:
- independent in articulating the answers to the two questions;
- thorough in presenting the topics;
- precise in representing the functionality of freehand sketches.

Exam dates will be announced in advance via the University of Bologna's AlmaEsami web platform. Registration for the exam is mandatory and possible up to three days before the exam date. At the exam, students must bring an identification document and a pen.

The use of AI tools during the exam is prohibited in any form, including chatbots, text generators, advanced translators, content synthesizers, and tools integrated into devices.


Any use of AI is considered a violation of the principle of honesty and fairness set forth in the Policy and may result in the instructor's cancellation of the exam. The instructor remains responsible for ensuring the exam's validity.


Only writing instruments (pens, ballpoint pens, pencils) and a ruler (if deemed necessary by the student) are permitted during the exam.

 

 STUDENTS WITH TEMPORARY OR PERMANENT DISABILITIES

Please contact the University office promptly: https://site.unibo.it/studenti-con-disabilita-e-dsa/en

The office will be responsible for suggesting any adjustments to the students concerned, which must however be submitted to the head teacher for approval 15 days in advance. The teacher will evaluate their suitability also in relation to the educational objectives of the course.

"In accordance with the University Code of Ethics, students are urged to maintain the utmost integrity. Any activity aimed at improperly altering the outcome of exams (e.g., cheating, plagiarism, accessing online learning resources, or using unauthorized AI tools) is prohibited. In particular, the mere possession of unauthorized equipment or materials during the exam will result in the immediate cancellation of the exam and reporting to the relevant authorities.

Conduct violating this prohibition may result in disciplinary proceedings or reporting to the relevant authorities, if criminally relevant; in the latter case, there is a risk that the students involved may face criminal proceedings."

Teaching tools

The course will be carried out through the use of:

- Tablet connected to the projector, used as an alternative to the blackboard.
- Each lesson will be uploaded on the VIRTUALE platform, as an aid to the students.

Office hours

See the website of Stefania Falfari