28658 - Energy Machines and Systems T-1

Learning outcomes

Providing students with knowledge regarding constructive, functional and management aspects of fluid machines and  of energy conversion systems, with a focus on generating stationary systems of electricity and heat used in industrial processes and in the tertiary and residential sectors.

Course contents

Requirements/Prior knowledge

A prior knowledge and understanding of physics, thermodynamics and chemistry is required to attend with profit this course.

In addition, students should know how to use mathematical tools useful for analyzing and modeling fluid machines and energy systems.

Fluent spoken and written Italian is a necessary pre-requisite: all lectures and tutorials, and all study material will be in Italian.

 

Course Contents

Primary energy sources

Potentiality, conversion systems and applications of solar, geothermic, hydroelectric, wind, wave tidal and nuclear energy.

Thermodynamic basics

Ideal gas compression and expansion: isentropic and polytropic work and efficiency, total enthalpy and temperature, speed of sound, polytropic transformations and thermodynamics diagrams.

Heat exchanger

Counter-flow, parallel-flow and cross-flow heat exchangers. main design aspects.

Averaged mean logarithmic and effectiveness-NTU methods.

Boiler and steam generator

Combustion: stoichiometric oxidation reactions, heating values, energy density, CO2 emission, adiabatic temperature.

Typologies and applications, steam generator efficiency and water circulations.

Gas Turbine

Thermodynamic analysis and applications of Brayton and Advance cycles (recuperated, intercooled, reheated, etc.)

Component description: compressors, combustion chamber, expander, etc.

Environmental impact

Steam power plant

Thermodynamic analysis of steam cycles (Rankine, Hirn, re-heated and regenerative ones).

Component description: steam generator, condenser, steam turbine, cooling systems, etc.

Environmental impact

Combined cycle power plant

Thermodynamic analysis of combined cycles with one or more pressure levels

Component description: heat recovery steam generator, condenser, steam turbine, cooling systems, etc.

Environmental impact

Cogeneration: Combined heat and power

Thermodynamics of CHP plants, comparative thermodynamic performance, economic assessment

Performance criteria for CHP plants

CHP applications and examples.

 

INTERNAL COMBUSTION ENGINES
Introduction

Historical Background - Diesel vs. Otto. ICE classification. Description of the operating cycle (2 and 4 strokes). Engine main parameters. Base architecture and "glimpse" of current automotive ICE (EURO V / VI). Motivations and basic concepts. Visit to DIN engine test cell.
Thermodynamic analysis based on (T, s) diagrams
Introduction to the analysis of the thermodynamic cycle (cp, cv , k, ..., transformations, analytical reports, heat and work and their graphical representation, determination of the thermodynamic efficiency, ...). Otto cycle as an example. Otto cycle and Diesel cycle: definitions and representation (T, s). Calculation of the thermodynamic efficiency of Otto and Sabathè cycles. Critical comparison of (T, s) diagrams: initial hypothesis of equal compression ratio and heat supplied, and subsequent critical (and more realistic) analysis. Average exhaust gas temperature determination via thermodynamic considerations.
Indicated cycle analysis
Ideal indicating diagrams (Otto, Diesel and Sabathè), limit and real cycles (spark ignition and compression ignition), and indicated (p,V) log-log diagrams. Matlab-based analysis of single effects over cycle efficiency. Valve lift diagrams, crankshaft mechanism function, indicated torque, indicated mean effective pressure (IMEP), mean indicated torque, thermal and inertial stresses. Displacement and cylinder number effects.
Net power evaluation via conversion efficiency analysis

 

Net work cycle (L0), mechanical efficiency, net output torque, brake mean effective pressure (BMEP), net power, total efficiency, specific fuel consumption, analysis of the expression of net mechanical power... Combustion, A/F ratio, lambda, base combustion reaction (CH4, C43H84). Analysis and definition of the various energy conversion efficiencies, volumetric (or charge) efficiency, thermal specific energy for spark-ignition and compression-ignition engines. Determination of net mechanical power via energy conversion efficiency analysis. Consequences àAdjustment of operating fluid quantity and quality (lambda effects over net power production: thermal specific energy versus lambda). Part load operation and the search for greater efficiency.
Part load operation analysis

 

• Indicating diagram à pumping work
• Willan model à the part load curse

 

Motivations for:

 

• Downsizing (+ turbocharging for SI engines )
• Hybrid systems

 

Part load operation àindicated cycle analysis via Matlab .
ICE performance curves
Engine parameters: range typical for CI (Compression Ignition) and SI (Spark Ignition) engines. Characteristic curves: torque, power and specific fuel consumption. Examples of current automotive applications. Representation via iso-specific fuel consumption or efficiency curves (comparison SI vs. CI).
Combustion
Premixed vs. diffusive combustion.
Combustion in spark-ignition (SI) engines

 

• Nominal combustion mode. Flame front propagation. Combustion. Corresponding pressure evolution in the combustion chamber.
• Knocking phenomenon and its consequences.
• Main control parameters of combustion in SI engines :
• Spark advance (SA): experimental curves, mapping the optimal SA value, engine speed effects over combustion duration and phase;
• Quality of the mixture (lambda): catalyst efficiency, CO, HC and NOx conversion efficiency. Need for closed-loop control. Scheme of the basic A/F controller.
• Analysis of the most influential factors on knocking tendency: spark ignition advance, A/F ratio, engine load, engine speed, compression ratio, combustion chamber geometry, ambient temperature and pressure, fuel characteristics. Standardized test for determining the octane number (RON/MON) of a given fuel .

 

Combustion in compression ignition (CI) engines

 

• Nominal combustion mode.
• Combustion phases (delay , premixed combustion , diffusive combustion, completion).
• Main combustion control parameters in CI engines (notes).

 

 

Polluting emissions: regulations, formation mechanisms and control
Euro I-II- III- IV -V- VI regulation. Mechanisms of formation of HC, CO, NOx and particulate matter, in SI engines and CI engines. After-treatment systems ('active' and 'passive'). The three-way catalytic converter. Particulate filters.

Readings/Bibliography

"Sistemi Energetici e macchine a fluido" G: Negri di Montenegro, M. Bianchi A. Peretto, III Edizione – Pitagora Editore

"Gas Turbine Theory" H. Cohen, G.F.C. Rogers, H.I.H. Saravanamuttoo, Longman scientific & technical

Motori Endotermici Alternativi, Giorgio Minelli, Pitagora Editrice.

Internal Combustion Engine Fundamentals, J.B. Heywood, McGraw-Hill.

Teaching methods

The course consists of 9 credits (CFU) divided into two modules: the first one (6 CFU) taught by prof. Michele Bianchi and the second one (3 CFU) by prof. Nicolò Cavina.
Both modules provide some lessons presenting numerical examples.

Assessment methods

The examination at the end of the course aims to assess the achievement of learning objectives, verifying the knowledge that the students have acquired about design aspects, structural, functional and management of fluid machines and energy systems.
The final grade is defined by a single oral exam, testing the student's knowledge in all topics covered in the 9 CFU.

Teaching tools

Teaching materials: teaching material presented in class will be made available to the student in electronic format via internet.

This material should be printed and brought to class. To download the teaching material: http://campus.unibo.it/ Username and password are reserved for students enrolled at the University of Bologna

 

Office hours

See the website of Michele Bianchi

See the website of Nicolò Cavina