87256 - Machines T

Learning outcomes

The students will achieve the knowledge on the basic thermodynamics and the fluid dynamics of fluid machinery with particular reference on:

- Fluid machinery layout, working principles, and classification.

- First Law of Thermodynamics for closed and open systems.

- The energy exchange between the fluid and the fixed/moving blade in roraty machinery.

- Centrifugal pump operational principles

- Volumetric pumps operational principles

- Volumetric reciprocating compressor operational principles

- Volumetric positive vane displacement compressor operational principles, with brief focus on vacuum pumps

- Internal combustion engine thermodynamics and combustion principles

- Heat Exchangers fundamentals applied to Fluid Machinery

- Centrifugal pumps

Course contents

A) THE ENERGY SCENARIO WITH EMPASIS ON PROPULSION SYSTEM FOR TRANSPORTATION (0.5 ECTS)

B) HEAT EXCHANGERS (1 ECTS)

Global heat transfer coefficient. Wall temperature. Fair and countercurrent heat exchangers. Temperature, thermal power diagram and definition of heat exchanger efficiency. Heat capacity per hour. Graphical evaluation of heat exchanger efficiency in the T-Q diagram. Logarithmic average DT and the e-NTU method.

C) RECIPROCATING DISPLACEMENT AND ROTARY COMPRESSORS (1 ECTS)

1. Fundamentals.

2. Reciprocating compressors: construction characteristics; compressor cycle; valves; capacity control. Indicating diagram.

3. Positive displacement compressors. Working principle; characteristics, advantages, disadvantages and application range of the different types.

4. Brief introduction to vacuum applications

D) RECIPROCATING DISPLACEMENT AND ROTARY HYDRAULIC PUMPS (1 ECTS)

1. Fundamentals.

2. Reciprocating pumps: construction characteristics; compressor cycle; valves; capacity control. Indicating diagram.

3. Positive displacement pumps. Working principle; characteristics.

4. Positive displacement piston pumps. Working principle; characteristics

5. Effect of pulsating flow rate on pump noise, cavitation and reliability.

E) CENTRIFUGAL PUMPS (1 ECTS)

Architecture and operating principle. Balance of the axial forces. Velocity triangles, blades channel. Analytic evaluation of the ideal head. Losses. Real head and no flow head. Operating point determination and off-design behavior. Euler approach limitations: flow deviation problem. Series and parallel connected pumps. Operating criticisms: suction and cavitation. Suction: problem definition and solutions. Cavitation: phenomenon explanation, NPSH parameter definition, cavitation conditions, NPSH trend as function of the flow rate, determination procedure

F) RECIPROCATING INTERNAL COMBUSTION ENGINES (1,5 ECTS)

1. Engine layouts, application overview, efficiency.

2. Engine classification criteria.

3. Spark ignited and compression ignition combustion system features. Limit to the delivered power in SI engines.

4. The indicating in-cylinder theoretical and actual traces.

5. The thermodynamic cycles and emphasis on volumetric compression ratio. The thermodynamic efficiency of Sabathè cycle.

6. Analytical derivation of the work per cycle, power and torque with emphasis on air trapped mass as limiting factor. The volumetric efficiency.

7. The indicated and brake mean effective pressure. Downsizing concept

8. Power, torque and brake specific fuel consumption diagrams

9. Load variation strategies for SI and CI engines

10. The application of Energy Balance to the n-cylinder pressure trace to derive the heat release rate

11. Clean and carbon neutral fuel based future ICE and comparison with BEV a FCEV solutions.

MODULE 2

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THERMODYNAMICS OF FLUID MACHINERY (3.0 ECTS)

1. Classification of Fluid Machinery. Types of thermodynamic cycles.

2. The first law of thermodynamics for closed and open systems. The Second law of thermodynamics.

3. Work transfer between fluids and fixed/moving blades in rotary machinery

4. Work transfer in compression expansion processes. Isentropic and polytropic compression and expansion efficiencies.

 

 

 

Readings/Bibliography

1. Lecture notes

2. Lectures notes available on Unibo web platform MOODLE, https://iol.unibo.it/

3. Book: " Sistemi Energetici e Macchine a Fluido" G: Negri di Montenegro, M. Bianchi A. Peretto-Pitagora Editore.

Teaching methods

Classrooom Lectures. Students are encouraged to attend Macchine T classes in order to improve their final learning outcomes. The course attendance is not mandatory and it does not have influence on the final examination score

Assessment methods

The assessment methods is intented to check the students outcomes with emphasis on the the full achievemnts of:

1. Thermo-dynamics principles applied to energy transfer or conversion in the fluid machinery presented

2. Knowledge of fluid machinery layouts, working principle and applications areas

3. Accuracy and robustness in the analytical derivation of equations and relations with focus on the clear and clean statement of goals, hypothesis and results achieved

The assessment of the learing outcomes will be performed through a written examination (time available is 70 minutes) including three open-end questions plus two multi-choice questions.

The mimimum score is 18/30, the maximum is 30/30 with honours.

The minimum score is not achieved if large deficineces in learning outcomes are exhibited: i.e., missing main hypothesis, miss any knowledge of machinery working principles and/or working cycles, etc.

Examinations schedule is available in advance on the University of Bologna web site AlmaEsami. Students willing to take the exam must join to the exam student list on the web site AlmaEsami.

Students are required to show their own ID before taking the exam

In case of health restrictions and depending on the University of Bologna acts, the written examination may be performed 'on-line' according to the University of Bologna guidelines and according to the guidelines made available on "Insegnamenti On Line" course web page.

Teaching tools

Course is given by teaching classes and students are encouraged to attend in order to improve the learning process and learning outcomes. Attending is not enforced and does not influence the final examination score.

Office hours

See the website of Gian Marco Bianchi

See the website of Stefania Falfari