Internal Combustion Engines

Base Knowledge

Course units in Thermodynamics, Fluid Mechanics and Heat Transfer.

Teaching Methodologies

a) Theoretical: Exposition by the teacher.

b) Theoretical – practical: In addition to the study of selected engine prototypes, they include the resolution of calculation exercises;

c) Practical work in the laboratory: Laboratory classes for experiments with engines and test hardware. These include: Compression and tightness tests. Electric / electronic control of injection and ignition systems. Starter. Oscillograms. Power balance. Exhaust gases. Determination of characteristic curves. Thermal Balance.

Learning Results

Objectives: 1-Understand the construction details and the operating principles; ability to install, operate and know how to intervene, through simple projects in the management of power, consumption and environmental impacts; know how to respond to maintenance and repair needs; select the different components and systems; know how to follow technological developments. 2-Know how to develop engine performance control experiments and interpret data collected in tests. Competences: 1-Know, understand the operation, know how to operate and know how to select different types of engines. 2-Know how to perform measurements, instrument and control the performance of engines. 3-Have the ability to install, operate and maintain engines. 4-Know how to apply fault detection techniques to engines. 5-Carrying out laboratory work: a) Compression and tightness tests. b) Tests and troubleshooting of engines. c) Motor test on dynamometric brake.

Program

PART I – ENGINE THEORY
1. Function, operation and design of thermal motors. Evolution, classification and nomenclature of engines.
2. Theoretical cycles of internal combustion engines: Fundamental principles of closed and open thermodynamic systems. Energy equation for open systems. Work done by a system. Flows of heat and energy associated with the operation of an internal combustion engine. Theoretical cycles and real cycles. Thermal performance. Mean pressure. Generalized cycle. Theoretical Otto cycle. Theoretical diesel cycle. Mixed Sabatté cycle. Analysis and comparison of theoretical cycles. Air cycle.
3.Fuels, combustion, operating fluid and emissions: Types of fuels. Chemistry of a fuel. Combustion chemistry with its release of heat. Formation of the mixture in positive ignition engines (SI) and compression ignition engines (CI). Characteristic numbers of a fuel and its additives. Octane number. Cetane number. Specific mass and calorific value. Other characteristics of a fuel. Environmental specifications for gasoline. Environmental specifications and diesel additives. Fuel performance in the vehicle. Operating fluid. Composition and transformations. Atmospheric air. Stoichiometric combustion. Stoichiometric ratio and real air – fuel ratio. Combustion with excess air. Dissociation with formation of carbon monoxide. Elementary combustion reactions and their combustion products.
4. Engine friction, lubrication and cooling: Main mechanisms for generating heat flow. Methods of calculating heat transfer and thermal stresses. Friction components. Limit and hydrodynamic lubrication. Lubricating oils. Lubricating oil properties and classifications. Viscosity and viscosity index. Oil additives. Selection and use of lubricants. Layout of lubrication systems and their components. Engine cooling. Layout of cooling systems and their components.
5. Real cycles and pressure diagrams: Characterization of the processes that integrate the real cycle. Indicated cycle and indicated average pressure. Troubleshooting based on examination of the diagram shown. Diagram of pressures inside the cylinder as a function of the angular displacement of the crankshaft for 2 and 4 stroke engines. Predicted indicated cycle.
6. Geometric and performance characteristics of an engine / Engine energy balance: Design of alternative four-stroke and two-stroke internal combustion engines. Wankel engine. Kinematics of internal combustion engines. Connecting rod – crank mechanism. Alternative forces of inertia and their influence on torque. Diagram of the resulting forces. Energy balance and yields involving thermodynamic and mechanical factors. Indicated parameters, mechanical losses due to friction, power absorbed by auxiliary systems. Effective or brake parameters. Characteristic curves. Consumption in SI and CI engines. Analysis of energy losses. Principle of sealing pistons with segments. Influence of load changes, volumetric efficiency and supercharging on engine performance maps. Similarity rules and indices with a view to defining an engine layout and estimating its mechanical power limits. Distribution diagram. Changes to ports and valves. Types of engine distribution. Phase inverters. Stability in engine operation. Exhaust gas recirculation (EGR). Motor energy balance.
7. 4-stroke engines: positive-ignition engines and compression-ignition engines. Function, classification and operation. Types of combustion chambers. Preparation of the mixture in SI and CI engines – principles and control. Fuel supply systems. Carburetors. Injection systems. Direct injection stratified load engines. HCCI ignition systems on SI engines. Combined electronic system – injection / ignition. Engines with hybrid combustion processes. CI engine injection systems. Direct injection (DI) systems. Indirect injection systems (IDI). Fuel injection equipment: injectors, injection pumps, common rail systems.
8. 2-stroke engines: Types of washing. Geometries and components. Crankcase compression.
9. Supercharging and turbocharging. Justification. Types of compressors. The turbocharger. Control of the supply pressure.

10. Ecological parameters and anti-pollution systems: Combustion in internal combustion engines. Formation of air pollutants and their treatment and control. Polluting emissions. NOx formation. Sources of unburned hydrocarbons. Soot formation. Alternative fuels. Pollutant reduction methods and technologies. Engine noise. Fuel cells.

11. Engine dynamometer test: Experimental means used to determine characteristic curves. Brake power and measurement: Friction brakes (Prony), hydraulic brakes (Froude), electric and aerodynamic.

PART II – DESCRIPTION OF MOTORS / THEORETICAL EXERCISES – PRACTICAL
12. Practical description of engines. Engine structure and construction. Connecting rod system and its most common defects: Block. Head. Cylinders, pistons and their dimensions. Number and arrangement of cylinders.

13. Operating fluid distribution system: Scheme and operation of different operating fluid distribution mechanisms. Distribution system: valve types, valve actuation systems, dynamic distribution behavior. Influence of the valve head and eccentric profile on flow characteristics. Distribution diagram: effects of the distribution diagram and variable distribution diagram. Collectors project. Two-stroke engines. Washing systems. Characteristics of flow flow ports. EGR. Main faults inherent to the distribution system.
14. SI engine power and ignition systems: Petrol engine power systems. Injection before the intake valve and direct injection. Theories and principles of operation of an injection pump and gasoline injectors. Injector holes. Control systems. Identification and function of the components that integrate a gasoline supply system. Diagnosis and adjustment of gasoline engine power systems using computational tools and technologies. Conventional ignition. Electronic and transistorized ignition. Automatic advances. Control systems. Spark plugs.
15. CI engine supply system: Diesel engine supply systems. Theories and principles of operation of an injection pump and diesel injectors. Injector holes. Control systems. Glowing candles. Identification and function of the components that integrate a diesel supply system. Diagnosis and adjustment of diesel engine power systems using computational tools and technologies.
16. Complementary systems in internal combustion engines; Engine cooling systems. Cooling system malfunctions. Lubrication systems. Malfunctions of the lubrication system. Starting and loading systems. Starting and charging methods of an engine. Starter. Alternator. Malfunctions in the starting and charging system of an engine.
17. Resolution of theoretical and practical exercises: Sequence of engine times for the different cylinders. Calculation of the main points of the cycles. Calculation of the ideal thermal yield. Calculation of average cycle pressure. Calculation of cylinder capacity, combustion chamber, total volume and compression ratio. Calculation of fluid force, inertia force and resultant force in the piston / connecting rod / crank system. Calculation of normal force, tangential force and motor torque. Calculation of distance traveled by the piston, lateral surface of the cylinder, connecting rod obliquity, instantaneous piston speed, average piston speed, piston acceleration and alternating force of inertia as a function of the angular displacement of the crankshaft. Selection of engines. Calculation of effective power and motor torque as a function of average effective pressure. Repair of an engine. Selection of new pistons and head gasket. Influence on average effective pressure and effective power. Calculations of yields (including volumetric), air mass flow rate, fuel mass flow rate (consumption) and air / fuel ratio. Thermal balance.

PART III – ENGINEERING LABORATORIES
18.Laboratory classes: 18.1. Engine performance analysis methods. 18.2. Experimental engine test methods: 18.2.1. Analysis of engine compression and tightness. 18.2.2. Analysis of electrical and electronic ignition systems, charging systems, power balance and exhaust gases. 18.3- Determination of engine characteristic curves.

19. Engine performance simulation software.

Curricular Unit Teachers

António Santos Simões

Internship(s)

NAO

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