Teacher

prof. Pietro GIANNATTASIO

Credits

6 CFU

Language

Italian

Objectives

This course is aimed at extending the theoretical and technical knowledge on reciprocating internal combustion engines, by developing the basic concepts introduced in the course of Macchine I. In particular, the most advanced technical solutions are examined with reference to modern design criteria which allow engines of high performance, reduced fuel consumption and low pollutant emissions to be obtained.

Acquired skills

- Detailed knowledge of the thermodynamics and gas dynamics of spark- and compression-ignition, four- and two-stroke engines.
- Characterization of the engine behaviour in its whole operating range.
- Knowledge of the influence of the various engine parameters on performance, fuel consumption and pollutant emissions.
- Up-to-date information on the most advanced technical solutions (variable valve timing, common rail, stratified-charge engines, etc.).
- Criteria and techniques for engine-load  and engine-supercharger matching.
- Preliminary design of intake and exhaust pipe systems, supercharging systems and combustion chambers.

Lectures and exercises (topics and specific content)

Internal combustion engine fundamentals: engine classifications and applications; geometrical properties and operating parameters; ideal gas, fuel-air and real cycles; indicated and brake parameters; characteristic losses and efficiencies; engine energy balance; engine operating characteristics; engine-load matching (14 hours).
Gas exchange processes in four-stroke engines: charging process and volumetric efficiency: quasi-static and dynamic effects, influence of engine speed, valve timing and air temperature; flow through valves; valve timing diagram; fixed and variable valve timing systems (6 hours).
Scavenging in two-stroke engines: the scavenging process; porting arrangements and scavenging flows; scavenging parameters and models; choice of the delivery ratio; influence of engine speed and exhaust-pipe back pressure on the scavenging process; scavenging blowers and use of the crankcase as the air pump (6 hours).
Unsteady flow in the pipe systems: inertia and wave effects in the pipe systems of four-stroke engines; pressure wave propagation in the exhaust pipe of two-stroke spark-ignition engines and design of the expansion chamber; variable geometry pipe systems (4 hours).
Supercharging of internal combustion engines: purposes of supercharging; classification of supercharging systems; mechanical supercharging; constant pressure and pulse turbocharging; charge intercooling; engine-supercharger matching; transient response of a supercharged engine; waste gate; variable geometry turbines; effects of supercharging on thermal, mechanical stresses and pollutant emissions (10 hours).
Fuel metering in spark-ignition engines: influence of the air/fuel ratio on performance, efficiencies and pollutant emissions; spark-ignition engine mixture requirements; fuel injection and main injection systems; the lambda sensor (3 hours).
Fuel injection in compression-ignition engines: Diesel engine requirements; duties of the injection system; main injection equipments; common rail; injector types; fuel spray behavior (3 hours).
Review of combustion fundamentals: premixed and diffusion burning; combustion rate; autoignition; flame propagation; laminar and turbulent combustion; turbulence generation within the cylinder, swirl, tumble and squish motions (2 hours).
Combustion in spark-ignition engines: combustion process characterization; flame development and speed; pressure development in the cylinder; cyclic variation; effects of the main engine parameters; stratified charge combustion; heat-release analysis and prediction; abnormal combustion, surface ignition and knock; design of the combustion chamber (4 hours).
Combustion in compression-ignition engines: combustion process characterization; ignition delay; premixed and diffusion burning; combustion chambers for large, medium and small size engines; indirect-injection (prechamber) diesel engines; heat-release analysis and prediction (4 hours).
Pollutant formation and control: formation mechanisms of CO, NOx, UHC and soot; influence of the main engine parameters on emissions; driving cycles; pollutant control; exhaust gas treatment, thermal reactors, catalytic converters, particulate traps (4 hours).
Exercises (10 hours).

References

- Teacher's notes 
- G. Ferrari - Motori a Combustione Interna - Ed. Il Capitello, Torino
- J. B. Heywood - Internal Combustion Engine Fundamentals - McGraw Hill, New York

Type of exam

Oral