Internal Combustion Engines. Basic Operation Principles

Chapter 1. Introduction 9
1.1. Engine type, definition and role, main parts of an engine, working principle 9
1.2. Engines classification and their operating cycles 14
1.3. Mixture preparation and quality of the air-fuel mixture 20
1.4. Engine design and technical parameters, operating rate 23

Chapter 2. Gases Exchange Processes 36
2.1. Gases exchange for the four-stroke engines, normal induction - intake and exhaust systems, volumetric efficiency coefficient 36
2.2. Investigation of the intake and exhaust processes 42
2.3. Valves timing setting 52
2.4. Influences of different parameters on the induction process 54
2.5. Mechanical supercharging, turbo-charging, cylinder scavenging 61
2.6. Gases exchange for the two strokes engines 66

Chapter 3. Compression and Expansion, Heat Transfer and Gases Motions 71
3.1. Necessity of the compression process, theoretical models of the engine cycles 71
3.2. Investigation of the gas-cylinder heat exchange process 82
3.3. Gas motions inside the cylinder, swirl ratio 88

Chapter 4. Physico-Chemical Bases of the Combustion Process 100
4.1. Oil fuels, physical and chemical properties 100
4.2. Thermodynamics, chemistry and physics of combustion, chemical composition of the fresh mixture and exhaust gases 112

Chapter 5. Combustion in Spark Ignition Engines 121
5.1. Essential characteristic phenomena, types of combustion 121
5.2. Combustion investigation, combustion stages and normal combustion theory, cycle by cycle variability 122
5.3. Abnormal combustion, description of phenomena, knock and surface ignition 140
5.4. Influences of different operating parameters on combustion: mixture quality, turbulence intensity, spark timing, load and speed 146
5.5. Influences of different design parameters on combustion: compression ratio, combustion chamber architecture, fuel quality 153

Chapter 6. Combustion in Compression Ignition Engines 160
6.1. Essential characteristic phenomena, processes associated to direct and indirect injection 160
6.2. Atomization of the liquid fuel jet, ignition delay, conditions for appropriate delay 163
6.3. Experimental investigation, normal combustion theory, combustion stages 170
6.4. Influences of different operating parameters on combustion: mixture quality, injection timing, load and speed 179
6.5. Influence of design parameters on diesel combustion: compression ratio, combustion chamber architecture, fuel quality 183

References 191

Since its discovery, the internal combustion engine has represented one of the most interesting and intensively studied machines. Its continuous and sustained development performed during more than 150 years made from this machine an extremely complex equipment, where knowledge of mechanics, thermodynamics, aerodynamics, chemistry, electronics and others technical sciences are involved. The increasing concern about the diminishing of petroleum base fuels availability, associated with the concern over the climate changes due to the greenhouse effect continuous increase, imposes a better view and understanding of the possibilities to control the combustion process for improving engines efficiency and reducing their pollutant emissions.

In this sense, this work represents first of all a support for the students from the University Politehnica of Bucharest, Faculty of Engineering in Foreign Languages, Mechanical Division, English Direction, interested in the Heat Engines course. This work based on particular references offers to these students the basics and the specific terminology necessary for the comprehension of the processes governing the internal combustion engines operation. It can be also used by other Master or Ph.D. students coming from other faculties, like Faculty of Mechanical Engineering or Faculty of Transportation, who are interested in understanding the internal combustion engines fundamentals. Moreover, this work offers some detailed information regarding the simulation activities which represent in the lasts
decades one of the most important section in the field of research activities dedicated to internal combustion engines development.

I would like to thank first of all Professor Nicolae Apostolescu for his help, because he spent part of his time reading the manuscript and giving me clear and valuable suggestions. I would also like to thank Mr. Ioan Ganea, AGIR publishing house director, who really helped me by being confident in the importance of this work and ensuring the best conditions for its occurrence.