《内燃机学》课程教学资源（书籍文献）Internal Combustion Engines，Edit by Kazimierz Lejda Pawel Wos，Second Edition.pdf_大学文库

PrefaceInternalcombustionengines(ICE)arethemainsourcesofpoweringforalmostallroad vehicles, yet many other machines too.Being under strength development for anumber of years, they have already reached a relatively high level of technicalexcellenceand nowtheyalsoproduce acceptableoutputparameters.Still, they are notdevoid of drawbacks.Harmful exhaust emissions can be pointed as the mostimportanthere.Thisproblemisthemainfocusof interestforautomotiveresearchersandengineers.Continuous decreaseofexhaust emission limits additionallyintensifiestheir efforts to produce more green engines and vehicles. On the other hand, rapiddevelopment of road transportation and the growth of end-users'demands towardmore and more comfortable, durable, reliable and fuel-saving vehicles unceasinglycalls for improvements in engine design and technology.Despite many attempts, replacing the internal combustion engine with other, butequally effective power source still fails.Therefore,extensive works on theimprovement of internal combustion engines should be carried out and the resultsneedtobewidelypublishedAs the answer toaboveexpectations,this book on internal combustion engines bringsout few chapters on the research activities through the wide range of current engineissues. The first section groups combustion-related papers including all research areasfromfuel delivery to exhaust emission phenomena.The second one deals with variousproblems on engine design,modeling,manufacturing,control and testing.Suchstructure should improve legibility of the book and helps to integrate all singularchapters as a logical whole.Wewish tothank InTech Publisher and areespeciallypleased to express same thanksto Ms.Viktorija Zgela for giving us an invitation and opportunity to be editors of thebook on internal combustion engines.Distinctive thanks are alsodue to Ms.RomanaVukelic and Ms.Marina Jozipovic, and Publishing Process Staff for theirhelp incoordinating thereviews,editingand printing ofthebook.Kazimierz Lejda and Pawel WosRzeszow University of Technology,Poland

Preface Internal combustion engines (ICE) are the main sources of powering for almost all road vehicles, yet many other machines too. Being under strength development for a number of years, they have already reached a relatively high level of technical excellence and now they also produce acceptable output parameters. Still, they are not devoid of drawbacks. Harmful exhaust emissions can be pointed as the most important here. This problem is the main focus of interest for automotive researchers and engineers. Continuous decrease of exhaust emission limits additionally intensifies their efforts to produce more green engines and vehicles. On the other hand, rapid development of road transportation and the growth of end-users’ demands toward more and more comfortable, durable, reliable and fuel-saving vehicles unceasingly calls for improvements in engine design and technology. Despite many attempts, replacing the internal combustion engine with other, but equally effective power source still fails. Therefore, extensive works on the improvement of internal combustion engines should be carried out and the results need to be widely published. As the answer to above expectations, this book on internal combustion engines brings out few chapters on the research activities through the wide range of current engine issues. The first section groups combustion-related papers including all research areas from fuel delivery to exhaust emission phenomena. The second one deals with various problems on engine design, modeling, manufacturing, control and testing. Such structure should improve legibility of the book and helps to integrate all singular chapters as a logical whole. We wish to thank InTech Publisher and are especially pleased to express same thanks to Ms. Viktorija Žgela for giving us an invitation and opportunity to be editors of the book on internal combustion engines. Distinctive thanks are also due to Ms. Romana Vukelić and Ms. Marina Jozipović, and Publishing Process Staff for their help in coordinating the reviews, editing and printing of the book. Kazimierz Lejda and Paweł Woś Rzeszów University of Technology, Poland

Chapter1Factors Determing Ignition and EfficientCombustioninModernEnginesOperatingonGaseousFuelsWladyslawMitianiecAdditional information is available at the end of the chapterhttp://dx.doi.org/10.5772/483061.IntroductionRecently in automotive industry the applying of gaseous fuels and particularlycompressed naturalgas both in SI and CI engines is moreoften met.Howeverapplicationof CNG in the spark ignition internal combustion engines is more real than never before.There are known many designs of the diesel engines fuelled by the natural gas, where thegas is injected into inlet pipes. Because of the bigger octane number of the natural gas thecompression ratio of SI engines can be increased, which takes effect on the increase of thetotal combustion efficiency. In diesel engines the compression ratio has to be decreased asa result of homogeneity of the mixture flown into the cylinder. Such mixture cannotinitiate the self-ignition in traditional diesel engines because of higher value of CNGoctane number.Direct injection of the compressed natural gas requires also high energysupplied by the ignition systems.A natural tendency in the development of the pistonengines is increasing of the air pressure in the inlet systems by applying of high level ofthe turbo-charging or mechanical charging. Naturally aspirated SI engine filled by thenatural gas has lower value of thermodynamic efficiency than diesel engine. Theexperiments conducted on SI engine fuelled by CNG with lean homogeneous mixturesshow that the better solution is the concept of the stratified charge with CNG injectionduring the compression stroke. The presented information in the chapter is based on theown research and scientific work partly described in scientific papers.There is a widerdiscussion of main factors influencing on ignition of natural gas in combustion engines,because of its high temperature of ignition, particularly at high pressure. The chapterpresents both theoretical considerations of CNG ignition and experimental work carriedoutatdifferentair-fuel ratios and initial pressure

Chapter 1 Factors Determing Ignition and Efficient Combustion in Modern Engines Operating on Gaseous Fuels Wladyslaw Mitianiec Additional information is available at the end of the chapter http://dx.doi.org/10.5772/48306 1. Introduction Recently in automotive industry the applying of gaseous fuels and particularly compressed natural gas both in SI and CI engines is more often met. However application of CNG in the spark ignition internal combustion engines is more real than never before. There are known many designs of the diesel engines fuelled by the natural gas, where the gas is injected into inlet pipes. Because of the bigger octane number of the natural gas the compression ratio of SI engines can be increased, which takes effect on the increase of the total combustion efficiency. In diesel engines the compression ratio has to be decreased as a result of homogeneity of the mixture flown into the cylinder. Such mixture cannot initiate the self-ignition in traditional diesel engines because of higher value of CNG octane number. Direct injection of the compressed natural gas requires also high energy supplied by the ignition systems. A natural tendency in the development of the piston engines is increasing of the air pressure in the inlet systems by applying of high level of the turbo-charging or mechanical charging. Naturally aspirated SI engine filled by the natural gas has lower value of thermodynamic efficiency than diesel engine. The experiments conducted on SI engine fuelled by CNG with lean homogeneous mixtures show that the better solution is the concept of the stratified charge with CNG injection during the compression stroke. The presented information in the chapter is based on the own research and scientific work partly described in scientific papers. There is a wider discussion of main factors influencing on ignition of natural gas in combustion engines, because of its high temperature of ignition, particularly at high pressure. The chapter presents both theoretical considerations of CNG ignition and experimental work carried out at different air-fuel ratios and initial pressure

4InternalCombustionEnginesGas engines play more and more important role in automotive sector.This is caused bydecreasing of crude oil deposits and ecologic requirements given by internationalinstitutions concerning to decreasing of toxic components in exhaust gases.Internalcombustion engines should reach high power with low specific fuel consumption andindicate very low exhaust gas emission of such chemical components as hydrocarbons,nitrogen oxides, carbon monoxide and particularly for diesel engines soot and particulatematters.Chemical components which are formed during combustion process depend onchemical structure of the used fuel. Particularly for spark ignition engines a high octanenumber of fuel is needed for using higher compression ratio which increases the thermalengine efficiency and also total efficiency.2.Thermal and dynamic properties of gas fuelsThe mixture of the fuel and oxygen ignites only above the defined temperature. Thistemperature is called as the ignition temperature (self-ignition point).It is depended onmany internal and external conditions and therefore it is not constant valueBesides thatformany gases and vapours there are distinguished two points: lower and higher ignitionpoints (detonation boundary). These two points determine the boundary values where theignition of the mixture can follow.The Table 1 presents ignition temperatures of thestoichiometric mixtures of the different fuels with the air.FuelFuelIgnition temperature[°]Ignitiontemperature[°C]Gasoline350-520Browncoal200-240Benzene520-600Hard coalatomised150-220Furnace oil 340250Coking coal500SootPropane500-600300-425650CharcoalNatural gas430 450Butane (n)City gas230-245Coke550-600FurnaceoilELTable 1. Ignition temperatures of the fuels in the air (mean values)The combustion mixture, which contains the fuel gas and the air, can ignite in strictlydefined limits of contents of the fuel in the air.The natural gas consists many hydrocarbons,however it includes mostly above 75%of methane.For the experimental test one used twotypes of the natural gas:1.the certified model gas G20 which contains 100% of methane compressed in the bottleswith pressure 200bar at lower heat value 47.2-49.2MJ/m32.the certified model gas G25that contain 86% of methane and 14% of N2 at lower heatvalue38.2-40.6MJ/m3.The natural gas delivered for the industry and households contains the following chemicalcompoundswithadequatemeanmassfraction ratios:methane-0.85,ethane-0.07,propane-0.04,n-butane-0.025,isobutene-0.005,n-pentane-0.005,isopentane-0.005

4 Internal Combustion Engines Gas engines play more and more important role in automotive sector. This is caused by decreasing of crude oil deposits and ecologic requirements given by international institutions concerning to decreasing of toxic components in exhaust gases. Internal combustion engines should reach high power with low specific fuel consumption and indicate very low exhaust gas emission of such chemical components as hydrocarbons, nitrogen oxides, carbon monoxide and particularly for diesel engines soot and particulate matters. Chemical components which are formed during combustion process depend on chemical structure of the used fuel. Particularly for spark ignition engines a high octane number of fuel is needed for using higher compression ratio which increases the thermal engine efficiency and also total efficiency. 2. Thermal and dynamic properties of gas fuels The mixture of the fuel and oxygen ignites only above the defined temperature. This temperature is called as the ignition temperature (self-ignition point). It is depended on many internal and external conditions and therefore it is not constant value. Besides that for many gases and vapours there are distinguished two points: lower and higher ignition points (detonation boundary). These two points determine the boundary values where the ignition of the mixture can follow. The Table 1 presents ignition temperatures of the stoichiometric mixtures of the different fuels with the air. Fuel Ignition temperature [C] Fuel Ignition temperature [C] Gasoline 350 - 520 Brown coal 200 - 240 Benzene 520 - 600 Hard coal atomised 150 - 220 Furnace oil  340 Coking coal  250 Propane  500 Soot 500 - 600 Charcoal 300 - 425 Natural gas  650 Butane (n) 430 City gas  450 Furnace oil EL 230 - 245 Coke 550 - 600 Table 1. Ignition temperatures of the fuels in the air (mean values) The combustion mixture, which contains the fuel gas and the air, can ignite in strictly defined limits of contents of the fuel in the air. The natural gas consists many hydrocarbons, however it includes mostly above 75% of methane. For the experimental test one used two types of the natural gas: 1. the certified model gas G20 which contains 100% of methane compressed in the bottles with pressure 200 bar at lower heat value 47.2 – 49.2 MJ/m3 2. the certified model gas G25 that contain 86% of methane and 14% of N2 at lower heat value 38.2 – 40.6 MJ/m3. The natural gas delivered for the industry and households contains the following chemical compounds with adequate mean mass fraction ratios: methane - 0.85, ethane - 0.07, propane - 0.04, n-butane - 0.025, isobutene - 0.005, n-pentane - 0.005, isopentane - 0.005

FactorsDetermingIgnitionand Efficient Combustion in Modern Engines Operatingon GaseousFuels5Becausethenatural gas containsmanyhydrocarbons with changeable concentration of theindividual species the heat value of the fuel is not constant. It influences also on the ignitionprocess depending on lower ignition temperature of the fuel and energy induced bysecondary circuit of the ignition coil. For comparison in Table 2 the ignition limits andtemperatures for some technical gases and vapours in the air at pressure 1.013 bars arepresented.Thedata showamuchbiggerignitiontemperatureforthenatural gas(640-670oC)thanforgasolinevapours(220°C).Forthisreasonthegasoline-airmixturerequiresmuch lower energy for ignition than CNG-air mixture. However, higher pressure duringcompression process in the engine with higher compression ratio in the charged SI enginecauses also higher temperature that can induce the sparking of the mixture by using also ahigh-energy ignition system.Becauseof lower contents ofthe carbon in thefuel, the enginesfuelledbythenaturalgasfromecologicalpointofviewemitmuchloweramountofCOanddecreasestheheateffectonourearth.Till now there are conducted only some laboratory experiments with the high-energyignition system for spark ignition engines with direct CNG injection, There are known theignition systems for low compressed diesel engines fuelled by CNG by the injection to theinlet pipes.Type of gasChemicalNormalizedIgnition limitsinIgnitionformuladensitythe airtemperature(air = 1)(%volumetric)in the air [°C]220Gasoline~CsHiz0.610.6-82.05Butane (n)CH1o1.88.54600.675-14640NaturalgasH0.67Natural gas L6-14670CH61,047510Ethane312.5Ethylene1,00425CH42.7 - 341.792-9470Gaspropane-butane50%CH4595Methane0.555-15PropaneCsHs1.564702,19.5City gas I0.475-385500.516-32550City gas IIco0.9712.5-74605CarbonmonoxideH20.074-76585HydrogenDiesel oil0.672300.66.5Table 2. Ignition limits and ignition temperatures of the most important technical gases and vapours inthe air at pressure 1,013 barCompositionandpropertiesofnaturalgasusedinexperimentaltestsarepresentedinTable3

Factors Determing Ignition and Efficient Combustion in Modern Engines Operating on Gaseous Fuels 5 Because the natural gas contains many hydrocarbons with changeable concentration of the individual species the heat value of the fuel is not constant. It influences also on the ignition process depending on lower ignition temperature of the fuel and energy induced by secondary circuit of the ignition coil. For comparison in Table 2 the ignition limits and temperatures for some technical gases and vapours in the air at pressure 1.013 bars are presented. The data show a much bigger ignition temperature for the natural gas (640 – 670 °C) than for gasoline vapours (220°C). For this reason the gasoline-air mixture requires much lower energy for ignition than CNG-air mixture. However, higher pressure during compression process in the engine with higher compression ratio in the charged SI engine causes also higher temperature that can induce the sparking of the mixture by using also a high-energy ignition system. Because of lower contents of the carbon in the fuel, the engines fuelled by the natural gas from ecological point of view emit much lower amount of CO2 and decreases the heat effect on our earth. Till now there are conducted only some laboratory experiments with the high-energy ignition system for spark ignition engines with direct CNG injection. There are known the ignition systems for low compressed diesel engines fuelled by CNG by the injection to the inlet pipes. Type of gas Chemical formula Normalized density (air = 1) Ignition limits in the air (% volumetric) Ignition temperature in the air [°C] Gasoline ~C8H17 0.61 0.6 - 8 220 Butane (n) C4H10 2.05 1.8 – 8.5 460 Natural gas H 0.67 5 - 14 640 Natural gas L 0.67 6 - 14 670 Ethane C2H6 1,047 3 – 12.5 510 Ethylene C2H4 1,00 2.7 - 34 425 Gas propane-butane 50% 1.79 2 - 9 470 Methane CH4 0.55 5 - 15 595 Propane C3H8 1.56 2,1 – 9.5 470 City gas I 0.47 5 - 38 550 City gas II 0.51 6 - 32 550 Carbon monoxide CO 0.97 12.5 - 74 605 Hydrogen H2 0.07 4 - 76 585 Diesel oil 0.67 0.6 – 6.5 230 Table 2. Ignition limits and ignition temperatures of the most important technical gases and vapours in the air at pressure 1,013 bar Composition and properties of natural gas used in experimental tests are presented in Table 3

6Internal Combustion EnginesNomenclatureNoUnitValueParameterorsymbol39,231[M]/Nm’]Q.1Combustionheat[M]/kg]51,892[MJ/Nm}]35,3722WaCalorific value46,788[M]/kg]3PsDensity in normal conditions[kg/Nm′]0,7564△0,586Relative density-5z0,9980Coefficient of compressibilityWs6[M]/Nm}]51,248Wobbenumber7L.9,401Stoichiometric constant[Nm?rue/Nm3]80,999CO2fromthecombustion[Nm/Nm}]Table 3. Properties of the natural gas used in experimental research3.Fuellingmethods andignitioningas dieselenginesSeveral fuelling methods of the natural gas are applied in modern compression ignitionengines,where the most popular are thefollowing cases:delivering the gas fuel into the inlet pipes by mixing fuel and air in the special mixersmall pressure injection of gaseous fuel into the pipe and ignition of the mixture in thecylinder by electric sparkhigh pressure direct injection of gaseous fuel particularly in high load engineThere are given thereasons of decreasing of compression ratio in twofirst methods and theaim of application ofgaseous fuels in CI engines (lowering of COz, elimination of soot andbetterformation offuelmixture).Applyingofthetwoofirstmethodsdecreasesthetotalengine efficiency in comparisonstandard diesel engine as a result of lowering ofcompression ratioandneedsdditiorhiglenergeticignition systemtosparkdisadvantages ofapplication1presentsanexampleofvariation of heat releastdu1-cylindercompressionignitionspiratedengineAndoria1HC102filledbyof diesel oil as ignition dose.Thistypeof engineisvery promisingbeoofkeepingthesamecompressionratio andcauseobtaining of higher total efficiency. NG in gaseous forms is pressured into the inlet pipe,next flows by the inlet valve into the cylinder.During compression stroke small dose ofdiesel oil is delivered by the injector into the combustion chamber as an ignition dose.Because ignition temperature of diesel oil is lower than that of natural gas the ignition startbegins from the outer sides of diesel oil streams. In a result of high temperature natural gasthe combustion process of the natural gas begins some degrees of CA later.The cylindercontains almost homogenous mixture before the combustion process and for this reasonburning of natural gas mixture proceeds longer than that of diesel oil.Figure1presentssimulation results carried out for this engine in KIVA3V program

6 Internal Combustion Engines No Parameter Nomenclature or symbol Unit Value 1 Combustion heat Qc [MJ/Nm3] [MJ/kg] 39,231 51,892 2 Calorific value Wd [MJ/Nm3] [MJ/kg] 35,372 46,788 3 Density in normal conditions  g [kg/Nm3] 0,756 4 Relative density  - 0,586 5 Coefficient of compressibility Z - 0,9980 6 Wobbe number WB [MJ/Nm3] 51,248 7 Stoichiometric constant Lo [Nm3fuel/Nm3air] 9,401 8 CO2 from the combustion - [Nm3/Nm3] 0,999 Table 3. Properties of the natural gas used in experimental research 3. Fuelling methods and ignition in gas diesel engines Several fuelling methods of the natural gas are applied in modern compression ignition engines, where the most popular are the following cases:  delivering the gas fuel into the inlet pipes by mixing fuel and air in the special mixer  small pressure injection of gaseous fuel into the pipe and ignition of the mixture in the cylinder by electric spark  high pressure direct injection of gaseous fuel particularly in high load engine There are given the reasons of decreasing of compression ratio in two first methods and the aim of application of gaseous fuels in CI engines (lowering of CO2, elimination of soot and better formation of fuel mixture). Applying of the two first methods decreases the total engine efficiency in comparison to standard diesel engine as a result of lowering of compression ratio and needs an additional high energetic ignition system to spark disadvantages of application of gas fuel in CI engines. Figure 1 presents an example of variation of heat release of dual fuel naturally aspirated 1-cylinder compression ignition engine Andoria 1HC102 filled by CNG and small amount of diesel oil as ignition dose. This type of engine is very promising because of keeping the same compression ratio and obtaining of higher total efficiency. NG in gaseous forms is pressured into the inlet pipe, next flows by the inlet valve into the cylinder. During compression stroke small dose of diesel oil is delivered by the injector into the combustion chamber as an ignition dose. Because ignition temperature of diesel oil is lower than that of natural gas the ignition start begins from the outer sides of diesel oil streams. In a result of high temperature natural gas the combustion process of the natural gas begins some degrees of CA later. The cylinder contains almost homogenous mixture before the combustion process and for this reason burning of natural gas mixture proceeds longer than that of diesel oil. Figure 1 presents simulation results carried out for this engine in KIVA3V program