This paper deals with the use of the internal combustion piston engine, which is a drive unit for micro-cogeneration units. The introduction is a brief statement of the nature of gas mixture compositions that are useful for the purposes of combustion engines, together with the basic physical and chemical properties relevant to the burning of this gas mixture. Specifically, we will discuss low-energy gases (syngases) and mixtures of natural gas with hydrogen. The second section describes the conversion of the Lombardini LGW 702 combustion engine that is necessary for these types of combustion gases. Before the experimental measurements, a simulation in the Lotus Engine simulation program was carried out to make a preliminary assessment of the impact on the performance of an internal combustion engine. The last section of the paper presents the experimental results of partial measurements of the performance and emission parameters of an internal combustion engine powered by alternative fuels

Chríbik, Andrej

Lach, Ján

Polóni, Marián

English

CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)

Acta Polytechnica Vol. 52 No. 3/2012Eﬀect of Gas Mixture Composition on the Parameters of anInternal Combustion EngineAndrej Chr´ıbik1, Maria´n Polo´ni1, Ja´n Lach11Slovak University of Technology in Bratislava, Faculty of Mechanical Engineering, Institute of Transport Technologyand Engineering Design, Department of Automobiles, Ships and Combustion Engines,Na´mestie slobody 17, 812 31 Bratislava, Slovak RepublicCorrespondence to: andrej.chribik@stuba.skAbstractThis paper deals with the use of the internal combustion piston engine, which is a drive unit for micro-cogenerationunits. The introduction is a brief statement of the nature of gas mixture compositions that are useful for the purposes ofcombustion engines, together with the basic physical and chemical properties relevant to the burning of this gas mixture.Speciﬁcally, we will discuss low-energy gases (syngases) and mixtures of natural gas with hydrogen. The second sectiondescribes the conversion of the Lombardini LGW 702 combustion engine that is necessary for these types of combustiongases. Before the experimental measurements, a simulation in the Lotus Engine simulation program was carried out tomake a preliminary assessment of the impact on the performance of an internal combustion engine. The last section ofthe paper presents the experimental results of partial measurements of the performance and emission parameters of aninternal combustion engine powered by alternative fuels.Keywords: natural gas, hydrogen, synthesis gas, engine parameters.1 IntroductionIn the current development of combustion engines,there is a trend to put emphasis not only on perfor-mance and cost parameters, but also on environmen-tal parameters, the aim being to achieve the mostacceptable values. The spotlight is also therefore onnon-traditional power sources. One of these energycarriers is hydrogen.A mixture of natural gas and hydrogen will aboveall be used to drive vehicles in urban areas, wherethere are higher requirements on complying withemission regulations. This mixture combines the ad-vantages of the individual components of the mixture.The current natural gas (H2NG0) is made up mainlyof methane (97 % vol.), and has a caloriﬁc value of50 MJ ·kg−1 and an octane number of 130. A combi-nation of this natural gas with oxygen to power inter-nal combustion engines can achieve multiple beneﬁtsin terms of combustion and emissions:– Limited ﬂammability – as the proportion of hy-drogen in the mixture with natural gas increases,the ﬂammability range also increases. A mixturethat contains 30 % of hydrogen has the theoret-ical ﬂammability range limit λ =(2.67 to 0.52),while when natural gas is burned λ =(1.92 to0.57).– Ignition delay time – adding hydrogen to naturalgas reduces the delay time of ignition, and in thecase of a 5 % proportion of hydrogen the delaytime is reduced to about one half of the delaywhen an internal combustion engine operates onnatural gas.– Burning rate – increasing the proportion of hy-drogen in the gas mixture increases the ﬂamespeed, and hence the time of burning the mix-ture itself, resulting in faster heat release.– Emissions – there is some reduction in the con-tent of carbon (CO2, CO, CHx), since the addi-tion of hydrogen increases the H/C ratio. How-ever, the addition of hydrogen increases theamount of NOx, because there is an increase inthe combustion temperature.The second fuel types that will be used for power-ing internal combustion engines in cogeneration unitsare called synthesis gases. These gases are derivedmainly by gasiﬁcation of wastes. The fuel composi-tion depends on the gasiﬁer that is used, and on thetype of waste. Synthesis gases can be divided into twobasic groups. The ﬁrst group is synthesis gas with a30 % proportion of inert gases, and the second groupis synthesis gas with a 60% proportion of inert gases.The ﬁrst group is characterized as fuel SYNGAS 1,with the following composition — (CH4 – 15 % H2 –25 % CO – 30 % CO2 – 25 % N2 – 5%). A typicalfuel in the second group is referred to as SYNGAS 2,and has the following composition — (CH4 – 10 %H2 – 15 % CO – 15 % CO2 – 10 % N2 – 50 %). In23Acta Polytechnica Vol. 52 No. 3/2012the rest of this paper these fuels (H2NG0, H2NG15,SYNGAS 1 and SYNGAS 2) will be used to drivea Lombardini LWG 702 internal combustion engine,and the parameters will be evaluated.2 Lombardini LGW 702combustion engineOur workplace has been applying H2NG gas mixtures(0 to 30 % vol. H2) to drive an LGW 702 internalcombustion engine. This is a two-cylinder gas enginewith electronically controlled richness of the mixture.The basic characteristics of the LGW 702 engine aresummarized in Table 1.Before the actual application of the gas mixturein a combustion engine, it was necessary to make asimulation analysis to obtain an indicative idea of thebehaviour of the internal combustion engine with agiven fuel mixture. Simulations were performed ona one-zone model of combustion for the LGW 702engine, in the Lotus Engine Simulation calculationprogram (LES). This program is used for simulatingthe operation of the internal combustion engine, andit is also used as a valuable source of information onthe operational parameters of the LGW 702 internalcombustion engine in reaction to various gas mixturesthat will be experimentally veriﬁed step-by-step.The basic parameters required as input data char-acterizing a fuel in the LES program are shown inTable 2.Figure 1 shows a model of the LGW 702 enginein the LES program. This model will serve us laterto optimize the combustion engine in terms of per-formance parameters for various types of fuel blends.Table 1: Main parameters of the LGW 702 internal combustion enginePrinciple of operation Spark ignitionNumber of cylinders and their positions 2, in-lineAngle of crank throw [◦] 360Displacement [cm3] 686Bore [mm]/Stroke[mm] 75/77.6Compression ratio [–] 12.5 : 1Double overhead camshafts, drive OHC, gearing beltValve timingIVO – 18◦ BTDC, IVC – 34◦ ABDCEVO – 32◦ BBDC, EVC – 32◦ ATDCPreparation of mixtureExternal, in a mixer, with electronic regulation ofthe air excess ratio, VOILA Plus systemCoolingBy liquid, with forced circulation,double circular, controlled with a thermostat,cooler ventilatedLubricationPressure, forced-feed lubrication,with ﬁltration, oil 1.6 lMass without ﬁllings [kg] 66Table 2: Basic physical-chemical properties of fuel mixturesFuelM H/C ρ r Hu Lt[kg · kmol−1] [–] [kg ·m−3] [J · kg−1 ·K−1] [kJ · kg−1] [kg · kg−1]H2NG0 16.64 3.93 0.705 499.7 48 825 17.00H2NG15 14.45 4.28 0.613 575.4 50 314 17.36SYNGAS 1 23.72 2.44 0.969 350.5 11 147 3.67SYNGAS 2 24.52 2.80 1.002 339.1 6 418 2.1124Acta Polytechnica Vol. 52 No. 3/2012Figure 1: Virtual model of the LGW 702 engine in the Lotus Engine Simulation programFigure 2: Course of the measured and calculated torque Mt, and speciﬁc fuel consumption mpe, depending onthe speed n of the LGW 702 engine for H2NG0 and H2NG15 mixturesFigure 3: Course of the calculated eﬀective eﬃciency ηe and the fuel consumption MF of the LGW 702 internalcombustion engine for various fuels for a stoichiometric mixture and a full load25Acta Polytechnica Vol. 52 No. 3/2012Figure 4: Course of the composition of the exhaust gases, measured behind the catalytic converter, in dependenceon the richness of the mixture, for blends H2NG0 (0 % vol. H2) and H2NG15 (15 % vol. H2) at full load andat an internal combustion engine speed of 1 800 min−13 Results of the simulationsand experimentsFigure 2 shows two basic indicators of the internalcombustion engine (torque and speciﬁc fuel consump-tion), which serve for comparing the simulation andthe experiment. A comparison of the simulations andthe experimental measurements showed that the dif-ference between the real engine and the virtual modelof the engine was approximately 2 %. The experi-mental results also showed that the torque of the en-gine in operation with H2NG15, compared to naturalgas (H2NG0), was on an average 2 % lower, which onan average meant a decrease of 0.8 N·m. The speciﬁcfuel consumption was on an average 3.3 % lower whenthe engine was running on the H2NG15 mixture thanwhen running on natural gas (H2NG0).Figure 3 shows a simulation of the eﬀective eﬃ-ciency and the fuel consumption for the four basicfuels listed above. The graph shows that the mosteﬀective eﬃciency was achieved when the engine op-erated on natural gas, and it was 30 % in the speedrange from 1 800 to 2 000 min−1.By contrast, the lowest eﬀective eﬃciency wasachieved when the engine operated on SYNGAS 2(60 % inert gases), and the eﬃciency being around11 % in the speed range from 1 200 to 2 000 min−1.The mass consumption of the fuel as a stoichiomet-ric mixture was highest when the engine operated onthe SYNGAS 2 mixture. In comparison with the useof SYNGAS 1, there was a rise in consumption ofabout 48 %. The decrease in the H2NG15 mass fuelmixture was about 3 % lower than when the engineoperated on natural gas (H2NG0).Several previously published results have showna signiﬁcant eﬀect of blending hydrogen into naturalgas with the aim to improve the emission parametersof internal combustion engines. The reason is thathydrogen blending increases the molar proportion ofH/C, thus reducing the emissions of CHx, CO andCO2. Figure 4 shows the course of the compositionof the exhaust gases, depending on the air excess ra-tio for various fuel types (H2NG0 and H2NG15). Ascan be seen, there is signiﬁcant production of car-bon monoxide CO in the operation of natural gas(H2NG0) in rich mixtures, where the inﬂuence ofoxygen deﬁciency prevents perfect oxidation of COto CO2. Conversely, the production of CO in leanmixtures is practically zero. The nature and courseof the CO yield is the same when the engine is run-ning on the H2NG15 mixture (15 % vol. H2).Complete combustion of hydrocarbon fuels pro-duces carbon dioxide CO2. It can be seen that thelargest proportion of CO2 is for a slightly lean mix-ture, with the highest combustion eﬃciency. Fromthis value, the proportion of CO2 decreases similarlyas in the rich mixture, which is caused by lack of oxy-gen to complete the conversion to CO2. The samesituation also arises in the lean mixture, because ofthe limited amount of carbon in the fuel. When theengine runs on the H2NG15 mixture, there is a 9 %reduction in CO2, on an average, throughout thecourse, compared to H2NG0. This is because theproportion of carbon in the fuel decreases.Nitrogen oxides NOx, in the case of engine op-eration on natural gas are formed by oxidation ofnitrogen and oxygen present in the air. Nitrogen andoxygen oxidize each other at high temperature. Ascan be seen, the highest growth occurs for a slightly26Acta Polytechnica Vol. 52 No. 3/2012lean mixture that has the highest combustion tem-perature with a relative abundance of oxygen. Withthe gradual transition into leaner areas, the amountof NOx decreases with lower combustion tempera-ture. In the area of rich mixtures with a lack of oxy-gen, there is a decrease in NOx. The course of NOxformation is similar to the combustion of H2NG15mixture, but due to the higher combustion temper-atures, the concentration of NOx increases to about35 % of the maximum NOx values.The formation of NOx is closely related to theproportion of residual oxygen in the exhaust gas. Inoperation with H2NG15 mixture, the formation islower by about 5 %, than in operation with H2NG0natural gas. As shown in Figure 4, an increase inthe admixture of hydrogen to natural gas increasesthe operating range of an internal combustion en-gine, mainly in lean mixtures. The addition of 15 %vol. hydrogen shifts the operating range of an inter-nal combustion engine from around λ = 1.35 to avalue of λ = 1.5.4 ConclusionMixtures of natural gas and hydrogen have a ma-jor advantage over other types of fuels for power-ing internal combustion engines: they produce lowerexhaust emissions, particularly unburned hydrocar-bons, namely carbon monoxide and carbon dioxide.However, adding hydrogen to natural gas increasesthe amounts of NOx, which can be partly removedin operation modes with lean mixtures. With an in-creasing proportion of hydrogen, there is a decreasein the performance parameters of the internal com-bustion engine. However, the beneﬁts include oper-ating the engine on a lean mixture at partial load,because with added hydrogen the operation range ofa combustion engine working with a lean mixture in-creases.Another beneﬁt of our investigation is its contri-bution to the application of synthesis gas in internalcombustion engines. Synthesis gases have signiﬁcantpotential for eﬀective utilization of low-energy gasesin co-generation units.AcknowledgementThis work was supported by the Slovak Re-search and Development Agency under contract No.APVV-0270-06 and contract No. APVV-0090-10.References[1] Akansu, S. O., Kahraman, N., Ceper, B.: Experi-mental study on a spark ignition engine fuelled bymethane-hydrogen mixtures, International Jour-nal of Hydrogen Energy, 32, 2007, p. 4 279–4 284.[2] Huang, Z., Bing, L.: Experimental Study on En-gine Performance and Emissions for an EngineFuelled with Natural Gas — Hydrogen Mixtures,Energy Fuels, 2006, p. 2 131–2 136.[3] Eichlseder, H., Klell, M.: Wasserstoﬀ in derFahrzeugtechnik. Vieweg+Teubner, 2008. ISBN3834804789.27

Effect of Gas Mixture Composition on the Parameters of an Internal Combustion Engine

Abstract

Similar works

Full text

Available Versions

CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)

Directory of Open Access Journals