PROCEEDINGS OF THE INSTITUTE OF VEHICLES 1(101)/2015

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1 PROCEEDINGS OF THE INSTITUTE OF VEHICLES 1(101)/2015 Ambrozik Tomasz 1 THE EFFECT OF EXHAUST GAS RECIRCULATION ON THE CONCENTRATION OF THE EXHAUST GAS COMPONENTS IN THE DIESEL ENGINE FUELLED BY DIESEL OIL AND FAME 1. Introduction Factors that reduce the harmful environmental impact of exhaust gas include biofuels and exhaust gas recirculation [3, 5, 7, 8, 10, 17]. In self-ignition engines, an appropriate quantity of air flows in to the cylinders, which is dependent on the engine operation conditions [2, 4, 20]. At the end of the compression process, a certain amount of fuel is injected to the cylinder, which forms an air-fuel mixture with the air contained in the cylinder. As a result of self-ignition, this air-fuel mixture is ignited and combusted. Therefore, the effective power and torque of a complete combustion engine depend on the quantity of fuel combusted in the cylinder. In self-ignition engines, the excess air factor is greater than 1, which means that the engine burns a lean mixture. These engines do not use trifunctional catalysts, because they are used in engines that burn a mixture with a composition close to the stoichiometric composition (λ=1). In selfignition engines, Storage Reduction Catalytic converters and SCR (Selective Catalytic Reduction) converters are used. This, however, increases the purchasing and operation costs of the engine. Another solution used simultaneously is the exhaust gas recirculation system, whose purpose is to reduce nitrogen oxides, NO X [14, 22, 23]. Two exhaust gas recirculation methods can be implemented, namely internal and external exhaust gas recirculation. Internal exhaust gas recirculation consists in either leaving a certain amount of exhaust gas from the preceding engine operation cycle in the cylinder or turning it back directly from the exhaust system to the cylinder. External exhaust gas recirculation involves the use of an external exhaust gas recirculation system to deliver part of the exhaust gas from the exhaust system to the intake system. An advantage of this method is the possibility of using a recirculated exhaust gas cooler. It reduces the exhaust gas temperature, thereby still more reducing the emissions of nitrogen oxides to the environment. The exhaust gas recirculation system operates at low and medium crankshaft rotational speeds and the same loads. However, while delivering part of the exhaust gas to the cylinder, the following condition must be satisfied: the quantity of oxygen contained in the air supplied to the cylinder must ensure the complete and total combustion of the fuel injected to the cylinder during the working cycle. Investigations into the effect of recirculated exhaust gas and the implementation of engine supply with alternative fuels on the combustion process and the emission of harmful exhaust gas components are being currently conducted in many scientific and research & development centres [1, 9, 12, 13, 15, 16, 19]. The compliance with the standards applicable in the European Union is required at the same time 6, 18]. Alternative fuels most often used in the EU are methyl esters of fatty acids contained in rape, soya, flax- 1 dr inż. Tomasz Ambrozik, Katedra Pojazdów Samochodowych i Transportu Wydziału Mechatroniki i Budowy Maszyn Politechniki Świętokrzyskiej, tambrozik@tu.kielce.pl 55

2 seed and sunflower oils. The above-mentioned plants are grown in Europe. These are biofuels of generation 1, as plants grown for consumption purposes are used for their production [11, 24]. Study [26] has shown that oil plants should not be randomly chosen for the production of biofuels. An example can be flax and rape, which exist in many varieties [27]. Different varieties of flax or rape might yield biofuels with very much varying physicochemical properties, which are influenced by the different fatty acid composition. For different rape, flax or sunflower varieties, different calorific values of fatty acid esters are also obtained. The calorific value is one of the crucial properties of a fuel designed for supplying an internal combustion engine. It determines the quantity of energy produced during the combustion process and, as a consequence, influences the effective power and the torque, as well as the engine unit fuel consumption, among other things. 2. The object of investigation and control and measuring apparatus The object of investigation was a four-cylinder HDI (High Pressure Direct Injection) internal combustion engine. The engine featured an exhaust gas recirculation system. The basic technical specifications of the engine are given in Table 1. The design of the engine was developed by PSA Peugeot Citroën in Parameter Table 1. Basic technical specifications of the engine 56 Value Cylinder arrangement in-line Number of cylinders 4 Injection type direct Compression ratio 17.6 Cylinder bore 85 mm Piston stroke 88 mm Engine capacity 1997 dm 3 Maximum engine power 66 kw at 4000 rpm Maximum engine torque 209 N m at 1900 rpm Idling rotational speed 800 rpm A view of the engine under investigation is shown in Figure 1. In this engine, the fuel is injected directly to the cylinder. The pressure of the fuel at the pump exit with the engine idling at a rotational speed of approx. 800 rpm is MPa, while at higher crankshaft rotational speeds, it is around 90 MPa. The engine is furnished with a fuel reservoir that enables a high pressure ranging from 20 MPa to 135 MPa to be maintained in it. Electromagnetic injectors allow multi-stage fuel injection to be executed. The engine is equipped with a turbocompressor that enables a greater quantity of air to be delivered to the engine. The turbine's rotor rotates along with the rotor of the compressor that pressurizes the air delivered to the intake system. The magnitude of supercharging pressure depends on the release valve setting. The engine features also an atmospheric pressure pickup. A signal from this pickup fed to the Central Control Unit is used for determining the air density and switching off the exhaust gas recirculation at the time when the engine is located at a high altitude above sea level, e.g. in a mountainous region. One of the crucial elements influencing the operation of the exhaust gas

3 recirculation (EGR) valve is the air mass flowmeter that measures the quantity of air sucked in by the engine. The air mass flowmeter is illustrated in Figure 2a. Depending on the signal sent by the flowmeter to it, the Central Control Unit determines the exhaust gas recirculation rate and reduces the emissions of harmful exhaust gas components to the atmosphere in transient engine operation conditions, e.g. during deceleration or acceleration. The air mass flowmeter is composed of an air temperature pickup, a metal measuring plate, a protection grid and an electrical connection. The metal measuring plate consists of a heating resistor and a negative temperature coefficient (NTC) thermistor. The job of the heating resistor is to maintain the measuring plate temperature within a preset temperature interval. The metal measuring plate enables the measurement of the mass of air flowing through the intake system. The next element influencing the EGR valve is the vacuum pump. The task of this pump is to create an appropriate negative pressure to cause the activation of exhaust gas recirculation. The operation of the vacuum pump activates the exhaust gas recirculation valve and the pneumatic EGR valve actuator. Figure 2b shows a view of the pneumatic exhaust gas recirculation valve. This valve is opened by negative pressure which, delivered to the pneumatic activator capsule, acts on the membrane. The valve is closed by a spring that forces the return movement of the valve head. The exhaust gas rate control phases are recorded in the Central Control Unit in the form of appropriate injection charts. The exhaust gas recirculation rate is set based on the injection chart stored in the Central Control Unit. Using pulse voltage, the Central Control Unit controls the exhaust gas recirculation controller, determines the exhaust gas recirculation rate, and corrects the exhaust gas recirculation controller pulse width so that the actual exhaust gas recirculation rate value be equal to the programmed (theoretical) value. For the engine under investigation, the exhaust gas recirculation system is activated when the engine crankshaft rotational speed is greater than 780 rpm and when the engine load is small, while the cooling liquid temperature is higher than 60 C. In the investigated engine, exhaust gas recirculation is switched off at the full load for a rotational speed greater than 3000 rpm and when the engine is located at an altitude of over1500 m above sea level. 57

4 a) b) Fig. 1. A view of the investigated engine. Fig. 2. A view of: a) the air flowmeter, b) the pneumatic exhaust gas recirculation valve. Figure 3 presents a view of the testing stand featuring the self-ignition engine and the AVL DiCom 4000 PL analyzer. 58

5 Fig. 3. A view of the testing stand. During testing, the engine was supplied with two fuels, respectively: diesel oil and pure rape oil fatty acid methyl esters. The physicochemical properties of the fuels are given in Table 2. Table 2. The basic physicochemical properties of diesel oil and rape oil methyl esters [21, 25] Parameter Units Diesel oil FAME Fatty acid methyl ester (FAME) contents <0,05 % (V/V) 97,9 % (m/m) Density at a temperature of 15 C kg/m 3 833,4 883,1 Kinematic viscosity at a temperature of 40 C mm 2 /s 2,596 4,55 Cetane number 51,0 51,3 Cloud point C Cold filter plugging point C Ignition point C 63,5 above 111 Sulphur content mg/kg 8,3 6,4 Water content mg/kg Particulate contents mg/kg 7, % distillation residue coking residue % (m/m) 0,01 0,21 3. Measurement results and their analysis During testing, the engine was running following the idling characteristics at three crankshaft rotational speeds, i.e. 1000, 2000 and 3000 rpm. The engine cooling liquid temperature during testing was 85 C. During the tests, the engine was supplied with two fuels, respectively: diesel oil and pure rape oil fatty acid methyl esters (FAME). During 59

6 testing, the engine was running at the factory adjustment setting and with the correctly operating EGR system. In the second case, the engine was running when an error occurred in the EGR control system and the EGR valve was not controlled. In the case when there is no pneumatic control, the exhaust gas recirculation valve is closed. Therefore, no exhaust gas is delivered to the cylinder during engine operation. Table 3 summarizes the results of the measurements of exhaust gas components: nitrogen oxides, NO X ; hydrocarbons, HC; carbon dioxide, CO 2 ; carbon monoxide, CO; oxygen, O 2 ; and the excess air number, λ, for the engine running following the idling characteristics, supplied with diesel oil and pure FAME, respectively, with the correctly operating exhaust gas recirculation valve and at three crankshaft rotational speeds, i.e. 1000, 2000 and 3000 rpm. Table 4 presents the measured concentrations of exhaust gas components: nitrogen oxides, NO X ; hydrocarbons, HC; carbon dioxide, CO 2 ; carbon monoxide, CO; oxygen, O 2 ; and the excess air number, λ, for the engine supplied with diesel oil and pure FAME, respectively, with the incorrectly operating exhaust gas recirculation valve and the engine running following the idling characteristics, at three crankshaft rotational speeds, i.e. 1000, 2000 and 3000 rpm. Table 3. The concentrations of exhaust gas components: nitrogen oxides, hydrocarbons, carbon dioxide, carbon monoxide, oxygen, and the excess air number for the engine supplied with diesel oil and FAME, respectively, with the correctly operating EGR valve. rotational speed, NO X, HC, CO 2, CO, O 2, λ rpm ppm ppm % % % diesel oil ,1 0,06 16,2 4, ,2 0,09 16,0 4, ,9 0,08 16,3 4,843 FAME ,1 0,06 16,3 4, ,9 0,10 16,5 4, ,0 0,09 17,7 6,868 Table 4. The concentrations of exhaust gas components: nitrogen oxides, hydrocarbons, carbon dioxide, carbon monoxide, oxygen, and the excess air number for the engine supplied with diesel oil and FAME, respectively, with the incorrectly operating EGR valve. rotational speed, NO X, HC, CO 2, CO, O 2, λ rpm ppm ppm % % % diesel oil ,5 0,04 16,8 5, ,9 0,08 17,4 7, ,3 0,07 17,0 5,919 FAME ,2 0,03 17,5 6, ,7 0,06 18,1 8, ,9 0,07 17,7 7,168 For the diesel oil-supplied engine, lower nitrogen oxide concentrations were obtained, compared to the engine supplied with the FAME biofuel. A higher exhaust gas 60

7 oxygen content and a greater excess air number value were obtained for the engine supplied with the FAME fuel. The larger amounts of nitrogen oxides and oxygen and the greater excess air number for the FAME-supplied engine may be due to the fact that the elementary composition of FAME has more oxygen compared to diesel oil. The oxygen contained in FAME makes the mixture formed in the cylinder better prepared for combustion, compared to the mixture created with diesel oil. In that case, the combustion process proceeds more intensively, which produces higher temperatures during combustion. Higher temperatures prevailing in the cylinder during the combustion process result in greater nitrogen oxide emissions. Lower carbon monoxide concentrations for the engine running with the correctly operating EGR valve were obtained when the engine was supplied with diesel oil. Higher hydrocarbon concentrations for the engine running with the incorrectly operating EGR valve were obtained when the engine was fed with diesel oil. Slightly higher carbon dioxide concentrations were obtained for the engine supplied with diesel oil. This is due to the fact that for the diesel oil-supplied engine the combustion process proceeded in a more complete and total manner. The comparison of the nitrogen oxide concentrations for the engine running with the correctly and incorrectly operating EGR valve shows that a greater NO X emission has been obtained for the incorrectly operating ERG valve. The EGR valve is controlled by negative pressure. When there is no negative pressure in the pneumatic EGR valve, the valve is closed. This means that in that case the exhaust gas does not come back to the cylinder and does not reduce the intensity of heat release during the combustion process. The exhaust gas fed back to the cylinder is an inert gas that does not participate in the combustion process. For the correctly operating EGR valve, greater oxygen and carbon dioxide concentrations and larger excess air number values were obtained, compared to the engine in which this valve was faulty. 4. Summary Based on the analysis of the results obtained from the performed investigation, the following conclusions can be drawn: - for the engine supplied with FAME, greater nitrogen oxide concentrations were obtained compared to the engine supplied with diesel oil, - for the engine supplied with pure FAME esters and with the correctly operating exhaust gas recirculation valve, lower nitrogen oxide concentrations were obtained, compared to the engine supplied with diesel oil, - for the engine with the correctly operating exhaust gas recirculation valve and supplied with pure FAME esters, greater carbon dioxide concentrations were obtained, compared to the engine supplied with diesel oil, - for the engine supplied with pure FAME esters and with the correctly operating exhaust gas recirculation valve, higher carbon monoxide concentrations were obtained, compared to the engine supplied with diesel oil, - for the engine with the correctly operating exhaust gas recirculation valve, lower oxygen concentrations and smaller excess air number values were obtained, compared to those values when the engine was supplied with diesel oil. To sum up, it can be stated that with the correctly operating exhaust gas recirculation valve, lower nitrogen oxide concentrations are obtained, which contributes to the compliance with the standards applicable in the European Union and has a favourable effect on the human natural environment. When the engine was fed with the 61

8 FAME fuel, greater nitrogen oxide emissions were obtained. These concentrations significantly decreased, when exhaust gas recirculation was executed in the engine. References: [1] Ambrozik A., Ambrozik T., Łagowski P.: Fuel impact on emissions of harmful components of the exhaust gas from the CI engine during cold start-up, Eksploatacja i Niezawodność - Maintenance and Reliability, 17/1, pp , [2] Ambrozik A.: Analiza cykli pracy czterosuwowych silników spalinowych, Politechnika Świętokrzyska, Kielce [3] Ambrozik T., Kosno M.: The effect of exhaust gas recirculation on the process of combustion in the self-ignition engine, Journal of KONES Powertrain and transport, Vol. 21, No. 2, pp.7-14, [4] Ambrozik T.: Internal combustion engine, on-line: Politechnika Świętokrzyska, Kielce, [5] Ambrozik T.: Wpływ recyrkulacji spalin na stężenia spalin w silniku FIAT MultiJet 1.3, Logistyka 4, pp. 7-16, [6] Chłopek Z.: Ochrona środowiska naturalnego, WKŁ, Warszawa, [7] Graba M., Bieniek A., Mamala J., Lecho A.: Sterowanie adaptacyjne systemem recyrkulacji spalin w aspekcie obniżenia emisji substancji szkodliwych dla klasycznego silnika ZS, Inżynieria Rolnicza 5(130), [8] Hibernik A., Samec N.: Effect of exhaust gas recirculation on diesel combustion, Journal of KONES Internal Combustion Engines 2004, vol. 11, No. 1-2, pp , [9] Idzior M., Karpiuk W., Borowczyk T.: Analiza wpływu temperatury biopaliw na makro- i mikrostrukturę rozpylanych strug, Postępy Nauki i Techniki, nr 15, pp , [10] Jaskólski J., Mikoda P., Łasocha J.: System EGR a zmniejszenie emisji substancji szkodliwych, Czasopismo Techniczne 7-M/2008, wyd. Politechniki Krakowskiej, pp , [11] Klimiuk E., Pawłowska M., Pokój T.: Biopaliwa. Technologie dla zrównoważonego rozwoju. Wyd. Naukowe PWN, Warszawa, [12] Kruczyński, S., Orliński P., Biernat, K.: Olej lniankowy jako biopaliwo dla silników o zapłonie samoczynnym, Przemysł Chemiczny, 91/1/2012, pp , [13] Kruczyński, S., Orliński, P.: Combustion of methyl esters of various origins in the agricultural engine, Indian Journal of Engineering & Materials Sciences, 20, pp , [14] Lejda K.: An influence of exhaust gas recirculation on NO X and other toxic components emission in diesel engines, TEKA Komisji Mot. Energ. Roln., pp , [15] Łagowski P.: Ocena wskaźników ekonomiczno-energetycznych i ekologicznych trubodoładowanego silnika o zapłonie wymuszonym 1.2 TSI. Logistyka 3, pp , [16] Łagowski P.: Wpływ ciśnienia doładowania na ekonomiczno-energetyczne i ekologiczne wskaźniki pracy silnika 1.3 MultiJet. Logistyka 6/

9 [17] Merkisz J., Piaseczny L.: Możliwości ograniczenia negatywnego wpływu recyrkulacji spalin na sprawność ogólną okrętowego silnika spalinowego napędu głównego, Archwium Motoryzacji 3, pp.1-10, [18] Merkisz J., Pielecha J., Radzimirski, J.: New Trends in Emission Control in the European Union, New York: Springer [19] Orliński P.: The influence of camelina oil ester additive to diesel fuel on selfignition angle in agricultural engine, Journal of Kones 2013, Vol. 20, No. 2, pp , [20] Orliński P: Wybrane zagadnienia procesu spalania paliw pochodzenia roślinnego w silnikach o zapłonie samoczynnym, Instytut Naukowo-Wydawniczy SPATIUM, Radom, [21] Orzeczenie laboratoryjne nr S/14541/0/01/2013 Olej napędowy. [22] Pietras D., Sobieszczański M.: Problemy regulacji silnika o zapłonie iskrowym z recyrkulacją spalin, Silniki spalinowe, Nr 2 (119), pp , [23] Postrzednik S., Żmudka Z., Przybyła G.: Influence of the exhaust gas recirculation on the oxygen contents and its excess ratio in the engine combustion chamber, Journal of KONES Powertrain and transport, Vol. 20, No. 3, pp , [24] Szlachta Z.: Zasilanie silników wysokoprężnych paliwami rzepakowymi. Wydawnictwo Komunikacji i Łączności, Warszawa [25] Świadectwo jakości nr wyrobu Biodiesel. [26] Wcisło G.: Analiza wpływu odmian rzepaku na własności biopaliw RME oraz parametry pracy silnika o zapłonie samoczynnym, wyd. FALL, Kraków [27] Wcisło G: Zastosowanie chromatografii gazowej do oceny rolniczych biopaliw typu RME i CSME ze względu na układ estrów kwasów tłuszczowych, Inżynieria Rolnicza 9(118), pp , Abstract The paper presents investigation results and the analysis of the effect of the correctly and incorrectly operating the exhaust gas recirculation system on the exhaust gas component concentrations and the excess air number. During testing, the engine was running following the idling characteristics at three crankshaft rotational speeds, i.e. 1000, 2000 and 3000 rpm. During the tests, the engine was supplied with commercial diesel oil and pure rape oil fatty acid methyl esters (FAME), respectively. The object of investigation was a self-ignition engine equipped with a common rail system and an exhaust gas recirculation system. Using an AVL DiCom 4000 exhaust gas analyzer, the concentrations of exhaust gas components, namely nitrogen oxides, hydrocarbons, carbon dioxide, carbon monoxide and oxygen, were measured. In addition, the excess air number was measured. Keywords: internal combustion engine, harmful exhaust gas components, exhaust gas recirculation 63

10 WPŁYW RECYRKULACJI SPALIN NA STĘŻENIA SKŁADNIKÓW SPALIN SILNIKA O ZS ZASILANEGO OLEJEM NAPĘDOWYM I FAME Streszczenie W artykule przedstawiono wyniki badań i analizę wpływu prawidłowo i nieprawidłowo działającego układu recyrkulacji spalin na stężenia składników spalin i współczynnik nadmiaru powietrza. Podczas badań silnik pracował według charakterystyki biegu luzem i przy trzech prędkościach obrotowych wału korbowego, tj. 1000, 2000 i 3000 obr/min. Podczas badań silnik zasilany był handlowym olejem napędowym i czystymi estrami metylowymi kwasów tłuszczowych oleju rzepakowego FAME. Obiektem badań był silnik o zapłonie samoczynnym wyposażony w system common rail i układ recyrkulacji spalin. Przy pomocy analizatora spalin AVL DiCom 4000 mierzono stężenia następujących składników spalin: tlenków azotu, węglowodorów, dwutlenku węgla, tlenku węgla i tlenu. Ponadto mierzono współczynnik nadmiaru powietrza. Słowa kluczowe: silnik spalinowy, szkodliwe składniki spalin, recyrkulacja spalin 64