Nghiên cứu mô phỏng đặc tính của động cơ xe máy khi sử dụng nhiên liệu xăng pha cồn etanol

JOLRNAL OF SCIENCE & TECHNOLOGV No 838-2011 SIMULATION STUDY OF MOTORCYCLE ENGINE'S CHARATERISTICS FUELED WITH ETHANOL-GASOLINE BLENDS NGHILN CIJU MO PHONG DAC TJNH CLIA D O N G CO XE M A Y KHI SIJ' DUNG NHIEN Ll£U XANG PHA CON ETANOL Le Anh Tuan', Pham Huu Truyen', \giiyen Due Khanh', Trieu Tien Chuan' 1) Hanoi University of Science and Technology 2) Vinh Technical Teachers Training University ABSTRACT This paper presents the simulation results of a motorcycle engine using ethanol-gasollne blended fuels with the various blended rates (0%, 5%, 10%, 20% and 85%) at wide-open throttle and different engine speeds of 3000, 5000 and 7500 rpm on one dimensional simulation software AVLBOOST The simulation results show that, respect to engine power, it Is not necessary to modify the engine to use fuel blends up to 20% ethanol (E20) as the engine power reduces less than 3.3% at rated operating regime The CO and HC concentrations reduce dramatically, which are 64%, 73%, 77%, and 90%, of CO reduction for E5, EIO, E20 and E85 fuel blends, respectively The NOx emission increases however with E5, EIO and E20 due to the air/fuel ratio approaching stoichiometric condition (lambda = 1) while It Is reduced with E85 as low combustion temperature resulting from lean mixture Finally, due to leaner mixtures the pressure rise rate Is lower and the longer combustion duration is observed as the ethanol content increases Thus the Ignition timing must be consider to have efficient combustion Keywords: Ethanol-gasoline blended fuel, AVL-BOOST simulahon, engine emissions TOM TAT Bii bio trinh biy kit qui md phdng ddng ca xe may sir dung nhlen lieu xang pha cin etanol vdi cic ti le khic (0%,, 5%, 10%>, 20%, vi 85%) d vi tri bwdm ga md cwc dai tal dc tic dd 3000, 5000 vi 7500 vdng/phut tren phin mim mo phdng mdt chiiu AVL-BOOST Kit qui da chi ring, xit vi khia canh cdng suit, khdng cin thiit phii diiu chinh dgng eg su' dung nhien lieu xing pha cdn vdl ty li cin tdi 20%, cdng suit cita ddng ca chi giam dwdi 3,3% d chi van hinh dinh mwc cua ddng eg Ndng phit thil CO va HC glim manh, phit thil CO glim lin Iwgt 64%,, 73%,, 77%, vi 90%, ddng ca sir dung nhien lieu E5, EIO, E20 vi E85 Tuy nhlen, phit thii NOx ting vdi nhiin liiu E5, EIO va E20 ty le khdng / nhlen lieu tiem can gii tri ly twdng (lambda = 1), dd, vdi nhiin lieu E85 thi NOx giim nhd nhiet chiy thip cd dwgc tir hon hgp nhat Cudi cung, hdn hgp nhat din, tdc tang ip suit giam va thdi glan chiy dii hgn ting ty le etanol hin hgp nhiin liiu Dg dd cin quan tim diiu chinh thdi diim danh lira nhim dat dwgc qui trlnh chay hiiu qui TCf khba: Nhien lieu xing pha etanol, mo phong tren AVL-BOOST, thai dpng ca I INTRODUCTION such as ethanol fuel, which is sustainable and more sociable to environment and more economical [2] In Vietnam, the number of motorcycles has been considerably increasing and concentrated in big cities as Hanoi and Ho Chi Minh City The recent statistic data indicates that, in the late of 2009, the number of motorcycle reached 28.5 millions [I], and is boosting with the annual growth rate up to 20% fhis becomes a significant issue because of the growing concern on emissions, public health and energy security Science, therefore, indispensably cultivates new altemative fuels The ethanol gasoline blended fuel has been developed since the mid of 20"' century and now widely used for spark ignition (SI) engines It has some dominant advantages in anti-knock characteristic and reduction of ignition delay [3,4], CO and HC emissions [5,6,7.8], Ihe fuel consumption however slightly increases [9] With the support of W'L-BOOST software, we would like to 119 JOI RNVl, OF SCIENCE* TECHNOLOGV • No 838-2011 heating value (LH\) and stoichiometric air-fuel ratio (AFR) are lower than those of pure gasoline (EO) Therefore, more fuel is expected to be consumed to obtain an equivelent perfonnance when using E5, EIO, E20 and ESS In addition, ethanol has a higher research octane number (RON) than gasoline; therefore, the RON increases monotically with the increase of ethanol content present a study about characteristics and other thermodynamic processes of a motorcycle engine fueled with ethanol-gasoline blends with the ethanol percentage ranging from 0% to 85% (EO to E85) The engine used for this study is a single cylinder carburetor Sl engine, the engine that shares about 95% of the total motorcycle's engine number in \ietnam The detailed specifications of this engine are listed in Table I III SIMULATION BOOST 3.1 Model set-up Table Specifications of test engine Engine type Bore Stroke Displacement volume Compression ratio Maximum power Fuel svstem Ignition timing MODEL ON AVL Base on the factual motorcycle engine, a simulation model is built with systemaficlv arranged elements on AVL-BOOST, as shown in Fiu Single - Sl engine 50 mm 49.5 mm 97 cm9.0:1 5.2 kW/7500 rpm Carburetor 30" BTDC II ETHANOL FUEL PROPERTIES Various blend rates of ethanol-gasoline fuels (EO E5, EIO, E20, E85) were used in this simulation The "E" designates ethanol and the number next to "E" designates the volume percentage of ethanol The E5 means that 5% ethanol (99.7% purity) was blended with 95% gasoline by volume Fig Simulation model SB stands for system boundary, CL air cleaner, MP - measuring point, R - restriction, I - carburetor, C - cylinder, CAT - catalyst, PL plennum Table shows the physical properties of the fuels used in this simulation Ethanol is an oxygenated fuel which contains an oxygen molecule in the fuel For this reason, its lower Table Properties of ethanol-gasoline blendedfuels (E(l E5 EIO, E20 and ESS) Property items Density (kg dnf at 25"C) Stoichiometric air-fuel ratio (weight) Lower heating value (kJ fig) RON (-) MON (-) EO 0.719 14.565 43 500 92 82 E5 0.7225 14.26 42 665 92.8 82.4 Test fuels EIO 0.729 13.957 41 830 936 82.7 E20 0.733 13.361 40 160 95.2 83.4 E85 0.7785 9.751 29 305 105.6 87.9 building on the phenomenological concept of vortex cascade and on fractal theory [10] 3.2 Fractal combustion model Fractal combustion model (FCM) is one of the most useful models in simulating Sl engines with turbulent flames It describes the phvsics of the small scales of turbulence It is well established that the flame front propagating within the turbulent flow field occuning inside the combustion chamber of an intemal combustion engine is a very thin and 120 JOt RNAL OF SCIENCE* TECHNOLOGV * No.838-2011 highly wrinkled surface This flame area, A- due to the above wrinkling, is much higher than the one occurring in a laminar buming process The latter, i.e the laminar flame area, AL, can be considered a smooth and spherical centered in the spark plug location The increase of the flame surface (Aj/Ai), is firstly responsible for the increase in the turbulent buming rate with respect to the laminar one The equation of turbulent burning speed can be expressed as: The overall burning rate can be consequently defined as a weighted mean of the two described combustion rates: dm^ (dm„ dm^ (4) = (1-"•.)( dt 'dt' \dt 11;: weight factor IV RESUUTS AND DISCUSSIONS 4.1 Engine power din^ MV'V^, with '1, ^R.lyl^-'^ Fig shows the influence of different blended fuels on reducing engine power when the supplying fuel was constantly kept Due to the decrease of LHV and the increase of AFR (lambda, "K increases), the engine power reduces when the ethanol content increases Average over all speeds, the engine power decreases 3.3% with E20, and 29.1% with E85, however, it is less than 1.1% with EIO Thus respect to the engine power, it is not necessary to modify the engine if the percentage of ethanol in the blend is less than 20% (1) S, nit,: mass burning rate ,S', .">/: turbulent, laminar flame speeds p_: density of unbumed mixture The complex ignition is simply assumed to start the computation at the end of kernel initiation process with a stable and spherically shaped smooth flame of about mm radius Flame wrinkling proceeds then starts at a rate which increases with both the instantaneous flame radius and the turbulence intensity The following expression is proposed for the computation of a non-dimensional flame wrinkling rate: ^ ^ • E5 • EIO • E20 DE85 3b cz o T3 25 •o 20 IU Q : 15 9; 10 °s CL r ^H 3000 - —r~ 5000 ^^ 7500 Engine speed (rpm) (2) Fig Influence of the blended fuels on the reduction of engine power (relative to EO) /',r,,: tunable reference radius Ur,,: reference engine speed To investigate the increase of supplying fuel when using different blended fuels, the engine power is constantly kept The results are shown in Fig 5" 80 S_- The most important characteristics of combustion completion relate to the effects of the wall on the buming process ("vvalleombustion" phenomena) The wall-combustion burning rate can be simply described by an exponential decay: S so • E5 • E10 nE20 ^ DE85 OJ 70 50 ' JO ~di~ =1 (3) ~ 30 •^20 g;10 T: being the characteristic time scale of the above process CO 3000 5000 7500 Engine speed (rpm) (in-in ): unbumed mass Fig Influence oflhe different blended fuels on the inct-ease of supplying fuel (relative lo EO) 121 JOI RNAL OF SCIENCE* TECHNOLOGV * >o SJB-JUi In oraer lo ::'.creasc he supply ing fuel the carnureior main jet Ji,ime :er must be widened as described in Table - BEI? HESS ^^H ^ f l i Table S Mean suprl\:':g *'ucl increase required llie increase o' main jet diameter 'relative to EIF - Blended fuels E5 EIO E:O E85 3.%;.- Main jet diameter increase (° o) 0.3S O."* 11.31 Pollutant emissions Ethanol itself provides more oxygen so that the combustion pr^vess is expected more complete which makes CO emission concentration tremendously decreases when increasing the ethanol content (see Fig.41 The average reduction of the CO emission over the considered engine speed is in tum 64'" o "3"' o " % , and 9i>\rfor E5 EIO E20 and E85 r-XC ~5-0D Engine soeed ,rpm^ Fig Inthience of the blended fuels on the increase ()' VQv emission Irelathe to Efli The concentration of HC emission also decreases with the increase of ethanol content however, the increase altitude is fluctuated with ES5 fuel depending on the engine speed as described in Fig The concentration of NOx emission is shown increasing with E5, EIO and E20 but decreasing vv ith E85 as depicted in Fig The Nt'ix concentration reaches peak with E20, when the combustion is about stoichiometric (/ approaches U With E85 fuel, the NOv emission is very low because of the low flame temperature resulted from lean mixture Fuel consumption f.'C /'.'•.";/t'',',t cif the blended *itels on the rcdiiclicvi ('•(.'(' cniissiou rcLilivc to EOe The brake specific fuel consumption (BSFCi of the same engine mnning with dilTerent ethanol-gasoline blended fuels is described in Fig." The BSFC is gradually increasing with higher ethanol content from E5 to E20 fuels, however this value is very high vv ith E85 fuel due to engine power reduction as mentioned in Fi2.2 Đ:;:ã LU /^;c _^ ''.".'.'.t';,t !>• the '^leiided •in.'^ on ihc rcdiiction • HC e"::ss:eiti rcLiiivc lo EOi =^ LJLL EngTe speed itpmt Fig The BSFC of tlie engine using diticrc'i; blended 'iic '^ to i.irgei the same engine s output JOURNAL OF SCIENCE* TECHNOLOGV * No 838-2011 4.4 Combustion characteristics In Fig 8, we compared the effects of each fuel on the profile of combustion temperature and combustion pressure in the range from 40° crank angle (CA) before top dead centre (BTDC) to 50°CR after top dead centre (ATDC) The results prove that the ignition delay reduces and combustion duration increases with higher percentage of ethanol, as shown in Table As oxygen atom is contained in the molecular of ethanol fuel, the ignition is initiated faster than that of gasoline, thus the ignition delay of ethanol fuel is reduced However due to leaner mixture, the flame propagation of the ethanol-gasoline blending fuel is weaker which makes combustion duration longer Table Influence of the blended fuels on the ignition delay and the combustion duration (relative to EO) Blended fuels Ignition delay reduction (%) Comb, duration increasing (%) ^xa: -2 -20 -10 10 20 30 Crank angle (deg) Fig ROHR VS CA at engine speed of 7500 rpm and WOT The rate of heat release (ROHR) of each fuel is calculated from measured cylinder pressure The effects of EO, E5, EIO, E20 and E85 on ROHR at engine speed of 7500 rpm and WOT are indicated in Fig As demonstrated in this figure, the ROHR decreased with the increase of ethanol content E5 EIO E20 ESS 7.27 9.09 13.64 42.73 V CONCLUSIONS 0.00 3.03 10.61 23.33 Simulation results have shown a complete picture of a carburetor motorcycle engine characteristics when fueled with different ethanol-gasoline blends, including pressure and temperature profiles, power, fuel consumption and exhaust emissions 3000 •40 30 -20 -10 _a> -EO •E5 •EIO •E20 £85 10 20 30 40 O 50 Crank angle (deg) Fig The profiles of combustion temperature and combustion pressure vs C.4 at engine speed if''500 rpm and wide-open throttle llVOT) .As shown in Fig.8, the pressure rise rates and pressure peaks of E5, EIO, E20 and E85 are lower than that of EO, which help reduce the noise of the engine In addition, as the pressure peaks tends to move away from the TDC in the positive crank angle due to lean mixture and longer combustion duration, the ignition time should be considered to set earlier Finally, the low combustion temperature of l';85 is the main reason for NOx emission reduction as mentioned in I is; As the engine power reduction is less than 3.3% at the rated operating regime, the blended fuels with less than 20% ethanol are allowed to use normally in the conventional engine without any modification unless any concern of materials compatibility is needed The CO concentration reduces dramatically with ethanol-gasoline blends The CO reduction is 64%, 73%, 77%, and 90% for E5 EIO, E20 and E85 fuels, respectively While CO emission of motorcycles predominates the total CO emission sources, using ethanol fuel benefits greatly in this aspect In addition, the HC emission is also reduced remarkably when using ethanolgasoline blends However NOx emission increases with E5, EIO and E20 due to the air fuel ratio approaches stoichiometric condition This bad effect can be reduced with higher ethanol content or with exhaust after treatment devices JOLRNAL OF SCIENCE* TECHNOLOGV • No 838-2011 The pressure profile indicates that due to leaner mixtures, the pressure rise rate is lower and the longer combustion duration is observed as the ethanol content increases Theretoie the appropriate ignition timing must be consider to have efficient combustion REFERENCES Le Anh Tu; Motorcycles emission control in Vietnam current status, challenges and measures Workshop on Traffic and Environment; Hanoi, Vielnam (2010) David Pimentel; Ethanol fuels: Energy security, economics, and the environment; Journal of Agricultural and Environment ethics; Volume 4, Number I Pages 1-13 (1991) M Gautam, D W Martin II; Combustion characteristics of higher-alcohol/gasoline blends; Part A: Joumal of Power and Energy; Volume 214, Number 5, Pages 497-511 (2000) M A R S Al-Baghdadi; Measurement and prediction study of the effect of ethanol blending on the perfomiance and pollutants emission of a four-stroke spark ignition engine; Part D: Joumal of Automobile Engineering; Volume 222, Number 5, Pages 859-873 (2008) Bala RM Elond AC, Rice RW; Emissions from IC engine fueled with alcohol-gasoline blends: a literature review; Joumal of Engineering for Gas Turbines and Power; Volume 111, Issue 3, Pages 424-431 (1989) Wei-Dong Hsieh, Rong-Hong Chen, Tsung-Lin Wu and Ta-Hui Lin; Engine performance and pollutant emission of an Sl engine using ethanol-gasoline blended fuels; Atmospheric Environment; Volume 36, Issue 3, Pages 403-410 (2002) Fikret Yiiksel and Bedri Yiiksel; The use of ethanol-gasoline blend as a fuel in an Sl engine; Renewable Energy; Volume 29, Issue 7, Pages 1181-1191 (2004), Le Anh Tuan, Pham Minh Tuan; Impacts of Gasohol E5 and EIO on Performance and Exhaust Emissions of In-used Motorcycle and Car: A Case Study in Vietnam; Vietnamese Joumal of Science and Technology, No 73B, p98-l04 (2010) H Serdar ^'iicesu, Adnan Sozen, Tolga Topgiil, Erol Arcaklioglu; Comparative study of mathematical and experimental analysis of spark ignition engine performance used ethanolgasoline blend fuel; Applied Thermal Engineering; Volume 27, Issues 2-3, Pages 358-368 (2006) 10 AVL-List GmbH: BOOST v.2009 Theory; Hans-List-Platz 1, A-8020 Graz, Austria (2009) Author's address Le Anh Tuan - Tel: (+84) 904.702.438 - Email: tuanla-ice''«ymail.hut.edu.vn School of Transportation Engineering Hanoi University of Science and Technology No 1, Dai Co Viet Str., Hanoi, Vietnam 124 ... fuel in an Sl engine; Renewable Energy; Volume 29, Issue 7, Pages 1181-1191 (2004), Le Anh Tuan, Pham Minh Tuan; Impacts of Gasohol E5 and EIO on Performance and Exhaust Emissions of In-used Motorcycle