juyen rap Long rrinn tioi ngni i\ noa noc Ca hoc Thiiy khi Todn qudc, Phan Thiet, 2008 55 Comparison in combustion characteristics of an indirect injection compression ignition engine fuelled with die[.]
juyen rap Long rrinn tioi ngni i\.noa noc Ca hoc Thiiy Todn qudc, Phan Thiet, 2008 55 Comparison in combustion characteristics of an indirect injection compression ignition engine fuelled with diesel and biodiesel Phan Minh Diic', Nguyen Van Dong', Kanit VVattanavichien^ Danang University, Danang, Vietnam 'Chitlalongkorn University, Bangkok, Thailand Abstract: This paper alms to identify the combustion characteristics of a high speed Indirect Infection (fDIj compression ignition (CI) engine operating with blodieseLThe • results shown arc revealing a comparison between diesel and biodiesel operation with respect to engine performance, energy consumption, heat release characteristics, and cyclic variation The results indicate that the engine achieved the same performance with both fuels, biodiesel operation gave higher energy consumption, the infection timing in biodiesel case was earlier, the Injection duration was longer and biodiesel comhustlan had slightly lower peak if heat release rate and longer late stage cf combustion Key words: Biodiesel diescl IDI heat release, cycle-by-cvcle variation So sanh dac diem qua trinh chay ciia dong co diesel phun gian tiep sii dung nhien lieu diesel va biodiesel Tom tiit: Nghien ciru nd)' nhdm xdc dinh ddc diem qud trinh chdy cua inc}l ddng ca diesel tdc cao phun gain tiip chay bdng nhien lieu biodiesel'Cdc ket qua thuc nghiem vd phdn tich the hien sir so sdnh khd ndng phdt cdng sadl suat lieu hao ndng lirang, dac tinh tda nhli'l, vd sir dn dinh cua ddng ca su dung hai loai nhien lieu diesel vd biodiesel Kel qud eho thiiy, chay bdng biodiesel ddng ca cd kha ndng hogt ddng duac a tdt cd cdc diem thir nghiem nhien sudi tieu hao ndng luang cao hern Ddng thdi, chay biodiesel thi thdi diem phun nhien lieu sdm han, thdi gian phun ddi han, tdc toa nliwt lan nhdt gidm chut it vd giai docin chdy sau keo ddi han Introduction Due to concern about the decrease of petroleum reserves and more stringent emission standards for petroleum-fueled diesel engines, the development of alternate energy sources has become increasingly important Alkyl esters of vegetable oils hold promise as fuel alternatives for diesel engines Many studies have shown that the alkyl esters of soybean, rapseed oil have similar fuel properties and engine performance compared with diesel fuel[I-4] Additionally, these alkyl esters arc nontoxic, biodegradable and renewable fuels that reduce exhaust emissions They, commonly known as biodiesel, may help to reduce greenhouse gas emissions since the carbon in the fuel is extracted from the atmosphere and very little energy is required for fuel production Biodiesel also possesses two additional advantages over diesel fuel, its high cetane number and its potential to reduce carbon monoxide, unbumed hydrocarbons, polycyclic aromatic hydrocarbons and particulate matter[5, 6] They not contain aromatic compounds and have very low sulfur levels these reductions increase as the amount of biodiesel blended into diesel fuel increases In Comparison in combustion characteristics of an indi''^^ injection compression ignition ensine fuelled with diesel and biodiSA^ 56 general, biodiesel increases NOx emissions when used as fuel in diesel engines These properties probably contribute to a portion of the emission reduction[7, 8] The presence o oxygen atoms in the esters assures more complete combustion and less formation of soot Depend on the sources, different alkyl esters would have different affect on the diesel engines' operation and combustion charatenstics[9-11] Although there have been many ot published studies on biodiesel in recent years[12-15], it seems that the information about palm-based biodiesel still lacks Therefore, m this investigation, the combustion characteristics of methyl esters of palm oil was identified, in comparison with commercial diesel fuel produced by PTT Co., Thailand Description 2.1 Test system 17,18 I 10 15 20 OO 24 16 13- 23 14 I G> 22 A ^ ^ (^OOO^ I _i 1- Engine la- Measured cylinder 2- Gear box 3- Dynamometer 4- Speed sensor 5- Pneumatic actuator 6- Fuel pump 7- Encoder Figure - Test system 10- Surge lank 19- Cooling fan 11-Orifice 20- Cooling water tank 12-Air filter 13- Exhaust gas temperature measurement 14- Exhaust gas pressure measurement 15- Water-out temperature measurement 16- Water-in temperature measurement 17- Ambient temperature 21 - Drain-water pipe 22- Inlet water, to water tank 23- Solenoid valve 24- Inlet water, to engine 25- AVL Pulse converter Phan Minh Dire, Nsuyen Vdn Ddns, Kami Wattanaviehien 8- Liquid fuel lank 9- Fuel flow meter measurement 18- Ambient pressure measurement PC2 - DEWETRON Indicating system 57 PCI - AVL Control unit This study was conducted wilh a 4-cylindcr naturally aspirated IDl CI engine, FORD WL, on a test bench at Internal Combustion Engine Research Laboratory, Chulalongkom University The engine's compression ratio is 21,6 It is equiped with a VE axial piston pump (ZEXEL), Pintle injectors with opening pressure of 11.5 MPa There was no modification for its liquid fuel system It was loaded by an eddy current dynamometer, AVL Alpha 40 and controlled by a AVL BME-300 monitoring unit Nn DEWETRON indicating system (DEWE-CA-5000-SE) was used to record the pressure history Pressure transducers (two \WL GUI2P and one Kistlcr 607C1) were used to capture pressure of main and pre combuslion chambers and fuel line Resolution of the pressure history was 0.2 crank angle degree Air consumption was measured by an orifice installed to a surge tank The liquid fuel flow rale was calculated as the ratio between the mass of fuel consumed and the corresponding time The consumed liquid fuel mass was measured by an ECU WEIGHT high precision electrical balance and the corresponding time was measured by an ALBA stop watch The tempcramrcs of ambient air, air in the surge tank, lubricant oil, cooling water, and exhaust gas were measured by thermal couples Ambient air pressure was measured by'a barometer Differential pressure between air in the surge tank and ambient was measured by an inclined manometer The test system is schematically shown in Figure 2.2 Fuels properties Commercial diesel fuel produced by PTT Co., Thailand wilh main properties given in Appendix A was used in this investigation, Biodiesel used has been produced by the Chemical Technology Institute, Chulalongkom University Its properties are shown in Appendix B All its properties except fiash point (available until the time that this study was conducted) matched the requirement according to ASTM D 6751 and BS EN 14214:2003 standards examinadon Experiments were conducted (at state) as the engine operated with the two selected high probability operating determined from the ECE15+EUDC test These test points are given in Table steady fuel at points cycle Table - Selected test points Brake torque [Nm] Speed [rpm] 2.3 Test procedures, definition and 1250 10 20 30 40 X X X X 70 X X X X X 2000 The cooling system was set to maintain the temperature of colling water, oriel from the X X X X 2750 engine, outlet from the engine, in a range from 83"C to 86°C Operation of the test engine was considered steady as there were narrow variation ranges of exhaust gas tempc-raturc, lube oil temperature, engine speed and torque, and fuel consumption Energy conversion efficiency and combustion characteristics were eon-cerned in this study includes Energy conversion efficiency (ECE) is defined by the ratio between the shaft-work output, P, produced by the engine and the chemical energy fiow rale (dE/dt) of Comparison in combustion characteristics of an ind"^ injection compression ig'tiition ensine fuelled with diesel and bjodj^^^ 5H the fuel injected to ihc engine ( E q l ) It is noticed for this study that the shaft work is ^hc gearbox's output shaft and during experiment, the gearbox raio was Energy conversion cfficcicncy fraction, (EF) is defined as the ratio of the energy conversion cfficcicncy m the two fuel cases, via Eq, ECE = P / ( d E / d t ) (1) = P / ( m , LHV) = T,(o/(m ,L1IV] (2) EF,, = E C E , / E C E „ Heat release model adapted from [16] was used to analyze the combustion process The net heat release equation for the combustion system is determined by Eq, 5, Here, y is the polytropic index of the fluid inside the combustion chambers Determination of start of fuel injection (SOI), start of combustion (SOC) and combustion duration has been dctcnnined from the fuel line pressures and the heal release rale[17] V, d(p; - P | ) dV, V, +V, dp, dQ Y (3) Y- r dt - dt y -1 dt dt The indicated mean effective pressure (IMEP) is a parameter related to the cylinder pressure history, which, in lurn is determined by various factors such as the rate of heal release due to combustion process, heat losses to the cylinder walls, and the cylinder volume change due to the piston nhotion Coefficient in IMEP (COVIMKP) has been used to evaluate the cycle-by-cycle variation (CCV)[ 17] l.MEP was calculated from 200 considered conseculi\e engine cycles It has been found that \ehicle drive-ability problems usually occur when COV,x,,,p exceeds about 10 percent [16] Standard devi-ation in IMEP can be determined by Eq, 5: STD,I M I - C (4) COV„ IMEP STD \ i i I' n-1 ^(IMEP-IMEP)' (5) The presented engine torque, pov\er output, and fuel consumption are the correction corresponding with standard condition according to ISO 3046 standard 2.4 Results and discussion Energy Energy Conversion Conversion Efficiency Efficiency Energy Fraction Energy ( C o n v e r s i o n Conversion Efficiency Elficiency Fraction "- '08 I 10 Corrtcitd Torqut i (Nm) Figure - ECE, 1250 /"/;/;/ Figure - ECE, 2000 rpm Phan Minh Dire, Nsuyen Vdn Ddng Kanit Waltanavichien The energy conversion efficiency and energy conversion efficiency fraction of the test engine, at different torques and speeds was shown in Figure to Figure As can be seen, the energy conversion eficieney, in biodiesel case, was lower at all speeds This deterioration in the energy conversion efficiency was in a range up to about 9% and tended to be higher at lower engine speeds and lower loads Energy t o n v e r s i o n Efficiency Energy Conversion Efficiency Fraction P 077 I „ or To Figure - ECE 2750 rpm ocvcfiive' OCVcflWH' QC2 • ' Ki ;-ta i2H)-z>o - 12a)-30O ^ ^ 1 -* - • — E c e e_3rjB - • - ece~D J ' j o -fOr-CF BO j r s a ^_y»^O.I30 M^ C orr»cr«d 0015 001 59 t QCC5 H ^ l 2CC020O — — —1—» 0015 12a>4X) ã 120208 Đ _ 120308 s Q01 _' oos ' " ' -• • |2ca>2oe E22i2cn>oe - ixco-Toe \ * Figure - COVi^^[:p - 1250 rpm 2CG0700 •- • J i2S)4oe ;|2CCD4DO • Figure - COV,^,[rp - 2000 rpm The CCW in IMEP in the operation with both fuels is comparable, as shown from Figure to Figure The IMEP variation with the both fuels was in the range from 1% to 2% At low speed (1250 rpm), the biodiesel always produced less IMEP variation whilst at high speeds (2000 and 2750 rpm) it produced higher IMEP variation at low load (20 and 40 Nm) but lower variation at higher load (70 Nm) COJdV^B' •1 • J 0015 275020O 27604)0 273>70O 001 J QUi \ 6^ 1 1• ^ " ;' , 2750208 2750458 276&;oe "^ mi Figure - COV^^^p -2750 rpm Normalized Relative Fuel Line Pressure 1250-20-0 1250-30-D 1250-40-D 1250-20-B 1250-30-B 1250-40-B -0.5 -10 10 Crank angle [deg] Figure - Normalized relative fuel line pressure 1250 rpm @ 20, 30, 40 Nm Normalized Relative Fuel Line Pressure 2000-20-D 2000-40-0 2000-70-0 2000-20-B Q 2000-40-B 2000-70-B -15 -10 10 25 Crank angle [deg] Figure -~ Normalized relative fuel line pressure, 2000 rpm @ 20, 40, 70 Nm Comparison in combustion characteristics injection 60 compression ignition engine fuelled N o r m a l i z e d Relative Fuel Line of an did" ^ diesel with diesel and bjoi Pressure 2750-30-D 2750- 40-D 2750-70-D 2750-30-B 2750-40-B 2750-70-B -20 -5 -10 -15 15 10 20 Crank angle [deg] Figure 10 - Normalized relative fuel Une pressure, 2750 rpm (qj 30, 40, 70 Nm StCJi I o ( l i i j e c l i o l i Start of Injection T o r ( I I I t? [ f J n i ] ' " " 9 29 1y 39 T o r q u o [Mm] "d 38/ 'j / ' a SOI 1_^2U D JOI 12-3a t) Figure II -SOI Figure 12 - SOI 2000 rpm 1250 rpm S t a r t of I n j e c t i o n Advances in fuel injection timing were observed as shown from Figure to Figure 10 and from Figure II to Error! Reference source not found The advances were 1.2 to 1.6, 1.4 to 1.8, and 1.6 to 2.4 degree at 1250, 2000, and 2750 rpm, respectively These advances, orresponding with this palmitic biodiesel agreed well with that observed in [15], -4 •ff :• ? ^ , ^ Heat Release Rate TD -a 20 ^ d • a 20 30 /X ^^V ^ a 67 Figure 13 - SOI, 2750 rpm b • 10 3S I SOI - B 50I a D ' • 20 -1 j ^ n -?n ' y^^^%v 20 77 o i\^ 10 S-10 - Heat Release Rate k j o r q u e INrnl unnr • 20 B b B « • 10 20 30 Crank angle [deg] Crank angle [deg] Pressure Rise Rate Pressure Rise Rate ^ 10 20 30 10 20 30 Crank angle [deg] Crank angle [deg] Main Chamber Pressure Main Chamber Pressure Crank angle [deg] Crank angle [deg] I Figure 14 - Heat release rate, pressure rise rate and main combustion chamber pressure, 2000 rpm @ 20 40 70 Nm with with the two fuels Figure 15 - Heat release rate, pressure rise rate, and nuiln chamber pressure, 1250 rp,yj , Phan Minh Dire, Nsuyen Vdn Ddns Kanit Wattanaviehien 61 hb^FfeteaseFfete It is revealed, from Figure 15 to Figure 16, that both the fuels experienced similar heat release rate are profile although there differences in each stage of combustion The chemical and physical processes occurring during 10 20 30 ignition delay period tend to be 4D 50 endothcrmic and cause the heat Oa1