Injection characteristics of a liquid phase lpg injection

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Injection characteristics of a liquid phase lpg injection

  1. 1. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering http://pid.sagepub.com/ A study on the injection characteristics of a liquid-phase liquefied petroleum gas injector for air-fuel ratio control Hansub Sim, Kangyoon Lee, Namhoon Chung and Myoungho Sunwoo Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 2005 219: 1037 DOI: 10.1243/095440705X34621 The online version of this article can be found at: http://pid.sagepub.com/content/219/8/1037 Published by: http://www.sagepublications.com On behalf of: Institution of Mechanical EngineersAdditional services and information for Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering can be found at: Email Alerts: http://pid.sagepub.com/cgi/alerts Subscriptions: http://pid.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav Citations: http://pid.sagepub.com/content/219/8/1037.refs.html >> Version of Record - Aug 1, 2005 What is This? Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  2. 2. 1037A study on the injection characteristics of a liquid-phaseliquefied petroleum gas injector for air–fuel ratio controlHansub Sim1, Kangyoon Lee2*, Namhoon Chung 2, and Myoungho Sunwoo21Department of Automotive Engineering, Jinju National University, Jinju, Republic of Korea2Department of Automotive Engineering, Hanyang University, Seoul, Republic of KoreaThe manuscript was received on 7 September 2004 and was accepted after revision for publication on 23 February 2005.DOI: 10.1243/095440705X34621 Abstract: Liquefied petroleum gas (LPG) is widely used as a gaseous fuel in spark ignition engines because of its considerable advantages over gasoline. However, the LPG engine suffers a torque loss because the vapour-phase LPG displaces a larger volume of air than do gasoline droplets. In order to improve engine power as well as fuel consumption and air–fuel ratio control, considerable research has been devoted to improving the LPG injection system. In the liquid-phase LPG injection systems, the injection rate of an injector is affected by the fuel temperature, injection pressure, and driving voltage. When injection conditions change, the air–fuel ratio should be accurately controlled in order to reduce exhaust emissions. In this study, correction factors for the fuel injection rate are developed on the basis of fuel temperature, injection pressure, and injector driving voltage. A compensation method to control the amount of injected fuel is proposed for a liquid-phase LPG injection control system. The experimental results show that the liquid-phase LPG injection system works well over the entire range of engine speeds and load conditions, and the air–fuel ratio can be accurately controlled by using the proposed compensation algorithm. Keywords: liquefied petroleum gas (LPG), air–fuel ratio, fuel injection rate, port fuel injection, correction factor, compensation algorithm1 INTRODUCTION engine suffers a torque loss because the vapour- phase LPG displaces a larger volume of air thanLiquefied petroleum gas (LPG) is widely used as an do gasoline droplets [2]. Therefore, it is necessaryalternative fuel for automobiles due to its efficient to develop a port fuel injection system for LPG-combustion characteristics and low pollution. LPG fuelled vehicles in order to improve engine power ashas a high octane number, which prevents engine well as to meet the strict emission requirements.knock, and a relatively high hydrogen-to-carbon ratio, Considerable research has been devoted to improvingwhich results in substantial reduction in the emission the LPG injection system [1–4]. The power perform-of carbon dioxide [1]. The LPG-fuelled vehicle, which ance of a liquid-phase LPG injection engine is nearlyis commercially available, uses vapour-phase LPG the same as that of a gasoline engine, and the exhaustas a fuel and has a vapour-mixing system in order emissions are lower [5]. In addition, the heavy-dutyto meter the LPG into the intake air upstream. LPG injection engine, which is a converted heavy-The vapour-mixing system does not provide a fast duty diesel engine, has superior power performanceair–fuel ratio control in transient engine operations to a diesel engine [6]. However, several challengesowing to the relatively long distance between the arise in the liquid-phase LPG injection system. Thefuel mixing system and the lambda sensor installed LPG is stored as a saturated mixture in the vehicle,in the exhaust system. In addition, compared with and the pressure in the LPG tank is the vapourgasoline-powered engines, the vapour-phase LPG pressure corresponding to the fuel temperature. Saturated liquids have a tendency to vaporize with* Corresponding author: Department of Automotive Engineering, any pressure drops or temperature increases. VapourHanyang University, 17 Haendang-dong, Seongdong-gu, Seoul lock can occur in the fuel lines or injectors, and this133-791, Republic of Korea. email: bikeman@ihanyang.ac.kr affects the amount of injected LPG [2]. Icing canD17204 © IMechE 2005 Proc. IMechE Vol. 219 Part D: J. Automobile Engineering Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  3. 3. 1038 Hansub Sim, Kangyoon Lee, Namhoon Chung, and Myoungho Sunwoooccur around the injector tip owing to the heat of Figure 2 shows the saturated vapour pressurevaporization [1]. In order to prevent vapour lock and for various mixtures of butane and propane asicing, high pressure needs to be maintained within a function of temperature. The saturated vapourthe fuel rail, and a thermal insulator can be attached pressure increases with increasing fuel temperatureto the injector tips [5]. The quantity of injected LPG and propane content. Considering that the propanevaries with injection pressure, fuel temperature, and composition of LPG is less than 30 per cent in theinjector driving voltage at constant injection duration. Republic of Korea, the saturated vapour pressure isIn this study, injection characteristics according to less than 0.6 MPa over the temperature range fromchanges in fuel temperature, injection pressure, −20 to 40 °C.and injector driving voltage are examined throughinjection experiments. A compensation algorithm forthe variations in injection conditions is proposed in 3 CHARACTERISTICS OF FUEL INJECTIONorder to control accurately the amount of injectedfuel. This compensation algorithm is verified through 3.1 Fundamentals of fuel injectionengine tests for air–fuel ratio control. Figure 3 shows a cross-sectional view of an LPG injector. The amount of injected fuel through an injector is determined by the well-known orifice flow2 PHYSICAL PROPERTIES OF LPG equation SLPG is composed of butane (C H ) and propane 2r Dp 4 10 m =C A f (3)(C H ). Butane consists of normal butane (n-butane) ˙ 3 8 f D d 1−(A /A )2and isobutane (i-butane). Therefore, the density of d uliquid-phase LPG can be expressed as A B v v v −1 r = p + nb + ib (1) LPG r r r p nb ib Figure 1 shows the density for various blendsof butane and propane as a function of tempera-ture. The density of n-butane varies from 0.528 to0.629 kg/l, and the density of propane varies from0.430 to 0.566 kg/l over the temperature range from−30 to 60 °C. At a fuel temperature of 20 °C, thedensity of liquid-phase LPG varies from 0.501 to0.579 kg/l. The saturated vapour pressure of LPG inthe fuel tank is expressed as [7] p =M p +M p +M p (2) vapour p p nb nb ib ib Fig. 2 Saturated vapour pressure of LPG as a function of fuel temperatureFig. 1 Density of LPG as a function of fuel temperature Fig. 3 Cross-sectional view of an injectorProc. IMechE Vol. 219 Part D: J. Automobile Engineering D17204 © IMechE 2005 Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  4. 4. Injection characteristics of a liquid-phase LPG injector 1039under the assumption of incompressible flow. The decreasing fuel temperature. The rate of change indischarge coefficient is determined from injection the propane temperature correction factor is steeperexperiments of liquid-phase LPG. Therefore, the than that of butane.amount of injected fuel is described as a function ofthe fuel density and the injection pressure difference. 3.3 Influence of the injection pressure The injection pressure, which is the difference3.2 Influence of the fuel temperature between the fuel rail pressure and the intake portThe density of LPG depends on the fuel temperature, pressure, varies with the engine operating conditions.as shown in Fig. 1. The fuel density is largely affected Therefore, the amount of injected fuel fluctuatesby the fuel temperature, which is influenced by according to the injection pressure. In order tothe ambient temperature and heat transfer from the analyse the influence of injection pressure on theengine compartment. As a result, the injected fuel injected fuel quantity, the fuel injection rate at anquantity varies with the fuel temperature. In order to arbitrary injection pressure is expressed asanalyse the influence of fuel temperature on the m =m ˙ ˙ F (7)injected fuel quantity, the fuel injection rate at an f,i f,base f,Dparbitrary fuel temperature is expressed as The pressure correction factor F is defined as f,Dp m =m F (4) S ˙ ˙ Dp f,i f,base f,r(T) F = f,i (8)The basic injection rate m ˙ at a standard tempera- f,Dp Dp f,base f,baseture and pressure difference is defined as Figure 5 shows how the pressure correction factor changes with injection pressure based on three m ˙ f,base =C A 2r D d f,base S DP 1−(A /A )2 d u f,base (5) pressure differences: 0.49, 0.98, and 1.96 MPa. The pressure correction factor increases as the pressureand the temperature correction factor F is defined difference increases. The higher the pressure differ- f,r(T)as ence, the lower is the rate of the change in the pressure correction factor. F f,r(T) = S f,i f,base r r (6) 3.4 Influence of the driving voltage Figure 4 shows the temperature correction factors The driving voltage of an injector creates a magneticfor propane and butane at various fuel temperatures. field in the solenoid. The magnetic field intensityThe temperature correction factor increases with induced in the solenoid is proportional to the driving voltage. Therefore, the amount of injected fuel varies with the driving voltage because of changes in theFig. 4 Temperature correction factor for propane and Fig. 5 Pressure correction factor as a function of butane pressure differenceD17204 © IMechE 2005 Proc. IMechE Vol. 219 Part D: J. Automobile Engineering Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  5. 5. 1040 Hansub Sim, Kangyoon Lee, Namhoon Chung, and Myoungho Sunwooopening delay of an injector. The injected fuel quan- dead time increases at high injection pressures andtities under arbitrary and standard driving voltages low driving voltages [8]. In this study, it is assumedare described as that the dynamic quantity of injected fuel is pro- portional to the injection duration. The amount of m =m ˙ t (9) f,Vi f,Vi f,Vi injected fuel under arbitrary fuel temperatures andand injection pressures can be expressed as m =m ˙ t (10) f,Vbase f,Vbase f,Vbase m =m t ˙ (14) f,i f,i f,irespectively. An equal amount of fuel must beinjected in order to maintain a constant air–fuel ratio and the basic amount of injected fuel also can beunder identical engine operating conditions. As a expressed asresult, the injection duration at an arbitrary drivingvoltage is expressed as m =m ˙ t (15) f,base f,base f,base m ˙ t = f,Vbase t (11) In order to investigate the influence of fuel tem- f,Vi m˙ f,base perature and injection pressure on the injected fuel f,ViIf the voltage correction factor F is defined as quantity, it is further assumed that the injection f,V duration is constant, and that the amount of injected m ˙ fuel depends substantially on the fuel temperature F = f,Vi (12) f,V m ˙ and the injection pressure. From equations (14) and f,Vbase (15), the injected fuel quantity is expressed asthen equation (11) can be rewritten as t m ˙ t = f,base (13) m = f,i m F f,Vi f,i m˙ f,base f,V f,base Figure 6 shows the voltage correction factor as a =F F m (16) f,r(T) f,Dp f,basefunction of driving voltage. The voltage correctionfactor has an increasing tendency according to the Therefore, the ratio of injected fuel quantity can beincrease in the driving voltage. determined as S S3.5 Compensation of the injection quantity m r Dp f,i =F F = f,i f,i (17)The dynamic quantity of injected fuel changes m f,r(T) f,Dp r Dp f,base f,base f,baseirregularly at the beginning of injection because ofthe injection dead time and is mainly affected by the The injected fuel quantity m is proportional to the f,iinjection pressure and battery voltage. The injection square root of the density ratio and the square root of the pressure difference. The air–fuel ratio must be maintained at a constant value under identical engine operating conditions regardless of variations in the fuel temperature and injection pressure. Therefore, an equal amount of fuel must be injected, and the equation m =m (18) f,i f,base is satisfied. Substituting equations (9), (14), and (15) into equation (18), the injection duration is expressed as a function of temperature correction factor and pressure correction factor as t t = f,base (19) f,i F F f,r(T) f,DpFig. 6 Voltage correction factor as a function of driving Considering the effects of the temperature, pressure, voltage and driving voltage on the amount of injectedProc. IMechE Vol. 219 Part D: J. Automobile Engineering D17204 © IMechE 2005 Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  6. 6. Injection characteristics of a liquid-phase LPG injector 1041fuel, the injection duration under arbitrary fuel tem- puter through the engine management system. Theperatures, injection pressures, and injector driving quantity of injected fuel is estimated on the basis ofvoltages can be described as measurements of the air mass flowrate at the inlet of the throttle body and the air–fuel ratio in the t t = f,base (20) exhaust manifold. The fuel temperature and injection f,i F F F f,r(T) f,Dp f,V pressure are changed during engine tests in order to investigate the influence of fuel temperature and injection pressure on the amount of fuel injected.4 EXPERIMENTAL DETAILS Figure 9 is the block diagram of the fuel injection controller which regulates the amount of injectedThe tested engine is a water-cooled Hyundai gasoline fuel.engine with an electronic engine control and a portfuel injection system. The engine specifications aregiven in Table 1, and the tested engine is shown in 5 ANALYSIS OF TEST RESULTSFig. 7. Figure 8 shows a schematic diagram of the experi- 5.1 Preliminary testmental set-up for the fuel injection control system.The injectors used in this study are identical with Various temperatures in the engine are measuredthose of a gasoline engine, and the injection pressure during the test run in order to investigate the effectis regulated by pressurized nitrogen gas. A pressure of the changes in fuel temperature. Figure 10 showstransducer and a thermocouple are installed in the temperature variations of the coolant, fuel, andthe fuel rail to measure the fuel temperature and intake air from engine start-up to the coolant tem-injection pressure. The amount of injected fuel and perature of 90 °C. This test is conducted at steady-ignition timing are controlled by a personal com- state operating conditions at an engine speed of 2000 r/min, an intake manifold absolute pressure of Table 1 Engine specifications 0.05 MPa, a fuel injection pressure of 0.59 MPa, and an injection duration of 4.3 ms. The engine has been Item Specifications soaked at a temperature of 0 °C before this test run. Type In-line four cylinder, DOHC The coolant temperature varies from 0 to 90 °C while Bore×stroke (mm) 75.5×83.5 the fuel temperature varies from 0 to 40 °C. Hence, Swept volume (cm3) 1495 Compression ratio 9.5 : 1 the basic amount of injected fuel is determined Firing order 1–3–4–2 under the conditions of a coolant temperature of Valve timing IVO 5° BTDC 90 °C and a fuel temperature of 40 °C. In addition, the IVC 35° ATDC pressure difference across the injector is 0.64 MPa, EVO 43° BTDC and the injection duration is 4.3 ms. EVC 5° ATDC Figure 11 shows the basic injection duration as a IVO, intake valve open; IVC, intake valve closed; function of the engine speed and the intake manifold EVO, exhaust valve open; EVC, exhaust valve closed; pressure. The tested engine is operated under steady- DOHC, dual overhead cam; BTDC, before top dead centre; ATDC, after top dead centre. state conditions at a coolant temperature of 90 °C, a fuel temperature of 40 °C, and a relative air–fuel ratio of 1.0. The relative air–fuel ratio is defined as the ratio of the actual air–fuel ratio to the stoichiometric ratio [9]. The basic injection duration increases with increasing intake manifold pressure and varies from 7.4 ms at low engine speeds and low engine loads to 10.3 ms at high engine speeds and high engine loads. These results show that the characteristics of injection duration for a liquid-phase LPG injection system are similar to those of a spark ignition engine. 5.2 Fuel temperature influence test Figure 12 shows the estimated and the measured fuel injection rates as functions of fuel temperature. The Fig. 7 Photograph of tested engine measured injection rates are calculated using theD17204 © IMechE 2005 Proc. IMechE Vol. 219 Part D: J. Automobile Engineering Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  7. 7. 1042 Hansub Sim, Kangyoon Lee, Namhoon Chung, and Myoungho Sunwoo Fig. 8 Schematic diagram of experimental setup (EMS, engine management system; CAS, crank- shaft angle sensor; TDC, top dead centre signal; MAP, manifold absolute pressure) Fig. 9 Block diagram of fuel injection controllermeasurements of the air mass flowrate upstream 0 to 40 °C. The estimated temperature correctionof the throttle body and the air–fuel ratio in the factors are determined using equation (6). Theexhaust manifold. The measured injection rates vary measured values are smaller than the estimatedfrom 0.761 to 0.796 g/s and increase with decreasing values. The temperature correction factors and thefuel temperature owing to the fuel density increase. differences between the measured and the estimatedThe lower the fuel temperature, the larger is the dis- values increase according to the decrease in the fuelcrepancy between the estimated and the measured temperature. This feature is a result of the decreaseinjection rates. This feature results from the increase in the injection rate due to the increase in fuelin fuel viscosity at low fuel temperatures. Figure 13 viscosity.shows the estimated and measured temperature The relative air–fuel ratios, with and withoutcorrection factors for fuel temperatures ranging from compensation for the effect of fuel temperature onProc. IMechE Vol. 219 Part D: J. Automobile Engineering D17204 © IMechE 2005 Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  8. 8. Injection characteristics of a liquid-phase LPG injector 1043Fig. 10 Temperature variations during engine warm-up Fig. 12 Injection rate as a function of fuel temperature Fig. 13 Temperature correction factorFig. 11 Basic injection duration (MAP, manifold pressure)injection duration, are plotted in Fig. 14. With tem-perature compensation, the relative air–fuel ratio ismaintained at around 1.0 with an error of 1 per cent.Without temperature compensation, the relative air–fuel ratio varies from 0.9 to 1.0. Consequently, it isappropriate to introduce the temperature correctionfactor in order to compensate for the changes in fueltemperature.5.3 Injection pressure influence testThe injected fuel quantity varies with the injectionpressure. This test is conducted under steady-state Fig. 14 Relative air–fuel ratios with and withoutoperating conditions at an engine speed of 2000 r/min, compensationD17204 © IMechE 2005 Proc. IMechE Vol. 219 Part D: J. Automobile Engineering Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  9. 9. 1044 Hansub Sim, Kangyoon Lee, Namhoon Chung, and Myoungho Sunwooan intake manifold absolute pressure of 0.05 MPa,a coolant temperature of 90 °C, and constant fueltemperature of 40 °C. The basic injection pressureis 0.59 MPa, and the injection duration is 4.3 ms.Injection pressure is controlled by nitrogen gasthrough a pressure regulator. Figure 15 shows the estimated and the measuredfuel injection rates as functions of injection pressure.The measured injection rates vary from 0.690 to0.973 g/s and increase with increasing injectionpressure. At injection pressures above 0.59 MPa, themeasured values are smaller than the estimatedvalues, and the difference becomes larger. This is aresult of the increase in the opening delay time ofthe injector. Figure 15 also shows the pressure correction factors Fig. 16 Relative air–fuel ratios with and withoutcalculated using the injection rate at an arbitrary compensationinjection pressure and the basic injection rate. Theestimated pressure correction factors are calculatedfrom equation (8). The pressure correction factor and 5.4 Evaluation testthe difference between the measured and estimatedvalues increase according to the increase in injection In order to validate the developed feedforward com-pressure. The measured values are smaller than the pensation algorithm, the tested engine is operatedestimated values above the basic injection pressure. at a constant-speed mode and at a constant-torqueThis feature also results from the increase in the mode respectively. The relative air–fuel ratio isopening delay time. measured using a lambda sensor. Figure 17 shows Figure 16 shows the relative air–fuel ratio as a the throttle movements used in the tests and thefunction of injection pressure with and without corresponding response of the intake manifoldcompensation for the effect of injection pressure on pressure. The injection control algorithms used forinjection duration. With pressure compensation, the the evaluation tests are the feedforward compen-relative air–fuel ratio is maintained at around 1.0 sation algorithms proposed in this study and awith an error of 1 per cent. Without pressure com- typical feedback air–fuel ratio control using a lambdapensation, the relative air–fuel ratio varies from 0.76 sensor.to 1.07. Therefore, it is advantageous to introduce the Figures 18 and 19 show the relative air–fuel ratiospressure correction factor in order to compensate for at constant-speed mode and constant-torque modethe changes in injection pressure.Fig. 15 Fuel injection rate and pressure correction Fig. 17 The throttle movement and the intake manifold factor as functions of injection pressure pressureProc. IMechE Vol. 219 Part D: J. Automobile Engineering D17204 © IMechE 2005 Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  10. 10. Injection characteristics of a liquid-phase LPG injector 1045 ratios at constant load torque and constant engine speed are similar. Therefore, the relative air–fuel ratio can be maintained at the target value of 1.0 with an error of 2 per cent by using the feedforward compen- sation algorithm for steady-state engine operations. 6 CONCLUSIONS There are many factors that influence the injection characteristics. In this study, three factors that influence the amount of injected fuel in a liquid- phase LPG engine are investigated. These factors are the fuel temperature, injection pressure, and injectorFig. 18 Air–fuel ratio at constant engine speed driving voltage. In order to compensate for variations (2000 r/min) in these factors, correction factors are proposed and verified through engine tests. The following con- clusions can be drawn from the validation tests of the compensation algorithms. 1. The injection conditions that influence the injection rate are investigated and mathematically formulated to implement an air–fuel ratio con- troller for a liquid-phase LPG injection engine. 2. A temperature correction factor is proposed to compensate for the effect of fuel temperature on injected fuel quantity and verified through engine tests. The relative air–fuel ratio using the non- compensated algorithm is 0.9 at a fuel tempera- ture of 0 °C while the relative air–fuel ratio using the temperature-compensated algorithm is 1.0. 3. In order to compensate for the effect of injection pressure on injected fuel quantity, a pressure correction factor is proposed. This factor is veri- fied through engine tests. The relative air–fuel ratioFig. 19 Air–fuel ratio at constant load torque (49 N m) is maintained at around 1.0 with pressure com- pensation while the relative air–fuel ratio varies from 0.76 to 1.07 without pressure compensation.respectively. The dotted curves represent the tested 4. A voltage correction factor is proposed andresult of only the feedforward algorithm, and the applied to the fuel injection controller in order tosolid curves represent the result of both the feed- compensate for the variations in battery voltage.forward plus feedback control. In Fig. 18, excursions This factor varies from 0.78 to 1.12 in the drivingin the relative air–fuel ratio are observed at the voltage range 9–15 V.moment of throttle transients, and the lambda spikes 5. The feedforward control scheme to compensateof the feedforward compensation are higher than for the changes in injection conditions is appliedthose of the feedforward plus feedback control by and evaluated during the engine experiment.3–7 per cent. Meanwhile the relative air–fuel ratio is 6. The relative air–fuel ratios for the feedforwardmaintained at the target value of 1.0 with an error of compensation algorithm and feedforward plus2 per cent for both control cases with a constant feedback control algorithm have values of 1.0throttle input. In Fig. 19, the lambda spikes of the with an error of 2 per cent except for fast throttlefeedforward compensation are higher than those of transients. In order to reduce the lambda spikesthe feedforward plus feedback control by 1 per cent. during fast throttle movements, conventional feed-During constant throttle input, the relative air–fuel back control techniques should be incorporated.D17204 © IMechE 2005 Proc. IMechE Vol. 219 Part D: J. Automobile Engineering Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012
  11. 11. 1046 Hansub Sim, Kangyoon Lee, Namhoon Chung, and Myoungho SunwooACKNOWLEDGEMENTS 7 The Korean Institute of Industrial Educators LP Gas Technology, 1979 (Semunsa, Seoul). 8 Song, C. S., Lee, Y. J., and You, S. J. A study on theThis research is supported in part by MOST (Ministry analysis of dynamic characteristics of the solenoidof Science and Technology) under the National valve of automotive transmission. J. Korean Soc.Research Laboratory (NRL) grant MI-0203-00-0058- Precision Engng, 1995, 12(8), 122–130.02-J00-00-031-00, and part of the project ‘Develop- 9 Heywood, J. B. Internal Combustion Engine Funda-ment of Partial Zero Emission Technology for Future mentals, 1988 (McGraw-Hill, New York).Vehicle’, and we are grateful for their financialsupport. APPENDIX NotationREFERENCES A area (m2) C discharge coefficient1 Sierens, R. An experimental and theoretical study of D F compensation factor liquid LPG injection. SAE paper 922363, 1992.2 Lutz, B. R., Stanglmaier, R. H., Matthews, R. D., m mass (kg) Cohen, J. T., and Wicker, R. The effects of fuel com- m˙ mass flowrate (g/s) position, system design, and operating conditions on M mole fraction in-system vaporization and hot start of a liquid-phase p pressure (MPa) LPG injection system. SAE paper 981388, 1998. t time (s)3 Kim, J. C., Cho, G. B., and Jeong, D. S. Characteristics T temperature (°C) of spray and combustion in direct injection LPG V voltage (V) engine according to combustion chamber shapes. In Spring Conference Proceedings of the Korean Society r density (kg/l) of Automotive Engineers, 2000, Vol. I, pp. 73–78.4 Sim, H. S., Lee, K. Y., Chung, N. H., and Sunwoo, M. v mass fraction Experimental analysis of a liquid-phase liquefied petroleum gas injector for a heavy-duty engine. Proc. Subscripts Instn Mech. Engrs, Part D: J. Automobile Engineering, b butane 2004, 218, 719–727. base standard conditions or states5 Vialle Alternative Fuel Systems BV, 2001, http:// d downstream www.vialle.nl/.6 Han, B. J., Kim, C. U., Kang, K. Y., and Lee, C. S. The f fuel effect of intake ratios on combustion performance in i arbitrary conditions or states a heavy-duty LPG engine. Trans. Korean Soc. Automot. p propane Engrs, 2001, 9(5), 46–53. u upstreamProc. IMechE Vol. 219 Part D: J. Automobile Engineering D17204 © IMechE 2005 Downloaded from pid.sagepub.com at INDIAN INST OF TECHNOLOGY on April 22, 2012

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