Investigation of Diesel Engine Performance Based on Simulation

Transcription

1 American Journal o Applied Sciences 5 (): 1-17, 8 ISSN Science Publications Investigation o Diesel Engine Perormance Based on Simulation Semin, Rosli Abu Bakar, Abdul Rahim Ismail Automotive Focus Group, Faculty o Mechanical Engineering, University Malaysia Pahang, Locked Bag 1, 5 Kuantan, Pahang, Malaysia Abstract: The single cylinder modeling and simulation or our-stroke direct-injection diesel engine requires the use o advanced analysis and development tools to carry out o perormance the diesel engine model. The simulation and computational development o modeling or the research use the commercial o GT-SUITE. sotware. In this research, the one dimensional modeling o single cylinder or our-stroke direct-injection diesel engine developed. The analysis o the model is combustion perormance process in the engine cylinder. The model simulation covers the ull engine cycle consisting o intake, compression, power and exhaust. In this model it can to know the diesel engine perormance eect with simulation and modeling in any speeds (rpm) parameters. The perormance trend o the diesel engine model developed result o this model based on the theoretical and computational model shows in graphics in the paper. Keywords: Diesel engines, perormance, simulation INTRODUCTION The diesel engines is a type o internal combustion engine, more speciically it is a compression ignition engine, in which the uel is ignited solely by the high temperature created by compression o the air-uel mixture [1, 5,, 9]. The engine operates using the diesel cycle. Unlike a gasoline engine, the incoming air is not throttled, so the engine would over-speed i this was not done. Older injection systems were driven by a gear system rom the engine [3, 5]. A our-stroke direct-injection diesel engine typical was measured and modeling in this paper. The GT- POWER computational model shown is one-cylinder diesel engine. GT-POWER is the leading engine simulation tool used by engine and vehicle makers and suppliers and is suitable or analysis o a wide range o engine issues []. GT-POWER is designed or steadystate and transient simulation and can be used or analyses o engine and powertrain control. It is applicable to all type o internal combustion engines and provides the user with many components to model any advanced concept. GT-POWER is based on onedimensional gas dynamics, representing the low and heat transer in the piping and in the other component o an engine system. GT-POWER is one dimensional model rom GT-SUITE sotware applications, see Riegler [8] and Bakar []. The details o the diesel engine design vary signiicantly over the engine perormance and size range. In particular, dierent combustion chamber geometries and uel injection characteristics are required to deal eectively with major diesel engine design problem achieving suiciently rapid uel-air mixing rates to complete the uel-burning process in the time available [9, 1, 11]. A wide variety o inlet port geometries, cylinder head and piston shapes, and uelinjection patterns are used to accomplish this over the diesel size range. The engine ratings usually indicate the highest power at which manuacturer expect their products to give satisactory o power, economy, reliability and durability under service conditions. Maximum torque and the speed at which it is achieved, is usually given also. According to Heywood [1] and Ganesan [7], that the importance o the diesel engine perormance parameters are geometrical properties, the term o eiciency and other related engine perormance parameters. The engine eiciencies are indicated thermal eiciency, brake thermal eiciency, mechanical eiciency, volumetric eiciency and relative eiciency. The other related engine perormance parameters are mean eective pressure, mean piston speed, speciic power output, speciic uel consumption, intake valve mach index, uel-air/air-uel ratio and the uel caloriic value. Corresponding Author: Semin, Automotive Focus Group, Faculty o Mechanical Engineering, University Malaysia Pahang, Locked Bag 1, MEC City Gambang, 5 Kuantan, Pahang, Malaysia, Tel: , Fax:

2 Am. J. Applied Sci., 5 (): 1-17, 8 In the diesel engine geometries design, diesel engine compression ratio is maximum cylinder volume or the displaced volume or swept (V d ) and clearance volume (V c ) divided by minimum cylinder volume (V c ). The diesel engine compression ratio as below: V + V d c c = (1) Vc r And the power delivered by the diesel engine and absorbed by the dynamometer is the product o torque and angular speed. Diesel engine power deinition as: P = NT () Every engines eiciencies deined by Ganesan [7]. Indicated thermal eiciency ( ith ) is the ratio o energy (E) in the indicated power (ip) to the input uel energy. Brake thermal eiciency ( bth ) is the ratio o energy in the brake power (bp), Mechanical eiciency ( m ) is deined as the ratio o brake power (bp) or delivered power to the indicated power (ip) or power provided to the piston and it can also be deined as the ratio o the brake thermal eiciency to the indicated thermal eiciency. Relative eiciency or eiciency ratio ( rel ) is the ratio o thermal eiciency o an actual cycle to that o the ideal cycle, the eiciency ratio is a very useul criteria which indicates the degree o development o the engine. The one o the very important parameters which decides the perormance o our-stroke engines is volumetric eiciency ( v ), where our-stroke engines have distinct suction stroke and thereore the volumetric eiciency indicates the breathing ability o the engine. The volumetric eiciency is the volume low rate o air into the intake system divided by the rate at which the volume is displaced by the system. The normal range o volumetric eiciency at ull throttle or SI engines is 8% to 85% and or CI engines is 85% to 9 %, Ganesan [7]. ith = ip E (3) bp bth = () E m = bp ip (5). ma v = () ρ V N / a disp Actual thermal eiciency = (7) rel Air - standard eiciency The other related engine perormance was deined by Heywood [1], Kowalewicz [5], Stone [] and Ganesan [7]. Mean eective pressure (mep) where n R is the number o crank revolutions or each power stroke per cylinder (two or our-stroke, one or two-stroke cycles) as: mep PnR V N = (8) d The measure o an engine s eiciency which will be called the uel conversion eiciency is given by Heywood [1] : W m Q HV ( Pn / N) c n = = = P R ( m nr / N) QHV m QHV (9) Speciic uel consumption as: m sc = (1) P In engine testing, both the air mass low rate m a and the uel mass low rate m are normally measured. The ratio o these low rates is useul in deining engine operating conditions are air/uel ratio (A/F) and uel/air ratio (F/A). The ollowing relationships between diesel engine perormance parameters can be developed. For power P: ma NQHV P = (11) n R v NVdQHV ρ a, i P = (1) For torque T : vvdqhv ρ a, i T = (13) π For mean eective pressure: 11

3 Am. J. Applied Sci., 5 (): 1-17, 8 mep = Q ρ ( F / ) (1) v HV a, i A The speciic power or the power per unit piston area is a measure o the engine designer s success in using the available piston area regardless o cylinder size. The speciic power as below: P A p v NLQHV ρ a, i = (15) Mean piston speed: P A p N S v p Q HV ρ, a i = (1) The speciic power is thus proportional to the product o mean eective pressure and mean piston speed [1]. These relationship illustrate the direct importance to engine perormance o high uel conversion eiciency, high volumetric eiciency, increasing the output o a given displacement engine by increasing the inlet air density, maximum uel/air ratio that can be useul burned in the engine and high mean piston speed. MATERIALS AND METHODS The development o the single cylinder modeling and simulation or our-stroke direct-injection (DI) diesel engine was presented in this paper. The speciication o the selected diesel engine model was presented in Table 1. Table 1: Speciication o the diesel engine Engine Parameters Value Bore (mm) 8. Stroke (mm) 7. Displacement (cc) 7. Number o cylinder 1 Connecting rod length (mm) Piston pin oset (mm) 1. Intake valve open ( CA) 395 Intake valve close ( CA) 53 Exhaust valve open ( CA) 17 Exhaust valve close ( CA) 8 Maximum intake valve open (mm) 7.95 Maximum exhaust valve open (mm) 7.95 Valve lit periodicity (deg) 3 The irst step to develop the GT-POWER modeling is open the diesel engine to measure the engine components size to input to the GT-POWER library o the all engine components data. To Create the GT- POWER model, select Window and then Tile With Template Library rom the menu. This will place the GT-POWER template library on the let hand side o the screen. The template library contains all o the available templates that can be used in GT-POWER. Some o these templates (those that will be needed in the project) need to be copied into the project beore they can be used to create objects and parts. For the purpose o this model, click on the icons listed and drag them rom the template library into the project library. Some o these are templates and some are objects that have already been deined and included in the GT- POWER template library. The engine in this model was breakdown to the tree system, there are intake system, engine cylinder and uel injection system, and exhaust system. In the selected diesel engine, the intake system its have any component, size and dierent data. The system was started rom environment till the intake valve. All o the intake system components in the GT-POWER model are environment, intrunnerairilter, air ilter, intrunner, inport, intvalve. Fig. 1 shows the intake system components. Every components in this system they need any data to complete the data orm and running the model. Engine cylinder and uel injection system is ocused in engine cylinder perormance were support diesel uel rom uel injection system, resh air intake system and exhaust gas to exhaust system. There are any components in the engine cylinder and uel injection system in the diesel engine, but the basic or all diesel engines is the same component. The components, size and data must be record and inserted to the GT-POWER orm. All o the engine cylinder and uel injection system component are injector, cylinder and engine. Fig. shows the engine cylinder and uel injection system components. Every components in this system they need any data to complete the data orm and running the model. The last system in the diesel engine is the exhaust system. In this system was started rom exhaust valve and inished in the environment. The GT-POWER components in the exhaust system are exhvalve, exhport, exhrunner, muler, exhrunnerexit, and environment. Fig. 3 shows the exhaust system components. Every components in this system they need any data to complete the data orm and running the model. 1

4 Am. J. Applied Sci., 5 (): 1-17, 8 Fig. 1: Intake system components Fig. : Engine cylinder & uel injection components rod length, pin oset, piston TDC clearance height, head bowl geometry, piston area and head area. Data in intake and exhaust system is geometry o all components. Data in throttles are throttle location and discharge coeicients versus throttle angle in both low directions. Data in uel injectors are location and number o injectors, number o nozzle holes and nozzle diameter, injection rate, uel type and LHV. Data in intake and exhaust valves are valve diameter, lit proile, discharge coeicient, valve lash. Data in ambient state are pressure, temperature and humidity. Perormance data can be very useul when tuning a model ater it has been built. Fig. 3: Exhaust system components Ater inished the every system model in the diesel engine system developed, its can to develop the diesel engine modeling using GT-POWER model. The diesel engine modeling using GT-POWER computational model, there are the intake system model, engine cylinder and uel injection system model, and exhaust system model. The intake system and the engine cylinder and uel injection system were connected in the intvalve in the intake system and cylinder in the engine cylinder and uel injection system. The engine cylinder and uel injection system connected to the exhaust system in the cylinder in the engine cylinder and uel injection system with exhvalve in the exhaust, shown in Fig.. All o this diesel engine components connected by oriiceconn. I the work was inish its can developed the diesel engine modeling using GT- POWER sotware. The Fig. 5 shows the diesel engine modeling using GT-POWER modeling. Data needed or building an engine model. A list o inormation that is needed to build a model in GT- POWER is included in library. Not every item will be needed or all models, and sometimes additional inormation will be needed, but the list is generally a good starting point. I the model is being built at an early design stage, determining optimal values or some o the items listed may be the purpose o the simulation. I this is the case, those particular attributes should be deined as parameters and run or a series o cases to determine an optimal value. Data in engine characteristics are compression ratio, iring order, inline or V coniguration, V-angle (optional), or stroke. Data in cylinder geometry are bore, stroke, connecting Fig. : Single-cylinder Diesel engine components Beore running the model the preparing to run the model simulation needed. Preparing to run the model simulation are review the completed model, run setup, case setup, plot requests and plot setup. All o the parameters in the model will be listed automatically in the case setup and each one must be deined or irst case o the simulation. Frequently, computation time can be reduced in steady state simulations by planning the order o the simulations and utilizing the initialization state in run setup. Cycle and/or time plots may be requested by selecting the appropriate plot rom the plot options older within each part. All plots requested in individual parts will be stored regardless o whether the user chooses to use plot setup. I the model has been prepared or simulation, the GT-POWER simulation may be started and this will start the simulation running. A window will he progress o simulation in the orm o scrolling text. Once the input has been read successully, the simulations will begin, and occasional reports o the progress will be given. 13

5 Am. J. Applied Sci., 5 (): 1-17, 8 Fig. : Exhaust valve lit Fig. 5: GT-POWER single-cylinder diesel engine RESULTS AND DISCUSSION Whenever a simulation is run, GT-SUITE produces several output iles that contain simulation results in various ormats. Most o the output is available in the post-processing application GT-POST. GT-POST is powerul tool that can be used to view animation and order analysis output []. Ater the simulations are inished, report tables that summarize the simulations can be produced. These reports contain important inormation about the simulation and simulation result in a tabular orm. The computational simulation o the engine model result is inormed the engine perormance. The running simulation result is all o the engine perormance data with the dierent engine speeds (rpm). This model was running on any dierent speed in rpm, there are,,, 8, 1, 1, 1, 1, 18,,,,, 8, 3, 3, 3, 3, 38,. In this paper the simulation result o engine perormance are exhaust valve lit, intake valve lit, air-uel ratio, indicated power (ip), brake power (bp), brake mean eective pressure (bmep), indicated mean eective pressure (imep), engine cylinder pressure, brake torque (bt), indicated torque (it), indicated speciic uel consumption (isc), brake speciic uel consumption (bsc). Fig. 7: Mass low rate in exhaust valve Fig. 8: Intake valve lit 1

6 Am. J. Applied Sci., 5 (): 1-17, 8 INDICATED POWER (kw) Indicated Power (kw) Fig. 11: Indicated power o engine model Fig. 9: Mass low rate in intake valve In the GT-POWER computational model the exhaust valve perormance is shows in Fig., in the engine model the exhaust valve open start rom 17 on crank angle degree and close in 8 on crank angle degree. The maximum exhaust valve lit o the model is 7.95mm. The intake valve open shown in Fig. 8, the intake valve start rom 395 on crank angle degree and close in 53 on crank angle degree. The maximum intake valve lit o the model is the same with exhaust valve lit 7.95mm. The mass low rate perormance o the intake valve and exhaust valve was shows in Fig. 7 and Fig. 9. The GT-POWER model simulation data output and igure o the intake and exhaust valve is the same with the original engine data. A/F Ratio AIR-FUEL RATIO Indicated power o an engine is tells about the health o the engine and also gives an indication regarding the conversion o chemical energy in the uel into heat energy. Indicated power is an important variable because it is the potential output o the cycle. Thereore, to justiy the measurement o indicated power, it must be more accurate than motoring and other indirect methods o measuring riction power. For obtaining indicated power the cycle pressure must be determined as a unction o cylinder volume. It may be noted that it is o no use to determine pressure accurately unless volume or crank angle can be accurately measured. In this model the engine indicated power perormance on variation speed shows in Fig. 11. The perormance o indicated power the engine model is with variation on engine speed. On engine speed is rpm the indicated power o engine is low, and i the engine speed is increase over than rpm the indicated power is increase until in 3 rpm. Ater the engine speed is over than 3 rpm the indicated power is decrease and go to down. The engine indicated power model lowest is.1335 kw on minimum engine speed (rpm) in rpm and the maximum indicated power o the engine model is 5.78 kw on engine speed is 3 rpm and ater the engine speed is up o 3 rpm the indicated power is decrease and go to down. BRAKE POWER (kw) Fig. 1: Air-uel ratio The air-uel ratio o the engine model perormance shows in Fig. 1 above, the air-uel ratio is high in the engine speed is low and the air-uel ratio is low in the engine speed is high. The highest o the air-uel ratio is 1.77 on engine speed 1 rpm and the lowest o the air-uel ratio is 7.53 on engine speed rpm. The trend o air-uel ratio is decrease i the engine speed is increase. Fig. 1: Brake power o engine model 15 Brake Power (kw)

7 Am. J. Applied Sci., 5 (): 1-17, 8 The brake power o the engine model is shows in Fig. 1. Brake power is usually measured by attaching a power absorption device to the drive-shat o the engine. Such a device sets up measurable orces counteracting the orces delivered by the engine, and the determined value o these measured orces is indicative o the orces being delivered. The perormance o the engine brake power model trend is the same with the engine indicated power. The brake power o engine lowest is.85 kw on minimum engine speed (rpm) in rpm and ater that i the engine speed is increase the brake power is increase too until on engine speed 3rpm. The maximum brake power o the engine model is.3139 kw on engine speed is 3 rpm and ater the engine speed is up o 3 rpm the brake power is decrease and go to down. The Fig. 13, Fig. 1 and Fig. 15 shows the indicated mean eective pressure, the brake mean eective pressure and pressure in engine cylinder o the diesel engine model simulation. Mean eective pressure is deined as that hypothetical constant pressure acting on the piston during its expansion stroke producing the same work output as that rom the actual cycle. The constant depends on the mechanism used to get the indicator diagram and has the units is bar/m. The mean eective pressure is quite oten used to calculate the perormance o an internal combustion engine. I the work output is indicated output then it is called indicated mean eect pressure. The highest pressure o the engine cylinder pressure is in TDCF, because this step is need the highest pressure to combustion. The highest pressure is 7.5 bar ater ignition on.9 crank angle degree. The highest indicated mean eective pressure and brake mean eective pressure is bar and. bar on both 8 rpm engine speed. Beore the engine speed is 8 rpm the imep and bmep is low and increase until on 8 rpm. Ater the engine speed is over than 8 rpm the imep and bmep is go to down. Pressure (Bar) BRAKE MEAN EFFECTIVE PRESSURE (Bar) Fig. 15: Brake mean eective pressure o model Fig. 15: Pressure in cylinder o engine model Brake Torque (N-m) BRAKE TORQUE (N-m) IMEP (Bar) INDICATED MEAN EFFECTIVE PRESSURE (Bar) Fig. 13: Indicated mean eective pressure o model 1 Fig. 1: Brake torque o engine model Engine torque in experiment is normally measured with a dynamometer. The engine torque is a measure o san engine s ability to do work and power is the rate at which work is done. In this model simulation the torque o the engine shows in Fig. 1 as a brake torque and Fig. 17 as a indicated torque. The maximum brake torque and indicated torque is in 8 rpm o engine speed. Beore the engine speed is 8 rpm brake torque and indicated torque is low and increase until on 8 rpm. Ater the engine speed is over than 8 rpm the brake torque and the indicated torque is go to down.

8 Am. J. Applied Sci., 5 (): 1-17, 8 IT (N-m) INDICATED TORQUE (N-m) Fig. 17: Indicated torque o engine model BRAKE SPECIFIC FUEL CONSUMPTION modeling brake torque maximum is 1.3 N-m in 8 rpm and indicated torque maximum is N- m in 8 rpm. In the engine speed is 8 rpm, the engine model shown the lowest o the brake speciic uel consumption and the indicated speciic uel consumption. To validate the GT-POWER model result must be compared with the experiment or theoretically. ACKNOWLEDGEMENTS We would like to acknowledge University Malaysia Pahang or providing the ellowship to support this research project. BSFC Fig. 18: Brake speciic uel consumption o model Speciic Fuel Consumption INDICATED SPECIFIC FUEL CONSUMPTION Fig. 19: Indicated speciic uel consumption o model The brake speciic uel consumption and indicated speciic uel consumption is shown in Fig. 18 and Fig. 19. The model shown that the brake and indicated speciic uel consumption is very high i the engine speed is low until in 1 rpm and high i the speed is over than 8 rpm. The model simulation result shown that the indicated and brake speciic uel consumption is minimum and economic on 8 rpm. CONCLUSION On the 7 cc o the single cylinder our-stroke direct injection diesel engine modeling shown that the highest brake power is.31 kw and indicator power is 5.75 kw in 3 rpm o engine speed. The engine 17 REFERENCES 1. Heywood, J.B., Internal Combustion Engine Fundamentals, McGraw-Hill, Singapore.. Gamma Technologies,. GT-POWER User s Manual Version.1, Gamma Technologies Inc. 3. Bakar, R.A., Semin., Ismail, A.R., 7. The Internal Combustion Engine Diversiication Technology And Fuel Research or The Future: A Review, AEESEAP Regional Symposium 7, Kuala Lumpur, Malaysia.. Bakar, R.A.; Semin.; Ismail, A.R., 7. Eect o Engine Perormance or Four-Stroke Diesel Engine Using Simulation, Proceeding o The 5 th International Conerence On Numerical Analysis in Engineering, Padang, Indonesia. 5. Kowalewicz, Andrzej, 198. Combustion System o High-Speed Piston I.C. Engines, Wydawnictwa Komunikacji i Lacznosci, Warszawa.. Stone. Richard, Introduction to Internal Combustion Engines-nd Edition, SAE Inc., USA. 7. Ganesan, V., Internal Combustion Engines Second Edition, Tata McGraw-Hill, New Delhi. 8. Riegler, U.G., Bargende, M.,. Direct coupled 1D/3D-CFD-computation (GT-Power/Star-CD) o the low in the switch-over intake system o an 8- cylinder SI engine with external exhaust gas recirculation, SAE Paper Baumgarter, Carsten.,. Mixture Formation in Internal Combustion Engines, Spinger, Berlin. 1. Baik, Seunghyun., 1. Development o Micro- Diesel Injector Nozzles Via MEMS Technology and Eects on Spray Characteristics, PhD Dissertation, Univ. o Wisconsin-Madison, USA. 11. Strauss, S., Zeng, Y.,. The Eect o Fuel Spray Momentum on Perormance and Emissions o Direct-Injected Two-Stroke Engines, SAE Paper,