Motorlu taşıtlarda bazı termik ve dinamik parametrelerin incelenmesi

Abstract

-Ml- The driving cycle named `A comparative Driving Cycle for City Passenger Buses ` considers a distance of BOO meters between two bus stations. The -fuel consumption of the bus for 10 bus stations is calculated. Then the distance between the bus stations is extended to 1000 meters and the fuel consumption is calculated for S bus station. The total travelling distance is constant for both situations. Thus the fuel consumption difference gives the fuel economy for the constant distance that is SOOO meters. If the model vehicle does not carry any extra load, there is no slope and the vehicle travels on a paved road (asphalt), the result is of 4.5 V. percent fuel economy. Since no power is transmitted to the tires of the vehicle, the effective engine power and thus the brake mean effective pressure can not be determined. So that the specific fuel consumption of the vehicle, when the clutch pedal is pressed or when no power is transmitted to the tires of the vehicle from its engine can not be determined by using the performance curves. In such cases the fuel consumption of the vehicle is calculated by means of idling fuel cosumption of the engine. If consumption is directly equal to the idling fuel consumtion. However, vhen the engine rate is different to the idling engine rate, the fuel consumption is different from the idling fuel consumption too. The fuel consumption in these situations is calculated by the equation m =m _.n /n,_, where `m _,` is the idling fuel *?> y yR e eR yR a consumption, `n _` is the idling engine rate and `n ` is the engine rate just before the clutc pedal is pressed. The computer program includes 13 subroutines. When the program is run, a selection menu is offered and according to the selection some of the subroutines are used.- XI ı- An important point to be emphasized is that the performance curves given in this study are drawn aproximately by means of the full throttle curves. The real performance curves of the model engine are supposed to be different. The computer program submitted in this study may be used to optimize the behaviour of the driver by adding some subroutines or making some reorganizations. For instance if the distance and the time are certain, the behaviour of the driver to minimize the fuel consumption can be determined. However, this topic does not exist in this study.

-vii- SUMMARY Unt.il the early seventiesit was not o-f such a great çare that energy demand would increase exponentially. Petroleum eri sis that took placein 1973 has updated the discussions about energy economy. The fuel consumption of a vehicle with a Internal Combustion Engine depends on an efficiency o-f the engine, the behaviour of the driver and the resistance forces acting on it. in this study that consists of three partsş a computer program to çalçulate the fuel consumption of a vehicle with an I.C. Engine has been prepared. General parameters related with the I.C. Engines and vehicles are explained in the first par t. The suni of the slope, aerodynamic, rolling and accelera- tion forces give the total resistance force acting on the vehicle. Reducing these resistance forces is of a vital importance to decrease the fuel consumption of a vehicle. For instance if the aerodynamic resistance is reduced by two thirds, about 1O % percent fuel economy can be expected. Reducing the slope to the half can lessen the fuel consumption by l O 7. percent. Rolling resistance reduced by two thirds may supply about 5 7. percent fuel economy. Measuring the fuel consumption of a vehicle requires quite high expenses. Instrumentation of laboratory in order to 4ı make fuel consumption measurements costs about 150,000 $. Further, just öne measurement in such a laboratory costs about 500 *.-viii- The term system simulation means observing a synthetic system that i mi t ateş the performance of a real system and simulation iB used when it is not possible ör not economical to observe the real system. it is much more economical to caluclate the fuel consumption of a vehicle by employing system simulation due to the high expences to measure it. A hartnare that costs about 1,20O * is enough to compute the.fuel comsumption. Another situation wher system simulation is employed is where the system is stili in the design state and no real system yet exist. The per-formance ör control o-f the system at off-design may be of interest, so the planned system is `run` in advice of its construction. This gives the advantage to test an imaginary vehicle. Also, the effect of changing some elements of the vehicle such as gears ör resistance forces may be observed. Mathematical model that is used to calculate the fuel consumption, in case velocity and gear relations are specified, is formed in the second chapter of this study. So that, first the performance curves are modeled. Although a l ine of constant brake specific fuel consumption is simi lar to an ellipse, equation of ellipse can not be used to model these lines. The development of numerical computers gives the advantage to fit some curves that are difficult to be expressed analytically. Polynomial Representation, Lagrange Interpolation and Newton-Gregory Forward methods that may be used to fit polinomals in two dimensions are studied in chapter 2.1. in örder to calculate brake mean specific fuel consumption, performance curves are modeled such that brake % mean effective pressure (pme) and effective rate of the engine (ne) are the variables. Newton-Gregory Forward Polynornîal interpolation method is used in main computer program.~İM - Since modeling performance cursev requires a lot of data, using the genaral form of these methods causes the polynomials to be of extremely high degrees. The higher the degree of the polynomial, the larger the errors and the longer the time needed to çalçul ate the brake mean specific fuel consumption. Using less data will reduce the errors and shorten the time to interpolate. in this study it has been decided to use an area of data consisting of three rows and four columns. The other data is not considered at this moment. This is achieved by a logic to select the area of data to be used. Using lower step size will alsa reduce the errors. Errors increase to the power of the degree of the step size. The logic mentioned above has been applied only in Newton-Gregory Forward polynomial interpolation certainly it could be applied to the other methods. Driving cycles are experiments which give the advantage to the vehicles to be compared with their fuel consumption ör exaust emission. Simulating the driving cycles allows them to be imitated by computers. in the third capter Europian Driving Cycle has been explained and it is ernphasized that this driving cycle is favorable för automobiles but not för vehicles such as buses and trucks. So that Modified Europian Driving Cycle is submitted in this study. in addition, thinhing that it would be an eMample to the erase that this computer program can be used, A Comparative Driving Cycle för City Passenger Buses is also presented. However, it should be pointed out that there is no claim that this cycles fits the real driving cycles of the city buses. An accelerating vehicle consumes some additional fuel. in such situations, because the engine *works closer to full throttle conditions the fuel-air miMtüre enjected into the cylinder has to be rich. That means a bad fuel economy. -.-x - Çal çul at i ng the acceleration resistance -force requires knowledge about the moment o-f inertia of the engine, the transmission system and the tires. it is difffcult to çal çul at e these moments o-f inertia. it has been tried to calculate soma of these values approMİmately. Power taken from the engine o-f a travelling vehicle is calculated by means of resistance forces and it is porved that the ef-fective power, the ef-fective torque ör the transmission efficiency of- the vehicle can be stated by a second degree equation depending on the other parametres. I-f the e-f-fective power ör e-f-fective torque ör transmission e-f-ficiency is known then the brake mean ef-fective pressure may be calculated. Also driving cycles allow the effective rate of the engine to be specified. These two parameters are used to interpolate the brake mean effective fuel consumption. Model vehicle whichthe numerical values given on Addition Bl are taken from,is the OTOMARSAN Mercedes-Benz O3O2 S. Ali other valuesrelated with the vehicle are calculated approximitely. The flOM chart of the computer program is given in chapter 3.3. Also a numerical applicaton of the program is given in chapter 3.4. Studying the curves demonstrating the change of the cuınulative fuel consumtion through time shows that the fuel consumption increases when the vehicle accelerates. This increase is because of the acceleration forces acting on the vehicle as resistance forces. Also it may be seen from the m T~t curves that the vehicle should not travel with a large acceleration at high gears relative to the lower gears in örder to reduce the fuel* consumption.-xi- The driving cycle named `A comparative Driving Cycle for City Passenger Buses ` considers a distance of BOO meters between two bus stations. The -fuel consumption of the bus for 1O bus stations is calculated. Then the distance betueen the bus stations is extended to 1OOO meters and the fuel consumption is calculated for S bus station. The total travelling distance is constant for both situations. Thus the fuel consumption difference gives the fuel economy for the constant distance that is SOOO meters. If the model vehicle does not carry any extra load, there is no slope and the vehicle travels on a paved road (asphalt), the result is of 4.5 7. percent fuel economy. Since no power is transmitted to the tires of the vehicle, the effective engine power and thus the brake mean effective pressure can not be determined. So that the specific fuel consumption of the vehicle, when the clutch pedal is pressed ör when no power is transmitted to the tires of the vehicle from its engine can not be determined by using the performance curves. in such cases the fuel consumption of the vehicle is calculated by means of idling fuel cosumption of the engine. If consumption is directly equal to the idling fuel consumtion. However, vhen the engine rate is different to the idling engine rate, the fuel consumption is different from the idling fuel consumption too. The fuel consumption in these situations is calculated by the equation m =m _.n /n ` where `m _` is the idling fuel ^ y yR e eR yRa consumption, `n _` is the idling engine rate and `n ` is the Br/E engine rate just before the clutc pedal is pressed. * The computer program includes 13 subroutines. When the program is run, a selection menu is offered and according to the selection some of the subroutines are used.- XI ı- An important point to be emphasized is that the performance curves given in this study are drawn aproximately by means of the full throttle curves. The real performance curves of the model engine are supposed to be different. The computer program submitted in this study may be used to optimize the behaviour of the driver by adding some subroutines or making some reorganizations. For instance if the distance and the time are certain, the behaviour of the driver to minimize the fuel consumption can be determined. However, this topic does not exist in this study.