Taşıtlarda yakıt sarfiyatına etki eden faktörler ve yakıt sarfiyatının belirlenmesi

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Tarih
1991
Yazarlar
Yelkencioğlu, Adnan
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Özet
İki ana Konu üzerine hazırlanan bu çalışmada, İIk iki bölümde yakıt sarfiyatına etki eden faktörler ele alınmış, literatüre dayan genel bilgiler verilmiştir. Taşıta etkiyen Kuvvetler belirlenerek, bu fiziki karakteristiklerin etkime oranları tanımlanmıştır. Bu bağlamda motor ve taşıta ait etki faktörleri ayrı ayrı ve detaylı bir biçimde incelenmeye çalışılmıştır. Bu inceleme yapılırken ileride yapılabilecek çalışmalara konu olabilir düşüncesiyle, konunun tarihsel gelişimi, hangi parametrelerde sınırlara gelindiği ve hangilerinde bir takım gelişmeler beklendiği belirtilmiştir. Çalışmanın diğer bir konusu olan yakıt sarfiyatının tespit edilişinde ise konu ile ilgili alarak yayınlanmış, uluslararası bir takım standartlar, özüne sadık kalınmaya çalışılarak, Bölüm 3.'de verilmiştir. Tanımlanan bu standartlardan SAE ve BİS standartları esas alınarak, BMC firmasının ürünü olan bir kamyon modeli ile testler gerçekleştirilmiştir. Alınan sonuçların modelin yakıt sarfiyatını ifade ettiği iddiası yoktur. Bölüm 5.'de ise, standartlarda belirlenen ancak test yolunda uygulanması çok güç olan seyir çevrimleri neticesi yakıt sarfiyatını hesaplamayı mümkün kılan bir program hazırlanmıştır. Program kullanılan araca ve motoruna ait belirli temel değerler verildiğinde rölanti, ivmelenme, sabit hızla hareket ve yavaşlama kombinasyonlarından oluşan bir çevrim boyunca taşıtın yakıt sarfiyatını hesaplamaktadır.
In this study two main subjects of the motor vehicles have been studided. Firstly, fuel economy factors have been described and then some of the standart methods to determine fuel consumption of a vehicle have been explained. In this day of energy uncertainty attention is sharply focused on every major energy user in the entire world. Clearly, one of the most impotant factors in the energy use equation is automotive transportation and in particular the automobile. It can be reliably predicted that the cost of petroleum-based energy will continue to increase and the supply will remain uncertain since many of the principal sources of this energy form are in relatively unstable areas of the world. Even wiht the appearance of petroleumlike synthetic gasoline, diesel fuel, or methanol derived from coal or oil shale, little impacat can be made on the basic supply structure in the next 10 - 20 years. A motor vehicle in motion is acted upon by various forces - the forces which move the vehicle and the forces which offer resistance to its motion. The principal motive force is the tractive force of the driving wheels. This force arises as a result of operation of the engine and depends on the interaction between the driving wheels and the road. The tractive force PR is determined as the ratio of the moment on the axle shaft to the radius of the driving wheels during uniform motion. Power is transmitted from the engine to the driving wheels by various units in the transmission. In this case some of the power is expended on overcomming friction between the gear teeth in the transmission gearbox and the driving axle, in the bearings and glands, and also on overcoming friction of the gears against the oil and on its splashing. For this reason, the tractive power, delivered to the driving wheels, when the motor vehicle runs uniformly, is less than the effective engine power expended on friction. VII The traction characteristic of a motor vehicle is a graphically represented, dependence of the tractive force on the motor vehicle speed. The traction characteristic is plotted from the results of stand or road tests or from calculated data. In order to carry out stand test, car is placed wiht its driving wheels on running drums of the stand and fastened by means of a wire rope through dynamometer to stationary post. At full throttle a hydraulic or electric brake is used to build up such resistance to the rotation of the running drums when their angular velocity remains constant. Fuel vis the most important material utilized by motor vehicles in large amounts. The cost of fuel amounts to 10 - 15 percent of all the transportation charges. For this reason, fuel must be used to the maximum effect without unwarranted losses. Fuel consumption of a motor vehicle depends on its design and technical state, on road and climatic conditions, skill of the driver and organization of the transportation process. Numerous vehicle factors aside from the power train have an important impact on overall fuel economy. Just as in the case of the engine, the relative emport of these vehicle factors is often dependent on the driving cycle. For example, aerodynamics are obviously more important at high speed than at low speed. It is generally observed that any change in a. parameter which results in lower fuel consumption will also result in a reduction in emissions. This is contrary to what often occurs in the engine where complex trade - off s are common. The important parameters influencing fuel consumption can be disaggregated into the following list : 1. Engine characteristics 2. Drive - train characteristics 3. Weight 4. Aerodynamics 5. Rolling resistance 6. Driving cycle 7. Driver nabits The sum of the slope, aerodynamic, rolling and accelaration resistance forces gives the total resistance force acting on the vehicle. Reducing these forces is of a vital importance to decrease the fuel consumption of a vehicle. VIII The automobiles of today are considerably better - than those of the past, particularly when one considers the total range of consumer value factors embodied in modern automobiles. This include safety, ride, handling, interior noise level, comfort, emission performance, and of course fuel economy. Many factors are responsible for the recent rapid improvement in fuel economy, and these same factors will continue to be important in the dramatic fuel economy improvements expected in the years just ahead. These factors include vehicle downsizing, tire improvements, reduced aerodynamic drag, the application of new light weight materials, more efficient automotive structures, and greatly improved engines and total drive trains. Perhaps a word of caution is warranted on the issue of fuel consumption and fuel economy. Often these terms are used interchangeably but of coarse one is really the inverse of the other. That is, good fuel economy means low- fuel consumption and viceversa. Generally, fuel economy is reported in miles per galloon or kilometers per liter. However in more technical circles fuel consumption is often discussed rather than "fuel economy. It is particularly important to use fuel consumption when dealing wiht the agregate performance of vehicles. For example, if you consider both a 10 mpg and a 20 mpg vehicle, the average of the two would suggest that the fuel economy would be 15 mpg, but this is incorrect. When averaging properly, using a consumption base, a 0,1 gal/mile (10 mpg) car and another of 0.05 (20 mpg) gal/mile car averages 0.15 gallons per 2 miles of travel or 0.075 gal/mile the inverse of which is 13.3 mpg. Throughout this work fuel consumption and fuel economy will be used so the reader is cautioned to carefully note the distinction between the two terms. A word of caution is in order when dealing wiht any fuel economy data that concerns the impact of the operating cycle on fuel economy. Without knowledge of the operating cycle, miles per gallon data comparison is meaningless. The cycle must be well defined. Currently, the manufacturers are required to conduct fuel economy tests according to the EPA urban driving cycle, which will be discussed later in this chapter. Fuel economy performance measured on this cycle is the published number used by the various manufacturers. The EPA also has a suburban test cycle that includes a significant fraction of simulated highway driving without the "stop and go" of the urban cycle, In order to determine compliance wiht the Corporate Average Fuel IX Economy (GAPE) standads established by the federal Government, the urban and suburban cycle fuel economies are combined according to the following formula :.^composite 0.55, 0.45 ------ "" *t* ' ? ?' ~ urban mpg highway mpg For determination of fuel consumption several standart methods have been aplied to a BMC product PATİH 214-26 truck. These standart methods have been defined in Part 5. The fuel consumption testing scheme is intended to give car buyers comparative information about the relative fuel economy of different models achieved in standart test. Most new cars have to undergo the standard tests to determine their fuel consumption and the results of those tests are recorded in official fuel economy certificates issued by the Department of Transport. Responsibilties of manufacturers, importers and dealers : The results of the standart tests have to be shown on labels fixed to every new car on display in showrooms for prospective car buyers to consult on request. In addition, where» reference is made in promotional literature such as advertisements, technical specifications and sales brochures to the fuel consumption of a new car, the results of all tests carried but must be quoted, (urban cycle, 90 km/h and 120 km/h where appropriate) in both miles per gallon and litres per 100 kilometres. What are the standat tests? The tests follow an internationally agreed procedure and consists of three parts : - a cycle simulating urban driving ; - a constant speed test at 56 mph (§0 km/h) ; and - for vehicle capable of sustaining the speed, - a constant speed test at 75 mph (120 km/h). The cars tested have to be run-in and must have been driven for at least 1.800 miles (3.000 kilometres) before testing. For comparative purposes, all results are from tests conducted wiht leaded fuel. Urban test cycle : The urban test cycle is carried out in a laboratory where equipment simulates the loads experienced under normal driving conditions and the standart patterns of urban driving. The car is driven from a fully warmed - up start and is taken through a cycle of acceleration, deceleration and idling wiht a maximum speed not exceeding 51 mph ;-'-: (50 km/h). 56unph (90 km/h) constant speed test : The constant speed test at 56 mph (90 km/h) is intended to be representative of open - road driving. It may be carried out in a laboratory or on a test track (under strictly controlled road and weather conditions). 75 mph (120 km/h) constant speed test : This test has to be carried out on cars wiht a maximum design speed of at least 130 km/h, and so not all cars have been tested at this speed. How representative of real - life driving are the standart tests : Because of the need to maintain strict comparability of results achieved by the standad tests they cannot be fully represantative of real - life driving conditions. Firstly, hardly any motorists drive in towns from a fully warmed - up start or outside towns at a constant 56 mph or 75 mph. Secondly, it is obviusly not practical to test each individual new car, thus only one production car is tested as being represantative of the model and it will have been carefully prepared by the manufacturer or importer to give as favourable a figure as possible. Thirdly, there are infinite variations in driving styles and in road, car and weather conditions, all of which can have a bearing on the results achieved, for these reasons the fuel consumption achieved on the road will not neces sarily accord wiht the official test results. The fuel consumption values which have been given in part 4. for BMC truck does not intend to give real life results. In part 5. a computer program has been prepared to calculate the fuel consumption of a vehicle beyond a determined driving cycle and motor - vehicle character iatics. General parameters relateu wiht the internal combustion engines and vehicles are explained. Performance curves of model engine are given in part 2. These values are used to calculate the fuel consumption of the engine for different loads which are applied beyond the driving cycles.
Açıklama
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1991
Anahtar kelimeler
Bilgisayar programları, Taşıtlar, Yakıt tüketimi, Computer programs, Vehicles, Fuel consumption
Alıntı