Tek rotorlu Wankel motorunun ateşleme ve püskürtme ünitelerinin (kontrol ünitesinin) tasarımı, imalatı ve bilgisayar arayüzü ile kontrolü
Designing, producing and computer based controlling ignition and injection units (control units) of a single rotor Wankel engine
- Tez No: 397826
- Danışmanlar: DOÇ. DR. CEMAL BAYKARA
- Tez Türü: Yüksek Lisans
- Konular: Mekatronik Mühendisliği, Mechatronics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2015
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Mekatronik Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 133
Özet
Bir enerji türünü mekanik işe çeviren makinelere genel olarak motor denir. Dönüştürülen enerji türlerine göre motorlar Isı(Termik), Elektrik, Nükleer veya Hidrolik olabilmektedirler. Isı (Termik) motorlarda yakıtların kimyasal enerjisi yanma ve oksidasyon sonucu önce ısı enerjisine dönüşür, bunun sonucunda gazların sıcaklığı ve basıncı hızla yükselir ve bu gazların genişlemesi ile mekanik iş elde edilir. Yakıtın kimyasal enerjisinin motorun (silindirin) içinde ısı enerjisine dönüştüğü İçten Yanmalı Motorlarda doğrudan basıncı ve sıcaklığı yükseltilmiş yanma ürünleri kullanılmaktadır. Bu motorlara örnek olarak Gaz Tribünleri, Jet, Dizel, Otto ve Wankel Motorları verilebilir. Silindir yapılarına göre karşılaştırıldığında, yanma ile pistonların aşağı yukarı itilmesi yerine düz bir diskin döndüğü Wankel Motorları dünyanın en verimli, devirli ve güçlü motorları arasında gösterilmektedir. 1950 ve 60'lı yıllarda Alman Mühendis Felix Wankel tarafından geliştirilen, şimdilerde ise daha teknolojik versiyonları sadece bazı Mazda modellerinde kullanılan Wankel motorları, klasik motorlara göre üçte iki oranında daha az hareketli parçaya sahiptir. İçten yanmalı olmasına karşın, daha farklı bir iç yapısı bulunmaktadır. Döner pistonlu motor olarak da bilinen bu motorlarda diğer içten yanmalı motorlardan farklı olarak, kenarları yayvanlaştırılmış üçgen şeklinde döner pistonlar kullanılır. Güç iletiminin doğrudan piston üzerine bağlı mil yardımı ile gerçekleştirilmesi sayesinde yapıları diğer motorlara göre daha az karmaşıktır. Düşük hacimden yüksek miktarda güç elde eden, basit, hafif bir motor olarak bilinen Wankel Motoru 1957'nin dünya hız rekorunu egale etmiştir. Yakıt tüketiminin fazlalığı ve ekonomik olmaması sebepleriyle yaygın olarak kullanılamamasına karşın yüksek motor devirlerine çıkabilmesi, verimli ve dayanıklı olması ve kompakt boyutları sayesinde spor otomobillerde tercih edilmiştir. Günümüzde de patentini elinde bulunduran Mazda Firmasının RX7 ve RX8 modellerinde Wankel Motoru kullanılmaktadır. Bu çalışmada deney standartları açısından tek rotorlu hale çevrilmiş bir Wankel Motoru için püskürtme ve ateşleme zamanlamaları (avansları) ile enjektör püskürtme süresi ve ateşleme bobini dolma süresi (dwell süresi) değişkenlerinin bilgisayardan kontrolü yapılacak bir kontrol mekanizması tasarlanmış ve imal edilmiştir. Mikrodenetleyici kontrol kartı olarak Arduino kullanılmış, ateşleme ve püskürtme sinyallerini güçlendirmek için sürücü rölelerden oluşan bir kontrol kutusu imal edilmiştir. Wankel motoru çevrimlerinin kontrolü ve motordan geri besleme almak için krank miline bir enkoder bağlanarak, sistemin işleyişi enkoder başlangıç sinyali sıkıştırma üst ölü noktasına gelecek şekilde tasarlanmıştır. Enjektör debisini hesaplamak için bir deney düzeneği oluşturulmuştur. Wankel motorunun çalışma prensibi hakkında bilgi verilmiş, ateşleme ve püskürtme elemanlarından ve bu elemanları seçerken hangi kriterlerin uygulanacağından bahsedilmiştir. Kontrol sistemi yük ve motor hızındaki değişimlere uyum sağlayacak şekilde tasarlanmıştır. Kontrol sistemi deney motoruna bağlanmadan önce kurulan gerçek zamanlı bir deney düzeneğinde denenmiş ve tasarım kriterlerine bağlı olarak sorunsuz şekilde çalıştığı gözlemlenmiştir. Ayrıca ileride sistem üzerinde yapılacak çeşitli deneylerde veri depolamak ve gerektiğinde bu verileri kullanabilmek için harici bir hafızalama elemanı (EEPROM) devresi imal edilmiş, imal edilen devre elektronik sisteme eklenmiştir. İleride üzerinde çalışacak araştırmacılara kaynak olması açısından hafızalama elemanının kontrolcü programa kurulumu ve üzerine veri yazıp okumak için gerekli yazılım çalışmaları hakkında detaylı bilgi verilmiştir.
Özet (Çeviri)
An engine or motor is a machine designed to convert one form of energy into mechanical energy. In terms of converted enegry types, engines are classified as Heat (Thermic), Electrical, Nuclear or Hydraulic. Electric motors are machines that convert electrical energy into mechanical energy. Electric motors are used to produce linear or rotary force (torque), and should be distinguished from devices such as magnetic solenoids and loudspeakers that convert electricity into motion but do not generate usable mechanical powers, which are respectively referred to as actuators and transducers. A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation). The hydraulic motor is the rotary counterpart of the hydraulic cylinder. In nuclear engines a working fluid, usually liquid hydrogen, is heated to a high temperature in a nuclear reactor and then expands through a rocket nozzle to create thrust. Thus it converts nuclear energy into mechanical energy. In heat motors, chemical energy of fuels transform to heat enegry by burning and oxidation, then the temperatues and pressures of gases fastly increase and as a result of the distant of gases, mechanical work occurs. Where a working fluid, contained internally, is heated by combustion in an external source, through the engine wall or a heat exchanger is called external combustion engine. where the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit is called internal combustion engine. Internal combustion engines use fuels that produce high temprature and pressure. Gas turbines, Jet, Diesel, Otto and Wankel engines can be given as examples of internal combustion engines. If we need to compare in the way of cylinder moulds, instead of the common piston engines which are reciprocating pistons, an eccentric rotary design converts pressure into rotating motion is in use in Wankel engines. Over the commonly used reciprocating piston designs, the Wankel engine delivers advantages of simplicity, smoothness, compactness, high revolutions per minute and a high power to weight ratio. In Wankel motors (namely rotary engines), parts rotate in one direction as opposed to the common piston engines which have pistons that moves in two opposite directions. The four-stroke cycle occurs in a moving combustion chamber inside of an oval shaped housing, and a rotor that is similiar in shape to a Reuleaux triangle with sides somewhat flatter. In the Wankel engine, the four strokes of a Otto cycle piston engine occur in the space between a three-sided symmetric rotor placed in a housing. In a Wankel engine, the oval-like epitrochoid-shaped housing surrounds a rotor which is triangular with bow-shaped flanks (often confused with a Reuleaux triangle, a three-pointed curve of constant width, but with the bulge in the middle of each side a bit more flattened). The theoretical shape of the rotor between the fixed corners is the result of a minimization of the volume of the geometric combustion chamber and a maximization of the compression ratio, respectively. The symmetric curve connecting two arbitrary apexes of the rotor is maximized in the direction of the inner housing shape with the constraint that is not in touch with the housing at any angle of rotation (an arc is not a solution of this optimization problem). The central drive shaft, called the“eccentric shaft”or“E-shaft”, passes through the center of the rotor and is supported by fixed bearings. The rotors ride on eccentrics (analogous to crankpins) integral to the eccentric shaft (analogous to a crankshaft). The rotors both rotate around the eccentrics and make orbital revolutions around the eccentric shaft. Seals at the corners of the rotor seal against the periphery of the housing, dividing it into three moving combustion chambers. The rotation of each rotor on its own axis is caused and controlled by a pair of synchronizing gears. A fixed gear mounted on one side of the rotor housing engages a ring gear attached to the rotor and ensures the rotor moves exactly 1/3 turn for each turn of the eccentric shaft. The power output of the engine is not transmitted through the synchronizing gears. The force of gas pressure on the rotor (to a first approximation) goes directly to the center of the eccentric part of the output shaft. Wankel engine developed by German engineer Felix Wankel in 1950's and 60's, has less moving parts (at the ratio of 2/3) than classical engines. And it's less complicated compared to the classical engines realizing power transmission by the help of shaft directly connected to the piston. Wankel engines known as getting maximum power in minimum volume conditions, equalized World Speed Record in 1957. The Wankel engine has advantages of compact design, low weight and high revolutions per minute. These advantages have given rotary engine applications in a variety of vehicles and devices, including automobiles (mostly sports cars), motorcycles, racing cars, aircraft, go-karts, jet skis, snowmobiles, chain saws and auxiliary power units. It's still used by the type of RX7 and RX8 engines in Mazda. In Mazda's RX-8 with the Renesis engine (that is used in my study converted into single rotor type), fuel economy met California State requirements, including California's low emissions vehicle (LEV) standards. This was achieved by a number of innovations. The exhaust ports, which in earlier Mazda rotaries were located in the rotor housings, were moved to the sides of the combustion chamber. This solved the problem of the earlier ash buildup in the engine, and thermal distortion problems of side intake and exhaust ports. A scraper seal was added in the rotor side, and by use of some ceramic-made parts in the engine. This approach allowed Mazda to eliminate overlap between intake and exhaust port openings, while simultaneously improuves the endurance of the exhaust area. The side port trapped the unburned fuel in the chamber, decreased the oil consumption, and improved the combustion stability in the low-speed and light load range. The HC emissions from the side exhaust port Wankel engine are 35–50% less than those from the peripheral exhaust port Wankel engines, because of near zero intake and exhaust port opening overlap. Because of the existing advantages, in this research especially electronical experiments were done with the mechanisms which mechanical engineers Taner Yıldırım and Özgür Tekeli built in their master dissertations. For the timing of injection and ignition also duration of injection and dwell time (that current is flowing through the primary winding and the magnetic field is building up in the coil) variables of the Wankel engine (which converted into single rotor type in terms of testing standarts) computer based electronic unit were designed and produced. Arduino is used as microprocessor control unit and to strenghten the signal of injection and ignition, an electronic control box consisted of driver relays was produced. To change injection and ignition parameters and to get feedback from the system, control program is written on PC with Visual Studio C#. To receive and send data between the system and computer, serial communication codes are written both in Arduino control program and C# interface program. To control of the cycles of engine and to get feedback, an incremental encoder was mounted on crank shaft and the starter signal of encoder has become equivalent to the compression of the top dead center of engine crank shaft. To evaluate the flow rate of injector, a testing mechanism was designed. It's given information about working principle of Wankel engine and referred about injection and ignition equipments and which criterions should be cared when they were chosen. Control system was able to design for adapting the conversions at different load and engine speed. Before connecting to the research engine, control system was tested on the real time testing mechanism which drived by a drill, and it is observed that the control system is working without problem depending upon design criterions. Also for the tests to be held on the system later on, to store the data and to be used when it is required, an external memory device unit (EEPROM - Electrically Erasable Programmable Read-Only Memory) was aded and incorporated into the electronic system. The main goal of storing data is to map ignition advance and injector flow rate due to throttle opening and revolution per minute. It's given detailed informations about how to set external memory up to the Arduino software and the way of write and read data, with regards to a source for the new researchers. To sum up this study, it's given detailed informations about mechanical working principle of internal combustion Wankel engine. An electronic control unit designed and produced to control injection and ignition parameters. To do that, a control program and computer based interface were created. The software and hardware submitted with minimal prices and designed as easier as it can to make for the future researhers easy to understand. A memory device founded for new researches.
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