Industrial computer controlled diesel engine fuel injection system

The diesel engines, which have started to play an active role in the human life together with the industrial revolution, have been researching for many years to increase the efficiency of the engine from one side and to reduce the fuel consumption on the other hand. Today, diesel engines have been used extensively in the automotive sector and they effect the environment directly, so above-mentioned studies have been accompanied also by researchs that will minimize the harm to the environment by releasing exhaust gases. Diesel engines belong to the internal combustion engine family, which means the energy conversion occurs in the cylinder inside the engine. They can be divided into 2 groups that are two-strokes and four strokes engines according to their working principle. Diesel engines can also be classified according to cylinder numbers and arrangement patterns, rated speed, piston connection patterns and piston direction of movements. The engine used in this thesis is a single-cylinder, 4-stroke, 3000 rpm rated speed and single-sided diesel engine. Diesel engines work under the principle that the fuel is sprayed into the compressed air at high pressure and temperature. Thus, the fuel that suddenly encounters with high temperature and pressure explodes in a flash. Due to the rapid increasing temperature, the air in the cylinder expands and the high pressure moves the piston linearly downwards. When the combustion is completed and the pressure in the cylinder returns to normal, the piston starts moving linearly upwards this time. This linear motion of the piston is converted to a rotational motion by means of some mechanical parts. The most important factor directly affecting engine efficiency, fuel consumption and exhaust gas emissions is the combustion of fuel. A good air fuel mixture should be obtained in order to a well burn effect. The first condition for achieving a good air fuel mixture is to compress the air sufficiently and allow the fuel to be homogeneously distributed in this compressed air. For this reason, different combustion chambers are designed. The designs of the combustion chambers not only directly affect the combustion efficiency, but also affects the operating noise level of the engine. The second condition for obtaining a good air fuel mixture is to be able to control the amount and pressure of the fuel to be injected onto the compressed air. This control is very limited without doubt with the engines, which have mechanical fuel delivery system. The mechanical fuel delivery system does not allow direct manipulation of the offset injection parameters. Due to mechanical systems cannot respond to this need, Common Rail fuel delivery systems have been developed. The Common Rail system is a direct fuel injection system that controls the injection pressure and timing of the cylinder-fed fuel. Unlike mechanically controlled systems, the control of the injection pressure and duration allows the engine efficiency to be increased while reducing the amount of exhaust gas emission. For this reason, today it is the most preferred structure both in passenger cars and in commercial vehicles. The CR system basically consists of three parts: low pressure layer, high pressure layer and electronic control elements. With these layers and elements, the fuel is delivered to the injectors via a common rail under pressure up to 2000 bar. The fuel reaching the injectors is injected into the cylinder for a desired period via an electronic control unit. The remarkable point here is that the amount of pressure and the duration of the spray can be adjusted independently of each other. The electronic control unit automatically adjusts the pressure and duration according to engine speed and load. The CR system may seem ideal for fuel injection but still has a number of inadequacies. One of these inadequacies is the electronic control unit does not allow us to change the injection parameters while the engine is running. In addition, the controller to be used for researches can be programmed from the outside. Many of the electronic control unit manufacturers do not allow this type of manipulation. The use of industrial computers for the fuel injection system of a diesel engine, which is the main idea of this thesis, was born from this inadequacy of ECU. There is a need for a controller that can perform real-time control and can be easily programmable for research and development activities on diesel engine efficiency. Industrial computers fully meet this necessity thanks to their hardware and software components. In addition to allowing real-time operation, an industrial computer performs control functions much faster and more precisely than PLCs due to its high processing power. In this study, EtherCAT communication protocol, XFC technology and TwinCAT programming software were used together with the industrial computer. EtherCAT is an ethernet-based protocol that can communicate on the fly at extremely high speeds. This makes it possible to exchange data for microseconds that is critical to be able to control of high-speed diesel engines. In combination with distributed clocks, XFC technology ensures that many different devices in the system are synchronized in down to one microsecond. TwinCAT is a programming interface that combines both hardware and software in one platform. It also turns an industrial computer to a powerful, real-time capable controller unit. TwinCAT and XFC allows us to use some function blocks for specific purposes such as recording the time stamp of a data event or providing an oversampled output signal. In this thesis, firstly an emulation application has been performed to see whether the industrial computer and the other technologies are enough to control of a real injector of a diesel engine. After the successful results on a test bench, a fuel injection control application of a real diesel engine by an industrial computer was performed. The purpose of such an application is to develop an easy to apply, flexible method that will provide a basis for future improvements in combustion efficiency, and therefore engine efficiency and fuel consumption reduction researches. In Chapter 1, the development of machines in human history is briefly explained and general information about diesel engines is given. In Chapter 2, the classification of diesel engines according to their various properties is mentioned and their working principles are given. Later, information on combustion processes and combustion chambers of the fuel, which is a very critical point in the operation of diesel engines, has been explicated. In Chapter 3, fuel injection systems used in diesel engines are briefly introduced, and then their types and operating principles are shown. The Common Rail" fuel injection system used in this study is covered and the tasks of the different layers are explained. In Chapter 4, the place of industrial computers in the control and automation world is discussed and some information has been given about how they performed real-time tasks. Then, technologies such as EtherCAT, XFC, and Distributed Clocks are explained in detail. Before an experiment was performed on a test set, an emulation application was carried out and the hardware and software used in this application were reported in detail. In Chapter 5, finally, in order to verify the results obtained in the emulation application, a real diesel engine test set was subjected to fuel injection control with an industrial computer and the results evaluated.