Ağır vasıta dizel motor egzoz manifoldu termomekanik yorulma test sistemi tasarımı, analizi ve doğrulanması

In past decades, there is a significant improvement in every respect of automotive industry. New special materials have been started to use. New technologies are also started to use in automotive industry. The engine is most important part of a vehicle for all time. With competition in the market, engine manufacturers need to manufacture more economically while guaranteeing higher performance and reducing exhaust emissions due to legal regulations and environmental issues. The main goal is to produce silent, low-cost and lighter new generation green engines with low exhaust emissions that also present higher performance and consume less fuel. There are many research studies on this issue and progresses to meet expectations. Increasing the peak firing pressure and improvements on the design has provided important solutions for these expectations. On the other side, thermal mechanical fatigue (TMF) occurring during the start-stop cycle of the engine has become an important issue with higher exhaust gas temperature and light designs. This issue should be taken into consideration more carefully with these modifications, increasing internal pressure and working temperature inside engines. Exhaust manifold is one of the parts exposed to the highest temperatures in a vehicle. In addition, its performance is very critical for new generation green engines. High silicon molybdenum (HiSiMo) ductile cast iron (DCI) is commonly used for high temperature engine parts, such as exhaust manifolds, which are also exposed to harsh thermal cycles. HiSiMo is an alloy developed specifically for such components. HiSiMo Grade 3 according to ASTM standards is the most powerful alloy used as exhaust manifold material. Materials show different mechanical and thermal properties with different temperature and working conditions. To obtain certain properties, physical tests with real working conditions and temperatures are necessary but costly and time-consuming. Critical parts such as exhaust manifold must be guaranteed for satisfying thermal mechanical fatigue behavior. Best way for TMF behavior test is the use of a test vehicle or using engine dynamometers to simulate the real road and combustion conditions. All parameters have an effect on the fatigue life but some of them have higher priority. In reality, a test vehicle is very close to a mass production step. After this stage, making design changes are very difficult. Automotive manufacturers prefer to complete the testing of these critical parts with special test rigs. Despite the complete engine requirement for a test vehicle or engine dynamometers, specific test rigs could work without a complete engine but still simulates the real situation. In recent years, specific test rigs are become very important and useful for research projects. TMF tests are commonly very long time consuming and expensive. Minimizing the test rig with only necessary parts and equipment provide more test opportunities with the same cost and facility. A new TMF test rig is designed for a heavy duty diesel engine exhaust manifold with using commercial CAD program CATIA V5. The TMF test rig will be installed at the Ford Otosan Kocaeli Plant Test Center. It is tried to use existing equipment such as natural gas burner and vibrational shaker. A finite element method program called HyperMesh is used for the calculation of natural frequencies of the new designed components and the design is revised to achieve the natural frequency targets. On the other hand, it is possible to achieve great profit in the design stage with computer-aided analysis. With the correct material and working conditions data, advanced TMF analysis give accurate results. To compare the test and analysis results is important for future works. Due to the cost and long time-consuming behavior, it is not desired to test all the design changes. To observe the effects of the numerous design iterations, TMF analysis is the best practical way. However, to verify material and working condition properties, TMF tests are required at the beginning. Commercial CFD analysis program STAR CCM+ is used for heat transfer analysis inside exhaust manifold during hot gas transfer. These CFD results are used on HyperMesh model and applied to ABAQUS program for structural analysis. To calculate a fatigue life result, commercial analysis software nCODE DESIGNLIFE is used. In this study, the main goal is to develop a methodology for thermal-mechanical fatigue life estimation of diesel engine components, design a thermal-mechanical fatigue test rig for exhaust manifold, simulate thermal-mechanical fatigue loading with some conditions in the software in a virtual environment to develop a reliable analysis methodology and verify the design of critical engine parts. In addition to cost advantages, pollution created by combustion of thousands of liters of fuel in engines will be reduced by using natural gas because the diesel/gasoline is not used in this TMF rig. Thus, an environmentally friendly test method is developed for green engines with less equipment and dependency to other engine parts.