<p>Over the years many investigations of the gas temperature at the exhaust valve have been made. Nevertheless the modeling of the gas temperature still remains an unsolved problem. This master thesis approaches the problem by attempting to model the exhaust gas temperature by using the standard sensors equipped in SI engines, together with an in-cylinder pressure sensor which is needed in order to develop certain models. The concept in the master thesis is based upon a parameterization of the ideal Otto cycle with tuning parameters which all have physical meanings. Input variables required for the parameterization model is obtained from a fix point iteration method. This method was developed in order to improve the estimates of residual gas fraction, residual gas temperature and variables dependent of those, such as temperature at intake valve closing. The mean value model of the temperature, at the exhaust valve, is based upon the assumption of the ideal gas law, and that the burned gases undergoe a polytropic expansion into the exhaust manifold. Input variables to the entire model are intake manifold pressure, exhaust manifold pressure, intake manifold temperature, engine speed, air mass flow, cylinder pressure, air-to-fuel equivalence ratio, volume, and ignition timing. A useful aspect with modeling the exhaust gas temperature is the possibility to implement it in turbo modeling. By modeling the exhaust gas temperature the control of the turbo can be enhanced, due to the fact that energy is temperature dependent. Another useful aspect with the project is that the model can be utilized in diagnostics, to avoid hardware redundency in the creation of the desired residuals.</p>

Over the years many investigations of the gas temperature at the exhaust valve have been made. Nevertheless the modeling of the gas temperature still remains an unsolved problem. This master thesis approaches the problem by attempting to model the exhaust gas temperature by using the standard sensors equipped in SI engines, together with an in-cylinder pressure sensor which is needed in order to develop certain models. The concept in the master thesis is based upon a parameterization of the ideal Otto cycle with tuning parameters which all have physical meanings. Input variables required for the parameterization model is obtained from a fix point iteration method. This method was developed in order to improve the estimates of residual gas fraction, residual gas temperature and variables dependent of those, such as temperature at intake valve closing. The mean value model of the temperature, at the exhaust valve, is based upon the assumption of the ideal gas law, and that the burned gases undergoe a polytropic expansion into the exhaust manifold. Input variables to the entire model are intake manifold pressure, exhaust manifold pressure, intake manifold temperature, engine speed, air mass flow, cylinder pressure, air-to-fuel equivalence ratio, volume, and ignition timing. A useful aspect with modeling the exhaust gas temperature is the possibility to implement it in turbo modeling. By modeling the exhaust gas temperature the control of the turbo can be enhanced, due to the fact that energy is temperature dependent. Another useful aspect with the project is that the model can be utilized in diagnostics, to avoid hardware redundency in the creation of the desired residuals.

Detta examensarbete utfördes på Scania CV AB och behandlar delar i lastbilens avgassystem som utsätts för korrosion och nötning. Huvudmålet med detta arbete är att utveckla en provmetod för livslängdsundersökning av flexibla slangar. En serie tester utfördes för att förstå grundorsakerna till brott och en FE-analys utfördes för att verifiera resultaten till dessa prov. En stor del av den flexibla slangen blir stel på grund av höga avgastemperaturer och som leder till plastisk deformation av slangen. Men de tre första lindningarna som ligger närmast motorn behåller sin flexibilitet på grund av kontinuerliga motorvibrationer. Slutsatsen är att huvudorsaken som gör att de flexibla slangarna går av, är slitage som leder till sprickinitiering. Den sprickan sprider sig i form av lågcykelutmattning d.v.s att det tar ganska kort tid tills brott sker i den flexibla slangen. Korrosion initierar mellan de icke-flexibla delar av slangen Korrosionshastigheten ökar med tiden och det orsakar små hål på ytorna. Baserat på testresultaten är den mest lämpliga stället för livslängdsundersökningar Scanias komponentprovceller. Genom att mäta slitagedjupet under repeterbara förhållanden som rekommenderas i rapporten och med hjälp av data från kundutfall, kan en livslängd uppskattas. För att kunna förbättra livslängden för de flexibla slangarna, rekommenderas att använda rostfritt stål typ 1.4828 vid tillverkning av dessa slangar bör varmformning användas, samt att avståndet mellan lagrena respektive tjockleken ökas. Flera tester med olika teststidsintervall behöver göras för att ta reda på nötningshastigheten. / This thesis was conducted at Scania CV AB with information based on corrosion and wear. The main goal of this work is to develop a test method to investigate the stripwounded hose’s lifetime. A series of tests were performed to understand the reasons of their failure and a FE analysis was performed to verify the results obtained from these tests. It was observed that a large part of stripwounded hose becomes stiff due to high temperatures of the exhaust gas. The high temperature leads to plastic deformation of the hose. In contrast, the three first windings closest to the engine keep their flexibility due to continuously engine vibrations while there is sign of wear between the layers in these three windings more than other parts of the stripwounded hose. Hence, it is concluded that the main reason for stripwounded hose’s unpredictable failures is wear which leads to crack initiation. The crack propagation is in type of low cycle fatigue which means that it takes a short time until the stripewounded hose breaks. Corrosion is initiated between the non-flexible parts of the hose. The rate of corrosion is increased by time and causes small holes on the surfaces. According to results from the experiments the most suitable location for the lifetime investigation is Scania’s component test cells . Several tests with different time spans needs to be performed. By measuring the wear depth rate under repeatable test conditions and bycomparing with stripwounded hoses from customer trucks, a lifetime can be estimated. To improve the fatigue lifetime of the stripwounded hoses, it is recommended to use stainless steel of type 1.4828, manufactured through hot-forming with larger distance between layers and thicker layers to find out the wear rate.