الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Despite their initial successes, submarine pioneers were still eager to find some means free their boats from the necessity of surfacing frequently for access to the atmospheric demanded by the gasoline or diesel engines that charged the batteries. Recently, an increasing demand for longer stay underwater, leading to increased interest in closed cycle diesel engine( CCDE) technology, so this technology had been used to fill the gap between the traditional methods used to generate power. As a result of using CCDE which causes a deficiency in engine power, more researches are needed to overcome this difficulty. Therefore this research aims to enhance the CCDE performance by introducing inert gases with synthetic air into the engine intake manifold. For this purpose a three dimension multi zone model is established using Computational Fluid Dynamic (CFD) code (Fluent 14.0) in order to model the compression, combustion and expansion processes in a direct injection diesel engine running under synthetic atmosphere operating conditions contaminated with different carbon dioxide concentrations. The complexity of the combustion process either for conventional and non-air mixtures with its associated fuel atomization, delay period , kinetics of reactions, turbulent mixing, non-equilibrium effects, heat release as well as heat transfer, etc., is taken into account in the numerical model. The model are validated by comparing its results with those obtained from a previous experiment which were performed in a single cylinder, air cooled diesel engine (Deutz FL511) with a displacement volume of 825 cm3, a power of 8.3 HP at constant speed of 1500 RPM. The validated model is used to predict the overall performance of a direct injection diesel engine operated with different intake contents of oxygen, helium, nitrogen, and carbon dioxide. In addition the beneficial effect of adding argon gas or helium gas to the intake charge on the engine performance is investigated. The results show that as the concentration of helium or argon increases, the mean cycle pressure increases and hence adding helium or argon has better effect on combustion process. Due to volume restriction of submarine, the results show that it can take the benefit of using argon or helium in CCDE to reduce the size of scraper which is used in removing CO2 from recycled exhaust and hence minimize the whole size of CCDE system. In this case concentrations of 25% CO2 as a recycled gas and 2% argon or 10 % helium as replacement gas instead of N2, can be used in order to recover the loss in engine power due to existence of CO2.