Numerical Simulation Of The Fuel Oil Injection Law's Influence On Marine Diesel Engine Performance

Due to the increasingly serious energy and emissions problems, as well as stringent exhaust emission standards, the development of marine diesel engine is facing with more and more severe challenge. Improving the economy, emission and noise of marine diesel engine are the important topics currently. Therefore, reducing pollutants emission by effective measures will be of important theoretical significance and practical value to control environmental pollution and delay energy crisis.Diesel economy,emission and noise are impacted on many factors, and the fuel oil injection law has a very important impact on combustion process and emission. The different injection law resulted in different cylinder pressure, temperature, heat release rate, etc. These parameters have a direct influence on engine economy,emission and noise. Extensive studies show that pilot injection is one of the effective methods of controlling diesel engine emission and combustion noise.In research of optimizing diesel engine's performance, traditional experimental and numerical simulation methods can be chose. Traditional experimental method has long development period,high research cost and lots of difficulties; numerical simulation has the following advantages:the lower research cost,Shorter design cycle,obtain parameters which are difficult for the bed experiments, and numerical simulation is used to demonstrate and optimize the modern diesel engine design project, forecast diesel engine's performance, research and improve the sample.The fuel oil injection law's influence on MAN B&W 6S50MC-C marine diesel engine performance in 115.4 r/min,75% operating condition load is performed by the AVL BOOST software in this paper. According to the diesel engine numerical simulation computation foundation and the AVL BOOST software computation principle, the diesel engine numerical simulation model is built up. On the base of the model, the propel character of the diesel engine is simulated. The result indicates the analog data can tally with the empirical datum and confirms that the model is correct. On the base of the model, firstly, the rectangle,ladder-shaped and pilot injection law's influence on diesel performance are compared, and the results indicate that pilot injection law is the best for improving the diesel engine performance; secondly, the performance of the single-injection and pilot injection are studied, injection timing and injection pressure's influence on diesel engine performance feature are studied in the single-injection, pilot injection oil mass and spray interval's influence on diesel engine performance feature are studied in the pilot injection; at last, nine pilot injection schemes which are consisted of 3%,5%,8% pilot injection oil mass and 50CA,100CA,150CA spray interval are formed, and pilot injection schemes' influence on the diesel engine performance are compared, from which the best pilot injection scheme is chose in the given operation load. Compared to the original engine, it decrease greatly the engine's NOx emission and noise, however, the power and economy are deceased slightly, so it achieves the purpose of this study.