Study Of Miller Cycle And Two Stage Regulated Turbocharging Ssytem On Marine Diesel

As the environment problems become increasingly prominent, therequirements of the International Maritime Organization(IMO) on marinediesel engine emission become stricter, therefore reducing NOx emissionfor the marine diesel engine becomes the key point in the future for thedevelopment of marine diesel engine.There are many methods to reduce the NOx emission of marine dieselengine, an important way is to use the miller cycle system which canreduce the NOx emission by reducing the cylinder combustion temperature.But citing miller cycle will cause the fresh air into the intake pipe beinsufficient, therefore, it is necessary to improve the inlet pressure to makeup for it, the higher the degree of miller, the higher for the inlet pressure isneeded.Therefore, in order to reduce the NOx emission and not affectingother work performance parameters at the same time, it is necessary toboth adopt miller cycle system and two stage turbocharging system toachieve the goal. But the difficulty is how to control valve timing toachieve miller cycle and how to choose the types of turbine, compressorand different regulatory measures to achieve the two-stage regulatedturbocharging system. It requires reasonably designing 14 variables tofinish the whole system matching work.Based on the problems above, this article reveals the interrelationshipamong the main performance parameters in the system throughtheoretically researching the miller cycle system and the two-stageregulated turbocharging system. Using GT-Power to simulate the diesel engine and get the optimal performance parameters to reduce NOxemission and fuel consumption by manually adjusting the main variablebased on the regularity discussed before. As this approach optimizes thetwo systems independently, so the efficiency and the optimization resultsare not so good. Finally, by using the optimization softwaremodeFRONTIER and GT-Power for coupling calculation to optimize twosets of systems simultaneously to achieve the best effect of optimization.Relative to the manual adjustment, the coupling calculation can achievelower NOx emission and lower fuel consumption, the former beingreduced by 3.86% and the latter by 45%,while being optimized manuallythe results can only reach 2.5% and 38%.