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| Influence and Optimization of Miller Cycle and Exhaust Gas Recirculation on Combustion Performance of a Turbocharged Gasoline Engine |
| DOI：10.13949/j.cnki.nrjgc.2020.05.007 |
| Key Words:Miller cycle external exhaust gas recirculation turbocharged direct injection gasoline engine combustion turbulent kinetic energy |
| Author Name | Affiliation | | ZHANG Zhendong, QU Zhuoshen, WANG Bo, CHEN Hong, Yin Congbo | 1.School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
2.Guangzhou Automobile Group Co., Ltd., Guangzhou 510640, China |
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| Abstract:In order to study the influence of Miller cycle and exhaust gas recirculation(EGR) on combustion performance at the best fuel consumption point and high load, a 15L turbocharged direct injection gasoline engine with EGR system was changed from Otto cycle operation to Miller cycle operation by modifying its intake cam profile. Results show that in a comparative test of two different operating modes of Miller cycle and Otto cycle, the pumping loss from the Miller cycle operation is smaller than from the Otto cycle operation. However, as the load increases, the influence of the Miller cycle begins to decrease, causing the difference in pumping loss between the two cycles to gradually become smaller, which hinders the improvement of the Miller cycle thermal efficiency. In addition, the Miller cycle also reduces the end of compression temperature, increasing the combustion duration and exhaust temperature, which makes it difficult to improve the fuel economy at the best fuel consumption point. Moreover, this study also compares the effect of EGR on Miller cycle and Otto cycle. With the increase of EGR rate, the thermal efficiency of both cycles increases first and then decreases. However, the use of Miller cycle reduces the intake time and valve lift, and then greatly decrease the in cylinder tumble ratio and turbulent kinetic energy, thus retarding the angle of 50% mass fraction burned(MBF50) and extending the combustion duration, which makes its thermal efficiency and fuel economy lower than the Otto cycle operation at high load. |
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