| 杜辉，江帆，邓水根，孔凡良.米勒循环及低压废气再循环技术对汽油机性能的影响研究[J].内燃机工程,2021,42(2):47-52. |
| Effects of Miller Cycle and Low-Pressure Exhaust Gas Recirculation on Gasoline Engine Performance |
| DOI：10.13949/j.cnki.nrjgc.2021.02.007 |
| Key Words:gasoline engine Miller cycle exhaust gas recirculation（EGR） economy |
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| Abstract:In the conceptual design stage of a 2.0 L turbocharged gasoline engine for a commercial vehicle, one-dimensional thermodynamic calculation was carried out using GT-Power software and the influence was studied of the Miller cycle technology and low-pressure exhaust gas recirculation (EGR) technology on the fuel economy. The simulation results show that both long Miller cycle and short Miller cycle have the optimal VVT angles for the fuel economy. At medium-high-speed region, the fuel economy of the short Miller cycle is better, because in the long Miller cycle, the reversal of air flow in cylinder is not possible due to high mass flow and velocity, and the Miller effect is reduced. In addition, the long Miller cycle has two pumping processes, resulting in more pumping loss than the short Miller cycle. At low-speed region, the fuel economy of the long Miller cycle is better because the boost pressure of the short Miller cycle is higher, resulting in more pumping loss than the long Miller cycle. For this gasoline engine, the short Miller cycle has obvious advantages. The low-pressure EGR technology can decrease the maximum temperature in cylinder and reduce knock tendency, hence crank angle of 50% mass fraction burned(CA50) being advanced properly to optimize the fuel economy. Furthermore, the increase of the total amount of EGR and fresh air also leads to an increase in cylinder peak pressure, contributing to a better fuel economy. In different operating conditions, the maximum temperature in cylinder decreases with the growth of the EGR rate. Therefore, within a certain range, the higher the EGR rate, the better the fuel economy and the lower the turbine inlet temperature. However, in the meantime more cooling power is required by the EGR cooler. As a result, the short Miller cycle technology is applied for the engine combustion development process, and the recommended EGR rate is 8%. In order to verify the simulation results, the engine performance test was carried out, and the experimental results are in good agreement with the simulation results. |
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