| As the crisis in energy grows and climate pollution mounts up, Fuel efficiency and emission reductions are the two consistent drivers for internal combustion engine development. Lean-burn technology can improve the thermal efficiency, reduce pumping losses, and help improve gasoline engine’ fuel economy and emissions, which has attracted ever-growing interest. Computer technology continues to develop and it offers facilities for the engine combustion process simulation. With the help of numerical simulation, it not only can greatly reduce test time and labor intensity, but also helps to understand the cylinder combustion process and propose the method for improving the combustion process, providing guidance for the engine design and the development of experimental programs. This article presents study work of the lean-burn gasoline-related simulation and experiment, which is conducted on domestic engine CA3GA2.First of all, a one-dimensional model for CA3GA2 gasoline engine is presented in this paper by using the AVL-boost software. Furthermore, a lean-burn simulation research is conducted, providing the simulation problems of fuel economy, emissions, vortex intensity and influence from EGR on NO_x emissions. The simulation results indicate that: As the air-fuel ratio increases, the engine fuel consumption decreases and when the air-fuel ratio is larger than 18, the downward trend becomes weak; The fuel consumption reaches its minimum at A/F=21. The CO emissions continue to decline as the air-fuel ratio increases; HC emissions increase after decrease with the air-fuel ratio increasing; NO_x emissions decrease after increase as the air-fuel ratio increases. As the swirl ratio increases, there is a tendency of increasing after decreasing in engine fuel consumption rate and the swirl ratio should be selected in the range of 0.8-1.2 for lower fuel consumption rate.Secondly, a 3-dimensional model for CA3GA2 gasoline engine is presented by using the AVL-fire software. Related simulation research is conducted including several aspects: influence from turbulence on velocity field, mean pressure, turbulent kinetic energy field and influence from EGR on temperature field. The simulation results show that: Varying the cross-sectional area of single side exerts an influence on the intensity of the vortex which reaches the maximum value at the baffle position of A2. At the initial stage of intake stroke, turbulent kinetic energy is centralized in the right region; As the crankshaft rotates, turbulent kinetic energy eventually becomes even. The temperature of the combustion process at 0%, 8%, 15% and 24% of EGR is 2020K、1800K、1600K and 1470K respectively, down gradient of about 10%.At the end of the paper, it is studied in the experiment that how different vortex intensity and different EGR rate have had different impacts upon lean burn gasoline engine fuel economy and emissions. Experimental results show that: The performance at baffle position of A2 is better than that at A0, reducing the HC, NO_x emissions and specific fuel consumption, namely, vortex flows with certain strength helps improves the fuel economy and emissions of lean-burn engine. NO_x emissions could be greatly decreased through using EGR. With the EGR rate continued to increase, NO_x emissions decrease continuously. However, if the rate of EGR is excessive, it would give rise to a significant increase in HC emissions and fuel economy deterioration, etc., so it is important to select reasonable EGR rate considering the emissions of the engine and fuel economy. |
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