# Design and Testing of a Gasoline Engine Muffler Based on the Principle of Split-Stream Rushing
## 3 Results
### Aerodynamic Performance Analysis of Split-Stream Rushing Muffler
#### 3.3.1 Aerodynamic Performance Simulation Test Results and Analysis
The rear section of the muffler was divided into three chambers by two perforated plates, all of which were perforated, and there were also holes in the inlet and outlet pipes. In the process of air flow, due to the short cavity, the high-speed air flow met the obstruction of the wall before it could diffuse. The outlet velocity of the muffler was 32 m/s, which represented a decrease in airflow velocity compared to the inlet velocity. * Analysis of pressure field simulation results  
Figure 18 shows the pressure contour of the flow field at an inlet flow rate of 40 m/s. The gas entered the muffler from the inlet pipe, and at that time, the pressure was about 4806 Pa and encountered the obstruction of the cone structure, which formed the accumulation of hydrostatic pressure, the pressure became larger, and the value reached about 5213 Pa. After that, the gas was split into two streams along the cone structure and entered the inner cavity of the muffler through the square holes located near the middle of the muffler's front section. The Pressure Loss was lower than the pressure outside the cavity as a result of the existence of square holes. Due to the existence of the square holes, the gas encountered an obstruction when entering the inner cavity, which generated a certain Pressure Loss, resulting in the pressure inside the cavity being lower than that outside the cavity. After that, the airflow entered the muffler through the inlet pipe at the back of the muffler. From the pressure contour, it could be observed that when the airflow passed through the muffler rear section inlet pipe, square holes, and orifices, the pressure decreased, which was due to the resistance loss caused by the sudden change in the cross-sectional area of the pipe. The Pressure Loss of the split-stream rushing muffler was 4525.41 Pa, while the Pressure Loss of the original muffler was 4673.21 Pa. A numerical comparison showed that the Pressure Loss of the split-stream rushing muffler was lower than that of the original muffler, which indicated that the aerodynamic performance of the split-stream rushing muffler was better than that of the original muffler. Figure 17: Velocity contour of flow field with inlet velocity of 40m/s. * Analysis of turbulent kinetic energy field simulation results  
Turbulent kinetic energy is a measure of the development or decay of turbulence and can be used to evaluate the stability of a flow. At the same time, turbulent kinetic energy can also be used as an important indicator to analyze the magnitude of internal regenerative noise. In fluid mechanics, the calculation and analysis of turbulent kinetic energy is of great significance for the in-depth study of the characteristics and mechanisms of flow. Figure 19 illustrates the turbulent kinetic energy contour for the inlet flow velocity of 40 m/s. The turbulent kinetic energy in the muffler was mainly distributed in the regions of the counterpoise holes, the connection between the front and rear chambers, and the perforated apertures. The maximum turbulent kinetic energy K was about 72 m\({}^{2}\)/s\({}^{2}\). It could be seen that under the condition of an inlet air velocity of 40 m/s, the muffler, on the whole, had a not-so-large internal turbulence intensity. Thus, the conclusion was drawn that the airflow regeneration noise was not significant.