出口管过渡圆弧对抗性消声器性能的影响及应用

Effects of outlet pipe transition circular arc on properties of reactive muffler and its application

为了降低基于声腔模态的进出口管布置原则设计的抗性消声器的压力损失,该文以典型的扩张式消声器和回流式消声器为例,探究了出口管过渡圆弧对其压力损失及传声损失的影响规律。结果表明：出口管施加过渡圆弧对传声损失的影响很小,却能有效降低压力损失;随着过渡圆弧半径的增大,压力损失的变化率减小。最后,在不改变总体尺寸的前提下,基于声腔模态的进出口管布置原则对消声器各抗性消声结构单元的进出口管进行重新布置：进口管和出口管的偏移距离从70 mm改为63 mm,中间管的偏移距离从70 mm改为0,进出口管间的偏移角度从135°改为90°;基于出口管过渡圆弧对压力损失的影响规律对各抗性消声结构单元出口管施加10 mm的过渡圆弧。改进后的消声器不仅传声损失有所提高,且压力损失也得到降低,在750-1500 Hz频率范围内平均传声损失增加了15.3 d B,入口气流速度为60 m/s时压力损失降低了25.20%。研究结果为综合运用基于声腔模态的进出口管布置原则及出口管过渡圆弧对压力损失的影响规律设计及改进消声器提供参考。

Based on the layout principles of inlet and outlet pipes, using the cavity acoustic modes to design muffler can get good acoustic attenuation, and for the inlet and outlet pipes are not coaxial, the pressure loss is larger when it is caused by the blocked air flow. Taking the expansion chamber and flow-reversing chamber as examples, firstly, comparative study about the effects of chamfer transition and circular arc transition on the pressure loss and transmission loss were made based on the finite element method. The results showed that the smooth transition of outlet pipe could decrease the pressure loss and did not affect the transmission loss at the same time; moreover, the properties of muffler with circular arc transition were much better than those of chamfer transition. On this basis, the coupling influences of transition circular arc radius and muffler size on the pressure loss and transmission loss were analyzed. It turned out that the transition circular arc of outlet pipe almost had no effect on the transmission loss but could effectively decrease pressure loss; moreover, this is a universal law and will not be changed with the change of type and size of the muffler. And with the increase of transition circular arc radius, the change rates of the pressure loss were decreasing. Further, under the premise of keeping the overall size, an automobile muffler was made a preliminary improvement by applying the layout principles of inlet and outlet pipes based on the cavity acoustic modes. After the preliminary improvement, the average transmission loss was increased by 15.8 d B in the frequency range of 750-1500 Hz, but the pressure loss was increased by 7.78% with the inlet velocity of 60 m/s. In order to decrease the pressure loss on the base of good acoustic attenuation performance, the further improvement of car muffler was made. The first chamber and third chamber of muffler could be seen as two simple flow-reversing mufflers, and 10 mm transition circular arcs were added at the entrance of outlet pipes on the basis of the preliminary improvement. Compared with the original muffler, the average transmission loss of final improved muffler in the frequency range of 750-1500 Hz was increased by 15.3 d B and slightly lower than that of preliminary improved muffler, however, the pressure loss was reduced by 25.20% with the inlet velocity of 60 m/s. In conclusion, the properties of muffler have been greatly improved after the further improvement. Integrated use of the layout principle of inlet and outlet based on the cavity acoustic modes and the effect laws of outlet pipe transition circular arc on the pressure loss can guide the muffler design.