Resistant mufflers are commonly used in the wide band noise control of the exhaust of tractor internal combustion engines due to their simple structure, broadband frequency performance and long service life. In this paper, a corrugated perforated pipe muffler was proposed based on an improved design of a straight-through perforated pipe muffler to reduce the exhaust noise of internal combustion engines. The acoustic attenuation performance of the corrugated perforated tube muffler under the action of nonuniform flow and a temperature gradient was predicted by using the one-way flow-acoustic coupling method, which combines computational fluid dynamics and the acoustic finite element method. The pressure loss and self-noise of the corrugated perforated tube muffler were compared with those of the straight-through perforated tube muffler. The influence of the structural parameters of the corrugated perforated tube mufflers on the transmission loss was analyzed. The significance level of the perforation diameter, peak height, distance between adjacent peaks, and peak width on the transmission loss of the corrugated perforated tube muffler was studied by multiple linear regression analysis.

Exhaust system noise is a major noise source of diesel tractor engines. In this article, this problem is improved by using bionics to alter the noise transmission route. By imitating the unique microstructures of owls, goshawks and sharks, the noise reduction effect was studied by designing bionic surface textures for the inner walls of exhaust tailpipes through bionic modification. Different shapes of textures (rectangle, sine, diamond, triangle, inverted triangle, and a combination of all 5 different shapes) with heights of 1.5 mm were designed for application on the inner walls of the exhaust tailpipes. Under the premise of not changing the structure and arrangement of the entire exhaust tailpipe system, bionic nonsmoothing and basic acoustic theories were used in 3D modeling, mesh discretization and acoustic simulation for each convex texture. The noise reduction effects on different tractor bionic exhaust tailpipes were studied while utilizing identical convex texture heights, and the convex texture with the best noise reduction effect was identified.

The exhaust tailpipe of a certain type of tractor was improved from the perspective of bionics, and bionic triangular convex texture was added to the inner surface of the exhaust tailpipe. The bionic tailpipe was proposed to improve noise reduction performance without changing the overall size parameters of the prototype tailpipe. Acoustics simulation software was used to predict the aeroacoustics noise and transmission loss of the exhaust tailpipe. Bionic exhaust tailpipes with triangular textures of different numbers of circumferential columns, height, and top angles were analyzed to study the noise reduction performance. The results showed that the proposed bionic exhaust tailpipes with triangular convex textures reduced the total sound pressure level and improved the transmission loss of the prototype exhaust tailpipe. To increase the transmission loss, a genetic algorithms (GA) optimized back-propagation neural network (BP) was used to optimize the bionic triangular convex texture parameters. By studying the aerodynamic noise reduction mechanism of bionic tailpipes, the research suggested that a secondary vortex appeared near the bionic texture and reduced aerodynamic drag and aeroacoustics noise. In addition, the sound pressure level amplitude nephogram, velocity vector nephogram, and velocity amplitude nephogram of the exhaust tailpipes were analyzed to study the vibration noise reduction mechanism of the bionic tailpipes. Then, the noise reduction performance was experimentally evaluated. The experimental results of the bionics exhaust tailpipes with triangular convex textures were analyzed and compared to that of the prototype tailpipe. The results demonstrated that the bionic exhaust tailpipes were able to attenuate noise.