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Abstract
In order to improve the acoustic attenuation performance of an exhaust muffler of a 175 series of agricultural diesel engine, automatic matched layer method of finite element is adopted on the basis of LMS Virtual.Lab software to simulate the non-reflecting boundary conditions, which can avoid the complex calculation and then figure out the value of propagated sound power directly and finally obtain the transmission loss of the exhaust muffler. Compared with the experimental data, it can be found that the error between the simulation and measured values is small, and it can be accurately simulated for the acoustic performance of the exhaust muffler at the frequencies smaller than 3000 Hz, which verifies the validity of the acoustic solution. An improved design that properly distributes the insertion length of intubation, increases the length-diameter ratio, and adds the length of the first expansion cavity is proposed for the poor acoustic attenuation performance in low and medium frequencies. Compared with the original design, the transmission loss value at low and medium frequencies obviously increases, so the acoustic attenuation performance at the frequencies becomes better.
Keywords
Diesel engine, exhaust muffler, transmission loss, acoustic simulation
Date received: 10 December 2014; accepted: 2 February 2015
Academic Editor: Hongwei Wu
(ProQuest: ... denotes formulae omitted)
Introduction
Along with the rising motor vehicle population, the noise pollution becomes serious and exhaust noise has become the main noise source of an engine, so the acoustic attenuation performance of an exhaust muffler which has been adopted as the most effective method in dealing with exhaust noise seems particularly important. 1,2 At present, the main research methods for measuring the acoustic performance of the exhaust muffler include transfer matrix method, finite element method, and boundary element method,3 while the finite element method has become the commonly used threedimensional analysis method because of its good adaptability. 4 Finite element method can simulate various types of mufflers, especially suitable for solving the muffler that has complex shape and cross-sectional structure; meanwhile, the acoustic precision is higher at low and medium frequencies.5-7 Since Clough et al. proposed the finite element technology that had achieved rapid development in the engineering field for the first time, many experts, both domestic and abroad, have been doing research on it intensively....