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Helmholtz resonator is a very common anechoic measure, and it is widely used in pipe acoustic fields. Based on the enlightenment of the classic Helmholtz resonator, this paper proposes a headrest resonator model and extends it to the acoustic field of the passenger cabin to improve the road noise in the car. Firstly, through the theoretical model of Helmholtz resonator, the relationship between its resonance frequency and the geometric size of the resonator is clarified. Secondly, the influence of the headrest resonator on the acoustic field characteristics of the car is studied through finite element simulation analysis. It is demonstrated that the headrest resonator is placed in the car, and the sound pressure distribution characteristics of the passenger's inner ear near the resonance frequency change significantly. At the same time, through 3D printing, a sample of the headrest resonator is made.

For fracture cracks that occurred in the tight coupling exhaust manifold durability test of a four-cylinder gasoline engine with EGR channel, causes and solutions for fracture failure were found with the help of CFD and FEA numerical simulations. Wall temperature and heat transfer coefficient of the exhaust manifold inside wall were first accurately obtained through the thermal-fluid coupling analysis, then thermal modal and thermoplastic analysis were acquired by using the finite element method, on account of the bolt pretightening force and the contact relationship between flange face and cylinder head. Results showed that the first-order natural frequency did not meet the design requirements, which was the main reason of fatigue fracture. However, when the first-order natural frequency was rising, the delta equivalent plastic strain was increasing quickly as well.

In order to predict the thermal fatigue life of the internal combustion engine exhaust manifold effectively, it was necessary to accurately obtain the unsteady heat transfer process between hot streams and exhaust manifold all the time. This paper began with the establishment of unsteady coupled heat transfer model by using serial coupling method of CFD and FEA numerical simulations, then the bidirectional thermal coupling analysis between fluid and structure was realized, as a result, the difficulty that the transient thermal boundary conditions were applied to the solid boundary was solved. What's more, the specific coupling mode, the physical quantities delivery method on the coupling interface and the surface mesh match were studied. On this basis, the differences between strong coupling method and portioned treatment for solving steady thermal stress numerical analysis were compared, and a more convenient and rapid method for solving static thermal stress was found.