Zhiyong Hao

Study on optimization method of GDI engine combustion noise based on noise-performance map

An optimization of GDI engine combustion noise was evaluated through experimental and simulation methods. First, finite element model of engine was established; the vibration response and combustion noise caused by combustion incentives were calculated by the direct frequency response method and the acoustic transfer vector method. Above of this, the pure combustion noise attenuation curve was defined. According to the combustion spectrum calculated, the optimized frequency range was determined. Then, combining with the analysis result of the combustion noise attenuation curve, the frequency position of cylinder pressure spectrum to be optimized was obtained. Besides this, the combustion parameters were measured through test and its relationship to cylinder pressure spectrum and engine power performance was studied, the noise-performance map was established. Based on optimized cylinder pressure spectrum and noise-performance map, the optimum values of combustion parameter were marked very quickly. The results show that, when the fuel injection timing optimization value was used, combustion noise was reduced most by 6.4 dB in the range of 0â–“1000 Hz, while torque reduced only by 3.8 Nm, which achieved the goals of the favoring NVH performance and engine power performance.

Aerodynamic noise radiating from the inter-coach windshield region of a high-speed train

The aerodynamic noise has been the dominant factor of noise issues in high-speed train as the traveling speed increases. The inter-coach windshield region is considered as one of the main aerodynamic noise sources; however, the corresponding characteristics have not been well investigated. In this paper, a hybrid method is adopted to study the aerodynamic noise around the windshield region. The effectiveness of simulation methods is validated by a simple case of cavity noise. After that, the Reynolds-averaged Navier–Stokes simulation is used to obtain the characteristics of flow field around the windshield region, which determine the aerodynamic noise. Then the nonlinear acoustic solver approach is employed to acquire the near-field noise, while the Ffowcs-Williams/Hawking equation is solved for far-field acoustic propagation. The results indicate that the windshield region is approximately an open cavity filled with severe disturbance flow. According to the analysis of sound pressure distribution in the near-acoustic field, both sides of the windshield region appear symmetrical two-lobe shape with different directivities. The results of frequency spectrum analysis indicate that the aerodynamic noise inside inter-coach space is a typical broadband one from 100 Hz to 5k Hz, and most acoustic power is restricted in the low-medium frequency range (below 500 Hz). In addition, the acoustic power in the low frequency range (below 100 Hz) is closely related to the cavity resonance with the resonance peak frequency of 42u2009Hz. The overall sound pressure level at different speeds shows that the acoustic power grows approximately 5th power of the train speed. Two forms of outside-windshields are designed to reduce the noise around the windshield region, and the results show the full-windshield form is better in noise reduction, which apparently eliminates interior cavity noise of inter-coach space and lessens the overall sound pressure level on the sides of near-field by about 13 dB.