Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is stron...Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is strongly perceived and may be a serious source of driver annoyance. Thus, many studies regarding the cavity noise mechanism and its reduction have already been conducted. In this work, a vibro-acoustic coupled analysis was conducted between a tire structure and air cavity. Using this analysis, we can more accurately simulate the tire noise performance in the region of the cavity resonance frequency. An analysis of the effects of variation of tire contour design factors was conducted, using design-of-experiments methods. Finally, a multi-objective optimization was performed using in-house codes to reduce the cavity noise level while minimizing the loss of other performances, such as diminished ride comfort and handling caused by the variations of contour. As a result of this optimization, an optimized contour shape was derived, which satisfied the multi-objective performances.展开更多
Mining operation, especially underground coal mining, always has the remarkable risks of ground control. Passive seismic velocity tomography based on simultaneous iterative reconstructive technique （SIRT） inversion ...Mining operation, especially underground coal mining, always has the remarkable risks of ground control. Passive seismic velocity tomography based on simultaneous iterative reconstructive technique （SIRT） inversion is used to deduce the stress redistribution around the longwall mining panel. The mining-induced microseismic events were recorded by mounting an array of receivers on the surface, above the active panel. After processing and filtering the seismic data, the three-dimensional tomography images of the p-wave velocity variations by SIRT passive seismic velocity tomography were provided. To display the velocity changes on coal seam level and subsequently to infer the stress redistribution, these three-dimensional tomograms into the coal seam level were sliced. In addition, the boundary element method （BEM） was used to simulate the stress redistribution. The results show that the inferred stresses from the passive seismic tomograms are conformed to numerical models and theoretical concept of the stress redistribution around the longwall panel. In velocity tomograms, the main zones of the stress redistribution arotmd the panel, including front and side abutment pressures, and gob stress are obvious and also the movement of stress zones along the face advancement is evident. Moreover, the effect of the advance rate of the face on the stress redistribution is demonstrated in tomography images. The research result proves that the SIRT passive seismic velocity tomography has an ultimate potential for monitoring the changes of stress redistribution around the longwall mining panel continuously and subsequently to improve safety of mining operations.展开更多
Investigations regarding the relation of noise performance for centrifugal pump operating in pump and turbine modes continue to be inadequate.This paper presents a series of comparisons of flow-induced noise for both ...Investigations regarding the relation of noise performance for centrifugal pump operating in pump and turbine modes continue to be inadequate.This paper presents a series of comparisons of flow-induced noise for both operation modes.The interior flow-borne noise and structure modal were verified through experiments.The flow-borne noise was calculated by the acoustic boundary element method(ABEM),and the flow-induced structure noise was obtained by the coupled acoustic boundary element method(ABEM)/structure finite element method(SFEM).The results show that in pump mode,the pressure fluctuation in the volute is comparable to that in the outlet pipe,but in turbine mode,the pressure fluctuation in the impeller is comparable to that in the draft tube.The main frequency of interior flow-borne noise lies at blade passing frequency(BPF)and it shifts to the 9th BPF for interior flow-induced structure noise.The peak values at horizontal plane appear at the 5th BPF,and at axial plane,they get the highest sound pressure level(SPL)at the 8th BPF.Comparing with interior noise,the SPL of exterior flow-induced structure noise is incredibly small.At the 5th BPF,the pump body,cover and suspension show higher SPL in both modes.The outer walls of turbine generate relatively larger SPL than those of the pump.展开更多
文摘Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is strongly perceived and may be a serious source of driver annoyance. Thus, many studies regarding the cavity noise mechanism and its reduction have already been conducted. In this work, a vibro-acoustic coupled analysis was conducted between a tire structure and air cavity. Using this analysis, we can more accurately simulate the tire noise performance in the region of the cavity resonance frequency. An analysis of the effects of variation of tire contour design factors was conducted, using design-of-experiments methods. Finally, a multi-objective optimization was performed using in-house codes to reduce the cavity noise level while minimizing the loss of other performances, such as diminished ride comfort and handling caused by the variations of contour. As a result of this optimization, an optimized contour shape was derived, which satisfied the multi-objective performances.
文摘Mining operation, especially underground coal mining, always has the remarkable risks of ground control. Passive seismic velocity tomography based on simultaneous iterative reconstructive technique （SIRT） inversion is used to deduce the stress redistribution around the longwall mining panel. The mining-induced microseismic events were recorded by mounting an array of receivers on the surface, above the active panel. After processing and filtering the seismic data, the three-dimensional tomography images of the p-wave velocity variations by SIRT passive seismic velocity tomography were provided. To display the velocity changes on coal seam level and subsequently to infer the stress redistribution, these three-dimensional tomograms into the coal seam level were sliced. In addition, the boundary element method （BEM） was used to simulate the stress redistribution. The results show that the inferred stresses from the passive seismic tomograms are conformed to numerical models and theoretical concept of the stress redistribution around the longwall panel. In velocity tomograms, the main zones of the stress redistribution arotmd the panel, including front and side abutment pressures, and gob stress are obvious and also the movement of stress zones along the face advancement is evident. Moreover, the effect of the advance rate of the face on the stress redistribution is demonstrated in tomography images. The research result proves that the SIRT passive seismic velocity tomography has an ultimate potential for monitoring the changes of stress redistribution around the longwall mining panel continuously and subsequently to improve safety of mining operations.
基金Project (51509111) supported by the National Natural Science Foundation of ChinaProject (2017M611721) supported by the China Postdoctoral Science Foundation+4 种基金Project (BY2016072-01) supported by the Association Innovation Fund of Production,Learning,and Research,ChinaProjects (GY2017001,GY2018025) supported by Zhenjiang Key Research and Development Plan,ChinaProjects (szjj2015-017,szjj2017-094) supported by the Open Research Subject of Key Laboratory of Fluid and Power Machinery,ChinaProject (GK201614) supported by Sichuan Provincial Key Lab of Process Equipment and Control,ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),China
文摘Investigations regarding the relation of noise performance for centrifugal pump operating in pump and turbine modes continue to be inadequate.This paper presents a series of comparisons of flow-induced noise for both operation modes.The interior flow-borne noise and structure modal were verified through experiments.The flow-borne noise was calculated by the acoustic boundary element method(ABEM),and the flow-induced structure noise was obtained by the coupled acoustic boundary element method(ABEM)/structure finite element method(SFEM).The results show that in pump mode,the pressure fluctuation in the volute is comparable to that in the outlet pipe,but in turbine mode,the pressure fluctuation in the impeller is comparable to that in the draft tube.The main frequency of interior flow-borne noise lies at blade passing frequency(BPF)and it shifts to the 9th BPF for interior flow-induced structure noise.The peak values at horizontal plane appear at the 5th BPF,and at axial plane,they get the highest sound pressure level(SPL)at the 8th BPF.Comparing with interior noise,the SPL of exterior flow-induced structure noise is incredibly small.At the 5th BPF,the pump body,cover and suspension show higher SPL in both modes.The outer walls of turbine generate relatively larger SPL than those of the pump.
