声呐波束形成处理通常输出各个方位上的目标能量信息,利用指向性极大值位置给出目标的大致方位。为了得到更加精确的目标方位估计,需要寻找对目标方位微小变化作出灵敏反应的物理量。分裂波束处理所输出的各个方位二子阵的相位差信息,...声呐波束形成处理通常输出各个方位上的目标能量信息,利用指向性极大值位置给出目标的大致方位。为了得到更加精确的目标方位估计,需要寻找对目标方位微小变化作出灵敏反应的物理量。分裂波束处理所输出的各个方位二子阵的相位差信息,对方位变化十分灵敏,其测向精度接近于克拉美罗下界,不需增加太大运算量即可显著提高声呐系统测向精度,在水声中得到了广泛研究和应用。对线阵分裂波束处理在水声探测中不同的应用进行了梳理和总结,重点阐述了基于分裂阵半波束处理的被动声呐宽带相关检测、主动声呐相位单元化处理、超波束形成和水下慢速目标相位差空时方差自动检测跟踪(Automatic Detection and Tracking,ADT)技术的原理、处理流程和结果。展开更多
Two small scale acoustic phased arrays with 4 elements have been designed and assembled in the laboratory. Experiments have been carried out with them. It is found that both directivity and radiation lobe width of the...Two small scale acoustic phased arrays with 4 elements have been designed and assembled in the laboratory. Experiments have been carried out with them. It is found that both directivity and radiation lobe width of the phased array can be regulated by changing the time delay between the input signals on neighboring elements. Results measured are in good agreement with those calculated. By using the phased array as an acoustic transmitter and hydrophone as a receiver, small scale acoustic well-logging simulations have been carried out both on an aluminum modei well and on a concrete one. Experimental results show that, by increasing the time delay of the input signals on neighboring elements, the steered radiation angle of the phased array becomes larger and larger, and generation conditions of the refracted compressional wave and the refracted shear wave are reached successively, and the refracted compressional wave, the refracted shear wave and the Stoneley wave are strengthened, respec-tively. Therefore, by choosing element spacing of a phased array and acoustic wave frequency appropriately, the main radiation lobe of the phased array can be widened to cover the first critical angle of all kinds of formations, which makes it possible to apply phased array acoustic well-logging in any formation continuously without regulating directivity of the phased array.展开更多
针对叶尖部位是影响近尾迹流动和声辐射的主要区域,提出V型叶尖结构,对其气动特性和叶尖区域声辐射的特征进行测试。结果发现:V型叶尖结构风力机在输出功率减小0.95%~3.50%的范围内,使得改型后风轮旋转基频及其谐波关系的频率所对应的...针对叶尖部位是影响近尾迹流动和声辐射的主要区域,提出V型叶尖结构,对其气动特性和叶尖区域声辐射的特征进行测试。结果发现:V型叶尖结构风力机在输出功率减小0.95%~3.50%的范围内,使得改型后风轮旋转基频及其谐波关系的频率所对应的旋转噪声减小2.7%~4.5%。同时对叶尖涡的脱落频率所对应的叶尖涡噪声产生影响,使之降低了2.8~9.0 d B,找到V型叶尖的高度是影响风轮旋转噪声和叶尖涡噪声降低的主要因素。展开更多
文摘声呐波束形成处理通常输出各个方位上的目标能量信息,利用指向性极大值位置给出目标的大致方位。为了得到更加精确的目标方位估计,需要寻找对目标方位微小变化作出灵敏反应的物理量。分裂波束处理所输出的各个方位二子阵的相位差信息,对方位变化十分灵敏,其测向精度接近于克拉美罗下界,不需增加太大运算量即可显著提高声呐系统测向精度,在水声中得到了广泛研究和应用。对线阵分裂波束处理在水声探测中不同的应用进行了梳理和总结,重点阐述了基于分裂阵半波束处理的被动声呐宽带相关检测、主动声呐相位单元化处理、超波束形成和水下慢速目标相位差空时方差自动检测跟踪(Automatic Detection and Tracking,ADT)技术的原理、处理流程和结果。
文摘Two small scale acoustic phased arrays with 4 elements have been designed and assembled in the laboratory. Experiments have been carried out with them. It is found that both directivity and radiation lobe width of the phased array can be regulated by changing the time delay between the input signals on neighboring elements. Results measured are in good agreement with those calculated. By using the phased array as an acoustic transmitter and hydrophone as a receiver, small scale acoustic well-logging simulations have been carried out both on an aluminum modei well and on a concrete one. Experimental results show that, by increasing the time delay of the input signals on neighboring elements, the steered radiation angle of the phased array becomes larger and larger, and generation conditions of the refracted compressional wave and the refracted shear wave are reached successively, and the refracted compressional wave, the refracted shear wave and the Stoneley wave are strengthened, respec-tively. Therefore, by choosing element spacing of a phased array and acoustic wave frequency appropriately, the main radiation lobe of the phased array can be widened to cover the first critical angle of all kinds of formations, which makes it possible to apply phased array acoustic well-logging in any formation continuously without regulating directivity of the phased array.
文摘针对叶尖部位是影响近尾迹流动和声辐射的主要区域,提出V型叶尖结构,对其气动特性和叶尖区域声辐射的特征进行测试。结果发现:V型叶尖结构风力机在输出功率减小0.95%~3.50%的范围内,使得改型后风轮旋转基频及其谐波关系的频率所对应的旋转噪声减小2.7%~4.5%。同时对叶尖涡的脱落频率所对应的叶尖涡噪声产生影响,使之降低了2.8~9.0 d B,找到V型叶尖的高度是影响风轮旋转噪声和叶尖涡噪声降低的主要因素。
