正演法压制分布式光纤声波传感系统“弹簧波”

分布式光纤声波传感系统采集到的VSP资料具有采样密度高、施工成本低的优点,也存在耦合效果差干扰波丰富的缺点,特别是光缆震荡产生的“弹簧波”干扰具有能量强、频带分布范围广、与有效波分离难度大的特点。本文针对常规的速度滤波方法不能有效压制“弹簧波”干扰的问题,利用统计法获得干扰波振幅、频率变化规律,正演“弹簧波”模型,从原始记录中衰减“弹簧波”,达到压制干扰的目的。实际资料成像效果表明,正演法压制分布式光纤传感系统“弹簧波”技术方法合理、有效。

井中悬挂式分布式光纤传感系统干扰波分析及压制

井中分布式光纤声波传感(DAS)系统作为新一代井中地震观测装备,与传统的井中三分量数字采集系统相比,具有施工安全、高效,一次激发即可实现全井段观测的优点。DAS系统具有传、感一体的特点,因此在井中光缆悬挂观测时无法实现光缆的完全推靠以及井口段光缆张力的有效减少,这导致地震资料采集时会产生较强的缆波和耦合干扰,从而影响地震资料的信噪比。从地震波的传播规律出发,分析了DAS井中观测干扰波的产生过程和特征,明确了DAS系统缆波干扰和“弹簧波”干扰是由波到达光缆时沿着光缆传播而形成。采用随机中值滤波技术压制缆波干扰以及模拟正反演法压制“弹簧波”干扰,提高了地震采集资料的信噪比。该方法在实际地震资料应用的结果表明:DAS干扰波的分析合理,噪声压制效果明显,去噪后的DAS数据能够获得较好的井中地震成像结果。

A new modeling approach of pressure waves at the inlet of internal combustion engines

This paper presents a new model used to describe the propagation of pressure waves at the inlet systems of internal combustion engine. In the first part, an analogy is made between the compressible air in a pipe and a mechanical ideal mass damper spring system. A new model is then presented and the parameters of this model are determined by the use of an experimental setup (shock tube test bench). With this model, a transfer function is defined in order to link directly the pressure and the air mass flow rate. In the second part, the model is included into an internal combustion engine simulation code. The results obtained with this code are compared to experimental ones which are measured on a one-cylinder engine test bench. This last one is driven by an electric motor in order to study only the effect of the pressure waves on the engine behavior. A good agreement is obtained between the experimental results and the numerical ones and the new approach is an alternative method for modeling the pressure wave phenomena in an internal combustion engine manifold.