旋转配流式扭转冲击钻具设计与分析

为了减轻硬地层PDC钻头的黏滑振动,实现提速增效,研制了一种新型旋转配流式扭转冲击钻具。基于工具结构与工作原理的分析,建立了摆锤运动数学模型,研究了摆锤的运动规律,分析了水力参数和结构参数对其冲击性能的影响,并通过室内实验验证了工具结构的可行性。结果表明,摆锤在不同的阶段均做非线性加速运动,摆锤冲击功、冲击功率均与钻井液排量和摆锤转动惯量呈正相关,而摆锤固有冲击频率与钻井液排量呈正相关,与摆锤转动惯量呈负相关。研究结果为工具的结构优化和推广应用提供了理论支撑。

旋转配流激振阀输出特性分析及试验验证

提出一种旋转配流激振阀,为研究进口压力和阀芯换向频率对旋转配流激振阀输出特性的影响规律,采用多参考系方法(multiple reference frame,MRF)进行流场动态仿真,获得旋转配流激振阀输出压力和流量的动态特性曲线,并搭建电液激振试验台对仿真结果进行验证。研究结果表明:进口压力由14 MPa增至16 MPa,旋转配流激振阀输出压力、流量峰值分别提高了1.16%和6.98%;阀芯换向频率由100 Hz增至180 Hz,输出压力、流量峰值分别降低了1.24%和18.6%;进口压力工况下,输出压力、流量的仿真和试验结果的平均误差分别为0.18%、2.14%;换向频率工况下,输出压力、流量的仿真和试验结果的平均误差分别为0.10%、1.76%。仿真和试验结果整体趋势基本一致,证实了旋转配流激振阀结构的合理性及仿真模型的正确性。

A novel control strategy for load converter of DC isolated distribution system under unbalanced loading conditions

A novel control strategy for the load converter supplying the unbalanced AC load in a DC isolated distribution system is presented. The control algorithm results in balanced and sinusoidal load voltages under unbalanced AC loading. The unbalanced load is characterized in the d-q-0 rotating coordinate based on symmetrical sequence components. Also, the mathematical model of the load converter in both a-b-c and d-q-0 coordinates is derived by using the average large signal model. Then, two control strategies for the load converter are presented. The first one uses the conventional d-q-0 controller to ensure the voltage and current regulation. The second one is a newly proposed control strategy based on the decomposition of the voltage and current into in-stantaneous positive, negative, and zero sequences. These three sequences are controlled independently in their own reference frames as DC signals. The performance of the load converter using these two control strategies is compared. Simulation results show the validity and capability of the newly proposed control strategy.