水力脉冲射流旋流流场数值模拟

为研究水力脉冲射流流场内旋流流场的变化特性,通过建立井底边界条件下单喷嘴脉冲射流冲击流场物理模型,对脉冲射流旋流流场进行了数值模拟研究。结果表明,非稳态旋流是脉冲射流流场的一个显著特征,对脉冲射流钻井提速起到重要作用,旋流速度和范围具有周期性变化且不随脉冲频率发生改变;在单周期内,旋流强度与脉冲射流速度变化具有一致性,旋流影响范围由前期的快速扩大到后期的缓慢扩大,一直保持增大趋势;旋流作用强于射流动能是脉冲射流产生局部脉动负压的主要原因,有利于降低压持效应;旋流流场改变钻头表面的压力分布,有利于提高钻头清洗效果。研究结果对指导脉冲射流提速技术具有一定的参考价值。

Numerical simulation research on hydro-pulsed jet swirl fluid flow field

In order to investigate the varying characteristics of swirl flow field within hydro-pulsed jet flow field, the numerical simulation research was conducted on the pulsed jet swirl flow field by building a physical model of single-nozzle pulsed jet impact flow field under bottom hole boundary condition. The result shows that the unstable swirl flow is a significant feature of pulsed jet flow field and plays an important part in accelerating pulsed jet drilling. The swirl flow rate and range change periodically and do not change with the pulse frequency. Within single cycle, the swirl flow is consistent with the change of pulsed jet rate, and range of influence of swirl flow changes from rapid expansion to later slow expansion, maintaining an expansion trend all the time. The swirl flow effect is superior to the jet energy, which is the main reason for local pulse negative pressure generated by pulsed jet. This helps reduce the chip hold-down effect. The swirl flow field changes the pressure distribution on bit surface and helps clean the bit. The research findings are of some reference value to guidance of pulsed jet accelerating technique.