Effects of pulsating fluid at nozzle inlet on the output characteristics of common and self‐excited oscillation nozzle.

High‐speed water jets are key technologies for increased production efficiency in oil drilling, and high‐speed self‐excited oscillating pulsed water jets (SEOPWs) offer many advantages compared to continuous jets for most industrial applications. Therefore, many studies have focused on this topic. However, the current studies on hydraulic pulsed jets have rarely extended to integrated modeling of the high‐speed water jet transmission process. To better apply the SEOPWs, based on fluid mechanics, the theoretical model of the plunger pump–pipeline–nozzle is established, and the sensitivity of different nozzles on the pulsating fluid is studied in the time domain. Furthermore, the vibration characteristics of the nozzle are further investigated in the frequency domain. The results show that the common nozzle has an enlarged role in the pressure amplitude, the Helmholtz nozzle enlarges the pressure peak and amplitude, and the amplification is more obvious with the speedy growth on the plunger pump. However, as the pipeline becomes longer, the difference between the pressure of the inlet and outlet does not change. Therefore, the nozzle is more sensitive to the change in the plunger pump speed. In the frequency domain, the secondary frequency peak for the Helmholtz nozzle is 1.26 times larger than the interference frequency, while it is 1.08 times for the common nozzle. Helmholtz nozzles tend to produce stronger natural vibrations than common nozzles. By comparing the impact force, the experimental results show good agreement with the simulated results. The study provides a theoretical basis for water jet‐assisted drilling in deep wells and lays the foundation for the better application of self‐oscillating impact drilling tools. [ABSTRACT FROM AUTHOR]