Abstract
The self-resonating waterjet (SRWJ) has been applied in petroleum, natural gas, and mining engineering ever since its strong erosion ability in deep-hole drilling was recognized. Aiming at further improving the working efficiency of SRWJs, the effects of the exit angle of the organ-pipe nozzle on the axial pressure oscillations of the jet were experimentally studied. Six exit angles of θ = 0°, 30°, 45°, 60°, 75°, and 90° were employed in the experiment, and the axial pressure oscillation peak (Pmax) and amplitude (Pa) were used for characterizing the performance of SRWJs. It was found that the exit angle greatly affects the axial pressure oscillations, including the development trends against the standoff distance and the magnitudes of Pmax and Pa. Under testing with two inlet pressures, the exit angle of θ = 0° always resulted in the greatest Pmax and Pa within the range of the testing standoff distance. With the increase of standoff distance, both Pmax and Pa first increased and then decreased when the exit angle was 0°; while they kept decreasing when the exit angle was 30°, 45°, 60°, 75°, and 90°. Moreover, the exit angles of θ = 90° and 60°, corresponding to inlet pressures of Pi = 10 MPa and 20 MPa, led to both the minimum magnitudes of Pmax and Pa under the experimental conditions. The results also indicate that the exit angle affects the interactions between the nozzle lip and the jet and help provide information for improving the working efficiency of SRWJs in practical applications.
Highlights
When water is pressurized and flows through a tiny orifice, a high-speed waterjet possessing strong impact power is generated
We studied the preferred Strouhal number used in self-resonating waterjet (SRWJ), and found that the optimum values are
Aiming at improving the efficiency of deep-hole drilling, the pressure oscillations of SRWJs were experimentally studied with organ-pipe nozzles of various exit angles
Summary
When water is pressurized and flows through a tiny orifice, a high-speed waterjet possessing strong impact power is generated. It is claimed that a high-speed waterjet is able to disintegrate most existing materials by transmitting high energy to an extremely small area and is extremely suitable for cutting hard rocks [1]. Waterjet technology is being widely used in the energy field as an efficiency operation assisting drilling [2]. Liu et al [3] studied the damage models of rock breaking assisted with a high-speed waterjet, in order to improve the life and working efficiency of conical cutters used in excavation. As waterjet technology has been efficiently used for slotting in coal mining of low permeability, Shen et al [4] investigated the mechanism of pressure relief and permeability enhancement under the waterjet slotting process.
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