Enhancement of cavitation intensity and erosion ability of submerged cavitation jet by adding micro-particles

The organ-pipe nozzle is widely used because of its generation of self-resonating cavitating jets which combines the advantages of cavitating jets and pulsed jets. In order to improve the working efficiency of organ-pipe nozzle by studying the influence of internal surface roughness on the characteristics of high pressure jet under high Reynolds numbers, the relations between turbulent boundary layer and surface roughness are theoretically analyzed, and the laws of the axial pressure fluctuation and the diffusion angle of the jet are investigated by experiment. The results show that, the peak pressure, the rage of pressure fluctuation and the diffusion angle are influenced more greatly by the surface roughness when the inlet pressure is greater. There exists a minimum roughness number, above which the diffusion angle starts to increase while the peak pressure and the rage of pressure fluctuation starts to decrease greatly. For a certain inlet pressure, there exists a critical roughness number, below which the axial pressure fluctuation increases at first and then decreases with the increase of stand-off distance, while above which the axis pressure fluctuation only decreases when the stand-off distance increases. Based on the experimental data, a preliminary mathematical model of the axial peak pressure relating to inlet pressure, internal surface roughness and stand-off distance was established by utilizing the principle of conservation of energy.

Experimental Investigation on the Influence of Internal Surface Roughness of Organ Pipe Nozzle on the Characteristics of High Pressure Jet

Effects of nozzle lip geometry on the cavitation erosion characteristics of self-excited cavitating waterjet

Microstructure effects on fracture failure mechanism of CrAl/CrAlN coating

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.

Effects of Nozzle Exit Angle on the Pressure Characteristics of SRWJs Used for Deep-Hole Drilling

Self-resonating pulsed waterjet (SRPW) is superior to plain waterjet in many ways and is being employed in numerous applications To further improve the performance of SRPW, the optimal value of the preferred Strouhal number (Sd), which is used to determine the chamber length of a self-resonating nozzle, was experimentally studied at inlet pressures of 10 MPa and 20 MPa The axial pressure oscillation peak and amplitude were used to evaluate the performance of SRPW, in order to find the optimum Sd value Results show that Sd value determines the self-resonance behavior of an organ-pipe nozzle and greatly affects the intensity of the axial pressure oscillation Under the experimental conditions, the optimum Sd values are 0315 and 0278 respectively, corresponding to inlet pressures of 10 MPa and 20 MPa Compared with the default value of 03 obtained from air jet experiment, the optimum Sd value at inlet pressure of 10 MPa is a little larger and oppositely a bit smaller at inlet pressure of 20 MPa Thus, if the inlet pressure is not considered, Sd value of 03 is reasonable for determining the chamber length of a self-resonating nozzle for generating effective SRPW

Experimental investigation of the preferred Strouhal number used in self-resonating pulsed waterjet

The invention discloses a front mixed abrasive jet generating device. The front mixed abrasive jet generating device is composed of a high-pressure pump, electromagnetic valves, a jet pump, an abrasive box, an abrasive tank, a high-pressure nozzle, a cutter, an abrasive concentration sensor, a vibrating ball. a stirring ball, an overflow valve, a self-vibration pulse nozzle and a control computer;the high-pressure nozzle is fixed at the top end of the abrasive tank and points to the center of the abrasive tank; the vibrating ball is fixed at the center of the spherical abrasive tank through two springs, and the stirring ball with the larger water density is static at the bottom of the cavity; the self-vibration pulse nozzle is fixed on one side of the bottom of the abrasive tank and points to the stirring ball; an outlet is formed in the upper part of the abrasive tank and is connected with the cutter through a high-pressure pipeline, and the abrasive concentration sensor is arrangednearby the outlet; and the two electromagnetic valves and the abrasive concentration sensor are connected with a control computer through a data line. Compared with the prior art, the front mixed abrasive jet generating device has the advantage that the uniformity degree of mixing of abrasive and water can be remarkably increased, the concentration of the abrasive can be accurately controlled, andthe potential safety hazard caused by the settlement of the abrasive can be avoided.

Front mixed abrasive jet generating device

The invention discloses a double-tank double-pump front mixed abrasive jet continuous working system The system comprises two high-pressure abrasive tanks for alternately feeding a pre-booster device The pre-booster device includes two groups of sand inlets and water inlets, the two groups of sand inlets and water inlets are connected to the two high-pressure abrasive tanks and water pumps corresponding to the abrasive tanks respectively, the two groups of sand inlets and water inlets are respectively provided with electromagnetic valves, the effective contact areas of the electromagnetic valves on both sides of the sand inlets and the water inlets are the same, the valves are opened and closed by a direct current motor, and the direct current motor is also provided with an energy accumulator for voltage regulation The outlet of the pre-booster device is connected to a nozzle through a pipeline The system aims at the problems that the switching of the abrasive tanks in the existingabrasive jet interrupts the sand supply and affects the cutting quality, and the pressure pulsation generated in the boost waiting and switching process is eliminated through the pre-booster device,thereby achieving the continuous work of the front mixed abrasive jet in a true sense

Double-tank double-pump front mixed abrasive jet continuous working system

The invention discloses an extrusion-type pulse jet flow generating device based on electromagnetic drive. The extrusion-type pulse jet flow generating device comprises an extrusion plunger piston fabricated by a ferromagnetic body, reset springs, two electromagnets and a containing cavity composed by connecting a shell body and a nozzle connection end cover, the containing cavity is divided intoan L cavity and an R cavity by the extrusion plunger piston, the two electromagnets are installed on two sides of the extrusion plunger piston correspondingly and are connected through the reset springs, an inlet of the shell body is connected with the L cavity and the R cavity through flow passages with one-way valves correspondingly, the L cavity and the R cavity are also connected through the flow passages with the one-way valves, and the nozzle connection end cover is internally provided with an outlet flow passage. According to the extrusion-type pulse jet flow generating device based onthe electromagnetic drive, the extrusion plunger piston is made to move in the left and right directions inside the containing cavity by means of the manner that the two electromagnets alternately generate magnetism, and then periodic extrusion is applied on the outlet flow passage to generate the pulse jet flow, pressure pulsation of a required pump delivery system can be greatly reduced, stepless frequency modulation can be performed on the pulse jet flow in a certain range, and feasible technical guarantee is provided for the application and research of pulse water jet flow.

Fan Qi

Papers

Experimental investigation of the preferred Strouhal number used in self-resonating pulsed waterjet

Effects of Nozzle Exit Angle on the Pressure Characteristics of SRWJs Used for Deep-Hole Drilling

Front mixed abrasive jet generating device

Double-tank double-pump front mixed abrasive jet continuous working system

Extrusion-type pulse jet flow generating device based on electromagnetic drive