Simply put, the pressure decreases on the walls of the nozzle itself, while the pressure of the outgoing water increases. With the increase of the pressure drop of the nozzle, the stagnation pressure of the orifice wall increases; when the pressure drop of the nozzle increases by a particular value, the pressurization value in the orifice also increases by the same value, e.g. the relative increase in the pressure drop of the nozzle is the same as that of the pressurization in the orifice (Table 3,. At the right end of the flow field, impact pressure increases with the growth of the nozzle pressure drop because the greater the nozzle pressure drop, the greater the kinetic energy and impact pressure. However, the slope of the axial pressure curve in the open hole is much smaller than that of the corresponding curve in the housing hole, and the attenuation range of the jet in the open hole is 90 to 110 mm.
When the SC-CO2 fluid reaches the nozzle cylinder section, pressure energy is converted into kinetic energy and axial pressures with different pressure drops of the nozzle decrease to become the confining pressure. According to the figure, with the increasing pressure drop of the nozzle, the orifice pressure and the pressurization of the jet also increase. In other words, for a nozzle of the same diameter, a larger flow rate is required to generate a greater pressure drop in the nozzle. The pressure drop of the nozzle, respectively, is 15, 20, 25, 30 MPa, which is the inlet pressure of the nozzle taken from 20, 25, 30, 35 MPa.
In addition, the quantitative analysis indicates that the increase in axial pressure is consistent with the increase in the nozzle pressure drop by the same value. In addition, the axial pressure drop length is approximately the same (70 to 80 mm), which indicates that the pressure drop with the nozzle affects the attenuation of the jet marginally and, despite the large difference in the pressure drop of the nozzle, as the distance between the jet increases, the axial pressure difference in the area is significantly reduced. The maximum static pressure in the hole is not at the entrance to the hole, but at the depth of the hole, without axial and radial pressure gradients, and all static pressure values are equal to the total pressure (fig. The greater the pressure drop of the nozzle, the greater the kinetic energy of the fluid at the outlet and the greater the hydrostatic pressure of the fluid in the drill channel; therefore, the pressurization of the jet is high. The nozzle pressure drop is defined as the difference between the nozzle inlet pressure and the nozzle outlet pressure.
The quantitative analysis also found that, in the open orifice, the pressure drop of the nozzle increases every additional 5 MPa and the pressurization of the orifice increases to 1.04 MPa; as for the same confinement pressure, if the pressure drop of the nozzle increases by the same value, the increase in the pressurization of the orifice is also constant. Jet pressurization is essentially the conversion of the kinetic energy of the fluid at high velocity at the nozzle outlet to the hydrostatic pressure of the fluid in the drill channel. The nozzle pressure of the nozzle hinge-type electrohydraulic servo valve that meets the design criteria is 20 to 100% of the oil supply pressure. The pressure and velocity distribution of six-diameter nozzles subject to different pressures and confinement pressures was obtained by numerical simulation, with a total of 44 combined groups of nozzle parameters. Under experimental conditions, when the pressure drop of the nozzle is 15 MPa, the orifice pressure is 11.8 MPa and the pressurization of the jet is approximately 6.8 MPa.
