Experimental study on the effect of high confining pressure on the jet performance of conical straight nozzle
In order to study the effect of high confining pressure on jet performance in deep wells,a high confining pressure loading device based on throttling control principle was used to carry out at 90 MPa confining pressure continuous jet with a single nozzle.The changes of jet axis dynamic pressure,nozzle pressure drop,flow coefficient and other parameters with confining pressure were analyzed.The results show that with the increase of confining pressure(0～90 MPa),the dynamic pressure along jet axis tends to change gently after it gradually decreases,and the larger the jet distance(dimensionless jet distance of 2～10),the smaller the jet attenuation amplitude(75%to 50%).For example,at 2 times the jet distance,the nozzle flow coefficient shows an increasing trend(0.8 to 0.98),and the nozzle pressure drop shows a decreasing trend,but the decreasing range is small(both are less than 6.25%),the greater the theoretical flow velocity(150～350 m/s),the greater the influence of the dynamic pressure along the jet axis on the confining pressure,and the smaller the increase of the nozzle flow coefficient(22.5%to 4.5%).The analysis shows that the cavitation phenomenon inside the nozzle and the resistance of the environmental medium to the jet are the main causes of the above phenomena,and the performance of the jet can be strengthened by changing the jet form and improving the flow coefficient.The research results have guiding significance for the design and type selection of water jet operation parameters in deep and ultra-deep wells.
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