A STUDY ABOUT THE EFFCT OF THE STRUCTURE PARAMETERS OF THE MULTI-ORIFICES NOZZLE ON NOZZLE DISCHARGE COEFFICIENT

摘要

As the "core" of radial jet drilling (RJD) technology, the multi-orifices nozzle must forcefully pulling the nozzle forward and effectively break the rock to form a radial hole. But nozzle discharge coefficient of the multi-orifices nozzle is always smaller than 0.6 in most cases that means only less than 36 percent hydraulic energy transfers to the fluid. It is extremely important to study the influence coefficients of the nozzle discharge coefficient. In this research, exact expression of the nozzle discharge coefficient was derived and effects of numbers of orifices and flow rate were studied by experiment. Results show that the nozzle discharge coefficient of multi-orifices nozzle depends on the discharge coefficient and weight ratio of each single orifice; the discharge coefficient of each orifice lies on its surface degree of finish, diameter, length, Reynolds number, and the complexity of the flow field; most of the energy loss of each orifice was caused by local resistance loss; the local resistance coefficient would slightly decrease with flow rate while greatly increase with the orifices due to the complicated flow. When a multi-orifices nozzle is designed, larger diameter and fewer number orifices are strongly recommended and optimal combination should be tested by experiment.