Abstract:The Downhole Drill string Absorption & Hydraulic Supercharging Device is a downhole tool for rock breaking,which is implement by using assiated ultrahigh pressure jet.Based on the working principle of the device of using vibration energy of the downhole drill string,the method of piston excitation is used to modulate ultrahigh pressure jet to improve the rate of penetration (ROP) in drilling well.In order to research the influence law of each parameter on working characteristics of the tool,theoretic basis was provided for its application on site.Based on the woring principle of the tool,mathematical model was established with simmulated analysis,and its working characteristics were researched.By taking the Effective rock water power (The power contained in drilling fluid which could break rock output by the device) as the optimization goal,the influence law was obtained between both the drilling parameters of tool and the ultrahigh pressure nozzle equivalent diameter with performance characteristic.The results show that along with increasing of the ultrahigh pressure nozzle equivalent diameter,the peak pressure output by the device is decreased,and increased along with increasing of both weight on bit and elastic stiffness.When the diameter of jet nozzle is at 3 mm,the effective rock breaking output of the device of water power is at maximum.Along with increasing of drilling pressure and rotational speed,the effective rock braking water power is increased.In order to achieve the best working effect of the device for rock breaking water power in unit time,there is an optimal combination of the parameters which between the drilling parameters and the ultrahigh pressure nozzle equivalent diameter.