Analysis of the Characteristics of the Rotary Impact Drilling Tool with an Elastic Element Accumulator

Conventional impact drilling tools can be characterized by low impact forces and instability in impact frequencies.To overcome these shortcomings,an innovative rotary impact drilling tool with an elastic element and cam structure has been developed.With the PDM drives,a hammer rotates and collides with the teeth of the anvil to generate impact load.Based on the dynamics of impact,a numerical model for the tool’s impact process was built.In addition,impact load of the innovative tool powered by mud pump was tested by using drilling pumps and a high speed stress acquisition system.Results showed that the impact load curves were close to harmonic curve at the peak impact force 18-43 kN,and that impact loads would increase with the increase of compression volumes of the elastic elements.This tool’s impact frequency was 25.7-37.2 Hz,and could be adjusted from flow rates of mud pump.Dynamic analysis and experimental results showed that the frequency was the product of the rotary rate of screw drill times the number of the teeth,which was proportional to the flow rates of drilling fluids.The impact load could be adjusted from the preload of the elastic elements and it would increase with increase of the preload in a power function.The impact durations was in positive power function with hammer weight and in a negative power function with the deformation coefficients of the teeth.The development of the rotary impact drilling tool with an elastic element accumulator may provide innovative design techniques and technical solutions for the development of rotary and percussion drilling operations.