RESEARCH OF THE DYNAMIC CHARACTERISTICS ON A NEW HYDRAULIC SYSTEM OF ELECTRO-HYDRAULIC HAMMER

A new typed hydraulic system of electro hydraulic hammer is researched and developed By means of power bond graphs the modeling and simulation to the dynamic characteristics of the new hydraulic system are performed The experimental research which is emphasized on the blowing stroke is also performed It is proved from the result of simulation and experiment that this new hydraulic system possesses such advantages as simplification of structure,flexibleness of operation and reliability of working Especially it possesses better dynamic characteristics

Employment of mud-pulse generator for improvement of efficiency of a wellbore producing in complex mining and geological conditions

In this study,the employment of mud-pulse generators to improve the efficiency of wellbores under complex mining and geological conditions is examined.A systemic analysis is made of the primary theoretical basis of the study.The benefits of a mud-pulse generator(a high-impulse hydraulic hammer)for wellbore production are stated based on the presented theoretical basis.The results not only show the benefits of mud-pulse generator employment but also provide an analysis of methods that can be used to improve the high-impulse hydraulic hammer efficiency.The acquired results have a substantial practical value not only for specialists,who research,develop,and manage wellbore operations,but also for engineers,who improve the process and modernize existing wellbores,and other experts in the field of wellbore production.

A time scale regard on percussion drilling

This paper examines the performance of three families of percussive drilling methods,Churn(CD),Down-the-Hole(DTH),and Top-Hammer(TH),through the prism of time scales.These time scales characterize different aspects of the dynamics of the drilling process.One time scale represents the travel time of an elastic perturbation in the hammer,while another one corresponds to the travel time in the drillstring and/or the bit assembly.The duration of the response of the bit/rock interface to an impulse load,and the duration of the pulse generated by the impact of the hammer in DTH and TH tools are two other time scales.Within the simplified modeling framework considered in this study,the dynamics of the percussion tools is at most controlled by three numbers,which are ratios of time scales.However,some of these numbers could be irrelevant depending on the design and class of the percussion drilling system,because they are either too small or too large and thus do not affect the dynamical response.For example,the energy transfer efficiency-the fraction of the impact energy effectively delivered to the rock-depends on one number when drilling with a TH tool,but on three numbers for a hydraulically powered DTH tool.This approach enables the identification of the point of maximum efficiency in the parametric space of the time scale ratios.The so-called sweet spot can thus be understood as representing an optimum match of the different timescales characterizing the drilling system.For instance,maximum performance is achieved with a TH tool if the two time scales controlling its dynamics are equal.