Structure Design And Experimental Research On Ice Drill Bit With Air Reverse Circulation

Polar regions have low temperatures and are far away from human pollution.Compared with other climate substitute indicators,they have the characteristics of large information,good fidelity,high time resolution,large time scale,and wide distribution area.They are the most critical to study global climate change.One of the regions.Obtaining a long-standing ice core is of great significance for rebuilding the historical evolution of the earth and predicting global climate change.Existing armored cable-type electric mechanical drilling tools require lifting and coring,high labor intensity and long coring assistance time,resulting in low work efficiency and high cost,and the use of drilling fluid circulation,which has certain damage and restrictions on the polar ecological environment.The rapid development of the polar drilling project.The air reverse circulation continuous core drilling technology has been widely used in the field of conventional geological core drilling because of its advantages of continuous core drilling,high drilling efficiency and high core rate,and no pollution to the core.If it is applied to polar ice drilling,the drilling efficiency of polar drilling will be greatly improved.The drill bit is a key component of air reverse circulation drilling,and its structure directly determines the reverse circulation effect.Based on the structure of air reverse circulation drill bit in the field of geological drilling,this paper designs a new type of ice drill reverse circulation drill bit with a cyclone for the characteristics of ice core drilling and the requirements for air injection parameters.The strong spiral flow at the cyclone generates a strong negative pressure on the bottom of the bit to improve the reverse circulation effect of the ice drill bit.In order to optimize the structure parameters of the bit cyclone,improve the reverse circulation effect,and analyze the influence law of the ice core on the reverse circulation effect,this paper designs a set of ice drill bit reverse circulation test test bench,and adopts the orthogonal test method to the bit cyclone Four structural parameters,such as the angle of rise of the spiral blade,the number of blades,the length of the blade,and the area ratio of the guide channel and the bottom spray channel,were tested and optimized.The results show that the angle of rise of the spiral blade is the factor that has the greatest impact on the reverse circulation effect,followed by the blade length and the area of the outlet channel of the cyclone.In order to study the influence of ice core on the reverse circulation effect of the drill bit and optimize the structure of the drill bit,the paper finally uses CFD simulation to numerically analyze the flow field inside the drill bit under different spiral rise angle conditions,and comparatively analyzes the different spiral blade rise angle,The influence of different ice core lengths on the energy loss caused by the internal resistance of the drill bit and the diversion of the bottom injection channel on the reverse circulation effect of the swirl bit.The results show that the reverse circulation effect of the cyclone bit is affected by the spiral effect,the energy loss caused by the resistance at the cyclone,and the diversion of the bottom jet channel.Different structural parameters of the cyclone will affect the ability of the cyclone to form a spiral and the resistance of the cyclone Have an impact,thereby affecting the reverse circulation effect of the swirl bit.The length of the ice core will also have a great influence on the reverse circulation effect of the cyclone bit.When the length of the ice core is higher than the position of the cyclone of the cyclone bit,the cyclone forms a stronger spiral in the annulus channel between the ice core and the inner tube Effect,when the length of the ice core is close to or lower than the position of the cyclone,the cyclone mainly forms a spiral flow in the central circular channel.At the same time,when there is an ice core,the pressure loss inside the drill bit and the split flow of the bottom spray channel are less than the ice core Serious,therefore,when the length of the ice core is close to or lower than the position of the cyclone,the bit reverse circulation effect is about 15% lower than that without the ice core,and when the length of the ice core is higher than the position of the cyclone,there is no obvious difference.Finally,a single variable experiment was carried out to test the angle and ice core on the reverse circulation effect of the drill.At the same time,the simulation results were compared and verified.It was found that the CFD simulation results were highly consistent with the experimental results,the maximum error was controlled within 10%,and the minimum error Only 0.9%,the optimal parameters of the helix rise angle are obtained.Based on the results of this test,the orthogonal parameters are used to obtain the parameter change rule and the numerical simulation of the effects of various factors on the internal flow field.Among the parameters,the structure with a spiral blade raising angle of 70 °,three blades,a blade length of 10 mm,and a cyclone channel area ratio of 6 has the best reverse circulation effect.Under the condition of no ice core,the suction rate of the optimal structure swirl drill bit can reach 38% under the condition of bottom spray channel,and the suction rate can reach 59% under the condition of no bottom spray channel.