Study On Flow Field And Slag Removal Efficiency Of Air Flush Drilling For Vertical Shaft Boring Machine

With the development of national economy,deep well construction has become the primary link in resource exploitation.The vertical shaft boring machine method is an important development direction in the construction of deep well.While the vertical shaft boring machine is used to carry out deep well construction,the technology of washing and slag cleaning is the most difficult point.The air washing has obvious advantages of saving water resources,reducing the cost of the project and the efficiency of drilling,and with the increase of solid resources exploitation and well sinking projects in arid and water-scarce areas in the west of China,the vertical shaft boring machine method using air flushing will show outstanding advantages.Therefore,the study of air well washing is imminent.This paper has carried out the numerical simulation research on the flow field of gas washing well and carried out the preliminary design of the model test rig.Firstly,according to the laboratory existing shaft well washing machine fluid systems,according to the characteristics of the air flush,the appropriate improvement,this paper expounds the main composition of the improved air flush system,explain the function of each component of the detailed structure characteristic and the connection between the various parts,and describe the flushing system on the work of the entire process,and analyzed the main parameters,the calculation and in combination with the actual working condition of the scope of the preliminary selection of main parameters.Secondly,the numerical simulation optimization of "geometric parameters" of the well cleaning system was carried out for the pure air flow field.Through theoretical analysis and preliminary numerical simulation,a reasonable numerical analysis model of the pure air flow field was established.Then,a single factor numerical analysis is carried out for eight influencing factors such as the Angle between the cutter head and the bottom hole,the clearance height at the bottom hole,the diameter of slag discharge pipe and the diameter of jet nozzle,and the optimal value or its value range of seven factors is obtained.On the basis of the orthogonal numerical analysis,the significant degree of the influence of different factors on the pure air bottom hole flow field under two indexes is obtained.The results show that the parameters that have the greatest influence on the flow field in the well are the inner diameter of the slagging pipe,and the Angle between the cutter head and the bottom of the well and the jet orifice are the ones with the least influence.Then,on the basis of pure air flow field numerical simulation,to join the cuttings particles,for numerical simulation of gas-solid two-phase flow,to the quality of the cuttings rate and total quality and rate of slag slag removal rate as the evaluation index,such as calculation and analysis of the inlet air flow discharge height the inner diameter of cuttings particle sludge discharge pipe parameters on the efficiency of the flushing slag discharge.Finally,the similarity criterion is derived based on similarity theory,the existing shaft well washing machine fluid systems in the laboratory model test bench,on the basis of appropriate improvements were made on air wash well,aimed at cutting wheel rotation speed seven factors such as inlet air flow to flush the effects of the discharge of a similar shrinkage ratio of 1:20 physical model experiment,the analysis of the influence law of various factors on the flushing efficiency,determine the optimal value of each factor under typical parameters and results of the model experiment and numerical simulation are the contrast analysis and confirm each other.Finally,based on the existing laboratory test bed of fluid well washing model of shaft drifter,an adaptive modification is carried out for the characteristics of air well washing.Then the knife dish seven factors such as speed,inlet air flow discharge effect problem of washing well,carried out a similar shrinkage ratio of 1:20 of physical model experiment,study the influence of some factors on the flushing efficiency rule,to determine the optimal value of the typical parameters under various factors,and the model experiment and numerical simulation results are analyzed in comparison.The paper has 101 figures,25 tables and 87 references.