Research On The Mine High Speed Rescue Pump And Thrust Bearing

Coal plays an important role in China national economic and social development.So the safety of coal mining is of great significance.However,coal mine flooding often happens in China,and the pumps used in rescue are bulky,heavy,difficult to disassemble and not suitable for rapid rescue.The study belongs to the project which is supported by the National Key Technology Support Program Project "R&D on quickly rescuing drainage equipment during the coal mine flooding process(an amphibious and moving drainage system)"(2013BAK06B02).The aim of this dissertation is to design and develop a new type of mine high speed rescue pump which has the advantages of big-power,high-head and small-structure.On the base of the foundation of the existing submersible pump,a mine high speed rescue pump which could meet the requirements of rapid rescue for modern coal mine flooding is proposed in the dissertation.Theoretical analysis,numerical calculation and experimental verification are used to study and revolve some key techniques around the mine high speed rescue pump.Specially,as the most important components,the overall structure,hydraulic performance,thrust bearings and cooling circuit are discussed respectively.The main work of the dissertation and creative achievements are as follows:1.The history and recent development of submersible pumps in the world are summarized in the dissertation.At the same time,a general review of the research progress of bearing lubrication theory and the water-lubricated thrust bearings are given,the related research results of motor cooling circuits are discussed.The research contents of the above three aspects are compared and analyzed in the paper.Besides,the research ideas and design concepts of the corresponding components of the mine high speed rescue pump are determined,which lay the foundation for the design and development of the mine high speed rescue pump.2.The dissertation takes the GFQ200-300 which is a typical model of 800 k W series as an example to illustrate the design progress of the overall structural and hydraulic components of the mine high speed rescue pump.The pump section is above the motor section,and the both sections are integrated with the same axis.Furthermore,the pump is adopted an independent motor cooling circuit,the seal of the wet submersible pump and a new high speed thrust bearing structure.After investigation,there are no similar products in the world compared to the pump which is proposed in the project.With the same flow rate and head,the length and weight of the prototype are reduced by 31% and 51.2% respectively compared with the pump in the current market.Through the prototype experiment,the design of the overall structure and hydraulic component of the mine high speed rescue pump is verified.3.The numerical simulation method is used to study the external characteristics and internal flow field distribution of the mine high speed rescue pump with different work conditions.The work conditions include six rotational speeds,four impeller diameters and nine matching modes between impeller and diffuser.The influence of the above factors on the pump are obtained by the way of the simulation results.Under different speeds,as the speed increases,the pressure increase effect applied to the rear of the impeller channel is smaller than that in the front part.Under different impeller outer diameters,the larger the outer diameter of the impeller,the larger relative error,the smaller the backflow loss in the gap between impeller and diffuser.Simultaneously,the impact loss at the inlet position of the diffuser also decreases.Under different blade number matching models of impeller and diffuser,at the design point,comparing to the changing of the diffuser blade number,the influence of the number of impeller blades has a more evident effect on the external characteristics of the mine high speed rescue pump when the other parameters remain unchanged.4.According to the theoretical model,the generalized Reynolds equation of the thrust bearing,the water film thickness equation and the viscosity temperature equation are solved by numerical discrete method.Taking GFQ200-300 as an example,the theoretical axial force is calculated on the base of the structure of the impeller and the whole unit.The relationship between the axial force and the rotational speed,the flow rate is indicated.When the mine high speed rescue pump runs at different speeds and flow rates,the direction and the value of the axial force are different.On the base of the calculation results of axial force,the Matlab code is used to solve the water film bearing capacity and water film thickness under different working conditions.Furthermore,the ansys workbench platform is used to study the influence of bearing width-to-length ratio on the distribution of water film and the amount of bearing deformation.The results show that 0.7 is the best width-length ratio of the thrust bearing in the mine high speed rescue pump.5.A multi-functional thrust bearing test bench is designed and built for studying the hydraulic performance of thrust plate and fluid film characteristics of thrust bearing.Specifically The external characteristic performance and the anti-cavitation performance of the thrust plate which are used as an auxiliary impeller at different temperatures,rotation speeds are systematically studied.According to the experiment results,the law of the rotational speed ratio is not applicable when the thrust disc is used as the auxiliary impeller,which is different from the traditional centrifugal pump.Furthermore,the crew efficiency is very low with 6.5%.Especially at 6000r/min speed,the maximum crew efficiency is only 6%.Moreover,the anti-cavitation performance of the thrust disc is inversely proportional to the rotational speed.Also,the hydraulic external characteristic curves under the above working conditions are acquired from experiments.In addition,the water film thickness under different working conditions and the pressure pulsation value at the monitoring point position are gained.Furthermore,the pressure pulsations are more susceptible to rotation speed.Then,the hydraulic performance and anti-cavitation performance of three volutes with different values of outlet position angle,which are 90°,45°and 0° respectively,are researched.The results reveal that the decrease of the angle of the outlet position leads the improvement of thrust hydraulic and reduction of anti-cavitation performance.The maximum head could be increased by about 1.47 times.At the speed of 6000r/min,the maximum crew efficiency of the unit can be improved to the value which is twice as high as that of the original structure.6.Taking the 1250 kW series as an example,the theory combined with the empirical formula is used to design the cooling circuit of the mine high speed rescue pump.The arrangement structure of the cooling pipe and the flow required for the internal circuit are determined.According to the current structure of the variable frequency high speed motor,two cooling circuits are proposed which include the positive and reverse cycles.By comparing the resistance and pressure drop of the two forms in calculation and CFD,it is found that the difference of highest temperature rise in the above two circuits are very small.However,in terms of lowest pressure in the loop,the value for positive loop is-1584.2k Pa which is much smaller than that in the reverse loop with the value of-107.03 k Pa.Considering avoiding cavitation,the reverse circulation loop is adopted for cooling.Finally,the feasibility and rationality of the cooling circuits are verified by experiments.