Study On Energy-Saving Mechanism And Application Of Viscoelastic Working Fluid For Water-Ring Gas Drainage Pump

The coal mine gas drainage pump,as the power source of the gas drainage system,has the problems of high energy consumption and low drainage efficiency,which need to be improved.In response to this situation,the team proposed a new optimization technology for gas pumps using viscoelastic solutions as working media,which effectively improves their drainage performance and expands good new technologies for safe gas drainage in China’s coal mines.However,the theoretical mechanism of this energy-saving and efficiency-improving technology is still unclear.Therefore,this thesis mainly explores the influence of viscoelastic material properties on the energy consumption of gas drainage pumps from the perspective of theory,experiments,and field applications,reveals the laws of viscoelastic fluid rheological behavior and energy loss in gas drainage pumps,and integrates the matching energy-saving and efficiency-improving technologies and processes for gas drainage pumps,achieving a significant improvement in the energy efficiency level of coal mine gas drainage systems.（1）The energy loss characteristics of the water working medium inside the gas drainage pump were revealed.Firstly,a computational fluid dynamics model of the gas drainage pump was established based on three turbulence models which are standard k-ε,Realizable k-ε,and SST k-ω.The axial power of the gas drainage pump was numerically calculated,and the average errors between the numerical and experimental results were found to be 4.07%,1.94%,and 0.98%,respectively.It was confirmed that the SST k-ωmodel provides more accurate calculation of the energy loss characteristics of the working fluid in the gas drainage pump.The performance characteristics of the gas drainage pump under different suction pressures,speeds,and working fluid flow rates were then analyzed in detail.The relationship between power and suction pressure was found to be mainly affected by the pressure difference between the inlet and outlet and the complex vortex energy loss structure inside the pump.Speed primarily affects the gas-liquid permeability,exhaust side pressure,and vortex energy loss structure,which in turn affect the performance of the gas pump.The working fluid flow rate affects the vortex energy loss shape of the exhaust gas and consequently impacts the pump performance.Overall,the power consumption of the gas drainage pump is related to the vortex energy loss structure inside it.Furthermore,it was demonstrated that theλ_ci criterion can provide a more comprehensive visualization of the distribution of the complex gas-liquid two-phase vortex energy loss structure inside the gas drainage pump.（2）The experiment identified the factors of viscoelastic properties of working fluids that affect the power consumption of gas drainage pumps.Firstly,a gas drainage pump performance test system and a viscoelastic working fluid rheological properties test system were established.The power consumption of Newtonian fluids and three types of viscoelastic working fluid solutions in gas drainage pumps were tested for a short period of time（<90 minutes）,and the results were analyzed as follows:when the concentrations were 1500,2500,3500,and 4500 ppm,the average energy-saving efficiencies of working fluid A solutions were 4.98%,7.41%,10.02%,and 11.86%,respectively;the average energy-saving efficiencies of working fluid B solutions were5.95%,9.28%,9.75%,and 11.13%,respectively;the average drag reduction energy-saving efficiencies of working fluid C solutions were 5.38%,7.38%,9.17%,and10.88%,respectively.At the same time,the rheological properties test results found that the rheological properties of working fluid A solutions and working fluid C solutions were similar,and the rheological properties of working fluid A solutions were relatively stable,with the shear thinning law being the most obvious.Based on the above research results,seven comparative schemes of rheological properties were selected for working fluid A solutions and working fluid C solutions with the same power,and the results showed that the rheological property parameter values of working fluid A solutions and working fluid C solutions were basically the same,indicating that the viscoelastic rheological property parameters were the main influencing factors affecting the power consumption of gas drainage pumps.Finally,based on the energy conversion theory,a method for calculating the average shear rate was proposed,and the stability of the energy-saving effect of viscoelastic working fluids in gas drainage pumps was analyzed.The results showed that the rheological properties of viscoelastic working fluids interacted with high-speed shear in gas pumps,causing the solutions to be unstable in a short period of time,and the optimization effect of gas drainage pumps accelerated the downward trend.（3）The impact of the viscosity properties of working fluids on the energy consumption of gas drainage pumps was explored.Firstly,the rheological test results of the viscoelastic properties of working fluids were analyzed,and it was found that they showed obvious shear thinning characteristics.The Carreau-Yasuda model was identified as an effective model for characterizing the viscosity properties of working fluids.Then,a fluid dynamics model of the gas drainage pump based on this model was established,and the power consumption of the gas pump under different concentrations was numerically analyzed.It was found that the viscosity properties have a negative impact on the power consumption of the gas pump,and the higher the concentration,the more obvious the viscosity properties of the working fluid,the more complex the distribution of vortex energy loss,and the worse the energy-saving effect of the gas pump.As the zero-shear viscosity and flow behavior index of the viscosity properties increase,the structure and quantity of vortex energy loss inside the pump body increase,and the energy consumption of the gas pump increases.As the non-elastic relaxation time constant value increases,the structure and quantity of vortex energy loss inside the pump body decrease,and the energy consumption of the gas pump is optimized.The comprehensive research shows that a single viscosity property cannot accurately describe the energy-saving behavior of viscoelastic working fluids in gas drainage pumps.（4）The impact of the elastic properties of viscoelastic working fluids on the energy consumption of gas drainage pumps was further explored.The Giesekus model and VOF models were coupled for the first time to establish a fluid dynamics model for calculating the energy loss characteristics inside the gas drainage pump caused by the elastic properties of working fluids.The power consumption results of the numerical calculation were verified through experiments.The elastic properties of viscoelastic working fluids with different concentrations were then analyzed for their impact on the energy-saving effect of gas drainage pumps.It was found that the higher the concentration,the more obvious the elastic behavior,the simpler the distribution of vortex energy loss,and the better the energy-saving effect of the gas pump.With the increase of the shear thinning coefficient and the solvent viscosity ratio,the energy consumption of the gas drainage pump showed a trend of first decreasing and then increasing,indicating that there are optimal values for these two elastic property parameters within the research range,which are 0.6 and 0.7,respectively.The elastic relaxation time has little effect on the power consumption of the gas drainage pump and can be ignored.The comprehensive research shows that viscoelastic working fluids mainly rely on viscoelasticity of the materials to affect the energy-saving effect by influencing the structure and quantity of vortex energy loss inside the gas drainage pump.（5）A ground semi-closed gas drainage pump energy-saving system based on viscoelastic working fluids was constructed for the actual situation in the Dongfeng well mining area of Zhangji coal mine in Huainan.A viscoelastic working fluid material with strong shear resistance was compounded,and the energy-saving effect of viscoelastic working fluids on gas pumps was theoretically and experimentally analyzed.Experimental tests showed that,at the initial operation,the energy-saving efficiency of working fluid A corresponding to concentrations of 2500ppm and4500ppm were 13.18%and 16.67%,respectively,while the energy-saving efficiency of compounded rubber were 16.73%and 18.37%,respectively,with the best energy-saving effect achieved with the compounded rubber at 4500ppm.At the same time,engineering application tests showed that after using the compounded material at4500ppm,the energy-saving efficiency could reach 25.0%under a pumping negative pressure of 33k Pa,with an expected net annual cost savings of 855,600 yuan for a single pump.The energy-saving effect of this technology is significant.This thesis includes 93 figures,27 tables,and 252 references.