Numerical Simulation And Experimental Study Of Adaptable Volute For Pressure Energy Generation

With the increasing proportion of natural gas in China’s energy structure and the rapid development of urban gas transmission and distribution pipelines,natural gas pressure energy recovery has attracted much attention.The pressure energy in the process of natural gas pressure reduction in gas pipeline can be transformed into other high-grade energy,and the recovery of pressure energy can improve the economy of natural gas pipeline network operation,which has engineering value.In this paper,compressed air is used as high pressure working medium and turbine expander is used as the core device.The experimental system of pressure energy power generation is built.The volute is studied by numerical simulation and system experiment to improve the efficiency of pressure energy power generation.In terms of numerical simulation,the rated condition simulation,variable condition simulation and variable model simulation are carried out on the volute.When the volute model a is simulated under rated conditions,the inlet and outlet pressures are 0.4MPa and 0.15MPa respectively,the rotational speed is 15000rpm,and the rated isentropic efficiency is 77.2%.Since it is difficult for the turbine to work under the rated condition all the time,the variable condition simulation of the volute model a is carried out.It is found that the factors affecting the flow rate of the centripetal turbine are pressure,rotational speed and temperature,in which the pressure is positively correlated and the temperature and rotational speed are negatively correlated.The isentropic efficiency increases first and then decreases with the increase of inlet pressure or rotational speed,which is negatively correlated with temperature.Since the volute model will limit the maximum isentropic efficiency of the turbine,the volute model a is improved from five aspects:gap,inlet section length,inlet pipe diameter,profile and guide vane,and the corresponding volute b～volute z is designed.Through the simulation analysis of the variable model,it is found that the isentropic efficiency of the turbine increases first and then decreases with the increase of the inlet section length or the inlet pipe diameter.The isentropic efficiency is negatively correlated with the clearance,weakly correlated with the profile at low rotational speed,and strongly correlated with the guide vane.When there is a guide vane,the maximum penetration equal entropy efficiency is 80.8%.In terms of experimental research,a set of pressure energy power generation experimental system is built based on volute model a,including air compression system,turbine power generation system,power storage system and instrument monitoring system.The experimental study was carried out on the volute a under variable working conditions.It was found that the power generation efficiency increased first and then decreased with the increase of inlet pressure or flow rate,and was weakly correlated with temperature.The maximum power generation efficiency was23.77%,and the corresponding inlet pressure and flow rate were 0.4MPa and 40Nm~3/h,respectively.Because the volute model will limit the upper limit of the pressure energy generation efficiency,according to the simulation analysis of the gap,the diameter of the volute inlet and the length of the inlet section,the volute c,the volute l and the volute s with high isentropic efficiency are selected,and the experimental study under variable working conditions is carried out.The research shows that co MPared with volute a,the maximum power generation efficiency increases by 1.35%,0.45%and 1.03%respectively,and the corresponding power generation power increases by 5.68%,1.89%and 4.34%respectively.In terms of performance optimization,based on the orthogonal test design rules and numerical simulation results,the volute a is further optimized from three aspects:clearance,inlet section length and inlet pipe diameter.A 3-factor 5-level orthogonal table is designed,and 25 combinations are selected according to the principle of uniform dispersion,and the corresponding volute a2～volute y2 are designed.The simulation results show that the isentropic efficiency of the volute d2 is the highest,and the maximum isentropic efficiency is 78.9%,which is 1.7%higher than that of the model a.The experimental study on the variable working condition of the volute d2 was carried out.It was found that co MPared with the model a,the power generation power under the optimal working condition increased from 286.70W to 303.47W,the power generation power increased by5.85%and the power generation efficiency increased by 1.61%.