| Domestic research on pressure energy recovery and utilization of gas pipeline network is mostly concentrated in large pressure regulating stations,and less attention is paid to small and medium-sized pressure regulating stations.If the pressure in the gas pipeline network can be fully recovered to provide energy for the operation of electrical equipment in small and medium-sized pressure regulating stations,it will effectively reduce costs and save energy.Turbine expander is small in size and high in efficiency,which is very suitable for recovering pressure energy of natural gas.Based on this,a centripetal turbine suitable for the pressure regulating conditions of small and medium-sized surge stations is designed and detailed study is conducted:Firstly,The pressure energy loss during the depressurization process of medium pressure natural gas is studied theoretically,and the analytical model is established to calculate the change of medium pressure natural gas and compressed air during the depressurization process.The research shows that the variation law of exergy of compressed air and natural gas in the process of depressurization is the same,but only slightly different in numerical value.For the sake of safety,this paper uses compressed air to replace natural gas for pressure energy generation experiment in the experimental process.Secondly,according to the pressure regulating conditions of small and medium-sized pressure regulating stations,the thermodynamic calculation of the centripetal turbine was carried out,and the one-dimensional design and three-dimensional modeling of the turbine were completed.CFX software was used to numerically simulate the turbine to study the aerodynamic performance of the turbine and obtain the internal flow field distribution of the turbine under design conditions.It is found that the isentropic efficiency of the turbine expender is 86.97%under the design condition,and the aerodynamic performance is good.In the rotor flow channel,the working fluid flow in the meridional channel and near the rim is poor.Additionally,the effects of rim clearance,axial length and wheel diameter ratio on turbine performance are studied.it indicated that the rim clearance has a considerable effect on the turbine performance and internal flow.The rim clearance has a great influence on the turbine performance and internal flow.With the increase of the rim clearance,the flow loss in the rotor passage increases,and the isentropic efficiency of the turbine decreases obviously.Axial length and wheel diameter ratio have little effect on turbine performance in a certain range.Then,the off-design performance of the turbine was studied by changing the rotational speed,inlet pressure and inlet temperature.The results verify that with the increase of rotational speed and inlet pressure,the isentropic efficiency of the turbine increases first and then decreases,reaching the maximum at the design condition.With the increase of inlet temperature,the isentropic efficiency of turbine has been reduced,and the influence of inlet temperature on turbine performance at low rotational speed is more obvious.Ultimately,the blade profile of turbine rotor was optimized by uniform design test method.After optimization,the surface pressure distribution of turbine rotor was more uniform,and the isentropic efficiency was increased to88.83%.Finally,an experimental platform for pressure energy generation was built,and the pressure energy generation experiment was carried out using the designed centripetal turbine expander.The influence of inlet pressure and flow rate on power generation and efficiency was mainly studied.The analysis revealed that the power generation increases with the increase of flow rate(Q)and expansion ratio(π),and the power generation efficiency increases first and then decreases with the increase of flow rate and expansion ratio.In the experiment,the maximum power generation using turbine expander to recover pressure energy is 390.68W,which can meet the needs of electrical equipment in small and medium-sized surge stations.The maximum shaft power is 473.75W;the highest power generation efficiency is 24.1%,and the average power generation efficiency is about20%.the highest shaft efficiency is 30.4%,and the conversion efficiency from shaft power to electric power is about 80%;the experimental uncertainty was 5.83%.The expansion ratio of the optimal working area of the pressure energy generation system is 2.5～4,and the flow rate is 30～55Nm~3/h. |
PDF Full Text Request