Study On Energy Capture Efficiency Of Turbines Under Complicated Sea Conditions

At present,most domestic hydro-turbine generator sets are at the stage of testing.Due to its economic advantages and convenient maintenance character,the floating platform support structure form has become the most commonly used supporting structure way for hydroelectric generating sets in China at this stage period.Therefore,the research on the performance of floating turbine and the factors influencing its performance are the problems that researchers need to solve now.In this paper,the research on energy capture efficiency of 2 * 150 KW vertical axis turbine with straight-blade five-cantilever supported by floating structure platform under complex sea condition was studied.First of all,on the theoretical level,the flow tube method double-multi stream tube model is introduced to establish the theoretical derivation model of the turbine impeller disk.During the integration of the micro-elements,the disk is divided into numerous stream pipes,and the whole disk is considered as two surfaces which the flow passes successively.The force and movement analysis of the impeller disk surface were studied,and then the calculation of the induced velocity was introduced,then the predict performance of the turbine under the static force was obtained.Its significance is to estimate the performance of the turbine in the steady flow from the basic mechanics theory,and provide theoretical reference for the numerical simulation analysis.After that,without considering the floating platform,the hydrodynamic performance of the turbine impeller flow field under different flow velocities and tip ratios were studied.Using the turbulence model under the RANS equation and considering the wall effect,using ANYSIS-FLUENT to simulate the transient force and torque of the turbine under unsteady conditions.The analysis on unsteady flow fields of turbine impellers under different conditions and different tip ratios were given.The comparisons of energy capture efficiency of turbine under different conditions were shown.Then study the movement of floating platform under complex sea conditions.The kinematics and dynamics equations of the platform based on the three-dimensional potential flow theory are established.By simplifying the UG model,the motion structure model of the platform is established and reasonable constraints are added.AQWA is used to analyze the kinematic response of the platform in frequency domain,based on the response of frequency domain analysis result as the initial value,simulated the motion response under the different wave load,different frequency and wave phase angle.Finally,by processing and analyzing the complex sea state data,the calculated working sea conditions and the ultimate sea conditions are selected.Combined with the environmental load data,the UDF is compiled to provide the turbine to define the movement of the turbine.An example is given to predict the change of energy capture efficiency under the single degree of freedom(pitch and roll)of turbine.The results show that the CFD numerical simulation method can obtain the energy capture efficiency of the turbine slightly larger than the theoretical flow tube method.Under the load of complex environment,the platform of the turbine is swayed,in which the amplitude of the pitch response is the largest,followed by the roll,sag and sway.Longitudinal motion has little effect on turbine energy capture;pitch motion has a small effect on the energy capture of the turbine.