The shortages of global conventional energy and environmental degradation have become the bottleneck and great challenge of social development and rapid economic growth. Therefore, the research and utilization of sustainable energy has been paid more and more attention and favor by the academic and engineering circles. Nearly 70% of the earth surface is covered by sea water, which has abundant tidal energy reserves and great potential for development as renewable energy. Tidal current turbine is a key equipment used to obtain and convert river, current and tidal energy into electric energy. The accurate predictions of the hydraulic performance of Tidal Current Turbines and the accurate quantification of the hydrodynamic load quantitative analysis on the rotor have important guiding significance for the hydraulic design and structural design of the Tidal Current Turbine. The incorrect quantification of the dynamic load quantitative analysis of the rotor will cause a large deviation in the design, which will lead to the failure of the blade or rotor during operation and affect the safe and stable operation of the system. In this paper, the boundary element model of steady and unsteady state of horizontal axis tidal turbine is established. The key parameters and its mechanism affecting the performance of Tidal Current Turbine are studied. The accurate performance prediction method of horizontal axis tidal current turbine is proposed, and the conditions and parameters selection principle for obtaining the best prediction results are given. On this basis, the interaction between surface wave and current and the dynamic load variation characteristics of turbine caused by the interaction are studied systematically. The influence law of key parameters is analyzed quantitatively. This work has important theoretical and engineering application value for guiding the hydraulic and structural design of Tidal Current Turbine and improving the safety and stability. Blade element momentum theory (BEMT) is a commonly used method to predict the performance of tidal current turbines and study the flow field of tidal turbines, especially the near wake flow field of blades. In this work, the BEMT is improved. By analyzing the two-dimensional hydrodynamic, lift and drag coefficients, a more accurate performance prediction method for tidal current turbines is established. The influence mechanism of hydrodynamic coefficients, Reynolds number and blade span position parameters on the hydrodynamic forces in the blade element section is clarified. Furthermore, the matching relationship between hydrodynamic coefficient and Reynolds number, blade span position parameters and turbine optimal performance are discussed. By using different Reynolds arrays to calculate the lift and drag coefficients under different Ncrit values, the influence of Ncrit parameters on the lift and drag coefficients is clarified, and the selection principles of Ncrit parameters and Reynolds number for accurate simulation of turbine performance are given. The results show that the improved BEMT model is in better agreement with the experimental data when the lift and drag coefficients are calculated at low Ncrit parameters and the Reynolds number is calculated at 75% span. In view of the shortcomings of traditional methods in simulating the wave and current of tidal turbines, the current dynamic parameters are added to BEM model, and the turbine model with fixed proportion is placed in the ocean current and wave environment. A simulation method closer to the actual wave and current environment is proposed, and the influence of wave and current coupling on turbine performance is studied. The influence mechanism of actual wave current environment on the dynamic load of turbine is clarified. In order to predict the dynamic load on the rotor of tidal current turbine, an improved unsteady boundary element model is proposed. Different wave models such as Dean model, Kishida model and Fenton model are combined to evaluate the accuracy of wave period, yaw misalignment, blade bending moment and axial thrust. At last the fifth order Fenton model is recommended to solve the long steep wave flow field calculation. In this work, the quantitative analysis method of dynamic load of Tidal Current Turbine is established. Through the quantitative analysis of dynamic load, the influence mechanism of turbine design parameters, wave parameters and incoming flow parameters on dynamic load of Tidal Turbine is explored. It is clearly pointed out that the important factors affecting dynamic load must be considered in the design stage of Tidal Turbine. The results show that, compared with the wave period, the velocity and height of the incoming flow have important effects on the dynamic load. Yaw misalignment will increase the oscillation frequency of blade bending moment. Excessive increase of turbine speed leads to significant increase of moment frequency oscillation, which will affect the safe and stable operation of turbine. Dynamic load changes are caused by the changes of operating conditions, wave parameters and incoming flow, which must be considered in the design stage of turbine to avoid rotor failure. In addition, the correct evaluation of the dynamic load can guide the selection of the best tidal station and avoid the selection in the bad environment. In order to break through the limitation of the linear superposition method, this paper combines the modified boundary element model with the linear wave theory and the nonlinear wave theory, and establishes a model and method for solving the wave current flow field with further consideration of the wave current interaction. Based on the prediction and study of the mutual induced characteristics among wave length, wave height, tidal velocity and tidal depth, the influence mechanism of wave height, wave length, water velocity and turbine immersion depth on turbine performance is revealed. The comparison of open test data shows that the wave current interaction model proposed in this paper can significantly reduce the load range of blade root bending moment and the prediction deviation of dynamic load.

Reducing the weight and size of axial compressor is required for reducing the cost of gas turbine and increasing thrust -to - weight ratio of the jet engine. This will lead to reducing the total number of stages for the same pressure ratio. Consequently, the pressure rise per stage will increase to deliver the same total pressure ratio for all stages. The only allowable choice for achieving that is to increase the blade loading. Increasing blade loading will be accompanied with three - dimensional flow separation. Flow separation is a major parameter affecting the compressor performance. When flow separation in compressor occur, it reduces the compressor efficiency, lowers the pressure rise capability and contributes to instability in compressors. In this case, the main challenge is to prov ide higher- pressure ratio per stage with flow separation prevention. In applied research, there is a lack of understanding of the nature and mechanism of the three - dimensional (3- D) flow separation in the axial compressor especi ally on the juncture of the endwall and blade corner region. In the current study, the 3 - D flow field in the axial compressor blade passage has been studied experimentally as well as numerically. For the experimental study part, a linear compressor cascade test section has been inst alled in an open loop wind tunnel. The experimental data was acquired for a Reynolds number Rec=2.98 × 10 5 based on the blade chord and the inlet flow conditions. The inlet velocity profile has been measured by calibrated five and seven-hole pressure probes connected to ATX sensor module data acquisition system. The received velocity profile is used as an inlet boundary to the computational domain used for the computational study part. Additional measurements for flow analysis and for later verification of the computational scheme have been performed; including the static pressure distribution on the endwall employing static pressure taps connected to digital micromanometers. The 3- D flow field ; 3- D flow velocity, static and total pressures, has been measured in the passage between the two expe rimental blades in the middle of the cascade using both five and seven- hole pressure probes. To investigate the loss mechanism through the cascade the total pressure loss coefficient has been calculated from the measured data. The computational fluid dynamics (CFD) study of the flow field is performed to gain a better understanding for the flow features. For this purpose, a 3- D domain included the constructed blade with the measured inlet flow conditions has been established with the help of CFD package calculations. The problem has been solved against the governing equations for continuity and momentum using two turbulence models; Spalart- Allmaras (S - A) and shear stress transport SST (k - ω). The calculated flow velocities in addition to the flow static and total pressures have been compared with the corresponding experimentally measured values throughout the blade passage. From both parts of study, the flow field development and total pressure loss progress through the ca scade have been investigated and compared. Moreover, the received data demonstrated a good agreement between the experimental and computational results. The predicted flow streamlines by numerical calculations showed regions characterized by flow separation and recirculation zones that could be used to enhance the understanding of the loss mechanism in compressor cascades. All measurements taken by the two probes, 5 and 7- hole pressure probes, have been analyzed and compared. The 5- hole pressure probe measu rements have showed more agreements with computational results than 7- hole probe. This result indicates that the use of 5- hole pressure probe can successfully represent more information regarding flow turbulence in comparison with the use of 7-hole pressur e probe. Furthermore S-A turbulence model calculations showed more consistence with experimental results than SST (k - ω) model.