Hydraulic turbines can convert tidal current energy into electric energy, and the addition of a deflector cover to the turbine can improve the efficiency of the turbine's energy harvesting. The angle of the inlet section and the angle of the outlet section of the deflector will further affect the final energy-acquisition efficiency.A threedimensional numerical model for turbine flow field analysis is established, and the RNG k-ε turbulence model is selected by CFD method, and the best angles of inlet section and outlet section are analysed by the method of sliding mesh to obtain the best angle of inlet section and outlet section separately, and then three groups of angles are selected near the best angle of inlet section and outlet section to make orthogonal comparisons. The energy acquisition efficiency of the turbine is calculated at different angles of the inlet and outlet sections of the deflector, and the turbine streamline distribution, velocity and pressure maps are analysed with and without the deflector.The study shows that the deflector can play the role of convergence of the downstream flow, which can improve the efficiency of the turbine energy acquisition, and the maximum energy acquisition efficiency is at the inlet angle of 29° and the outlet angle of 40 °, and the maximum energy acquisition efficiency can be improved by about 32 percent.

1. Introduction
2. Numerical method
    2.1 control equations
    2.2 Turbulence model
    2.3 Energy efficiency
3. Computational model
    3.1 Computational models
    3.2 Flow filed region and boundary conditons
    3.3 Irrelevance verification
    3.4 Grid plot
4. Analysis conditions
5. Analysis results
    5.1 Energy efficiency results
    5.2 Flow field analysis
6. Conclusion
References

• Zekai SUNa(Naval Architecture and Port Engineering College, Shandong Jiao Tong University, Weihai 264209, China)
• Guang SUN(Naval Navigation and shipping College, Shandong Jiao Tong University, Weihai 264209, China)
• Haihua LIN(Naval Architecture and Port Engineering College, Shandong Jiao Tong University, Weihai 264209, China)