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Hydraulic Yaw System for Wind Turbines with New Compact Hydraulic Motor Principle

Hydraulic Yaw System for Wind Turbines with New Compact Hydraulic Motor Principle. EWEA 2011, 14-17 March, Brussels Rasmus M. Sørensen*, Liftra & Department of Mechanical and Manufacturing Engineering, Aalborg University, Denmark

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Hydraulic Yaw System for Wind Turbines with New Compact Hydraulic Motor Principle

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  1. Hydraulic Yaw System for Wind Turbines with New Compact Hydraulic Motor Principle EWEA 2011, 14-17 March, Brussels Rasmus M. Sørensen*, Liftra & Department of Mechanical and Manufacturing Engineering, Aalborg University, Denmark Ole Ø. Mouritsen, Department of Mechanical and Manufacturing Engineering, Aalborg University, Denmark Michael R. Hansen, Department of Engineering, University of Agder, Norway Per E. Fenger, Liftra, Denmark Funded by: Liftra Danish Agency for Science Technology and Innovation

  2. Agenda • Introduction • Motor principle • Simulation • Prototype tests • Compare simulation and prototype results • Conclusion

  3. Introduction • The main goal is to develop a new hydraulic motor principle that is suited for the yaw system with a view to avoid the fundamental disadvantages associated with the gear wheel connections used today. • The volumetric efficiency is critical for large low speed high torque motors, whereas the leakage flow of the new hydraulic motor principle is highlighted in this presentation. • The aim of this work is to develop a fluid structural simulation model that is capable of predicting the critical structural deflections of the motor.

  4. Motor Principle • The vanes are hydraulic actuated. • The leakage flow to the drain is the focus of the work.

  5. Characteristics of the Motor Principle • The specific displacement, i.e. the displacement per outer motor volume is favourable when comparing with existing hydraulic motors. Potentially, this allows for very compact motors used for direct drive applications with high torque requirements. It has a specific displacement substantially higher than that of commercially available motors. • Specific displacement for the prototype is around 3 times higher than that for the world ‘s largest radial piston motors from Hagglunds.

  6. The Hydraulic Motor in a Wind Turbine • Small hydraulic motors in mesh with the yaw gear rim. The high reduction gearboxes are saved. • Large hydraulic motor shaped as a ring in the same size as the existing yaw gear rim. The motor has e.g. 40 chambers located in a radius equal to that of the tower.

  7. Fluid Structural Simulation • The aim is to calculate the structural deflections of the housing. • Solving Reynolds equation for the pressure distribution across the end faces of the rotor. • Applying the pressure distribution as the load input to the structural FEM deflection calculations on the housings.

  8. Simulation Results • The pressure distribution across the end faces of the rotor. • The pressures are the load input to the structural FEM calculations. • The input and the boundary conditions is measured pressures.

  9. Simulation Results • Deflections of the housing. • The calculated node deflections are input to next fluid calculation.

  10. Prototype • 6 chambers. • Outer diameter of the prototype is 340mm. • Displacement is D = 1.75 l/rev. • Theoretically T = 2240Nm, when Δp = 80 bar. • Compensation volumes. • Moving coil actuator with a 0.1 μm resolution encoder.

  11. Test Results • The volumetric efficiency is decreased with the structural deflections of the housing.

  12. Deflection Comparison • It is considered inexact to validate the FSI simulation by comparing absolute dimensions in the μm range. • The theoretical deflection difference is 26 μm and the measured deflection difference is 40 μm. • The percentage deviation is a concern.

  13. Conclusion • The FSI simulation is reflecting the behaviour and the volumetric efficiency trends of the prototype motor, but the boundary conditions in the FEM model must be calibrated by examining a wider range of tests. • The test results show that the volumetric efficiency can be kept at an acceptable level by the use of compensation pressure volumes.

  14. Hydraulic Yaw System Perspectives • Designing the motor to withstand a maximum working pressure far beyond the nominal working pressure. • Active damping by regulating the pressures in the stop volumes. • Include the yaw bearing in the motor.

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