Hydraulic pitch control system for wind turbines: Advanced modeling and verification of an hydraulic accumulator

To study the thermal processes, a simplified axisymmetric CFD model of the accumulator is developed. The results show that the main heat transfer losses are associated with heat diffusion in the solid parts of the accumulator, making up to 20% of the total heat losses. It is also shown that the heat transfer processes and the thermal time constant are tightly connected to variations in gas mass, in rate of change of volume and compression ratios. Comparison with experimental results validate the CFD model accurately, showing high level of agreement and repeatability between the predicted pressures and temperatures and the experimental measurements.