Why is Reynolds number important for turbine blade designSol

Why is Reynolds number important for turbine blade design?

Solution

At present, the radius of wind turbine rotors ranges from several meters to one hundred meters, or even more, which extends Reynolds number of the airfoil profile from the order of 105 to 107. When the influence of Reynolds number on the aerodynamic design of a wind turbine blade is studied. Two kinds of multi-objective optimization are involved: one is based on the maximum power coefficient (CPopt) and the ultimate load, and the other is based on the ultimate load and the annual energy production (AEP). It is found that under the same configuration, the optimal design has a larger CPopt or AEP (CPopt//AEP) for the same ultimate load, or a smaller load for the same CPopt//AEP at higher Reynolds number. At a certain tip-speed ratio or ultimate load, the blade operating at higher Reynolds number should have a larger chord length and twist angle for the maximum Cpopt//AEP. If a wind turbine blade is designed by using an airfoil database with a mismatched Reynolds number from the actual one, both the load andCpopt//AEP will be incorrectly estimated to some extent.Reynolds number of the airfoil profile is defined as Re = Uc/, where, U is the relative velocity of airfoil profile, c is the chord length, and is the kinematic viscosity. As a dimensionless number expressing the ratio of inertial forces to viscous forces, Reynolds number has a great influence on the flow characteristics. Hence, airfoils at different Reynolds numbers exhibit distinctive performance, directly affecting the aerodynamic design of wind turbine rotors. As Reynolds number changes, the blade shape needs to be adjusted to ensure that the blade operates under optimal conditions, thus bringing a new topic to the design of large-scale wind turbines. However, research on the effect of Reynolds number is still very limited.