The following equations are the calculation for the local inflow angle and local chord length at each blade element according to the values of “a” and “aT” that maximize blade efficiency ( Burton et al., 2001 and Jung et al., 2005).
equation(8)
View the MathML sourcetanϕ(μ)=1-aλμ(1+aT)
equation(9)
View the MathML sourceC(μ)=2πRNλCL×4λ2μ2aT(1-a)2+(λμ(1+aT))2
where ϕ is the inflow angle and C(μ) is the chord length at position μ.
Generally, the chord length calculated based on the above formula tends to be very slim at the tip and has the tendency to suddenly become thick towards the root, creating difficulties in the stage of actual production. Additionally, an overly thick blade plane near the root requires more materials and therefore lowers the overall economic feasibility and efficiency of the rotor. Thus, the chord length design focused on the μ = 0.3–0.7 section, the section that has the greatest impact on rotor blade performance, and adjusts the remaining chord length. Structural stability, convenience in production, and cost reduction are all considered in the design.
Eq. (10) is the calculation for the local incidence angle, β(μ) according to the local inflow angle, and it represents the degree of local blade section twist in the stage of blade design.
equation(10)
β(μ)=ϕ(μ)-α
The following equations are the calculation for the local inflow angle and local chord length at each blade element according to the values of “a” and “aT” that maximize blade efficiency ( Burton et al., 2001 and Jung et al., 2005).equation(8)View the MathML sourcetanϕ(μ)=1-aλμ(1+aT)equation(9)View the MathML sourceC(μ)=2πRNλCL×4λ2μ2aT(1-a)2+(λμ(1+aT))2where ϕ is the inflow angle and C(μ) is the chord length at position μ.Generally, the chord length calculated based on the above formula tends to be very slim at the tip and has the tendency to suddenly become thick towards the root, creating difficulties in the stage of actual production. Additionally, an overly thick blade plane near the root requires more materials and therefore lowers the overall economic feasibility and efficiency of the rotor. Thus, the chord length design focused on the μ = 0.3–0.7 section, the section that has the greatest impact on rotor blade performance, and adjusts the remaining chord length. Structural stability, convenience in production, and cost reduction are all considered in the design.Eq. (10) is the calculation for the local incidence angle, β(μ) according to the local inflow angle, and it represents the degree of local blade section twist in the stage of blade design.equation(10)β(μ)=ϕ(μ)-α
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