Wind Energy Handbook. Michael Barton Graham

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      (3.50a)

      At the outer edge of the rotor μ = 1 and a^′ = a^′_t, so

      (3.50b)

Equation (3.2) is consistent with the earlier Eqs. (3.32) and (3.33).

With drag included the thrust Eq. (3.48) can be reduced to

(3.51)

      where the parameter _.

If the pressure drop term Δp_d2 is not ignored, the right hand side of Eq. (3.51) becomes 8πμ{a(1 − a) + (a^′λμ)²}. The additional term (a^′λμ)² is small and usually negligible except very close to the rotor axis or at low tip speed ratios.

The torque Eq. (3.49) simplifies to

(3.52)

      It is convenient to put

(3.53a)

      and

(3.53b)

Solving Eqs. (3.51) and (3.52) to obtain values for the flow induction factors a and a' using 2‐D aerofoil characteristics requires an iterative process for which the following equations, derived from (3.51), (3.52), and (3.53a and b), are convenient. The right hand sides are evaluated using existing values of the flow induction factors, yielding simple equations for the next iteration of the flow induction factors:

(3.54a)

(3.55)

If the additional pressure‐drop term Δp_d2 at the rotor due to wake rotation is included in the analysis, following from Eq. (3.48), Eq. (3.54a) becomes

(3.54b) СКАЧАТЬ