Blade Element Theory for Wind Turbines - Small Wind Turbines: Analysis, Design, and Application - page 51

newa = (1 + sqrt( faca - 1))/2;
else
newa = (1 - sqrt(1 - faca))/2;
end
diffa = abs(a - newa);
a = 0.5*(a + newa); % Average old and new a
adash = a*C_adash/(C_a*lamr); % Eq. (3.15)
end
Ngam = 0.5*Numb*Ut*Ut*chord(i)*C_adash/(1 - a);
delthr = Numb*Ut*Ut*chord(i)*delr/pi; % Eq. 3.10
deltor = delthr*rad(i)*C_adash; % Eq. 3.11
delthr = delthr*C_a; % Complete Eq. 3.10
thrust = thrust + delthr; % Sum the rotor thrust
torque = torque + deltor; % Sum the rotor torque
fprintf(out_format, rad(i), j, aoa, a, Cl, Cd, deltor, Re)
end
cp = torque*lambda; % Find the power coefficient
fprintf(' \n')
fprintf(' Cp = %5f, Ct = %5f \n', cp, thrust)
power = 0.5*cp*rho*U0^3*pi*r_tip^2; % Find Power in Watts
thrust = 0.5*thrust*rho*U0^2*pi*r_tip^2; % Find Thrust in N
fprintf(' Power = %5e Watts, Thrust = %5e Newtons \n',...
power, thrust)
fprintf(' \n')
end
end
This program requires the input data file '' rad_ch_tw.dat '' which contains the
radius, chord, and twist of the blade elements. To simulate the experiments of
Anderson et al. [ 2 ], tcdist.m uses a curve fit to the data in Table 3.1 :
function tcdist(nbes, pitch, r_tip, r_hub_in)
% M - file to give chord and twist distribution of the blade used by
% M. B. Anderson et al. ( 1982 ) .
% The output is written to rad_ch_tw.dat where r_tip is in m
% radius is normalized by tip radius and angles are in degrees.
% Variables are:
% nbes - number of blade elements
% pitch - blade pitch or setting angle in degrees
% r_tip - radius of tip (m)
% r_hub_in - radius of hub (m)
% rad(i) - radius of the centre of element i