function eta = effturbine_eps80(ns,ds,PR)
% File created by Violette Mounier (2017) - LAMD EPFL
% This function evaluates the performance of a radial inflow turbine, function of the following inputs:
% - ns [-] : specific speed
% - ds [-] : specific diameter
% - PR [-] : Pressure ratio [-]
% It is valid for a shroud to tip radius ratio  epsilon = 0.8
% For an isentropic efficiciency above 0.5 :
% 0.2 < ns < 1  
% 2.2 < ds < 8.2
% 1.5 < PR < 8.5

%% Inputs
x3=PR;
x2=ds;
x1=ns;

%% Model
eta=+-0.847004.*x3+0.183341.*x3.^2+-0.0206191.*x3.^3+0.0011903.*x3.^4+1.16083.*x2+0.125911.*x2.*x3+-0.0239935.*x2.*x3.^2+0.00211338.*x2.*x3.^3+...
-9.71452e-05.*x2.*x3.^4+-0.47569.*x2.^2+0.00485297.*x2.^2.*x3+-0.000618488.*x2.^2.*x3.^2+5.99324e-05.*x2.^2.*x3.^3+0.0703793.*x2.^3+-0.000675056.*x2.^3.*x3+...
4.34419e-05.*x2.^3.*x3.^2+-0.00454563.*x2.^4+-9.38914e-06.*x2.^4.*x3+-3.55851.*x1+3.35722.*x1.*x3+-0.4107.*x1.*x3.^2+0.0233538.*x1.*x3.^3+-0.000576578.*x1.*x3.^4+...
-2.09492.*x1.*x2+-0.680696.*x1.*x2.*x3+0.063013.*x1.*x2.*x3.^2+-0.00182329.*x1.*x2.*x3.^3+1.3461.*x1.*x2.^2+0.0295.*x1.*x2.^2.*x3+-0.00256274.*x1.*x2.^2.*x3.^2+...
-0.170926.*x1.*x2.^3+0.000838944.*x1.*x2.^3.*x3+0.0061846.*x1.*x2.^4+6.21099.*x1.^2+-3.90722.*x1.^2.*x3+0.242593.*x1.^2.*x3.^2+-0.00533661.*x1.^2.*x3.^3+...
3.48052.*x1.^2.*x2+0.63317.*x1.^2.*x2.*x3+-0.0150439.*x1.^2.*x2.*x3.^2+-1.40478.*x1.^2.*x2.^2+-0.0251384.*x1.^2.*x2.^2.*x3+0.0960514.*x1.^2.*x2.^3+...
-11.3194.*x1.^3+2.45491.*x1.^3.*x3+-0.0681121.*x1.^3.*x3.^2+1.56161.*x1.^3.*x2+-0.278978.*x1.^3.*x2.*x3+-0.142618.*x1.^3.*x2.^2+4.97105.*x1.^4+...
-0.500726.*x1.^4.*x3+-0.487511.*x1.^4.*x2+0.0290328.*1+-0.606463.*x1.^5+0.000114413.*x2.^5+-2.21491e-05.*x3.^5;
end
