function eta = effturbine_eps50(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 = 0.5
% For an isentropic efficiciency above 0.5 :
% 0.15 < ns < 0.7  
% 3 < ds < 9
% 1.5 < PR < 8.5

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

%% Model
eta=+5.353976.*x3+-0.817832.*x3.^2+0.1070457.*x3.^3+-0.004352997.*x3.^4+10.30475.*x2+-1.364852.*x2.*x3+0.08681798.*x2.*x3.^2+...
-0.01269729.*x2.*x3.^3+0.0005059793.*x2.*x3.^4+-1.567382.*x2.^2+0.1693688.*x2.^2.*x3+0.0006522438.*x2.^2.*x3.^2+0.0001572885.*x2.^2.*x3.^3+...
0.1054241.*x2.^3+-0.01077004.*x2.^3.*x3+-0.0001312936.*x2.^3.*x3.^2+-0.002871063.*x2.^4+0.0002754964.*x2.^4.*x3+173.0294.*x1+-18.73254.*x1.*x3+...
1.427275.*x1.*x3.^2+-0.1982459.*x1.*x3.^3+0.00964881.*x1.*x3.^4+-53.31055.*x1.*x2+4.004818.*x1.*x2.*x3+0.01981087.*x1.*x2.*x3.^2+...
0.004643071.*x1.*x2.*x3.^3+6.648305.*x1.*x2.^2+-0.5005172.*x1.*x2.^2.*x3+-0.003853916.*x1.*x2.^2.*x3.^2+-0.2942446.*x1.*x2.^3+...
0.01843034.*x1.*x2.^3.*x3+0.003175486.*x1.*x2.^4+-469.4202.*x1.^2+27.01231.*x1.^2.*x3+-0.06221591.*x1.^2.*x3.^2+...
-0.01218976.*x1.^2.*x3.^3+108.9453.*x1.^2.*x2+-3.261935.*x1.^2.*x2.*x3+-0.1134703.*x1.^2.*x2.*x3.^2+-10.0432.*x1.^2.*x2.^2+...
0.345679.*x1.^2.*x2.^2.*x3+0.2438532.*x1.^2.*x2.^3+629.0072.*x1.^3+-26.13959.*x1.^3.*x3+0.5479741.*x1.^3.*x3.^2+...
-79.55022.*x1.^3.*x2+0.07388251.*x1.^3.*x2.*x3+3.117388.*x1.^3.*x2.^2+-454.2922.*x1.^4+10.47425.*x1.^4.*x3+24.17679.*x1.^4.*x2+...
-27.3268.*1+139.0318.*x1.^5+1.544509e-05.*x2.^5+-5.563154e-05.*x3.^5;

end...
