cantera/ext/tpx/Methane.cpp

// Methane

#include "Methane.h"
#include <math.h>
#include <iostream>
using namespace std;

namespace tpx {

static const double 
    M = 16.04996,
    Tmn = 90.68,
    Tmx = 1700.0,
    Tc = 190.555,
    Pc = 4.5988e6,
    Roc= 160.43,
    To = 90.68,
    Tt = 90.68,
    Pt=11743.5675,
    R = 5.18253475866e2,
    Gamma=3.72992471469e-5,
    alpha = 1.5,		//Used with Psat
    alpha1 = .36,		//used with ldens;
    Rot=451.562,
    beta=2009.152,
    u0 = 357696.0858,
    s0 = -1918.035071;

static const double Ameth[] =
    {  -7.25929210183, 4.13766054566e2, -6.32167316855e3,
	3.34015577724e5, -1.68253379982e7, 1.87884851902e-2, -1.18673201223e1,
	2.09062618015e3, -4.07532656958e5, -5.73917603241e-5,4.37711441593e-2,
       -4.38766500673, 1.13524630779e-5, -5.07028240949e-5, 2.28002199522e-2,
	9.25611329590e-9, 1.33865662546e-10, -1.65439044196e-7, 1.81030980110e-10,
	5.45753645958e5, -3.63192281933e7, 4.81463473761, 1.56633022620e5,
	7.89977010972e-5, 1.39993881210e-2, -1.70656092212e-11, -4.55256623445e-5,
       -2.29314170748e-14,8.31548197665e-12, 6.84673626259e-20,
       -4.70845544152e-17, 5.21465091383e-16  };

static const double Dmeth[]=
	{  -1.78860165e-1, 4.83847500e-2, -1.84898700e-2  };

static const double Fmeth[]=
	{  4.77748580, 1.76065363, -5.67888940e-1, 1.32786231  };

static const double Gmeth[]=
	{  1.34740610e3, 1.35512060e2, -2.93910458e1, 2.12774600, 2.44656600e3  };

// double rt, rt2, rt3, egrho;

double methane::C(int i, double rt, double rt2) {
   switch(i) {
   case 0 : 
      return Ameth[0] * T + Ameth[1] * sqrt(T) + Ameth[2] + (Ameth[3] + Ameth[4] * rt) * rt;
   case 1 : 
      return Ameth[5] * T + Ameth[6] + rt * (Ameth[7] + Ameth[8] * rt);
   case 2 :
      return Ameth[9] * T + Ameth[10] + Ameth[11] * rt; 
   case 3 :
      return Ameth[12];
   case 4 :
      return rt*(Ameth[13] + Ameth[14]*rt);
   case 5 :
      return Ameth[15]*rt;
   case 6 : 
      return rt*(Ameth[16] + Ameth[17]*rt);
   case 7 : 
      return Ameth[18]*rt2;
   case 8 : 
      return rt2*(Ameth[19] + Ameth[20]*rt);
   case 9 : 
      return rt2*(Ameth[21] + Ameth[22]*rt2);
   case 10 : 
      return rt2*(Ameth[23] + Ameth[24]*rt);
   case 11 : 
      return rt2*(Ameth[25] + Ameth[26]*rt2);
   case 12 : 
      return rt2*(Ameth[27] + Ameth[28]*rt);
   case 13 : 
      return rt2*(Ameth[29] + Ameth[30]*rt + Ameth[31]*rt2);
   default :
	  return 0.0;
      }
   }

double methane::Cprime(int i, double rt, double rt2, double rt3) {
   switch(i) {
   case 0 : 
      return Ameth[0] + 0.5*Ameth[1]/sqrt(T) - (Ameth[3] + 2.0*Ameth[4]*rt)*rt2; 
   case 1 : 
      return Ameth[5] - rt2*(Ameth[7] + 2.0*Ameth[8]*rt); 
   case 2 :
      return Ameth[9] - Ameth[11]*rt2; 
   case 3 :
      return 0.0;
   case 4 :
      return -rt2*(Ameth[13] + 2.0*Ameth[14]*rt);
   case 5 :
      return -Ameth[15]*rt2;
   case 6 : 
      return -rt2*(Ameth[16] + 2.0*Ameth[17]*rt);
   case 7 : 
      return -2.0*Ameth[18]*rt3; 
   case 8 : 
      return -rt3*(2.0*Ameth[19] + 3.0*Ameth[20]*rt);
   case 9 : 
      return -rt3*(2.0*Ameth[21] + 4.0*Ameth[22]*rt2);
   case 10 : 
      return -rt3*(2.0*Ameth[23] + 3.0*Ameth[24]*rt);
   case 11 : 
      return -rt3*(2.0*Ameth[25] + 4.0*Ameth[26]*rt2);
   case 12 : 
      return -rt3*(2.0*Ameth[27] + 3.0*Ameth[28]*rt);
   case 13 : 
      return -rt3*(2.0*Ameth[29] + 3.0*Ameth[30]*rt + 4.0*Ameth[31]*rt2);
   default :
	  return 0.0;
      }
   } 

double methane::W(int n, double egrho) {
   return (n == 0 ? (1.0 - egrho)/(2.0*Gamma) : 
	   (n*W(n-1, egrho) - 0.5*pow(Rho,2*n)*egrho)/Gamma);
   }

double methane::H(int i, double egrho) {
   return (i < 8 ? pow(Rho,i+2) : pow(Rho,2*i-13)*egrho); 
   }

double methane::I(int i, double egrho) {
   return (i < 8 ? pow(Rho,i+1)/double(i+1) : W(i-8, egrho)); 
   }

double methane::up(){
   double rt = 1.0/T;
   double rt2 = rt*rt;
   double rt3 = rt*rt2;
   double egrho = exp(-Gamma*Rho*Rho);
   double t3 = pow(T,1.0/3.0);
   
   double sum = 0.0;
   for (int i=0; i<14; i++)
      sum += (C(i, rt, rt2) - T*Cprime(i, rt, rt2, rt3))*I(i, egrho);

   sum += T*(Gmeth[0] + 0.75*Gmeth[1]*t3 + 0.6*Gmeth[2]*t3*t3 + 0.5*Gmeth[3]*T)
          + Gmeth[4]*beta/(exp(beta*rt) - 1.0) + u0;
   return sum + m_energy_offset;
   }

double methane::sp() {
   double rt = 1.0/T;
   double rt2 = rt*rt;
   double rt3 = rt*rt2;
   double egrho = exp(-Gamma*Rho*Rho);
   double t3 = pow(T,1.0/3.0);
   double sum = 0.0;
   sum = s0 - R*log(Rho);
   for (int i=0; i<14; i++)
      sum -= Cprime(i, rt, rt2, rt3)*I(i, egrho);
   sum += Gmeth[0]*log(T) + 3.0*Gmeth[1]*t3 + 1.5*Gmeth[2]*t3*t3 + Gmeth[3]*T
          + Gmeth[4]*(beta*rt + beta*rt/(exp(beta*rt) - 1.0)
          - log(exp(beta*rt) - 1.0));
   return sum + m_entropy_offset;
   }

double methane::Pp(){
   double rt = 1.0/T;
   double rt2 = rt*rt;
   double egrho = exp(-Gamma*Rho*Rho);

   double P = Rho*R*T;
   for(int i=0; i<14; i++)
      P += C(i, rt, rt2)*H(i, egrho);
   return P;
   }

//equation s3
double methane::Psat(){
double x = (1.0 - Tt/T)/(1.0 - Tt/Tc);
double result;
if ((T < Tmn) || (T > Tc)) set_Err(TempError); 
result = Fmeth[0]*x + Fmeth[1]*x*x + Fmeth[2]*x*x*x + 
         Fmeth[3]*x*pow(1-x, alpha);
return exp(result)*Pt;
}


//equation D3
double methane::ldens(){
double result;
double sum;
double w;
if ((T < Tmn) || (T > Tc)) set_Err(TempError); 
w = (Tc - T)/(Tc - Tt);
sum = Dmeth[0]*(1.0 - pow(w, 2.0/3.0)) + Dmeth[1]*(1.0 - pow(w, 4.0/3.0))
      + Dmeth[2]*(1.0 - pow(w, 2));
result = pow(w,alpha1)*exp(sum);
result *= (Rot-Roc);
result += Roc;
return result;
}

 double methane::Tcrit() {return Tc;}
 double methane::Pcrit() {return Pc;}
 double methane::Vcrit() {return 1.0/Roc;}
 double methane::Tmin() {return Tmn;}
 double methane::Tmax() {return Tmx;}
 char * methane::name() {return "methane";}
 char * methane::formula() {return "CH4";}
 double methane::MolWt() {return M;}

}