fgpiston.cpp

来自「6 DOF Missle Simulation」· C++ 代码 · 共 910 行 · 第 1/3 页

//  double AFR = 10+(12*(1-Mixture));// mixture 10:1 to 22:1
//  m_dot_fuel = m_dot_air / AFR;
  m_dot_fuel = (m_dot_air * equivalence_ratio) / 14.7;
  FuelFlow_gph = m_dot_fuel
    * 3600            // seconds to hours
    * 2.2046            // kg to lb
    / 6.0;            // lb to gal_us of gasoline
//    / 6.6;            // lb to gal_us of kerosene
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
 * Calculate the power produced by the engine.
 *
 * Currently, the JSBSim propellor model does not allow the
 * engine to produce enough RPMs to get up to a high horsepower.
 * When tested with sufficient RPM, it has no trouble reaching
 * 200HP.
 *
 * Inputs: ManifoldPressure_inHg, p_amb, RPM, T_amb,
 *   Mixture_Efficiency_Correlation, Cycles, MaxHP
 *
 * Outputs: Percentage_Power, HP
 */

void FGPiston::doEnginePower(void)
{
  if (Running) {
    double T_amb_degF = KelvinToFahrenheit(T_amb);
    double T_amb_sea_lev_degF = KelvinToFahrenheit(288);

    // FIXME: this needs to be generalized
    double ME, friction, percent_RPM, power;  // Convienience term for use in the calculations
    ME = Mixture_Efficiency_Correlation->GetValue(m_dot_fuel/m_dot_air);

    percent_RPM = RPM/MaxRPM;
    friction = 1 - (percent_RPM * percent_RPM * percent_RPM * percent_RPM/10);
    if (friction < 0 ) friction = 0;
    power = friction;

    if ( Magnetos != 3 ) power *= SparkFailDrop;


    HP = (FuelFlow_gph * 6.0 / BSFC )* ME * suction_loss * power;

  } else {

    // Power output when the engine is not running
    if (Cranking) {
      if (RPM < 10) {
        HP = StarterHP;
      } else if (RPM < IdleRPM*0.8) {
        HP = StarterHP + ((IdleRPM*0.8 - RPM) / 8.0);
        // This is a guess - would be nice to find a proper starter moter torque curve
      } else {
        HP = StarterHP;
      }
    } else {
      // Quick hack until we port the FMEP stuff
      if (RPM > 0.0)
        HP = -1.5;
      else
        HP = 0.0;
    }
  }
  Percentage_Power = HP / MaxHP ;
//  cout << "Power = " << HP << "  RPM = " << RPM << "  Running = " << Running << "  Cranking = " << Cranking << endl;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
 * Calculate the exhaust gas temperature.
 *
 * Inputs: equivalence_ratio, m_dot_fuel, calorific_value_fuel,
 *   Cp_air, m_dot_air, Cp_fuel, m_dot_fuel, T_amb, Percentage_Power
 *
 * Outputs: combustion_efficiency, ExhaustGasTemp_degK
 */

void FGPiston::doEGT(void)
{
  double delta_T_exhaust;
  double enthalpy_exhaust;
  double heat_capacity_exhaust;
  double dEGTdt;

  if ((Running) && (m_dot_air > 0.0)) {  // do the energy balance
    combustion_efficiency = Lookup_Combustion_Efficiency->GetValue(equivalence_ratio);
    enthalpy_exhaust = m_dot_fuel * calorific_value_fuel *
                              combustion_efficiency * 0.33;
    heat_capacity_exhaust = (Cp_air * m_dot_air) + (Cp_fuel * m_dot_fuel);
    delta_T_exhaust = enthalpy_exhaust / heat_capacity_exhaust;
    ExhaustGasTemp_degK = T_amb + delta_T_exhaust;
    ExhaustGasTemp_degK *= 0.444 + ((0.544 - 0.444) * Percentage_Power);
  } else {  // Drop towards ambient - guess an appropriate time constant for now
    combustion_efficiency = 0;
    dEGTdt = (RankineToKelvin(Atmosphere->GetTemperature()) - ExhaustGasTemp_degK) / 100.0;
    delta_T_exhaust = dEGTdt * dt;
    ExhaustGasTemp_degK += delta_T_exhaust;
  }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
 * Calculate the cylinder head temperature.
 *
 * Inputs: T_amb, IAS, rho_air, m_dot_fuel, calorific_value_fuel,
 *   combustion_efficiency, RPM, MaxRPM
 *
 * Outputs: CylinderHeadTemp_degK
 */

void FGPiston::doCHT(void)
{
  double h1 = -95.0;
  double h2 = -3.95;
  double h3 = -140.0; // -0.05 * 2800 (default maxrpm)

  double arbitary_area = 1.0;
  double CpCylinderHead = 800.0;
  double MassCylinderHead = 8.0;

  double temperature_difference = CylinderHeadTemp_degK - T_amb;
  double v_apparent = IAS * 0.5144444;
  double v_dot_cooling_air = arbitary_area * v_apparent;
  double m_dot_cooling_air = v_dot_cooling_air * rho_air;
  double dqdt_from_combustion =
    m_dot_fuel * calorific_value_fuel * combustion_efficiency * 0.33;
  double dqdt_forced = (h2 * m_dot_cooling_air * temperature_difference) +
    (h3 * RPM * temperature_difference / MaxRPM);
  double dqdt_free = h1 * temperature_difference;
  double dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;

  double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;

  CylinderHeadTemp_degK +=
    (dqdt_cylinder_head / HeatCapacityCylinderHead) * dt;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
 * Calculate the oil temperature.
 *
 * Inputs: CylinderHeadTemp_degK, T_amb, OilPressure_psi.
 *
 * Outputs: OilTemp_degK
 */

void FGPiston::doOilTemperature(void)
{
  double idle_percentage_power = 0.023;        // approximately
  double target_oil_temp;        // Steady state oil temp at the current engine conditions
  double time_constant;          // The time constant for the differential equation
  double efficiency = 0.667;     // The aproximate oil cooling system efficiency // FIXME: may vary by engine

//  Target oil temp is interpolated between ambient temperature and Cylinder Head Tempurature
//  target_oil_temp = ( T_amb * efficiency ) + (CylinderHeadTemp_degK *(1-efficiency)) ;
  target_oil_temp = CylinderHeadTemp_degK + efficiency * (T_amb - CylinderHeadTemp_degK) ;

  if (OilPressure_psi > 5.0 ) {
    time_constant = 5000 / OilPressure_psi; // Guess at a time constant for circulated oil.
                                            // The higher the pressure the faster it reaches
					    // target temperature.  Oil pressure should be about
					    // 60 PSI yielding a TC of about 80.
  } else {
    time_constant = 1000;  // Time constant for engine-off; reflects the fact
                           // that oil is no longer getting circulated
  }

  double dOilTempdt = (target_oil_temp - OilTemp_degK) / time_constant;

  OilTemp_degK += (dOilTempdt * dt);
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
 * Calculate the oil pressure.
 *
 * Inputs: RPM, MaxRPM, OilTemp_degK
 *
 * Outputs: OilPressure_psi
 */

void FGPiston::doOilPressure(void)
{
  double Oil_Press_Relief_Valve = 60; // FIXME: may vary by engine
  double Oil_Press_RPM_Max = MaxRPM * 0.75;    // 75% of max rpm FIXME: may vary by engine
  double Design_Oil_Temp = 358;          // degK; FIXME: may vary by engine
  double Oil_Viscosity_Index = 0.25;

  OilPressure_psi = (Oil_Press_Relief_Valve / Oil_Press_RPM_Max) * RPM;

  if (OilPressure_psi >= Oil_Press_Relief_Valve) {
    OilPressure_psi = Oil_Press_Relief_Valve;
  }

  OilPressure_psi += (Design_Oil_Temp - OilTemp_degK) * Oil_Viscosity_Index * OilPressure_psi / Oil_Press_Relief_Valve;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

string FGPiston::GetEngineLabels(string delimeter)
{
  std::ostringstream buf;

  buf << Name << " Power Available (engine " << EngineNumber << " in HP)" << delimeter
      << Name << " HP (engine " << EngineNumber << ")" << delimeter
      << Name << " equivalent ratio (engine " << EngineNumber << ")" << delimeter
      << Name << " MAP (engine " << EngineNumber << ")" << delimeter
      << Thruster->GetThrusterLabels(EngineNumber, delimeter);

  return buf.str();
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

string FGPiston::GetEngineValues(string delimeter)
{
  std::ostringstream buf;

  buf << PowerAvailable << delimeter << HP << delimeter
      << equivalence_ratio << delimeter << MAP << delimeter
      << Thruster->GetThrusterValues(EngineNumber, delimeter);

  return buf.str();
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//
//    The bitmasked value choices are as follows:
//    unset: In this case (the default) JSBSim would only print
//       out the normally expected messages, essentially echoing
//       the config files as they are read. If the environment
//       variable is not set, debug_lvl is set to 1 internally
//    0: This requests JSBSim not to output any messages
//       whatsoever.
//    1: This value explicity requests the normal JSBSim
//       startup messages
//    2: This value asks for a message to be printed out when
//       a class is instantiated
//    4: When this value is set, a message is displayed when a
//       FGModel object executes its Run() method
//    8: When this value is set, various runtime state variables
//       are printed out periodically
//    16: When set various parameters are sanity checked and
//       a message is printed out when they go out of bounds

void FGPiston::Debug(int from)
{
  if (debug_lvl <= 0) return;

  if (debug_lvl & 1) { // Standard console startup message output
    if (from == 0) { // Constructor

      cout << "\n    Engine Name: "         << Name << endl;
      cout << "      MinManifoldPressure: " << MinManifoldPressure_inHg << endl;
      cout << "      MaxManifoldPressure: " << MaxManifoldPressure_inHg << endl;
      cout << "      MinMaP (Pa):         " << minMAP << endl;
      cout << "      MaxMaP (Pa): "         << maxMAP << endl;
      cout << "      Displacement: "        << Displacement             << endl;
      cout << "      MaxHP: "               << MaxHP                    << endl;
      cout << "      Cycles: "              << Cycles                   << endl;
      cout << "      IdleRPM: "             << IdleRPM                  << endl;
      cout << "      MaxThrottle: "         << MaxThrottle              << endl;
      cout << "      MinThrottle: "         << MinThrottle              << endl;

      cout << endl;
      cout << "      Combustion Efficiency table:" << endl;
      Lookup_Combustion_Efficiency->Print();
      cout << endl;

      cout << endl;
      cout << "      Power Mixture Correlation table:" << endl;
      Power_Mixture_Correlation->Print();
      cout << endl;

      cout << endl;
      cout << "      Mixture Efficiency Correlation table:" << endl;
      Mixture_Efficiency_Correlation->Print();
      cout << endl;

    }
  }
  if (debug_lvl & 2 ) { // Instantiation/Destruction notification
    if (from == 0) cout << "Instantiated: FGPiston" << endl;
    if (from == 1) cout << "Destroyed:    FGPiston" << endl;
  }
  if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
  }
  if (debug_lvl & 8 ) { // Runtime state variables
  }
  if (debug_lvl & 16) { // Sanity checking
  }
  if (debug_lvl & 64) {
    if (from == 0) { // Constructor
      cout << IdSrc << endl;
      cout << IdHdr << endl;
    }
  }
}
} // namespace JSBSim