fgpiston.cpp

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

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

FGPiston::~FGPiston()
{
  delete Lookup_Combustion_Efficiency;
  delete Power_Mixture_Correlation;
  delete Mixture_Efficiency_Correlation;
  Debug(1); // Call Debug() routine from constructor if needed
}

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

void FGPiston::ResetToIC(void)
{
  FGEngine::ResetToIC();

  ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
  MAP = Atmosphere->GetPressure() * psftopa;
  double airTemperature_degK = RankineToKelvin(Atmosphere->GetTemperature());
  OilTemp_degK = airTemperature_degK;
  CylinderHeadTemp_degK = airTemperature_degK;
  ExhaustGasTemp_degK = airTemperature_degK;
  EGT_degC = ExhaustGasTemp_degK - 273;
  Thruster->SetRPM(0.0);
  RPM = 0.0;
  OilPressure_psi = 0.0;
}

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

double FGPiston::Calculate(void)
{
  if (FuelFlow_gph > 0.0) ConsumeFuel();

  Throttle = FCS->GetThrottlePos(EngineNumber);
  ThrottlePos = MinThrottle+((MaxThrottle-MinThrottle)*Throttle );
  Mixture = FCS->GetMixturePos(EngineNumber);

  //
  // Input values.
  //

  p_amb = Atmosphere->GetPressure() * psftopa;
  p_amb_sea_level = Atmosphere->GetPressureSL() * psftopa;
  T_amb = RankineToKelvin(Atmosphere->GetTemperature());

  RPM = Thruster->GetRPM() * Thruster->GetGearRatio();

  IAS = Auxiliary->GetVcalibratedKTS();

  doEngineStartup();
  if (Boosted) doBoostControl();
  doMAP();
  doAirFlow();
  doFuelFlow();

  //Now that the fuel flow is done check if the mixture is too lean to run the engine
  //Assume lean limit at 22 AFR for now - thats a thi of 0.668
  //This might be a bit generous, but since there's currently no audiable warning of impending
  //cutout in the form of misfiring and/or rough running its probably reasonable for now.
//  if (equivalence_ratio < 0.668)
//    Running = false;

  doEnginePower();
if(HP<0.1250)
  Running = false;

  doEGT();
  doCHT();
  doOilTemperature();
  doOilPressure();

  if (Thruster->GetType() == FGThruster::ttPropeller) {
    ((FGPropeller*)Thruster)->SetAdvance(FCS->GetPropAdvance(EngineNumber));
    ((FGPropeller*)Thruster)->SetFeather(FCS->GetPropFeather(EngineNumber));
  }

  PowerAvailable = (HP * hptoftlbssec) - Thruster->GetPowerRequired();

  return Thruster->Calculate(PowerAvailable);
}

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

double FGPiston::CalcFuelNeed(void)
{
  double dT = State->Getdt() * Propulsion->GetRate();
  FuelFlow_pph = FuelFlow_gph * 6.0; // Assumes 6 lbs / gallon
  FuelFlowRate = FuelFlow_pph / 3600.0;
  FuelExpended = FuelFlowRate * dT;
  return FuelExpended;
}

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

int FGPiston::InitRunning(void) {
  Magnetos=3;
  //Thruster->SetRPM( 1.1*IdleRPM/Thruster->GetGearRatio() );
  Thruster->SetRPM( 1000 );
  Running=true;
  return 1;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
 * Start or stop the engine.
 */

void FGPiston::doEngineStartup(void)
{
  // Check parameters that may alter the operating state of the engine.
  // (spark, fuel, starter motor etc)
  bool spark;
  bool fuel;

  // Check for spark
  Magneto_Left = false;
  Magneto_Right = false;
  // Magneto positions:
  // 0 -> off
  // 1 -> left only
  // 2 -> right only
  // 3 -> both
  if (Magnetos != 0) {
    spark = true;
  } else {
    spark = false;
  }  // neglects battery voltage, master on switch, etc for now.

  if ((Magnetos == 1) || (Magnetos > 2)) Magneto_Left = true;
  if (Magnetos > 1)  Magneto_Right = true;

  // Assume we have fuel for now
  fuel = !Starved;

  // Check if we are turning the starter motor
  if (Cranking != Starter) {
    // This check saves .../cranking from getting updated every loop - they
    // only update when changed.
    Cranking = Starter;
    crank_counter = 0;
  }

  if (Cranking) crank_counter++;  //Check mode of engine operation

  if (!Running && spark && fuel) {  // start the engine if revs high enough
    if (Cranking) {
      if ((RPM > IdleRPM*0.8) && (crank_counter > 175)) // Add a little delay to startup
        Running = true;                         // on the starter
    } else {
      if (RPM > IdleRPM*0.8)                            // This allows us to in-air start
        Running = true;                         // when windmilling
    }
  }

  // Cut the engine *power* - Note: the engine may continue to
  // spin if the prop is in a moving airstream

  if ( Running && (!spark || !fuel) ) Running = false;

  // Check for stalling (RPM = 0).
  if (Running) {
    if (RPM == 0) {
      Running = false;
    } else if ((RPM <= IdleRPM *0.8 ) && (Cranking)) {
      Running = false;
    }
  }
}

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

/**
 * Calculate the Current Boost Speed
 *
 * This function calculates the current turbo/supercharger boost speed
 * based on altitude and the (automatic) boost-speed control valve configuration.
 *
 * Inputs: p_amb, BoostSwitchPressure, BoostSwitchHysteresis
 *
 * Outputs: BoostSpeed
 */

void FGPiston::doBoostControl(void)
{
  if(BoostSpeed < BoostSpeeds - 1) {
    // Check if we need to change to a higher boost speed
    if(p_amb < BoostSwitchPressure[BoostSpeed] - BoostSwitchHysteresis) {
      BoostSpeed++;
    }
  } else if(BoostSpeed > 0) {
    // Check if we need to change to a lower boost speed
    if(p_amb > BoostSwitchPressure[BoostSpeed - 1] + BoostSwitchHysteresis) {
      BoostSpeed--;
    }
  }
}

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

/**
 * Calculate the manifold absolute pressure (MAP) in inches hg
 *
 * This function calculates manifold absolute pressure (MAP)
 * from the throttle position, turbo/supercharger boost control
 * system, engine speed and local ambient air density.
 *
 * TODO: changes in MP should not be instantaneous -- introduce
 * a lag between throttle changes and MP changes, to allow pressure
 * to build up or disperse.
 *
 * Inputs: minMAP, maxMAP, p_amb, Throttle
 *
 * Outputs: MAP, ManifoldPressure_inHg
 */

void FGPiston::doMAP(void)
{
    suction_loss = RPM > 0.0 ? ThrottlePos * MaxRPM / RPM : 1.0;
    if (suction_loss > 1.0) suction_loss = 1.0;
    MAP = p_amb * suction_loss;

    if(Boosted) {
      // If takeoff boost is fitted, we currently assume the following throttle map:
      // (In throttle % - actual input is 0 -> 1)
      // 99 / 100 - Takeoff boost
      // 96 / 97 / 98 - Rated boost
      // 0 - 95 - Idle to Rated boost (MinManifoldPressure to MaxManifoldPressure)
      // In real life, most planes would be fitted with a mechanical 'gate' between
      // the rated boost and takeoff boost positions.
      double T = Throttle; // processed throttle value.
      bool bTakeoffPos = false;
      if(bTakeoffBoost) {
        if(Throttle > 0.98) {
          //cout << "Takeoff Boost!!!!\n";
          bTakeoffPos = true;
        } else if(Throttle <= 0.95) {
          bTakeoffPos = false;
          T *= 1.0 / 0.95;
        } else {
          bTakeoffPos = false;
          //cout << "Rated Boost!!\n";
          T = 1.0;
        }
      }
      // Boost the manifold pressure.
      double boost_factor = BoostMul[BoostSpeed] * suction_loss * RPM/RatedRPM[BoostSpeed];
      if (boost_factor < 1.0) boost_factor = 1.0;  // boost will never reduce the MAP
      MAP *= boost_factor;
      // Now clip the manifold pressure to BCV or Wastegate setting.
      if(bTakeoffPos) {
        if(MAP > TakeoffMAP[BoostSpeed]) {
          MAP = TakeoffMAP[BoostSpeed];
        }
      } else {
        if(MAP > RatedMAP[BoostSpeed]) {
          MAP = RatedMAP[BoostSpeed];
        }
      }
    }

  // And set the value in American units as well
  ManifoldPressure_inHg = MAP / inhgtopa;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
 * Calculate the air flow through the engine.
 * Also calculates ambient air density
 * (used in CHT calculation for air-cooled engines).
 *
 * Inputs: p_amb, R_air, T_amb, MAP, Displacement,
 *   RPM, volumetric_efficiency, ThrottlePos
 *
 * TODO: Model inlet manifold air temperature.
 *
 * Outputs: rho_air, m_dot_air
 */

void FGPiston::doAirFlow(void)
{
  rho_air = p_amb / (R_air * T_amb);
  double displacement_SI = Displacement * in3tom3;
  double swept_volume = (displacement_SI * (RPM/60)) / 2;
  double v_dot_air = swept_volume * volumetric_efficiency * suction_loss;

  double rho_air_manifold = MAP / (R_air * T_amb);
  m_dot_air = v_dot_air * rho_air_manifold;
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
 * Calculate the fuel flow into the engine.
 *
 * Inputs: Mixture, thi_sea_level, p_amb_sea_level, p_amb, m_dot_air
 *
 * Outputs: equivalence_ratio, m_dot_fuel
 */

void FGPiston::doFuelFlow(void)
{
  double thi_sea_level = 1.3 * Mixture; // Allows an AFR of infinity:1 to 11.3075:1
  equivalence_ratio = thi_sea_level * 101325.0 / p_amb;