-/*******************************************************************************
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Module: FGPiston.cpp
- Author: Jon S. Berndt
+ Author: Jon S. Berndt, JSBSim framework
+ Dave Luff, Piston engine model
Date started: 09/12/2000
Purpose: This module models a Piston engine
--------------------------------------------------------------------------------
09/12/2000 JSB Created
-********************************************************************************
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
-*******************************************************************************/
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+
+#include <sstream>
#include "FGPiston.h"
+#include "FGPropulsion.h"
+#include "FGPropeller.h"
+
+namespace JSBSim {
+
+static const char *IdSrc = "$Id$";
+static const char *IdHdr = ID_PISTON;
+
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+CLASS IMPLEMENTATION
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+
+FGPiston::FGPiston(FGFDMExec* exec, FGConfigFile* Eng_cfg, int engine_number)
+ : FGEngine(exec, engine_number),
+ R_air(287.3),
+ rho_fuel(800), // estimate
+ calorific_value_fuel(47.3e6),
+ Cp_air(1005),
+ Cp_fuel(1700)
+{
+ string token;
+
+ Type = etPiston;
+ crank_counter = 0;
+ OilTemp_degK = 298;
+ MinManifoldPressure_inHg = 6.5;
+ MaxManifoldPressure_inHg = 28.5;
+ ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
+ minMAP = 21950;
+ maxMAP = 96250;
+ MAP = Atmosphere->GetPressure() * 47.88; // psf to Pa
+ CylinderHeadTemp_degK = 0.0;
+ Displacement = 360;
+ MaxHP = 0;
+ Cycles = 2;
+ IdleRPM = 600;
+ Magnetos = 0;
+ ExhaustGasTemp_degK = 0.0;
+ EGT_degC = 0.0;
+
+ dt = State->Getdt();
+
+ // Supercharging
+ BoostSpeeds = 0; // Default to no supercharging
+ BoostSpeed = 0;
+ Boosted = false;
+ BoostOverride = 0;
+ bBoostOverride = false;
+ bTakeoffBoost = false;
+ TakeoffBoost = 0.0; // Default to no extra takeoff-boost
+ int i;
+ for (i=0; i<FG_MAX_BOOST_SPEEDS; i++) {
+ RatedBoost[i] = 0.0;
+ RatedPower[i] = 0.0;
+ RatedAltitude[i] = 0.0;
+ BoostMul[i] = 1.0;
+ RatedMAP[i] = 100000;
+ RatedRPM[i] = 2500;
+ TakeoffMAP[i] = 100000;
+ }
+ for (i=0; i<FG_MAX_BOOST_SPEEDS-1; i++) {
+ BoostSwitchAltitude[i] = 0.0;
+ BoostSwitchPressure[i] = 0.0;
+ }
+
+ // Initialisation
+ volumetric_efficiency = 0.8; // Actually f(speed, load) but this will get us running
+
+ // First column is thi, second is neta (combustion efficiency)
+ Lookup_Combustion_Efficiency = new FGTable(12);
+ *Lookup_Combustion_Efficiency << 0.00 << 0.980;
+ *Lookup_Combustion_Efficiency << 0.90 << 0.980;
+ *Lookup_Combustion_Efficiency << 1.00 << 0.970;
+ *Lookup_Combustion_Efficiency << 1.05 << 0.950;
+ *Lookup_Combustion_Efficiency << 1.10 << 0.900;
+ *Lookup_Combustion_Efficiency << 1.15 << 0.850;
+ *Lookup_Combustion_Efficiency << 1.20 << 0.790;
+ *Lookup_Combustion_Efficiency << 1.30 << 0.700;
+ *Lookup_Combustion_Efficiency << 1.40 << 0.630;
+ *Lookup_Combustion_Efficiency << 1.50 << 0.570;
+ *Lookup_Combustion_Efficiency << 1.60 << 0.525;
+ *Lookup_Combustion_Efficiency << 2.00 << 0.345;
+
+ Power_Mixture_Correlation = new FGTable(13);
+ *Power_Mixture_Correlation << (14.7/1.6) << 78.0;
+ *Power_Mixture_Correlation << 10 << 86.0;
+ *Power_Mixture_Correlation << 11 << 93.5;
+ *Power_Mixture_Correlation << 12 << 98.0;
+ *Power_Mixture_Correlation << 13 << 100.0;
+ *Power_Mixture_Correlation << 14 << 99.0;
+ *Power_Mixture_Correlation << 15 << 96.4;
+ *Power_Mixture_Correlation << 16 << 92.5;
+ *Power_Mixture_Correlation << 17 << 88.0;
+ *Power_Mixture_Correlation << 18 << 83.0;
+ *Power_Mixture_Correlation << 19 << 78.5;
+ *Power_Mixture_Correlation << 20 << 74.0;
+ *Power_Mixture_Correlation << (14.7/0.6) << 58;
+
+ Name = Eng_cfg->GetValue("NAME");
+ Eng_cfg->GetNextConfigLine();
+ while (Eng_cfg->GetValue() != string("/FG_PISTON")) {
+ *Eng_cfg >> token;
+ if (token == "MINMP") *Eng_cfg >> MinManifoldPressure_inHg;
+ else if (token == "MAXMP") *Eng_cfg >> MaxManifoldPressure_inHg;
+ else if (token == "DISPLACEMENT") *Eng_cfg >> Displacement;
+ else if (token == "MAXHP") *Eng_cfg >> MaxHP;
+ else if (token == "CYCLES") *Eng_cfg >> Cycles;
+ else if (token == "IDLERPM") *Eng_cfg >> IdleRPM;
+ else if (token == "MAXTHROTTLE") *Eng_cfg >> MaxThrottle;
+ else if (token == "MINTHROTTLE") *Eng_cfg >> MinThrottle;
+ else if (token == "NUMBOOSTSPEEDS") *Eng_cfg >> BoostSpeeds;
+ else if (token == "BOOSTOVERRIDE") *Eng_cfg >> BoostOverride;
+ else if (token == "TAKEOFFBOOST") *Eng_cfg >> TakeoffBoost;
+ else if (token == "RATEDBOOST1") *Eng_cfg >> RatedBoost[0];
+ else if (token == "RATEDBOOST2") *Eng_cfg >> RatedBoost[1];
+ else if (token == "RATEDBOOST3") *Eng_cfg >> RatedBoost[2];
+ else if (token == "RATEDPOWER1") *Eng_cfg >> RatedPower[0];
+ else if (token == "RATEDPOWER2") *Eng_cfg >> RatedPower[1];
+ else if (token == "RATEDPOWER3") *Eng_cfg >> RatedPower[2];
+ else if (token == "RATEDRPM1") *Eng_cfg >> RatedRPM[0];
+ else if (token == "RATEDRPM2") *Eng_cfg >> RatedRPM[1];
+ else if (token == "RATEDRPM3") *Eng_cfg >> RatedRPM[2];
+ else if (token == "RATEDALTITUDE1") *Eng_cfg >> RatedAltitude[0];
+ else if (token == "RATEDALTITUDE2") *Eng_cfg >> RatedAltitude[1];
+ else if (token == "RATEDALTITUDE3") *Eng_cfg >> RatedAltitude[2];
+ else cerr << "Unhandled token in Engine config file: " << token << endl;
+ }
+
+ minMAP = MinManifoldPressure_inHg * 3376.85; // inHg to Pa
+ maxMAP = MaxManifoldPressure_inHg * 3376.85;
+
+ // Set up and sanity-check the turbo/supercharging configuration based on the input values.
+ if(TakeoffBoost > RatedBoost[0]) bTakeoffBoost = true;
+ for(i=0; i<BoostSpeeds; ++i) {
+ bool bad = false;
+ if(RatedBoost[i] <= 0.0) bad = true;
+ if(RatedPower[i] <= 0.0) bad = true;
+ if(RatedAltitude[i] < 0.0) bad = true; // 0.0 is deliberately allowed - this corresponds to unregulated supercharging.
+ if(i > 0 && RatedAltitude[i] < RatedAltitude[i - 1]) bad = true;
+ if(bad) {
+ // We can't recover from the above - don't use this supercharger speed.
+ BoostSpeeds--;
+ // TODO - put out a massive error message!
+ break;
+ }
+ // Now sanity-check stuff that is recoverable.
+ if(i < BoostSpeeds - 1) {
+ if(BoostSwitchAltitude[i] < RatedAltitude[i]) {
+ // TODO - put out an error message
+ // But we can also make a reasonable estimate, as below.
+ BoostSwitchAltitude[i] = RatedAltitude[i] + 1000;
+ }
+ BoostSwitchPressure[i] = Atmosphere->GetPressure(BoostSwitchAltitude[i]) * 47.88;
+ //cout << "BoostSwitchAlt = " << BoostSwitchAltitude[i] << ", pressure = " << BoostSwitchPressure[i] << '\n';
+ // Assume there is some hysteresis on the supercharger gear switch, and guess the value for now
+ BoostSwitchHysteresis = 1000;
+ }
+ // Now work out the supercharger pressure multiplier of this speed from the rated boost and altitude.
+ RatedMAP[i] = Atmosphere->GetPressureSL() * 47.88 + RatedBoost[i] * 6895; // psf*47.88 = Pa, psi*6895 = Pa.
+ // Sometimes a separate BCV setting for takeoff or extra power is fitted.
+ if(TakeoffBoost > RatedBoost[0]) {
+ // Assume that the effect on the BCV is the same whichever speed is in use.
+ TakeoffMAP[i] = RatedMAP[i] + ((TakeoffBoost - RatedBoost[0]) * 6895);
+ bTakeoffBoost = true;
+ } else {
+ TakeoffMAP[i] = RatedMAP[i];
+ bTakeoffBoost = false;
+ }
+ BoostMul[i] = RatedMAP[i] / (Atmosphere->GetPressure(RatedAltitude[i]) * 47.88);
+
+ // TODO - get rid of the debugging output before sending it to Jon
+ //cout << "Speed " << i+1 << '\n';
+ //cout << "BoostMul = " << BoostMul[i] << ", RatedMAP = " << RatedMAP[i] << ", TakeoffMAP = " << TakeoffMAP[i] << '\n';
+ }
-/*******************************************************************************
-************************************ CODE **************************************
-*******************************************************************************/
+ if(BoostSpeeds > 0) {
+ Boosted = true;
+ BoostSpeed = 0;
+ }
+ bBoostOverride = (BoostOverride == 1 ? true : false);
+ //cout << "Engine is " << (Boosted ? "supercharged" : "naturally aspirated") << '\n';
-FGPiston::FGPiston(FGFDMExec* fdex, string enginePath, string engineName, int num) :
- FGEngine(fdex, enginePath, engineName, num)
+ Debug(0); // Call Debug() routine from constructor if needed
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+FGPiston::~FGPiston()
+{
+ Debug(1); // Call Debug() routine from constructor if needed
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+double FGPiston::Calculate(void)
{
+ if (FuelFlow_gph > 0.0) ConsumeFuel();
+
+ Throttle = FCS->GetThrottlePos(EngineNumber);
+ Mixture = FCS->GetMixturePos(EngineNumber);
+
+ //
+ // Input values.
//
+
+ p_amb = Atmosphere->GetPressure() * 47.88; // convert from lbs/ft2 to Pa
+ p_amb_sea_level = Atmosphere->GetPressureSL() * 47.88;
+ T_amb = Atmosphere->GetTemperature() * (5.0 / 9.0); // convert from Rankine to Kelvin
+
+ 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();
+ doEGT();
+ doCHT();
+ doOilTemperature();
+ doOilPressure();
+
+ if (Thruster->GetType() == FGThruster::ttPropeller) {
+ ((FGPropeller*)Thruster)->SetAdvance(FCS->GetPropAdvance(EngineNumber));
+ }
+
+ PowerAvailable = (HP * hptoftlbssec) - Thruster->GetPowerRequired();
+
+ return Thrust = Thruster->Calculate(PowerAvailable);
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * 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 > 450) && (crank_counter > 175)) // Add a little delay to startup
+ Running = true; // on the starter
+ } else {
+ if (RPM > 450) // 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 <= 480) && (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)
+{
+ if(RPM > 10) {
+ // Naturally aspirated
+ MAP = minMAP + (Throttle * (maxMAP - minMAP));
+ MAP *= p_amb / p_amb_sea_level;
+ 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.
+ MAP *= BoostMul[BoostSpeed];
+ // 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];
+ }
+ }
+ }
+ } else {
+ // rpm < 10 - effectively stopped.
+ // TODO - add a better variation of MAP with engine speed
+ MAP = Atmosphere->GetPressure() * 47.88; // psf to Pa
+ }
+
+ // And set the value in American units as well
+ ManifoldPressure_inHg = MAP / 3376.85;
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * 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
+ *
+ * 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 rho_air_manifold = MAP / (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;
+ 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;
+ equivalence_ratio = thi_sea_level * p_amb_sea_level / p_amb;
+ m_dot_fuel = m_dot_air / 14.7 * equivalence_ratio;
+ FuelFlow_gph = m_dot_fuel
+ * 3600 // seconds to hours
+ * 2.2046 // kg to lb
+ / 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, p_amb_sea_level, RPM, T_amb,
+ * equivalence_ratio, 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 ManXRPM; // Convienience term for use in the calculations
+ if(Boosted) {
+ // Currently a simple linear fit.
+ // The zero crossing is moved up the speed-load range to reduce the idling power.
+ // This will change!
+ double zeroOffset = (minMAP / 2.0) * (IdleRPM / 2.0);
+ ManXRPM = MAP * (RPM > RatedRPM[BoostSpeed] ? RatedRPM[BoostSpeed] : RPM);
+ // The speed clip in the line above is deliberate.
+ Percentage_Power = ((ManXRPM - zeroOffset) / ((RatedMAP[BoostSpeed] * RatedRPM[BoostSpeed]) - zeroOffset)) * 107.0;
+ Percentage_Power -= 7.0; // Another idle power reduction offset - see line above with 107.
+ if (Percentage_Power < 0.0) Percentage_Power = 0.0;
+ // Note that %power is allowed to go over 100 for boosted powerplants
+ // such as for the BCV-override or takeoff power settings.
+ // TODO - currently no altitude effect (temperature & exhaust back-pressure) modelled
+ // for boosted engines.
+ } else {
+ ManXRPM = ManifoldPressure_inHg * RPM; // Note that inHg must be used for the following correlation.
+ Percentage_Power = (6e-9 * ManXRPM * ManXRPM) + (8e-4 * ManXRPM) - 1.0;
+ Percentage_Power += ((T_amb_sea_lev_degF - T_amb_degF) * 7 /120);
+ if (Percentage_Power < 0.0) Percentage_Power = 0.0;
+ else if (Percentage_Power > 100.0) Percentage_Power = 100.0;
+ }
+
+ double Percentage_of_best_power_mixture_power =
+ Power_Mixture_Correlation->GetValue(14.7 / equivalence_ratio);
+
+ Percentage_Power *= Percentage_of_best_power_mixture_power / 100.0;
+
+ if(Boosted) {
+ HP = Percentage_Power * RatedPower[BoostSpeed] / 100.0;
+ } else {
+ HP = Percentage_Power * MaxHP / 100.0;
+ }
+
+ } else {
+
+ // Power output when the engine is not running
+ if (Cranking) {
+ if (RPM < 10) {
+ HP = 3.0; // This is a hack to prevent overshooting the idle rpm in
+ // the first time step. It may possibly need to be changed
+ // if the prop model is changed.
+ } else if (RPM < 480) {
+ HP = 3.0 + ((480 - RPM) / 10.0);
+ // This is a guess - would be nice to find a proper starter moter torque curve
+ } else {
+ HP = 3.0;
+ }
+ } else {
+ // Quick hack until we port the FMEP stuff
+ if (RPM > 0.0)
+ HP = -1.5;
+ else
+ HP = 0.0;
+ }
+ }
+ //cout << "Power = " << HP << '\n';
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * 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 / 100.0);
+ } else { // Drop towards ambient - guess an appropriate time constant for now
+ dEGTdt = (298.0 - 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
+ *
+ * Outputs: CylinderHeadTemp_degK
+ */
+
+void FGPiston::doCHT(void)
+{
+ double h1 = -95.0;
+ double h2 = -3.95;
+ double h3 = -0.05;
+
+ 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);
+ 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: Percentage_Power, running flag.
+ *
+ * Outputs: OilTemp_degK
+ */
+
+void FGPiston::doOilTemperature(void)
+{
+ double idle_percentage_power = 2.3; // approximately
+ double target_oil_temp; // Steady state oil temp at the current engine conditions
+ double time_constant; // The time constant for the differential equation
+
+ if (Running) {
+ target_oil_temp = 363;
+ time_constant = 500; // Time constant for engine-on idling.
+ if (Percentage_Power > idle_percentage_power) {
+ time_constant /= ((Percentage_Power / idle_percentage_power) / 10.0); // adjust for power
+ }
+ } else {
+ target_oil_temp = 298;
+ 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
+ *
+ * Outputs: OilPressure_psi
+ */
+
+void FGPiston::doOilPressure(void)
+{
+ double Oil_Press_Relief_Valve = 60; // FIXME: may vary by engine
+ double Oil_Press_RPM_Max = 1800; // 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;
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+string FGPiston::GetEngineLabels(string delimeter)
+{
+ std::ostringstream buf;
+
+ buf << Name << "_PwrAvail[" << EngineNumber << "]" << delimeter
+ << Name << "_HP[" << EngineNumber << "]" << delimeter
+ << Name << "_equiv_ratio[" << EngineNumber << "]" << delimeter
+ << Name << "_MAP[" << 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 << " 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;
+
+ }
+ }
+ 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;
+ }
+ }
+}
+
+double
+FGPiston::CalcFuelNeed(void)
+{
+ return FuelFlow_gph / 3600 * 6 * State->Getdt() * Propulsion->GetRate();
}
+} // namespace JSBSim
projects / flightgear.git / blobdiff