/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-#include "FGDefs.h"
+#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)
- : FGEngine(exec),
- MinManifoldPressure_inHg(6.5),
- MaxManifoldPressure_inHg(28.5),
- Displacement(360),
- MaxHP(200),
- Cycles(2),
- IdleRPM(900),
- // Set constants
- CONVERT_CUBIC_INCHES_TO_METERS_CUBED(1.638706e-5),
- R_air(287.3),
- rho_fuel(800), // estimate
- calorific_value_fuel(47.3e6),
- Cp_air(1005),
- Cp_fuel(1700),
- running(true), // FIXME: FGEngine already has 'Running'
- cranking(false)
+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 = 200;
+ 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() != "/FG_PISTON") {
+ 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 == "IDLERPM") *Eng_cfg >> IdleRPM;
else if (token == "MAXTHROTTLE") *Eng_cfg >> MaxThrottle;
else if (token == "MINTHROTTLE") *Eng_cfg >> MinThrottle;
- else if (token == "SLFUELFLOWMAX") *Eng_cfg >> SLFuelFlowMax;
+ 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;
}
- if (debug_lvl > 0) {
- 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 << " SLFuelFlowMax: " << SLFuelFlowMax << 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);
- Type = etPiston;
- EngineNumber = 0; // FIXME: this should be the actual number
- OilTemp_degK = 298; // FIXME: should be initialized in FGEngine
+ // 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';
+ }
- dt = State->Getdt();
+ if(BoostSpeeds > 0) {
+ Boosted = true;
+ BoostSpeed = 0;
+ }
+ bBoostOverride = (BoostOverride == 1 ? true : false);
- // Initialisation
- volumetric_efficiency = 0.8; // Actually f(speed, load) but this will get us running
+ //cout << "Engine is " << (Boosted ? "supercharged" : "naturally aspirated") << '\n';
- if (debug_lvl & 2) cout << "Instantiated: FGPiston" << endl;
+ Debug(0); // Call Debug() routine from constructor if needed
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
FGPiston::~FGPiston()
{
- if (debug_lvl & 2) cout << "Destroyed: FGPiston" << endl;
+ Debug(1); // Call Debug() routine from constructor if needed
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-float FGPiston::Calculate(float PowerRequired)
+double FGPiston::Calculate(void)
{
- float h,EngineMaxPower;
-
- // FIXME: calculate from actual fuel flow
- ConsumeFuel();
+ if (FuelFlow_gph > 0.0) ConsumeFuel();
Throttle = FCS->GetThrottlePos(EngineNumber);
Mixture = FCS->GetMixturePos(EngineNumber);
//
// Input values.
//
- // convert from lbs/ft2 to Pa
- p_amb = Atmosphere->GetPressure() * 48;
- p_amb_sea_level = Atmosphere->GetPressureSL() * 48;
- // convert from Rankine to Kelvin
- T_amb = Atmosphere->GetTemperature() * (5.0 / 9.0);
- RPM = Propulsion->GetThruster(EngineNumber)->GetRPM();
- if (RPM < IdleRPM) // kludge
- RPM = IdleRPM;
+
+ 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();
- if (Mixture >= 0.5) {
- doEngineStartup();
- doManifoldPressure();
- doAirFlow();
- doFuelFlow();
- doEnginePower();
- doEGT();
- doCHT();
- doOilTemperature();
- doOilPressure();
- } else {
- HP = 0;
+ 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) - PowerRequired;
- return PowerAvailable;
+ PowerAvailable = (HP * hptoftlbssec) - Thruster->GetPowerRequired();
+
+ return Thrust = Thruster->Calculate(PowerAvailable);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
- * Look up the power/mixture correlation.
- *
- * FIXME: this should use JSBSim's interpolation support.
+ * Start or stop the engine.
*/
-static float Power_Mixture_Correlation(float thi_actual)
+void FGPiston::doEngineStartup(void)
{
- float AFR_actual = 14.7 / thi_actual;
- const int NUM_ELEMENTS = 13;
- float AFR[NUM_ELEMENTS] =
- {(14.7/1.6), 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, (14.7/0.6)};
- float mixPerPow[NUM_ELEMENTS] =
- {78, 86, 93.5, 98, 100, 99, 96.4, 92.5, 88, 83, 78.5, 74, 58};
- float mixPerPow_actual = 0.0f;
- float factor;
- float dydx;
+ // 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.
- int i;
- int j = NUM_ELEMENTS;
+ if ((Magnetos == 1) || (Magnetos > 2)) Magneto_Left = true;
+ if (Magnetos > 1) Magneto_Right = true;
- for (i=0;i<j;i++) {
- if (i == (j-1)) {
- dydx = (mixPerPow[i] - mixPerPow[i-1]) / (AFR[i] - AFR[i-1]);
- mixPerPow_actual = mixPerPow[i] + dydx * (AFR_actual - AFR[i]);
- return mixPerPow_actual;
- }
- if ((i == 0) && (AFR_actual < AFR[i])) {
- dydx = (mixPerPow[i] - mixPerPow[i-1]) / (AFR[i] - AFR[i-1]);
- mixPerPow_actual = mixPerPow[i] + dydx * (AFR_actual - AFR[i]);
- return mixPerPow_actual;
- }
- if (AFR_actual == AFR[i]) {
- mixPerPow_actual = mixPerPow[i];
- return mixPerPow_actual;
- }
- if ((AFR_actual > AFR[i]) && (AFR_actual < AFR[i + 1])) {
- factor = (AFR_actual - AFR[i]) / (AFR[i+1] - AFR[i]);
- mixPerPow_actual = (factor * (mixPerPow[i+1] - mixPerPow[i])) + mixPerPow[i];
- return mixPerPow_actual;
+ // 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
}
}
- cerr << "ERROR: error in FGNewEngine::Power_Mixture_Correlation\n";
- return mixPerPow_actual;
+ // 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;
+ }
+ }
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
/**
- * Look up the combustion efficiency.
+ * 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
*
- * FIXME: this should use JSBSim's interpolation support.
+ * Outputs: BoostSpeed
*/
-static float Lookup_Combustion_Efficiency(float thi_actual)
+void FGPiston::doBoostControl(void)
{
- const int NUM_ELEMENTS = 11;
- float thi[NUM_ELEMENTS] = {0.0, 0.9, 1.0, 1.05, 1.1, 1.15, 1.2, 1.3, 1.4, 1.5, 1.6}; //array of equivalence ratio values
- float neta_comb[NUM_ELEMENTS] = {0.98, 0.98, 0.97, 0.95, 0.9, 0.85, 0.79, 0.7, 0.63, 0.57, 0.525}; //corresponding array of combustion efficiency values
- //combustion efficiency values from Heywood, "Internal Combustion Engine Fundamentals", ISBN 0-07-100499-8
- float neta_comb_actual = 0.0f;
- float factor;
-
- int i;
- int j = NUM_ELEMENTS; //This must be equal to the number of elements in the lookup table arrays
-
- for (i=0;i<j;i++) {
- if(i == (j-1)) {
- // Assume linear extrapolation of the slope between the last two points beyond the last point
- float dydx = (neta_comb[i] - neta_comb[i-1]) / (thi[i] - thi[i-1]);
- neta_comb_actual = neta_comb[i] + dydx * (thi_actual - thi[i]);
- return neta_comb_actual;
- }
- if(thi_actual == thi[i]) {
- neta_comb_actual = neta_comb[i];
- return neta_comb_actual;
+ if(BoostSpeed < BoostSpeeds - 1) {
+ // Check if we need to change to a higher boost speed
+ if(p_amb < BoostSwitchPressure[BoostSpeed] - BoostSwitchHysteresis) {
+ BoostSpeed++;
}
- if((thi_actual > thi[i]) && (thi_actual < thi[i + 1])) {
- //do linear interpolation between the two points
- factor = (thi_actual - thi[i]) / (thi[i+1] - thi[i]);
- neta_comb_actual = (factor * (neta_comb[i+1] - neta_comb[i])) + neta_comb[i];
- return neta_comb_actual;
+ } else if(BoostSpeed > 0) {
+ // Check if we need to change to a lower boost speed
+ if(p_amb > BoostSwitchPressure[BoostSpeed - 1] + BoostSwitchHysteresis) {
+ BoostSpeed--;
}
}
-
- //if we get here something has gone badly wrong
- cerr << "ERROR: error in FGNewEngine::Lookup_Combustion_Efficiency\n";
- return neta_comb_actual;
-}
-
-//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-/**
- * Start or stop the engine.
- */
-
-void FGPiston::doEngineStartup(void)
-{
- // TODO: check magnetos, spark, starter, etc. and decide whether
- // engine is running
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
- * Calculate the nominal manifold pressure in inches hg
+ * Calculate the manifold absolute pressure (MAP) in inches hg
*
- * This function calculates nominal manifold pressure directly
- * from the throttle position, and does not adjust it for the
- * difference between the pressure at sea level and the pressure
- * at the current altitude (that adjustment takes place in
- * {@link #doEnginePower}).
+ * 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: MinManifoldPressure_inHg, MaxManifoldPressure_inHg, Throttle
+ * Inputs: minMAP, maxMAP, p_amb, Throttle
*
- * Outputs: ManifoldPressure_inHg
+ * Outputs: MAP, ManifoldPressure_inHg
*/
-void FGPiston::doManifoldPressure(void)
+void FGPiston::doMAP(void)
{
- ManifoldPressure_inHg = MinManifoldPressure_inHg +
- (Throttle * (MaxManifoldPressure_inHg - MinManifoldPressure_inHg));
+ 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, ManifoldPressure_inHg, Displacement,
+ * 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);
- float rho_air_manifold = rho_air * ManifoldPressure_inHg / 29.6;
- float displacement_SI = Displacement * CONVERT_CUBIC_INCHES_TO_METERS_CUBED;
- float swept_volume = (displacement_SI * (RPM/60)) / 2;
- float v_dot_air = swept_volume * volumetric_efficiency;
+ 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;
}
void FGPiston::doFuelFlow(void)
{
- float thi_sea_level = 1.3 * Mixture;
+ 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.
*
- * <p>Currently, the JSBSim propellor model does not allow the
+ * 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.</p>
+ * 200HP.
*
- * Inputs: ManifoldPressure_inHg, p_amb, p_amb_sea_level, RPM, T_amb,
+ * Inputs: ManifoldPressure_inHg, p_amb, p_amb_sea_level, RPM, T_amb,
* equivalence_ratio, Cycles, MaxHP
*
* Outputs: Percentage_Power, HP
void FGPiston::doEnginePower(void)
{
- float True_ManifoldPressure_inHg = ManifoldPressure_inHg * p_amb / p_amb_sea_level;
- float ManXRPM = True_ManifoldPressure_inHg * RPM;
- // FIXME: this needs to be generalized
- Percentage_Power = (6e-9 * ManXRPM * ManXRPM) + (8e-4 * ManXRPM) - 1.0;
- float T_amb_degF = (T_amb * 1.8) - 459.67;
- float T_amb_sea_lev_degF = (288 * 1.8) - 459.67;
- Percentage_Power =
- Percentage_Power + ((T_amb_sea_lev_degF - T_amb_degF) * 7 /120);
- float Percentage_of_best_power_mixture_power =
- Power_Mixture_Correlation(equivalence_ratio);
- Percentage_Power =
- Percentage_Power * Percentage_of_best_power_mixture_power / 100.0;
- if (Percentage_Power < 0.0)
- Percentage_Power = 0.0;
- else if (Percentage_Power > 100.0)
- Percentage_Power = 100.0;
- HP = Percentage_Power * MaxHP / 100.0;
+ 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,
+ * 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)
{
- combustion_efficiency = Lookup_Combustion_Efficiency(equivalence_ratio);
- float enthalpy_exhaust = m_dot_fuel * calorific_value_fuel *
- combustion_efficiency * 0.33;
- float heat_capacity_exhaust = (Cp_air * m_dot_air) + (Cp_fuel * m_dot_fuel);
- float 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);
+ 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;
+ }
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGPiston::doCHT(void)
{
- float h1 = -95.0;
- float h2 = -3.95;
- float h3 = -0.05;
-
- float arbitary_area = 1.0;
- float CpCylinderHead = 800.0;
- float MassCylinderHead = 8.0;
-
- float temperature_difference = CylinderHeadTemp_degK - T_amb;
- float v_apparent = IAS * 0.5144444;
- float v_dot_cooling_air = arbitary_area * v_apparent;
- float m_dot_cooling_air = v_dot_cooling_air * rho_air;
- float dqdt_from_combustion =
+ 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;
- float dqdt_forced = (h2 * m_dot_cooling_air * temperature_difference) +
+ double dqdt_forced = (h2 * m_dot_cooling_air * temperature_difference) +
(h3 * RPM * temperature_difference);
- float dqdt_free = h1 * temperature_difference;
- float dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;
-
- float HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
-
- CylinderHeadTemp_degK = dqdt_cylinder_head / HeatCapacityCylinderHead;
+ 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;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGPiston::doOilTemperature(void)
{
- float idle_percentage_power = 2.3; // approximately
- float target_oil_temp; // Steady state oil temp at the current engine conditions
- float time_constant; // The time constant for the differential equation
+ 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) {
+ 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
+ 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
+ time_constant = 1000; // Time constant for engine-off; reflects the fact
+ // that oil is no longer getting circulated
}
- float dOilTempdt = (target_oil_temp - OilTemp_degK) / time_constant;
+ double dOilTempdt = (target_oil_temp - OilTemp_degK) / time_constant;
OilTemp_degK += (dOilTempdt * dt);
}
void FGPiston::doOilPressure(void)
{
- float Oil_Press_Relief_Valve = 60; // FIXME: may vary by engine
- float Oil_Press_RPM_Max = 1800; // FIXME: may vary by engine
- float Design_Oil_Temp = 85; // FIXME: may vary by engine
- // FIXME: WRONG!!! (85 degK???)
- float Oil_Viscosity_Index = 0.25;
+ 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;
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-void FGPiston::Debug(void)
+string FGPiston::GetEngineLabels(string delimeter)
+{
+ std::ostringstream buf;
+
+ buf << Name << "_PwrAvail[" << EngineNumber << "]" << delimeter
+ << Name << "_HP[" << EngineNumber << "]" << delimeter
+ << Thruster->GetThrusterLabels(EngineNumber, delimeter);
+
+ return buf.str();
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+string FGPiston::GetEngineValues(string delimeter)
+{
+ std::ostringstream buf;
+
+ buf << PowerAvailable << delimeter << HP << 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)
{
- //TODO: Add your source code here
+ return FuelFlow_gph / 3600 * 6 * State->Getdt() * Propulsion->GetRate();
}
+} // namespace JSBSim