namespace JSBSim {
-static const char *IdSrc = "$Id: FGPiston.cpp,v 1.64 2011/08/04 13:45:42 jberndt Exp $";
+static const char *IdSrc = "$Id: FGPiston.cpp,v 1.71 2012/04/07 01:50:54 jentron Exp $";
static const char *IdHdr = ID_PISTON;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
MaxHP = 200;
MinManifoldPressure_inHg = 6.5;
MaxManifoldPressure_inHg = 28.5;
+ ManifoldPressureLag=1.0;
ISFC = -1;
volumetric_efficiency = 0.85;
Bore = 5.125;
FMEPStatic = 46500;
Cooling_Factor = 0.5144444;
StaticFriction_HP = 1.5;
+ StarterGain = 1.;
+ StarterTorque = -1.;
+ StarterRPM = -1.;
// These are internal program variables
bBoostOverride = false;
bTakeoffBoost = false;
TakeoffBoost = 0.0; // Default to no extra takeoff-boost
+ BoostLossFactor = 0.0; // Default to free boost
+
int i;
for (i=0; i<FG_MAX_BOOST_SPEEDS; i++) {
RatedBoost[i] = 0.0;
// Read inputs from engine data file where present.
- if (el->FindElement("minmp")) // Should have ELSE statement telling default value used?
+ if (el->FindElement("minmp"))
MinManifoldPressure_inHg = el->FindElementValueAsNumberConvertTo("minmp","INHG");
if (el->FindElement("maxmp"))
MaxManifoldPressure_inHg = el->FindElementValueAsNumberConvertTo("maxmp","INHG");
+ if (el->FindElement("man-press-lag"))
+ ManifoldPressureLag = el->FindElementValueAsNumber("man-press-lag");
if (el->FindElement("displacement"))
Displacement = el->FindElementValueAsNumberConvertTo("displacement","IN3");
if (el->FindElement("maxhp"))
Ram_Air_Factor = el->FindElementValueAsNumber("ram-air-factor");
if (el->FindElement("cooling-factor"))
Cooling_Factor = el->FindElementValueAsNumber("cooling-factor");
+ if (el->FindElement("starter-rpm"))
+ StarterRPM = el->FindElementValueAsNumber("starter-rpm");
+ if (el->FindElement("starter-torque"))
+ StarterTorque = el->FindElementValueAsNumber("starter-torque");
if (el->FindElement("dynamic-fmep"))
FMEPDynamic= el->FindElementValueAsNumberConvertTo("dynamic-fmep","PA");
if (el->FindElement("static-fmep"))
BoostManual = (int)el->FindElementValueAsNumber("boostmanual");
if (el->FindElement("takeoffboost"))
TakeoffBoost = el->FindElementValueAsNumberConvertTo("takeoffboost", "PSI");
+ if (el->FindElement("boost-loss-factor"))
+ BoostLossFactor = el->FindElementValueAsNumber("boost-loss-factor");
if (el->FindElement("ratedboost1"))
RatedBoost[0] = el->FindElementValueAsNumberConvertTo("ratedboost1", "PSI");
if (el->FindElement("ratedboost2"))
RatedAltitude[2] = el->FindElementValueAsNumberConvertTo("ratedaltitude3", "FT");
}
- while(table_element = el->FindNextElement("table")) {
+ while((table_element = el->FindNextElement("table")) != 0) {
name = table_element->GetAttributeValue("name");
try {
if (name == "COMBUSTION") {
}
}
- StarterHP = sqrt(MaxHP) * 0.4;
+
+ volumetric_efficiency_reduced = volumetric_efficiency;
+
+ if(StarterRPM < 0.) StarterRPM = 2*IdleRPM;
+ if(StarterTorque < 0)
+ StarterTorque = (MaxHP)*0.4; //just a wag.
+
displacement_SI = Displacement * in3tom3;
RatedMeanPistonSpeed_fps = ( MaxRPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNumber);
property_name = base_property_name + "/power-hp";
PropertyManager->Tie(property_name, &HP);
+ property_name = base_property_name + "/friction-hp";
+ PropertyManager->Tie(property_name, &StaticFriction_HP);
property_name = base_property_name + "/bsfc-lbs_hphr";
PropertyManager->Tie(property_name, &ISFC);
+ property_name = base_property_name + "/starter-norm";
+ PropertyManager->Tie(property_name, &StarterGain);
property_name = base_property_name + "/volumetric-efficiency";
PropertyManager->Tie(property_name, &volumetric_efficiency);
property_name = base_property_name + "/map-pa";
PropertyManager->Tie(property_name, &BoostSpeed);
property_name = base_property_name + "/cht-degF";
PropertyManager->Tie(property_name, this, &FGPiston::getCylinderHeadTemp_degF);
- property_name = base_property_name + "/engine-rpm";
- PropertyManager->Tie(property_name, this, &FGPiston::getRPM);
property_name = base_property_name + "/oil-temperature-degF";
PropertyManager->Tie(property_name, this, &FGPiston::getOilTemp_degF);
property_name = base_property_name + "/oil-pressure-psi";
PropertyManager->Tie(property_name, this, &FGPiston::getOilPressure_psi);
property_name = base_property_name + "/egt-degF";
PropertyManager->Tie(property_name, this, &FGPiston::getExhaustGasTemp_degF);
+ if(BoostLossFactor > 0.0) {
+ property_name = base_property_name + "/boostloss-factor";
+ PropertyManager->Tie(property_name, &BoostLossFactor);
+ property_name = base_property_name + "/boostloss-hp";
+ PropertyManager->Tie(property_name, &BoostLossHP);
+ }
// Set up and sanity-check the turbo/supercharging configuration based on the input values.
if (TakeoffBoost > RatedBoost[0]) bTakeoffBoost = true;
Thruster->SetRPM(0.0);
RPM = 0.0;
OilPressure_psi = 0.0;
+ BoostLossHP = 0.;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
RunPreFunctions();
- RPM = Thruster->GetRPM() * Thruster->GetGearRatio();
+ TotalDeltaT = ( in.TotalDeltaT < 1e-9 ) ? 1.0 : in.TotalDeltaT;
+
+/* The thruster controls the engine RPM because it encapsulates the gear ratio and other transmission variables */
+ RPM = Thruster->GetEngineRPM();
+
MeanPistonSpeed_fps = ( RPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
IAS = in.Vc;
double FGPiston::CalcFuelNeed(void)
{
FuelExpended = FuelFlowRate * in.TotalDeltaT;
+ if (!Starved) FuelUsedLbs += FuelExpended;
return FuelExpended;
}
int FGPiston::InitRunning(void)
{
Magnetos=3;
- in.MixtureCmd[EngineNumber] = in.PressureRatio/1.3;
- in.MixturePos[EngineNumber] = in.PressureRatio/1.3;
+ in.MixtureCmd[EngineNumber] = in.PressureRatio*1.3;
+ in.MixturePos[EngineNumber] = in.PressureRatio*1.3;
Thruster->SetRPM( 2.0*IdleRPM/Thruster->GetGearRatio() );
Running = true;
return 1;
if ((Magnetos == 1) || (Magnetos > 2)) Magneto_Left = true;
if (Magnetos > 1) Magneto_Right = true;
- // Assume we have fuel for now
- fuel = !Starved;
+// We will 'run' with any fuel flow. If there is not enough fuel to make power it will show in doEnginePower
+ fuel = FuelFlowRate > 0.0 ? 1 : 0;
// 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 will continue to
+ // spin depending on prop Ixx and freestream velocity
- // 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;
+ if ( Running ) {
+ if (!spark || !fuel) Running = false;
+ if (RPM < IdleRPM*0.8 ) Running = false;
+ } else { // !Running
+ if ( spark && fuel) { // start the engine if revs high enough
+ if (RPM > IdleRPM*0.8) // This allows us to in-air start
+ Running = true; // when windmilling
}
}
+
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGPiston::doBoostControl(void)
{
- if(BoostManual) {
+ if(bBoostManual) {
if(BoostSpeed > BoostSpeeds-1) BoostSpeed = BoostSpeeds-1;
if(BoostSpeed < 0) BoostSpeed = 0;
} else {
* Inputs: p_amb, Throttle,
* MeanPistonSpeed_fps, dt
*
- * Outputs: MAP, ManifoldPressure_inHg, TMAP
+ * Outputs: MAP, ManifoldPressure_inHg, TMAP, BoostLossHP
*/
void FGPiston::doMAP(void)
double map_coefficient = Ze/(Ze+Z_airbox+Zt);
- // Add a one second lag to manifold pressure changes
- double dMAP=0;
- if (in.TotalDeltaT > 0.0)
- dMAP = (TMAP - p_ram * map_coefficient) * in.TotalDeltaT;
- else
- dMAP = (TMAP - p_ram * map_coefficient) / 120;
+ // Add a variable lag to manifold pressure changes
+ double dMAP=(TMAP - p_ram * map_coefficient);
+ if (ManifoldPressureLag > TotalDeltaT) dMAP *= TotalDeltaT/ManifoldPressureLag;
TMAP -=dMAP;
double boost_factor = (( BoostMul[BoostSpeed] - 1 ) / RatedRPM[BoostSpeed] ) * RPM + 1;
MAP = TMAP * 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];
+ if(!bBoostOverride) {
+ if (bTakeoffPos) {
+ if (MAP > TakeoffMAP[BoostSpeed]) MAP = TakeoffMAP[BoostSpeed];
+ } else {
+ if (MAP > RatedMAP[BoostSpeed]) MAP = RatedMAP[BoostSpeed];
+ }
}
} else {
MAP = TMAP;
}
+ if( BoostLossFactor > 0.0 )
+ {
+ double gamma = 1.414; // specific heat constants
+ double Nstage = 1; // Nstage is the number of boost stages.
+ BoostLossHP = ((Nstage * TMAP * v_dot_air * gamma) / (gamma - 1)) * (pow((MAP/TMAP),((gamma-1)/(Nstage * gamma))) - 1) * BoostLossFactor / 745.7 ; // 745.7 convert watt to hp
+ } else {
+ BoostLossHP = 0;
+ }
+
// And set the value in American units as well
ManifoldPressure_inHg = MAP / inhgtopa;
}
*
* TODO: Model inlet manifold air temperature.
*
- * Outputs: rho_air, m_dot_air
+ * Outputs: rho_air, m_dot_air, volumetric_efficiency_reduced
*/
void FGPiston::doAirFlow(void)
double gamma = 1.3; // specific heat constants
// loss of volumentric efficiency due to difference between MAP and exhaust pressure
// Eq 6-10 from The Internal Combustion Engine - Charles Taylor Vol 1
- double ve =((gamma-1)/gamma) +( CompressionRatio -(p_amb/MAP))/(gamma*( CompressionRatio - 1));
+ double mratio = MAP < 1. ? CompressionRatio : p_amb/MAP;
+ if (mratio > CompressionRatio) mratio = CompressionRatio;
+ double ve =((gamma-1)/gamma) +( CompressionRatio -(mratio))/(gamma*( CompressionRatio - 1));
rho_air = p_amb / (R_air * T_amb);
double swept_volume = (displacement_SI * (RPM/60)) / 2;
- double v_dot_air = swept_volume * volumetric_efficiency *ve;
+ volumetric_efficiency_reduced = volumetric_efficiency *ve;
+ v_dot_air = swept_volume * volumetric_efficiency_reduced;
double rho_air_manifold = MAP / (R_air * T_amb);
m_dot_air = v_dot_air * rho_air_manifold;
void FGPiston::doEnginePower(void)
{
- IndicatedHorsePower = 0;
+ IndicatedHorsePower = -StaticFriction_HP;
FMEP = 0;
if (Running) {
- // FIXME: this needs to be generalized
- double ME, percent_RPM, power; // Convienience term for use in the calculations
+ double ME, power; // Convienience term for use in the calculations
ME = Mixture_Efficiency_Correlation->GetValue(m_dot_fuel/m_dot_air);
- percent_RPM = RPM/MaxRPM;
// Guestimate engine friction losses from Figure 4.4 of "Engines: An Introduction", John Lumley
FMEP = (-FMEPDynamic * MeanPistonSpeed_fps * fttom - FMEPStatic);
if ( Magnetos != 3 ) power *= SparkFailDrop;
- IndicatedHorsePower = (FuelFlow_pph / ISFC )* ME * power;
+ IndicatedHorsePower = (FuelFlow_pph / ISFC )* ME * power - StaticFriction_HP; //FIXME static friction should depend on oil temp and configuration;
} else {
// Power output when the engine is not running
+ double torque, k_torque, rpm; // Convienience term for use in the calculations
+
+ rpm = RPM < 1.0 ? 1.0 : RPM;
if (Cranking) {
- if (RPM < 10) {
- IndicatedHorsePower = StarterHP;
- } else if (RPM < IdleRPM*0.8) {
- IndicatedHorsePower = StarterHP + ((IdleRPM*0.8 - RPM) / 8.0);
- // This is a guess - would be nice to find a proper starter moter torque curve
- } else {
- IndicatedHorsePower = StarterHP;
- }
- }
+ if(RPM<StarterRPM) k_torque = 1.0-RPM/(StarterRPM);
+ else k_torque = 0;
+ torque = StarterTorque*k_torque*StarterGain;
+ IndicatedHorsePower = torque * rpm / 5252;
+ }
}
// Constant is (1/2) * 60 * 745.7
// (1/2) convert cycles, 60 minutes to seconds, 745.7 watts to hp.
double pumping_hp = ((PMEP + FMEP) * displacement_SI * RPM)/(Cycles*22371);
- HP = IndicatedHorsePower + pumping_hp - StaticFriction_HP; //FIXME static friction should depend on oil temp and configuration
+HP = IndicatedHorsePower + pumping_hp - BoostLossHP;
// cout << "pumping_hp " <<pumping_hp << FMEP << PMEP <<endl;
PctPower = HP / MaxHP ;
// cout << "Power = " << HP << " RPM = " << RPM << " Running = " << Running << " Cranking = " << Cranking << endl;
} else { // Drop towards ambient - guess an appropriate time constant for now
combustion_efficiency = 0;
dEGTdt = (RankineToKelvin(in.Temperature) - ExhaustGasTemp_degK) / 100.0;
- if (in.TotalDeltaT > 0.0)
- delta_T_exhaust = dEGTdt * in.TotalDeltaT;
- else
- delta_T_exhaust = dEGTdt / 120;
+ delta_T_exhaust = dEGTdt * TotalDeltaT;
ExhaustGasTemp_degK += delta_T_exhaust;
}
double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
- if (in.TotalDeltaT > 0.0)
- CylinderHeadTemp_degK +=
- (dqdt_cylinder_head / HeatCapacityCylinderHead) * in.TotalDeltaT;
- else
- CylinderHeadTemp_degK +=
- (dqdt_cylinder_head / HeatCapacityCylinderHead) / 120.0;
+ CylinderHeadTemp_degK +=
+ (dqdt_cylinder_head / HeatCapacityCylinderHead) * TotalDeltaT;
+
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
double dOilTempdt = (target_oil_temp - OilTemp_degK) / time_constant;
- if (in.TotalDeltaT > 0.0)
- OilTemp_degK += (dOilTempdt * in.TotalDeltaT);
- else
- OilTemp_degK += (dOilTempdt / 120.0);
+ OilTemp_degK += (dOilTempdt * TotalDeltaT);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
cout << " Bore: " << Bore << endl;
cout << " Stroke: " << Stroke << endl;
cout << " Cylinders: " << Cylinders << endl;
- cout << " Cylinders Head Mass: " <<CylinderHeadMass << endl;
+ cout << " Cylinders Head Mass: " << CylinderHeadMass << endl;
cout << " Compression Ratio: " << CompressionRatio << endl;
cout << " MaxHP: " << MaxHP << endl;
cout << " Cycles: " << Cycles << endl;
cout << " Dynamic FMEP Factor: " << FMEPDynamic << endl;
cout << " Static FMEP Factor: " << FMEPStatic << endl;
+ cout << " Starter Motor Torque: " << StarterTorque << endl;
+ cout << " Starter Motor RPM: " << StarterRPM << endl;
+
cout << endl;
cout << " Combustion Efficiency table:" << endl;
Lookup_Combustion_Efficiency->Print();
projects / flightgear.git / blobdiff