INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+#include <iostream>
#include <sstream>
#include "FGPiston.h"
-#include "models/FGAtmosphere.h"
-#include "models/FGAuxiliary.h"
-#include "models/FGPropulsion.h"
#include "FGPropeller.h"
-#include <iostream>
using namespace std;
namespace JSBSim {
-static const char *IdSrc = "$Id: FGPiston.cpp,v 1.54 2010/11/30 12:17:10 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;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS IMPLEMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-FGPiston::FGPiston(FGFDMExec* exec, Element* el, int engine_number)
- : FGEngine(exec, el, engine_number),
+FGPiston::FGPiston(FGFDMExec* exec, Element* el, int engine_number, struct Inputs& input)
+ : FGEngine(exec, el, engine_number, input),
R_air(287.3), // Gas constant for air J/Kg/K
rho_fuel(800), // estimate
- calorific_value_fuel(47.3e6),
+ calorific_value_fuel(47.3e6), // J/Kg
Cp_air(1005), // Specific heat (constant pressure) J/Kg/K
Cp_fuel(1700),
standard_pressure(101320.73)
{
+ Element *table_element;
string token;
+ string name="";
// Defaults and initializations
Type = etPiston;
- dt = FDMExec->GetDeltaT();
// These items are read from the configuration file
// Defaults are from a Lycoming O-360, more or less
MaxHP = 200;
MinManifoldPressure_inHg = 6.5;
MaxManifoldPressure_inHg = 28.5;
+ ManifoldPressureLag=1.0;
ISFC = -1;
volumetric_efficiency = 0.85;
Bore = 5.125;
FMEPDynamic= 18400;
FMEPStatic = 46500;
Cooling_Factor = 0.5144444;
+ StaticFriction_HP = 1.5;
+ StarterGain = 1.;
+ StarterTorque = -1.;
+ StarterRPM = -1.;
// These are internal program variables
+ Lookup_Combustion_Efficiency = 0;
+ Mixture_Efficiency_Correlation = 0;
crank_counter = 0;
Magnetos = 0;
minMAP = 21950;
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;
BoostSwitchPressure[i] = 0.0;
}
- // 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;
-
- Mixture_Efficiency_Correlation = new FGTable(15);
- *Mixture_Efficiency_Correlation << 0.05000 << 0.00000;
- *Mixture_Efficiency_Correlation << 0.05137 << 0.00862;
- *Mixture_Efficiency_Correlation << 0.05179 << 0.21552;
- *Mixture_Efficiency_Correlation << 0.05430 << 0.48276;
- *Mixture_Efficiency_Correlation << 0.05842 << 0.70690;
- *Mixture_Efficiency_Correlation << 0.06312 << 0.83621;
- *Mixture_Efficiency_Correlation << 0.06942 << 0.93103;
- *Mixture_Efficiency_Correlation << 0.07786 << 1.00000;
- *Mixture_Efficiency_Correlation << 0.08845 << 1.00000;
- *Mixture_Efficiency_Correlation << 0.09270 << 0.98276;
- *Mixture_Efficiency_Correlation << 0.10120 << 0.93103;
- *Mixture_Efficiency_Correlation << 0.11455 << 0.72414;
- *Mixture_Efficiency_Correlation << 0.12158 << 0.45690;
- *Mixture_Efficiency_Correlation << 0.12435 << 0.23276;
- *Mixture_Efficiency_Correlation << 0.12500 << 0.00000;
-
-
// 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"))
MaxHP = el->FindElementValueAsNumberConvertTo("maxhp","HP");
+ if (el->FindElement("static-friction"))
+ StaticFriction_HP = el->FindElementValueAsNumberConvertTo("static-friction","HP");
if (el->FindElement("sparkfaildrop"))
SparkFailDrop = Constrain(0, 1 - el->FindElementValueAsNumber("sparkfaildrop"), 1);
if (el->FindElement("cycles"))
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");
}
- StarterHP = sqrt(MaxHP) * 0.4;
+ while((table_element = el->FindNextElement("table")) != 0) {
+ name = table_element->GetAttributeValue("name");
+ try {
+ if (name == "COMBUSTION") {
+ Lookup_Combustion_Efficiency = new FGTable(PropertyManager, table_element);
+ } else if (name == "MIXTURE") {
+ Mixture_Efficiency_Correlation = new FGTable(PropertyManager, table_element);
+ } else {
+ cerr << "Unknown table type: " << name << " in piston engine definition." << endl;
+ }
+ } catch (std::string str) {
+ throw("Error loading piston engine table:" + name + ". " + str);
+ }
+ }
+
+
+ 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
pmep *= inhgtopa * volumetric_efficiency;
double fmep = (FMEPDynamic * RatedMeanPistonSpeed_fps * fttom + FMEPStatic);
double hp_loss = ((pmep + fmep) * displacement_SI * MaxRPM)/(Cycles*22371);
- ISFC = ( 1.1*Displacement * MaxRPM * volumetric_efficiency *(MaxManifoldPressure_inHg / 29.92) ) / (9411 * (MaxHP+hp_loss));
+ ISFC = ( 1.1*Displacement * MaxRPM * volumetric_efficiency *(MaxManifoldPressure_inHg / 29.92) ) / (9411 * (MaxHP+hp_loss-StaticFriction_HP));
// cout <<"FMEP: "<< fmep <<" PMEP: "<< pmep << " hp_loss: " <<hp_loss <<endl;
}
if ( MaxManifoldPressure_inHg > 29.9 ) { // Don't allow boosting with a bogus number
*
*
*/
-
if(Z_airbox < 0.0){
double Ze=PeakMeanPistonSpeed_fps/RatedMeanPistonSpeed_fps; // engine impedence
Z_airbox = (standard_pressure *Ze / maxMAP) - Ze; // impedence of airbox
Z_throttle=(PeakMeanPistonSpeed_fps/((IdleRPM * Stroke) / 360))*(standard_pressure/minMAP - 1) - Z_airbox;
// Z_throttle=(MaxRPM/IdleRPM )*(standard_pressure/minMAP+2); // Constant for Throttle impedence
+// Default tables if not provided in the configuration file
+ if(Lookup_Combustion_Efficiency == 0) {
+ // 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;
+ }
+
+ // First column is Fuel/Air Ratio, second is neta (mixture efficiency)
+ if( Mixture_Efficiency_Correlation == 0) {
+ Mixture_Efficiency_Correlation = new FGTable(15);
+ *Mixture_Efficiency_Correlation << 0.05000 << 0.00000;
+ *Mixture_Efficiency_Correlation << 0.05137 << 0.00862;
+ *Mixture_Efficiency_Correlation << 0.05179 << 0.21552;
+ *Mixture_Efficiency_Correlation << 0.05430 << 0.48276;
+ *Mixture_Efficiency_Correlation << 0.05842 << 0.70690;
+ *Mixture_Efficiency_Correlation << 0.06312 << 0.83621;
+ *Mixture_Efficiency_Correlation << 0.06942 << 0.93103;
+ *Mixture_Efficiency_Correlation << 0.07786 << 1.00000;
+ *Mixture_Efficiency_Correlation << 0.08845 << 1.00000;
+ *Mixture_Efficiency_Correlation << 0.09270 << 0.98276;
+ *Mixture_Efficiency_Correlation << 0.10120 << 0.93103;
+ *Mixture_Efficiency_Correlation << 0.11455 << 0.72414;
+ *Mixture_Efficiency_Correlation << 0.12158 << 0.45690;
+ *Mixture_Efficiency_Correlation << 0.12435 << 0.23276;
+ *Mixture_Efficiency_Correlation << 0.12500 << 0.00000;
+ }
+
string property_name, base_property_name;
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 + "/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;
// But we can also make a reasonable estimate, as below.
BoostSwitchAltitude[i] = RatedAltitude[i] + 1000;
}
- BoostSwitchPressure[i] = Atmosphere->GetPressure(BoostSwitchAltitude[i]) * psftopa;
+ BoostSwitchPressure[i] = GetStdPressure100K(BoostSwitchAltitude[i]) * psftopa;
//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() * psftopa + RatedBoost[i] * 6895; // psi*6895 = Pa.
+ RatedMAP[i] = standard_pressure + RatedBoost[i] * 6895; // 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];
bTakeoffBoost = false;
}
- BoostMul[i] = RatedMAP[i] / (Atmosphere->GetPressure(RatedAltitude[i]) * psftopa);
+ BoostMul[i] = RatedMAP[i] / (GetStdPressure100K(RatedAltitude[i]) * psftopa);
}
{
FGEngine::ResetToIC();
- ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
- MAP = Atmosphere->GetPressure() * psftopa;
+ ManifoldPressure_inHg = in.Pressure * psftoinhg; // psf to in Hg
+ MAP = in.Pressure * psftopa;
TMAP = MAP;
- double airTemperature_degK = RankineToKelvin(Atmosphere->GetTemperature());
+ double airTemperature_degK = RankineToKelvin(in.Temperature);
OilTemp_degK = airTemperature_degK;
CylinderHeadTemp_degK = airTemperature_degK;
ExhaustGasTemp_degK = airTemperature_degK;
Thruster->SetRPM(0.0);
RPM = 0.0;
OilPressure_psi = 0.0;
+ BoostLossHP = 0.;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
void FGPiston::Calculate(void)
{
- RunPreFunctions();
+ // Input values.
- if (FuelFlow_gph > 0.0) ConsumeFuel();
+ p_amb = in.Pressure * psftopa;
+ double p = in.TotalPressure * psftopa;
+ p_ram = (p - p_amb) * Ram_Air_Factor + p_amb;
+ T_amb = RankineToKelvin(in.Temperature);
- Throttle = FCS->GetThrottlePos(EngineNumber);
- Mixture = FCS->GetMixturePos(EngineNumber);
+ RunPreFunctions();
- // Input values.
+ TotalDeltaT = ( in.TotalDeltaT < 1e-9 ) ? 1.0 : in.TotalDeltaT;
- p_amb = Atmosphere->GetPressure() * psftopa;
- double p = Auxiliary->GetTotalPressure() * psftopa;
- p_ram = (p - p_amb) * Ram_Air_Factor + p_amb;
- T_amb = RankineToKelvin(Atmosphere->GetTemperature());
+/* The thruster controls the engine RPM because it encapsulates the gear ratio and other transmission variables */
+ RPM = Thruster->GetEngineRPM();
- RPM = Thruster->GetRPM() * Thruster->GetGearRatio();
MeanPistonSpeed_fps = ( RPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
- IAS = Auxiliary->GetVcalibratedKTS();
+ IAS = in.Vc;
doEngineStartup();
if (Boosted) doBoostControl();
doOilPressure();
if (Thruster->GetType() == FGThruster::ttPropeller) {
- ((FGPropeller*)Thruster)->SetAdvance(FCS->GetPropAdvance(EngineNumber));
- ((FGPropeller*)Thruster)->SetFeather(FCS->GetPropFeather(EngineNumber));
+ ((FGPropeller*)Thruster)->SetAdvance(in.PropAdvance[EngineNumber]);
+ ((FGPropeller*)Thruster)->SetFeather(in.PropFeather[EngineNumber]);
}
- PowerAvailable = (HP * hptoftlbssec) - Thruster->GetPowerRequired();
- Thruster->Calculate(PowerAvailable);
+ LoadThrusterInputs();
+ Thruster->Calculate(HP * hptoftlbssec);
RunPostFunctions();
}
double FGPiston::CalcFuelNeed(void)
{
- double dT = FDMExec->GetDeltaT() * Propulsion->GetRate();
- FuelExpended = FuelFlowRate * dT;
+ FuelExpended = FuelFlowRate * in.TotalDeltaT;
+ if (!Starved) FuelUsedLbs += FuelExpended;
return FuelExpended;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-int FGPiston::InitRunning(void) {
+int FGPiston::InitRunning(void)
+{
Magnetos=3;
- p_amb = Atmosphere->GetPressure() * psftopa;
- double mix= p_amb / (101325.0*1.3);
- FCS->SetMixturePos(EngineNumber, mix);
- Thruster->SetRPM( 2.*IdleRPM/Thruster->GetGearRatio() );
- //Thruster->SetRPM( 1000 );
- Running=true;
-// cout <<"Set Running in FGPiston. RPM:" << Thruster->GetRPM()*Thruster->GetGearRatio() <<" Pressure:"<<p_amb<<" Mixture:"<< mix <<endl;
+ 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 may continue to
- // spin if the prop is in a moving airstream
- if ( Running && (!spark || !fuel) ) Running = false;
+ // Cut the engine *power* - Note: the engine will continue to
+ // spin depending on prop Ixx and freestream velocity
- // 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 Zt = (1-Throttle)*(1-Throttle)*Z_throttle; // throttle impedence
+ double Zt = (1 - in.ThrottlePos[EngineNumber])*(1 - in.ThrottlePos[EngineNumber])*Z_throttle; // throttle impedence
double Ze= MeanPistonSpeed_fps > 0 ? PeakMeanPistonSpeed_fps/MeanPistonSpeed_fps : 999999; // engine impedence
double map_coefficient = Ze/(Ze+Z_airbox+Zt);
- // Add a one second lag to manifold pressure changes
- double dMAP = (TMAP - p_ram * map_coefficient) * dt;
+ // Add a variable lag to manifold pressure changes
+ double dMAP=(TMAP - p_ram * map_coefficient);
+ if (ManifoldPressureLag > TotalDeltaT) dMAP *= TotalDeltaT/ManifoldPressureLag;
+
TMAP -=dMAP;
// Find the mean effective pressure required to achieve this manifold pressure
bool bTakeoffPos = false;
if (bTakeoffBoost) {
- if (Throttle > 0.98) {
+ if (in.ThrottlePos[EngineNumber] > 0.98) {
bTakeoffPos = true;
}
}
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));
-// FGAtmosphere::GetDensity() * FGJSBBase::m3toft3 / FGJSBBase::kgtoslug;
+ 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::doFuelFlow(void)
{
- double thi_sea_level = 1.3 * Mixture; // Allows an AFR of infinity:1 to 11.3075:1
+ double thi_sea_level = 1.3 * in.MixturePos[EngineNumber]; // Allows an AFR of infinity:1 to 11.3075:1
equivalence_ratio = thi_sea_level * 101325.0 / p_amb;
-// double AFR = 10+(12*(1-Mixture));// mixture 10:1 to 22:1
+// double AFR = 10+(12*(1-in.Mixture[EngineNumber]));// mixture 10:1 to 22:1
// m_dot_fuel = m_dot_air / AFR;
m_dot_fuel = (m_dot_air * equivalence_ratio) / 14.7;
FuelFlowRate = m_dot_fuel * 2.2046; // kg to lb
+ if(Starved) // There is no fuel, so zero out the flows we've calculated so far
+ {
+ equivalence_ratio = 0.0;
+ FuelFlowRate = 0.0;
+ m_dot_fuel = 0.0;
+ }
FuelFlow_pph = FuelFlowRate * 3600; // seconds to hours
FuelFlow_gph = FuelFlow_pph / 6.0; // Assumes 6 lbs / gallon
}
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 - 1.5; //FIXME 1.5 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;
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;
+ combustion_efficiency * 0.30;
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) * PctPower);
} 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;
+ dEGTdt = (RankineToKelvin(in.Temperature) - ExhaustGasTemp_degK) / 100.0;
+ delta_T_exhaust = dEGTdt * TotalDeltaT;
+
ExhaustGasTemp_degK += delta_T_exhaust;
}
}
double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
CylinderHeadTemp_degK +=
- (dqdt_cylinder_head / HeatCapacityCylinderHead) * dt;
+ (dqdt_cylinder_head / HeatCapacityCylinderHead) * TotalDeltaT;
+
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
double dOilTempdt = (target_oil_temp - OilTemp_degK) / time_constant;
- OilTemp_degK += (dOilTempdt * dt);
+ OilTemp_degK += (dOilTempdt * TotalDeltaT);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
OilPressure_psi += (Design_Oil_Temp - OilTemp_degK) * Oil_Viscosity_Index * OilPressure_psi / Oil_Press_Relief_Valve;
}
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+//
+// This is a local copy of the same function in FGStandardAtmosphere.
+
+double FGPiston::GetStdPressure100K(double altitude) const
+{
+ // Limit this equation to input altitudes of 100000 ft.
+ if (altitude > 100000.0) altitude = 100000.0;
+
+ double alt[5];
+ const double coef[5] = { 2116.217,
+ -7.648932746E-2,
+ 1.0925498604E-6,
+ -7.1135726027E-12,
+ 1.7470331356E-17 };
+
+ alt[0] = 1;
+ for (int pwr=1; pwr<=4; pwr++) alt[pwr] = alt[pwr-1]*altitude;
+
+ double press = 0.0;
+ for (int ctr=0; ctr<=4; ctr++) press += coef[ctr]*alt[ctr];
+ return press;
+}
+
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
string FGPiston::GetEngineLabels(const string& delimiter)
{
std::ostringstream buf;
- buf << Name << " Power Available (engine " << EngineNumber << " in HP)" << delimiter
+ buf << Name << " Power Available (engine " << EngineNumber << " in ft-lbs/sec)" << delimiter
<< Name << " HP (engine " << EngineNumber << ")" << delimiter
<< Name << " equivalent ratio (engine " << EngineNumber << ")" << delimiter
<< Name << " MAP (engine " << EngineNumber << " in inHg)" << delimiter
{
std::ostringstream buf;
- buf << PowerAvailable << delimiter << HP << delimiter
+ buf << (HP * hptoftlbssec) << delimiter << HP << delimiter
<< equivalence_ratio << delimiter << ManifoldPressure_inHg << delimiter
<< Thruster->GetThrusterValues(EngineNumber, delimiter);
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();