INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+#include <iostream>
#include <sstream>
#include "FGPiston.h"
-#include <models/FGPropulsion.h>
#include "FGPropeller.h"
+using namespace std;
+
namespace JSBSim {
-static const char *IdSrc = "$Id$";
+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)
+ Cp_fuel(1700),
+ standard_pressure(101320.73)
{
+ Element *table_element;
string token;
+ string name="";
// Defaults and initializations
Type = etPiston;
- dt = State->Getdt();
// 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 = -0.1;
+ volumetric_efficiency = 0.85;
Bore = 5.125;
Stroke = 4.375;
Cylinders = 4;
+ CylinderHeadMass = 2; //kg
CompressionRatio = 8.5;
+ Z_airbox = -999;
+ Ram_Air_Factor = 1;
+ PeakMeanPistonSpeed_fps = 100;
+ 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;
BoostSpeed = 0;
Boosted = false;
BoostOverride = 0;
+ BoostManual = 0;
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"))
Stroke = el->FindElementValueAsNumberConvertTo("stroke","IN");
if (el->FindElement("cylinders"))
Cylinders = el->FindElementValueAsNumber("cylinders");
+ if (el->FindElement("cylinder-head-mass"))
+ CylinderHeadMass = el->FindElementValueAsNumberConvertTo("cylinder-head-mass","KG");
+ if (el->FindElement("air-intake-impedance-factor"))
+ Z_airbox = el->FindElementValueAsNumber("air-intake-impedance-factor");
+ if (el->FindElement("ram-air-factor"))
+ 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"))
+ FMEPStatic = el->FindElementValueAsNumberConvertTo("static-fmep","PA");
+ if (el->FindElement("peak-piston-speed"))
+ PeakMeanPistonSpeed_fps = el->FindElementValueAsNumber("peak-piston-speed");
if (el->FindElement("numboostspeeds")) { // Turbo- and super-charging parameters
BoostSpeeds = (int)el->FindElementValueAsNumber("numboostspeeds");
if (el->FindElement("boostoverride"))
BoostOverride = (int)el->FindElementValueAsNumber("boostoverride");
+ if (el->FindElement("boostmanual"))
+ 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
- // Create IFSC and VE to match the engine if not provided
- int calculated_ve=0;
- if (volumetric_efficiency < 0) {
- volumetric_efficiency = MaxManifoldPressure_inHg / 29.92;
- calculated_ve=1;
- }
+ // Create IFSC to match the engine if not provided
if (ISFC < 0) {
- double pmep = MaxManifoldPressure_inHg > 29.92 ? 0 : 29.92 - MaxManifoldPressure_inHg;
- pmep *= inhgtopa;
- double fmep = (18400 * (2*(Stroke/12)*(MaxRPM/60)) * fttom + 46500)/2;
+ double pmep = 29.92 - MaxManifoldPressure_inHg;
+ pmep *= inhgtopa * volumetric_efficiency;
+ double fmep = (FMEPDynamic * RatedMeanPistonSpeed_fps * fttom + FMEPStatic);
double hp_loss = ((pmep + fmep) * displacement_SI * MaxRPM)/(Cycles*22371);
- ISFC = ( Displacement * MaxRPM * volumetric_efficiency ) / (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
MaxManifoldPressure_inHg = 29.9;
- if (calculated_ve) volumetric_efficiency = 1.0;
}
minMAP = MinManifoldPressure_inHg * inhgtopa; // inHg to Pa
maxMAP = MaxManifoldPressure_inHg * inhgtopa;
+// For throttle
+/*
+ * Pm = ( Ze / ( Ze + Zi + Zt ) ) * Pa
+ * Where:
+ * Pm = Manifold Pressure
+ * Pa = Ambient Pressre
+ * Ze = engine impedance, Ze is effectively 1 / Mean Piston Speed
+ * Zi = airbox impedance
+ * Zt = throttle impedance
+ *
+ * For the calculation below throttle is fully open or Zt = 0
+ *
+ *
+ *
+ */
+ if(Z_airbox < 0.0){
+ double Ze=PeakMeanPistonSpeed_fps/RatedMeanPistonSpeed_fps; // engine impedence
+ Z_airbox = (standard_pressure *Ze / maxMAP) - Ze; // impedence of airbox
+ }
+ // Constant for Throttle impedence
+ 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, &MAP);
property_name = base_property_name + "/map-inhg";
PropertyManager->Tie(property_name, &ManifoldPressure_inHg);
+ property_name = base_property_name + "/air-intake-impedance-factor";
+ PropertyManager->Tie(property_name, &Z_airbox);
+ property_name = base_property_name + "/ram-air-factor";
+ PropertyManager->Tie(property_name, &Ram_Air_Factor);
+ property_name = base_property_name + "/cooling-factor";
+ PropertyManager->Tie(property_name, &Cooling_Factor);
+ property_name = base_property_name + "/boost-speed";
+ 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);
}
BoostSpeed = 0;
}
bBoostOverride = (BoostOverride == 1 ? true : false);
+ bBoostManual = (BoostManual == 1 ? true : false);
Debug(0); // Call Debug() routine from constructor if needed
}
{
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.;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-double FGPiston::Calculate(void)
+void FGPiston::Calculate(void)
{
- if (FuelFlow_gph > 0.0) ConsumeFuel();
+ // Input values.
- Throttle = FCS->GetThrottlePos(EngineNumber);
- // calculate the throttle plate angle. 1 unit is approx pi/2 radians.
- ThrottleAngle = MinThrottle+((MaxThrottle-MinThrottle)*Throttle );
- Mixture = FCS->GetMixturePos(EngineNumber);
+ 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);
- //
- // Input values.
- //
+ RunPreFunctions();
- p_amb = Atmosphere->GetPressure() * psftopa;
- T_amb = RankineToKelvin(Atmosphere->GetTemperature());
+ 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();
- 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();
//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;
+
+ // if (equivalence_ratio < 0.668)
+ // Running = false;
doEnginePower();
if (IndicatedHorsePower < 0.1250) Running = false;
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();
+ LoadThrusterInputs();
+ Thruster->Calculate(HP * hptoftlbssec);
- return Thruster->Calculate(PowerAvailable);
+ RunPostFunctions();
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
double FGPiston::CalcFuelNeed(void)
{
- double dT = State->Getdt() * 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;
- //Thruster->SetRPM( 1.1*IdleRPM/Thruster->GetGearRatio() );
- Thruster->SetRPM( 1000 );
- Running=true;
+ 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;
}
// (spark, fuel, starter motor etc)
bool spark;
bool fuel;
-
// Check for spark
Magneto_Left = false;
Magneto_Right = false;
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(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--;
+ if(bBoostManual) {
+ if(BoostSpeed > BoostSpeeds-1) BoostSpeed = BoostSpeeds-1;
+ if(BoostSpeed < 0) BoostSpeed = 0;
+ } else {
+ if(BoostSpeed < BoostSpeeds - 1) {
+ // Check if we need to change to a higher boost speed
+ if(p_amb < BoostSwitchPressure[BoostSpeed] - BoostSwitchHysteresis) {
+ BoostSpeed++;
+ }
+ } if(BoostSpeed > 0) {
+ // Check if we need to change to a lower boost speed
+ if(p_amb > BoostSwitchPressure[BoostSpeed - 1] + BoostSwitchHysteresis) {
+ BoostSpeed--;
+ }
}
}
}
* from the throttle position, turbo/supercharger boost control
* system, engine speed and local ambient air density.
*
- * Inputs: p_amb, Throttle, ThrottleAngle,
+ * Inputs: p_amb, Throttle,
* MeanPistonSpeed_fps, dt
*
- * Outputs: MAP, ManifoldPressure_inHg, TMAP
+ * Outputs: MAP, ManifoldPressure_inHg, TMAP, BoostLossHP
*/
void FGPiston::doMAP(void)
{
- // estimate throttle plate area.
- double throttle_area = ThrottleAngle*ThrottleAngle;
- // Internal Combustion Engine in Theory and Practice, Volume 2. Charles Fayette Taylor. Revised Edition, 1985 fig 6-13
- double map_coefficient = 1-((MeanPistonSpeed_fps*MeanPistonSpeed_fps)/(24978*throttle_area));
+ 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);
- if ( map_coefficient < 0.1 ) map_coefficient = 0.1;
+ // Add a variable lag to manifold pressure changes
+ double dMAP=(TMAP - p_ram * map_coefficient);
+ if (ManifoldPressureLag > TotalDeltaT) dMAP *= TotalDeltaT/ManifoldPressureLag;
- // Add a one second lag to manifold pressure changes
- double dMAP = (TMAP - p_amb * map_coefficient) * dt;
TMAP -=dMAP;
// Find the mean effective pressure required to achieve this manifold pressure
// Fixme: determine the HP consumed by the supercharger
- PMEP = TMAP - p_amb; // Fixme: p_amb should be exhaust manifold pressure
+ PMEP = (TMAP - p_amb) * volumetric_efficiency; // Fixme: p_amb should be exhaust manifold pressure
if (Boosted) {
// If takeoff boost is fitted, we currently assume the following throttle map:
bool bTakeoffPos = false;
if (bTakeoffBoost) {
- if (Throttle > 0.98) {
+ if (in.ThrottlePos[EngineNumber] > 0.98) {
bTakeoffPos = true;
}
}
// Boost the manifold pressure.
- double boost_factor = BoostMul[BoostSpeed] * RPM/RatedRPM[BoostSpeed];
- if (boost_factor < 1.0) boost_factor = 1.0; // boost will never reduce the MAP
+ 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;
}
* (used in CHT calculation for air-cooled engines).
*
* Inputs: p_amb, R_air, T_amb, MAP, Displacement,
- * RPM, volumetric_efficiency, ThrottleAngle
+ * RPM, volumetric_efficiency,
*
* 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 = 1.4; // specific heat constants
+ double gamma = 1.3; // specific heat constants
// loss of volumentric efficiency due to difference between MAP and exhaust pressure
- double ve =((gamma-1)/gamma)+( CompressionRatio -(p_amb/MAP))/(gamma*( CompressionRatio - 1));
+// Eq 6-10 from The Internal Combustion Engine - Charles Taylor Vol 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::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
}
/**
* 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, RPM, T_amb,
+ * Inputs: ManifoldPressure_inHg, p_amb, RPM, T_amb, ISFC,
* Mixture_Efficiency_Correlation, Cycles, MaxHP, PMEP,
+ * MeanPistonSpeed_fps
*
- * Outputs: PctPower, HP
+ * Outputs: PctPower, HP, FMEP, IndicatedHorsePower
*/
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 as a percentage of rated HP + a percentage of rpm + a percentage of Indicted HP
-// friction = 1 - (percent_RPM * percent_RPM * percent_RPM/10);
- FMEP = (-18400 * MeanPistonSpeed_fps * fttom - 46500);
+// Guestimate engine friction losses from Figure 4.4 of "Engines: An Introduction", John Lumley
+ FMEP = (-FMEPDynamic * MeanPistonSpeed_fps * fttom - FMEPStatic);
power = 1;
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;
}
}
* Calculate the cylinder head temperature.
*
* Inputs: T_amb, IAS, rho_air, m_dot_fuel, calorific_value_fuel,
- * combustion_efficiency, RPM, MaxRPM, Displacement
+ * combustion_efficiency, RPM, MaxRPM, Displacement, Cylinders
*
* Outputs: CylinderHeadTemp_degK
*/
double h2 = -3.95;
double h3 = -140.0; // -0.05 * 2800 (default maxrpm)
- double arbitary_area = 1.0;
+ double arbitary_area = Displacement/360.0;
double CpCylinderHead = 800.0;
- double MassCylinderHead = 8.0;
+ double MassCylinderHead = CylinderHeadMass * Cylinders;
double temperature_difference = CylinderHeadTemp_degK - T_amb;
- double v_apparent = IAS * 0.5144444;
+ double v_apparent = IAS * Cooling_Factor;
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 / MaxRPM);
- double dqdt_free = h1 * temperature_difference;
+ double dqdt_free = h1 * temperature_difference * arbitary_area;
double dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;
double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
CylinderHeadTemp_degK +=
- (dqdt_cylinder_head / HeatCapacityCylinderHead) * dt;
+ (dqdt_cylinder_head / HeatCapacityCylinderHead) * TotalDeltaT;
+
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if (OilPressure_psi > 5.0 ) {
time_constant = 5000 / OilPressure_psi; // Guess at a time constant for circulated oil.
// The higher the pressure the faster it reaches
- // target temperature. Oil pressure should be about
- // 60 PSI yielding a TC of about 80.
+ // target temperature. Oil pressure should be about
+ // 60 PSI yielding a TC of about 80.
} else {
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);
+ 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(string delimeter)
+string FGPiston::GetEngineLabels(const string& delimiter)
{
std::ostringstream buf;
- buf << Name << " Power Available (engine " << EngineNumber << " in HP)" << delimeter
- << Name << " HP (engine " << EngineNumber << ")" << delimeter
- << Name << " equivalent ratio (engine " << EngineNumber << ")" << delimeter
- << Name << " MAP (engine " << EngineNumber << " in inHg)" << delimeter
- << Thruster->GetThrusterLabels(EngineNumber, delimeter);
+ 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
+ << Thruster->GetThrusterLabels(EngineNumber, delimiter);
return buf.str();
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-string FGPiston::GetEngineValues(string delimeter)
+string FGPiston::GetEngineValues(const string& delimiter)
{
std::ostringstream buf;
- buf << PowerAvailable << delimeter << HP << delimeter
- << equivalence_ratio << delimeter << ManifoldPressure_inHg << delimeter
- << Thruster->GetThrusterValues(EngineNumber, delimeter);
+ buf << (HP * hptoftlbssec) << delimiter << HP << delimiter
+ << equivalence_ratio << delimiter << ManifoldPressure_inHg << delimiter
+ << Thruster->GetThrusterValues(EngineNumber, delimiter);
return buf.str();
}
cout << " Bore: " << Bore << endl;
cout << " Stroke: " << Stroke << endl;
cout << " Cylinders: " << Cylinders << endl;
+ cout << " Cylinders Head Mass: " << CylinderHeadMass << endl;
cout << " Compression Ratio: " << CompressionRatio << endl;
cout << " MaxHP: " << MaxHP << endl;
cout << " Cycles: " << Cycles << endl;
cout << " IdleRPM: " << IdleRPM << endl;
- cout << " MaxThrottle: " << MaxThrottle << endl;
- cout << " MinThrottle: " << MinThrottle << endl;
+ cout << " MaxRPM: " << MaxRPM << endl;
+ cout << " Throttle Constant: " << Z_throttle << endl;
cout << " ISFC: " << ISFC << endl;
- cout << " Volumentric Efficiency: " << volumetric_efficiency << endl;
+ cout << " Volumetric Efficiency: " << volumetric_efficiency << endl;
+ cout << " PeakMeanPistonSpeed_fps: " << PeakMeanPistonSpeed_fps << endl;
+ cout << " Intake Impedance Factor: " << Z_airbox << 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;
projects / flightgear.git / blobdiff