#include "FGPiston.h"
#include "FGPropulsion.h"
+namespace JSBSim {
+
static const char *IdSrc = "$Id$";
static const char *IdHdr = ID_PISTON;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
FGPiston::FGPiston(FGFDMExec* exec, FGConfigFile* Eng_cfg) : FGEngine(exec),
- CONVERT_CUBIC_INCHES_TO_METERS_CUBED(1.638706e-5),
R_air(287.3),
rho_fuel(800), // estimate
calorific_value_fuel(47.3e6),
{
string token;
+ Type = etPiston;
+ crank_counter = 0;
+ EngineNumber = 0;
+ OilTemp_degK = 298;
MinManifoldPressure_inHg = 6.5;
MaxManifoldPressure_inHg = 28.5;
+ ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
+ CylinderHeadTemp_degK = 0.0;
Displacement = 360;
MaxHP = 200;
Cycles = 2;
IdleRPM = 600;
-
- Name = Eng_cfg->GetValue("NAME");
- Eng_cfg->GetNextConfigLine();
- while (Eng_cfg->GetValue() != string("/FG_PISTON")) {
- *Eng_cfg >> token;
- if (token == "MINMP") *Eng_cfg >> MinManifoldPressure_inHg;
- else if (token == "MAXMP") *Eng_cfg >> MaxManifoldPressure_inHg;
- else if (token == "DISPLACEMENT") *Eng_cfg >> Displacement;
- else if (token == "MAXHP") *Eng_cfg >> MaxHP;
- else if (token == "CYCLES") *Eng_cfg >> Cycles;
- else if (token == "IDLERPM") *Eng_cfg >> IdleRPM;
- else if (token == "MAXTHROTTLE") *Eng_cfg >> MaxThrottle;
- else if (token == "MINTHROTTLE") *Eng_cfg >> MinThrottle;
- else if (token == "SLFUELFLOWMAX") *Eng_cfg >> SLFuelFlowMax;
- else cerr << "Unhandled token in Engine config file: " << token << endl;
- }
-
- Type = etPiston;
- crank_counter = 0;
- EngineNumber = 0;
- OilTemp_degK = 298;
- ManifoldPressure_inHg = Atmosphere->GetPressure() * 0.014138; // psf to in Hg
+ Magnetos = 0;
+ ExhaustGasTemp_degK = 0.0;
+ EGT_degC = 0.0;
dt = State->Getdt();
*Power_Mixture_Correlation << 20 << 74.0;
*Power_Mixture_Correlation << (14.7/0.6) << 58;
+ Name = Eng_cfg->GetValue("NAME");
+ Eng_cfg->GetNextConfigLine();
+ while (Eng_cfg->GetValue() != string("/FG_PISTON")) {
+ *Eng_cfg >> token;
+ if (token == "MINMP") *Eng_cfg >> MinManifoldPressure_inHg;
+ else if (token == "MAXMP") *Eng_cfg >> MaxManifoldPressure_inHg;
+ else if (token == "DISPLACEMENT") *Eng_cfg >> Displacement;
+ else if (token == "MAXHP") *Eng_cfg >> MaxHP;
+ else if (token == "CYCLES") *Eng_cfg >> Cycles;
+ else if (token == "IDLERPM") *Eng_cfg >> IdleRPM;
+ else if (token == "MAXTHROTTLE") *Eng_cfg >> MaxThrottle;
+ else if (token == "MINTHROTTLE") *Eng_cfg >> MinThrottle;
+ else cerr << "Unhandled token in Engine config file: " << token << endl;
+ }
+
Debug(0); // Call Debug() routine from constructor if needed
}
double FGPiston::Calculate(double PowerRequired)
{
- // FIXME: calculate from actual fuel flow
- ConsumeFuel();
+ if (FuelFlow_gph > 0.0) ConsumeFuel();
Throttle = FCS->GetThrottlePos(EngineNumber);
Mixture = FCS->GetMixturePos(EngineNumber);
p_amb_sea_level = Atmosphere->GetPressureSL() * 48;
T_amb = Atmosphere->GetTemperature() * (5.0 / 9.0); // convert from Rankine to Kelvin
- RPM = Propulsion->GetThruster(EngineNumber)->GetRPM();
- //if (RPM < IdleRPM) RPM = IdleRPM; // kludge
+ RPM = Propulsion->GetThruster(EngineNumber)->GetRPM() *
+ Propulsion->GetThruster(EngineNumber)->GetGearRatio();
IAS = Auxiliary->GetVcalibratedKTS();
- if (Mixture >= 0.3) {
doEngineStartup();
doManifoldPressure();
doAirFlow();
doFuelFlow();
- doEnginePower();
+
+ //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();
- } else {
- HP = 0;
- }
PowerAvailable = (HP * hptoftlbssec) - PowerRequired;
return PowerAvailable;
void FGPiston::doEngineStartup(void)
{
- // TODO: check magnetos, spark, starter, etc. and decide whether
- // engine is running
-
// Check parameters that may alter the operating state of the engine.
// (spark, fuel, starter motor etc)
bool spark;
if (Magnetos > 1) Magneto_Right = true;
// Assume we have fuel for now
- fuel = true;
+ fuel = !Starved;
// Check if we are turning the starter motor
if (Cranking != Starter) {
crank_counter = 0;
}
- //Check mode of engine operation
- // ACK - unfortunately this hack doesn't work in JSBSim since the RPM is reset
- // each iteration by the propeller :-(
- if (Cranking) {
- crank_counter++;
- if (RPM <= 480) {
- RPM += 100;
- if (RPM > 480)
- RPM = 480;
- } else {
- // consider making a horrible noise if the starter is engaged with
- // the engine running
- }
- // TODO - find a better guess at cranking speed
- }
+ if (Cranking) crank_counter++; //Check mode of engine operation
- // if ((!Running) && (spark) && (fuel) && (crank_counter > 120)) {
-
- if ((!Running) && (spark) && (fuel)) {
- // start the engine if revs high enough
- if (RPM > 450) {
- // For now just instantaneously start but later we should maybe crank for
- // a bit
- Running = true;
- // RPM = 600;
+ 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
}
}
- if ( (Running) && ((!spark)||(!fuel)) ) {
- // Cut the engine
- // note that we only cut the power - the engine may continue to
- // spin if the prop is in a moving airstream
- Running = false;
- }
+ // 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;
- // And finally a last check for stalling
+ // Check for stalling (RPM = 0).
if (Running) {
- //Check if we have stalled the engine
if (RPM == 0) {
Running = false;
} else if ((RPM <= 480) && (Cranking)) {
- // Make sure the engine noise dosn't play if the engine won't
- // start due to eg mixture lever pulled out.
Running = false;
}
}
ManifoldPressure_inHg = MinManifoldPressure_inHg +
(Throttle * (MaxManifoldPressure_inHg - MinManifoldPressure_inHg));
} else {
- ManifoldPressure_inHg = Atmosphere->GetPressure() * 0.014138; // psf to in Hg
+ ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
}
}
{
rho_air = p_amb / (R_air * T_amb);
double rho_air_manifold = rho_air * ManifoldPressure_inHg / 29.6;
- double displacement_SI = Displacement * CONVERT_CUBIC_INCHES_TO_METERS_CUBED;
+ 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;
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
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGPiston::doEnginePower(void)
{
ManifoldPressure_inHg *= p_amb / p_amb_sea_level;
- double ManXRPM = ManifoldPressure_inHg * RPM;
- // FIXME: this needs to be generalized
- Percentage_Power = (6e-9 * ManXRPM * ManXRPM) + (8e-4 * ManXRPM) - 1.0;
- double T_amb_degF = (T_amb * 1.8) - 459.67;
- double T_amb_sea_lev_degF = (288 * 1.8) - 459.67;
- Percentage_Power =
- Percentage_Power + ((T_amb_sea_lev_degF - T_amb_degF) * 7 /120);
- double Percentage_of_best_power_mixture_power =
- Power_Mixture_Correlation->GetValue(14.7 / 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;
-
- //Hack
- if (!Running) {
+
+ if (Running) {
+ double ManXRPM = ManifoldPressure_inHg * RPM;
+ double T_amb_degF = KelvinToFahrenheit(T_amb);
+ double T_amb_sea_lev_degF = KelvinToFahrenheit(288);
+
+ // FIXME: this needs to be generalized
+ Percentage_Power = (6e-9 * ManXRPM * ManXRPM) + (8e-4 * ManXRPM) - 1.0;
+ Percentage_Power += ((T_amb_sea_lev_degF - T_amb_degF) * 7 /120);
+
+ 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 (Percentage_Power < 0.0) Percentage_Power = 0.0;
+ else if (Percentage_Power > 100.0) Percentage_Power = 100.0;
+
+ HP = Percentage_Power * MaxHP / 100.0;
+
+ } else {
+
+ // Power output when the engine is not running
if (Cranking) {
- if (RPM < 480) {
- HP = 3.0 + ((480 - RPM) / 10.0);
+ 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;
}
double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
- CylinderHeadTemp_degK = dqdt_cylinder_head / HeatCapacityCylinderHead;
+ CylinderHeadTemp_degK +=
+ (dqdt_cylinder_head / HeatCapacityCylinderHead) * dt;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
{
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 = 85; // FIXME: may vary by engine
- // FIXME: WRONG!!! (85 degK???)
+ 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;
cout << " IdleRPM: " << IdleRPM << endl;
cout << " MaxThrottle: " << MaxThrottle << endl;
cout << " MinThrottle: " << MinThrottle << endl;
- cout << " SLFuelFlowMax: " << SLFuelFlowMax << endl;
cout << endl;
cout << " Combustion Efficiency table:" << endl;
}
}
+double
+FGPiston::CalcFuelNeed(void)
+{
+ return FuelFlow_gph / 3600 * 6 * State->Getdt() * Propulsion->GetRate();
+}
+
+} // namespace JSBSim
projects / flightgear.git / blobdiff