/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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
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;
}
crank_counter = 0;
EngineNumber = 0;
OilTemp_degK = 298;
+ ManifoldPressure_inHg = Atmosphere->GetPressure() * 0.014138; // psf to in Hg
dt = State->Getdt();
double FGPiston::Calculate(double PowerRequired)
{
- // FIXME: calculate from actual fuel flow
ConsumeFuel();
Throttle = FCS->GetThrottlePos(EngineNumber);
IAS = Auxiliary->GetVcalibratedKTS();
- if (Mixture >= 0.5) {
+ if (Mixture >= 0.3) {
doEngineStartup();
doManifoldPressure();
doAirFlow();
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) {
void FGPiston::doManifoldPressure(void)
{
- ManifoldPressure_inHg = MinManifoldPressure_inHg +
- (Throttle * (MaxManifoldPressure_inHg - MinManifoldPressure_inHg));
+ if (Running || Cranking) {
+ ManifoldPressure_inHg = MinManifoldPressure_inHg +
+ (Throttle * (MaxManifoldPressure_inHg - MinManifoldPressure_inHg));
+ } else {
+ ManifoldPressure_inHg = Atmosphere->GetPressure() * 0.014138; // psf to in Hg
+ }
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the air flow through the engine.
*
+ * At this point, ManifoldPressure_inHg still represents the sea-level
+ * MP, not adjusted for altitude.
+ *
* Inputs: p_amb, R_air, T_amb, ManifoldPressure_inHg, Displacement,
* RPM, volumetric_efficiency
*
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)
{
- double True_ManifoldPressure_inHg = ManifoldPressure_inHg * p_amb / p_amb_sea_level;
- double ManXRPM = True_ManifoldPressure_inHg * RPM;
+ 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;
void FGPiston::doEGT(void)
{
- combustion_efficiency = Lookup_Combustion_Efficiency->GetValue(equivalence_ratio);
- double enthalpy_exhaust = m_dot_fuel * calorific_value_fuel *
- combustion_efficiency * 0.33;
- double heat_capacity_exhaust = (Cp_air * m_dot_air) + (Cp_fuel * m_dot_fuel);
- double 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;
+ }
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
cout << " IdleRPM: " << IdleRPM << endl;
cout << " MaxThrottle: " << MaxThrottle << endl;
cout << " MinThrottle: " << MinThrottle << endl;
- cout << " SLFuelFlowMax: " << SLFuelFlowMax << endl;
cout << endl;
cout << " Combustion Efficiency table:" << endl;
}
if (debug_lvl & 16) { // Sanity checking
}
+ if (debug_lvl & 64) {
+ if (from == 0) { // Constructor
+ cout << IdSrc << endl;
+ cout << IdHdr << endl;
+ }
+ }
}
+double
+FGPiston::CalcFuelNeed(void)
+{
+ return FuelFlow_gph / 3600 * State->Getdt() * Propulsion->GetRate();
+}