/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-#include "FGDefs.h"
#include "FGPiston.h"
#include "FGPropulsion.h"
CLASS IMPLEMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-FGPiston::FGPiston(FGFDMExec* exec, FGConfigFile* Eng_cfg)
- : FGEngine(exec),
- MinManifoldPressure_inHg(6.5),
- MaxManifoldPressure_inHg(28.5),
- Displacement(360),
- MaxHP(200),
- Cycles(2),
- IdleRPM(600),
- // Set constants
- CONVERT_CUBIC_INCHES_TO_METERS_CUBED(1.638706e-5),
- R_air(287.3),
- rho_fuel(800), // estimate
- calorific_value_fuel(47.3e6),
- Cp_air(1005),
- Cp_fuel(1700)
+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),
+ Cp_air(1005),
+ Cp_fuel(1700)
{
string token;
+ MinManifoldPressure_inHg = 6.5;
+ MaxManifoldPressure_inHg = 28.5;
+ Displacement = 360;
+ MaxHP = 200;
+ Cycles = 2;
+ IdleRPM = 600;
+
Name = Eng_cfg->GetValue("NAME");
Eng_cfg->GetNextConfigLine();
- while (Eng_cfg->GetValue() != "/FG_PISTON") {
+ 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 == "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;
}
- if (debug_lvl > 0) {
- cout << "\n Engine Name: " << Name << endl;
- cout << " MinManifoldPressure: " << MinManifoldPressure_inHg << endl;
- cout << " MaxManifoldPressure: " << MaxManifoldPressure_inHg << endl;
- cout << " Displacement: " << Displacement << endl;
- cout << " MaxHP: " << MaxHP << endl;
- cout << " Cycles: " << Cycles << endl;
- cout << " IdleRPM: " << IdleRPM << endl;
- cout << " MaxThrottle: " << MaxThrottle << endl;
- cout << " MinThrottle: " << MinThrottle << endl;
- cout << " SLFuelFlowMax: " << SLFuelFlowMax << endl;
- }
-
Type = etPiston;
- EngineNumber = 0; // FIXME: this should be the actual number
- OilTemp_degK = 298; // FIXME: should be initialized in FGEngine
+ crank_counter = 0;
+ EngineNumber = 0;
+ OilTemp_degK = 298;
+ ManifoldPressure_inHg = Atmosphere->GetPressure() * 0.014138; // psf to in Hg
dt = State->Getdt();
*Lookup_Combustion_Efficiency << 1.60 << 0.525;
*Lookup_Combustion_Efficiency << 2.00 << 0.345;
- cout << endl;
- cout << " Combustion Efficiency table:" << endl;
- Lookup_Combustion_Efficiency->Print();
- cout << endl;
-
Power_Mixture_Correlation = new FGTable(13);
*Power_Mixture_Correlation << (14.7/1.6) << 78.0;
*Power_Mixture_Correlation << 10 << 86.0;
*Power_Mixture_Correlation << 20 << 74.0;
*Power_Mixture_Correlation << (14.7/0.6) << 58;
- cout << endl;
- cout << " Power Mixture Correlation table:" << endl;
- Power_Mixture_Correlation->Print();
- cout << endl;
-
- if (debug_lvl & 2) cout << "Instantiated: FGPiston" << endl;
+ Debug(0); // Call Debug() routine from constructor if needed
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
FGPiston::~FGPiston()
{
- if (debug_lvl & 2) cout << "Destroyed: FGPiston" << endl;
+ Debug(1); // Call Debug() routine from constructor if needed
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-float FGPiston::Calculate(float PowerRequired)
+double FGPiston::Calculate(double PowerRequired)
{
- float h,EngineMaxPower;
-
- // FIXME: calculate from actual fuel flow
ConsumeFuel();
Throttle = FCS->GetThrottlePos(EngineNumber);
IAS = Auxiliary->GetVcalibratedKTS();
- if (Mixture >= 0.5) {
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;
+ 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;
bool fuel;
- static int crank_counter = 0;
// Check for spark
Magneto_Left = false;
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) {
}
//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;
+ // Do nothing !! - cranking power output is now handled in the doPower section
} else {
// consider making a horrible noise if the starter is engaged with
// the engine running
}
- // TODO - find a better guess at cranking speed
}
// 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 (Cranking) {
+ if ((RPM > 450) && (crank_counter > 175)) {
+ //Add a little delay to startup on the starter
+ Running = true;
+ }
+ } else {
+ if (RPM > 450) {
+ Running = true;
+ //This allows us to in-air start when windmilling
+ }
}
}
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
*
void FGPiston::doAirFlow(void)
{
rho_air = p_amb / (R_air * T_amb);
- float rho_air_manifold = rho_air * ManifoldPressure_inHg / 29.6;
- float displacement_SI = Displacement * CONVERT_CUBIC_INCHES_TO_METERS_CUBED;
- float swept_volume = (displacement_SI * (RPM/60)) / 2;
- float v_dot_air = swept_volume * volumetric_efficiency;
+ double rho_air_manifold = rho_air * ManifoldPressure_inHg / 29.6;
+ double displacement_SI = Displacement * CONVERT_CUBIC_INCHES_TO_METERS_CUBED;
+ 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;
}
void FGPiston::doFuelFlow(void)
{
- float thi_sea_level = 1.3 * Mixture;
+ 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
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the power produced by the engine.
*
- * <p>Currently, the JSBSim propellor model does not allow the
+ * 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.</p>
+ * 200HP.
*
* Inputs: ManifoldPressure_inHg, p_amb, p_amb_sea_level, RPM, T_amb,
* equivalence_ratio, Cycles, MaxHP
void FGPiston::doEnginePower(void)
{
- float True_ManifoldPressure_inHg = ManifoldPressure_inHg * p_amb / p_amb_sea_level;
- float ManXRPM = True_ManifoldPressure_inHg * RPM;
+ ManifoldPressure_inHg *= p_amb / p_amb_sea_level;
+ if (Running) {
+ double ManXRPM = ManifoldPressure_inHg * RPM;
// FIXME: this needs to be generalized
- Percentage_Power = (6e-9 * ManXRPM * ManXRPM) + (8e-4 * ManXRPM) - 1.0;
- float T_amb_degF = (T_amb * 1.8) - 459.67;
- float T_amb_sea_lev_degF = (288 * 1.8) - 459.67;
- Percentage_Power =
- Percentage_Power + ((T_amb_sea_lev_degF - T_amb_degF) * 7 /120);
- float 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) {
+ 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;
+ } 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;
}
void FGPiston::doEGT(void)
{
- combustion_efficiency = Lookup_Combustion_Efficiency->GetValue(equivalence_ratio);
- float enthalpy_exhaust = m_dot_fuel * calorific_value_fuel *
- combustion_efficiency * 0.33;
- float heat_capacity_exhaust = (Cp_air * m_dot_air) + (Cp_fuel * m_dot_fuel);
- float 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;
+ }
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGPiston::doCHT(void)
{
- float h1 = -95.0;
- float h2 = -3.95;
- float h3 = -0.05;
-
- float arbitary_area = 1.0;
- float CpCylinderHead = 800.0;
- float MassCylinderHead = 8.0;
-
- float temperature_difference = CylinderHeadTemp_degK - T_amb;
- float v_apparent = IAS * 0.5144444;
- float v_dot_cooling_air = arbitary_area * v_apparent;
- float m_dot_cooling_air = v_dot_cooling_air * rho_air;
- float dqdt_from_combustion =
+ double h1 = -95.0;
+ double h2 = -3.95;
+ double h3 = -0.05;
+
+ double arbitary_area = 1.0;
+ double CpCylinderHead = 800.0;
+ double MassCylinderHead = 8.0;
+
+ double temperature_difference = CylinderHeadTemp_degK - T_amb;
+ double v_apparent = IAS * 0.5144444;
+ 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;
- float dqdt_forced = (h2 * m_dot_cooling_air * temperature_difference) +
+ double dqdt_forced = (h2 * m_dot_cooling_air * temperature_difference) +
(h3 * RPM * temperature_difference);
- float dqdt_free = h1 * temperature_difference;
- float dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;
+ double dqdt_free = h1 * temperature_difference;
+ double dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;
- float HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
+ double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
CylinderHeadTemp_degK = dqdt_cylinder_head / HeatCapacityCylinderHead;
}
void FGPiston::doOilTemperature(void)
{
- float idle_percentage_power = 2.3; // approximately
- float target_oil_temp; // Steady state oil temp at the current engine conditions
- float time_constant; // The time constant for the differential equation
+ double idle_percentage_power = 2.3; // approximately
+ double target_oil_temp; // Steady state oil temp at the current engine conditions
+ double time_constant; // The time constant for the differential equation
if (Running) {
target_oil_temp = 363;
// that oil is no longer getting circulated
}
- float dOilTempdt = (target_oil_temp - OilTemp_degK) / time_constant;
+ double dOilTempdt = (target_oil_temp - OilTemp_degK) / time_constant;
OilTemp_degK += (dOilTempdt * dt);
}
void FGPiston::doOilPressure(void)
{
- float Oil_Press_Relief_Valve = 60; // FIXME: may vary by engine
- float Oil_Press_RPM_Max = 1800; // FIXME: may vary by engine
- float Design_Oil_Temp = 85; // FIXME: may vary by engine
+ 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???)
- float Oil_Viscosity_Index = 0.25;
+ double Oil_Viscosity_Index = 0.25;
OilPressure_psi = (Oil_Press_Relief_Valve / Oil_Press_RPM_Max) * RPM;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
-void FGPiston::Debug(void)
+//
+// The bitmasked value choices are as follows:
+// unset: In this case (the default) JSBSim would only print
+// out the normally expected messages, essentially echoing
+// the config files as they are read. If the environment
+// variable is not set, debug_lvl is set to 1 internally
+// 0: This requests JSBSim not to output any messages
+// whatsoever.
+// 1: This value explicity requests the normal JSBSim
+// startup messages
+// 2: This value asks for a message to be printed out when
+// a class is instantiated
+// 4: When this value is set, a message is displayed when a
+// FGModel object executes its Run() method
+// 8: When this value is set, various runtime state variables
+// are printed out periodically
+// 16: When set various parameters are sanity checked and
+// a message is printed out when they go out of bounds
+
+void FGPiston::Debug(int from)
{
- //TODO: Add your source code here
+ if (debug_lvl <= 0) return;
+
+ if (debug_lvl & 1) { // Standard console startup message output
+ if (from == 0) { // Constructor
+
+ cout << "\n Engine Name: " << Name << endl;
+ cout << " MinManifoldPressure: " << MinManifoldPressure_inHg << endl;
+ cout << " MaxManifoldPressure: " << MaxManifoldPressure_inHg << endl;
+ cout << " Displacement: " << Displacement << endl;
+ cout << " MaxHP: " << MaxHP << endl;
+ cout << " Cycles: " << Cycles << endl;
+ cout << " IdleRPM: " << IdleRPM << endl;
+ cout << " MaxThrottle: " << MaxThrottle << endl;
+ cout << " MinThrottle: " << MinThrottle << endl;
+
+ cout << endl;
+ cout << " Combustion Efficiency table:" << endl;
+ Lookup_Combustion_Efficiency->Print();
+ cout << endl;
+
+ cout << endl;
+ cout << " Power Mixture Correlation table:" << endl;
+ Power_Mixture_Correlation->Print();
+ cout << endl;
+
+ }
+ }
+ if (debug_lvl & 2 ) { // Instantiation/Destruction notification
+ if (from == 0) cout << "Instantiated: FGPiston" << endl;
+ if (from == 1) cout << "Destroyed: FGPiston" << endl;
+ }
+ if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
+ }
+ if (debug_lvl & 8 ) { // Runtime state variables
+ }
+ 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();
+}
projects / flightgear.git / blobdiff