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flightgear/src/FDM/JSBSim/FGPiston.cpp
ehofman 2080773f37 Cygwin fixes.
2006-01-04 12:49:07 +00:00

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/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Module: FGPiston.cpp
Author: Jon S. Berndt, JSBSim framework
Dave Luff, Piston engine model
Date started: 09/12/2000
Purpose: This module models a Piston engine
------------- Copyright (C) 2000 Jon S. Berndt (jsb@hal-pc.org) --------------
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA.
Further information about the GNU General Public License can also be found on
the world wide web at http://www.gnu.org.
FUNCTIONAL DESCRIPTION
--------------------------------------------------------------------------------
This class descends from the FGEngine class and models a Piston engine based on
parameters given in the engine config file for this class
HISTORY
--------------------------------------------------------------------------------
09/12/2000 JSB Created
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <sstream>
#include "FGPiston.h"
#include "FGPropulsion.h"
#include "FGPropeller.h"
namespace JSBSim {
static const char *IdSrc = "$Id$";
static const char *IdHdr = ID_PISTON;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS IMPLEMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
FGPiston::FGPiston(FGFDMExec* exec, FGConfigFile* Eng_cfg, int engine_number)
: FGEngine(exec, engine_number),
R_air(287.3),
rho_fuel(800), // estimate
calorific_value_fuel(47.3e6),
Cp_air(1005),
Cp_fuel(1700)
{
string token;
Type = etPiston;
crank_counter = 0;
OilTemp_degK = 298;
MinManifoldPressure_inHg = 6.5;
MaxManifoldPressure_inHg = 28.5;
ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
minMAP = 21950;
maxMAP = 96250;
MAP = Atmosphere->GetPressure() * 47.88; // psf to Pa
CylinderHeadTemp_degK = 0.0;
Displacement = 360;
MaxHP = 0;
Cycles = 2;
IdleRPM = 600;
Magnetos = 0;
ExhaustGasTemp_degK = 0.0;
EGT_degC = 0.0;
dt = State->Getdt();
// Supercharging
BoostSpeeds = 0; // Default to no supercharging
BoostSpeed = 0;
Boosted = false;
BoostOverride = 0;
bBoostOverride = false;
bTakeoffBoost = false;
TakeoffBoost = 0.0; // Default to no extra takeoff-boost
int i;
for (i=0; i<FG_MAX_BOOST_SPEEDS; i++) {
RatedBoost[i] = 0.0;
RatedPower[i] = 0.0;
RatedAltitude[i] = 0.0;
BoostMul[i] = 1.0;
RatedMAP[i] = 100000;
RatedRPM[i] = 2500;
TakeoffMAP[i] = 100000;
}
for (i=0; i<FG_MAX_BOOST_SPEEDS-1; i++) {
BoostSwitchAltitude[i] = 0.0;
BoostSwitchPressure[i] = 0.0;
}
// Initialisation
volumetric_efficiency = 0.8; // Actually f(speed, load) but this will get us running
// 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;
Power_Mixture_Correlation = new FGTable(13);
*Power_Mixture_Correlation << (14.7/1.6) << 78.0;
*Power_Mixture_Correlation << 10 << 86.0;
*Power_Mixture_Correlation << 11 << 93.5;
*Power_Mixture_Correlation << 12 << 98.0;
*Power_Mixture_Correlation << 13 << 100.0;
*Power_Mixture_Correlation << 14 << 99.0;
*Power_Mixture_Correlation << 15 << 96.4;
*Power_Mixture_Correlation << 16 << 92.5;
*Power_Mixture_Correlation << 17 << 88.0;
*Power_Mixture_Correlation << 18 << 83.0;
*Power_Mixture_Correlation << 19 << 78.5;
*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 if (token == "NUMBOOSTSPEEDS") *Eng_cfg >> BoostSpeeds;
else if (token == "BOOSTOVERRIDE") *Eng_cfg >> BoostOverride;
else if (token == "TAKEOFFBOOST") *Eng_cfg >> TakeoffBoost;
else if (token == "RATEDBOOST1") *Eng_cfg >> RatedBoost[0];
else if (token == "RATEDBOOST2") *Eng_cfg >> RatedBoost[1];
else if (token == "RATEDBOOST3") *Eng_cfg >> RatedBoost[2];
else if (token == "RATEDPOWER1") *Eng_cfg >> RatedPower[0];
else if (token == "RATEDPOWER2") *Eng_cfg >> RatedPower[1];
else if (token == "RATEDPOWER3") *Eng_cfg >> RatedPower[2];
else if (token == "RATEDRPM1") *Eng_cfg >> RatedRPM[0];
else if (token == "RATEDRPM2") *Eng_cfg >> RatedRPM[1];
else if (token == "RATEDRPM3") *Eng_cfg >> RatedRPM[2];
else if (token == "RATEDALTITUDE1") *Eng_cfg >> RatedAltitude[0];
else if (token == "RATEDALTITUDE2") *Eng_cfg >> RatedAltitude[1];
else if (token == "RATEDALTITUDE3") *Eng_cfg >> RatedAltitude[2];
else cerr << "Unhandled token in Engine config file: " << token << endl;
}
minMAP = MinManifoldPressure_inHg * 3376.85; // inHg to Pa
maxMAP = MaxManifoldPressure_inHg * 3376.85;
// Set up and sanity-check the turbo/supercharging configuration based on the input values.
if(TakeoffBoost > RatedBoost[0]) bTakeoffBoost = true;
for(i=0; i<BoostSpeeds; ++i) {
bool bad = false;
if(RatedBoost[i] <= 0.0) bad = true;
if(RatedPower[i] <= 0.0) bad = true;
if(RatedAltitude[i] < 0.0) bad = true; // 0.0 is deliberately allowed - this corresponds to unregulated supercharging.
if(i > 0 && RatedAltitude[i] < RatedAltitude[i - 1]) bad = true;
if(bad) {
// We can't recover from the above - don't use this supercharger speed.
BoostSpeeds--;
// TODO - put out a massive error message!
break;
}
// Now sanity-check stuff that is recoverable.
if(i < BoostSpeeds - 1) {
if(BoostSwitchAltitude[i] < RatedAltitude[i]) {
// TODO - put out an error message
// But we can also make a reasonable estimate, as below.
BoostSwitchAltitude[i] = RatedAltitude[i] + 1000;
}
BoostSwitchPressure[i] = Atmosphere->GetPressure(BoostSwitchAltitude[i]) * 47.88;
//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() * 47.88 + RatedBoost[i] * 6895; // psf*47.88 = Pa, 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] + ((TakeoffBoost - RatedBoost[0]) * 6895);
bTakeoffBoost = true;
} else {
TakeoffMAP[i] = RatedMAP[i];
bTakeoffBoost = false;
}
BoostMul[i] = RatedMAP[i] / (Atmosphere->GetPressure(RatedAltitude[i]) * 47.88);
// TODO - get rid of the debugging output before sending it to Jon
//cout << "Speed " << i+1 << '\n';
//cout << "BoostMul = " << BoostMul[i] << ", RatedMAP = " << RatedMAP[i] << ", TakeoffMAP = " << TakeoffMAP[i] << '\n';
}
if(BoostSpeeds > 0) {
Boosted = true;
BoostSpeed = 0;
}
bBoostOverride = (BoostOverride == 1 ? true : false);
//cout << "Engine is " << (Boosted ? "supercharged" : "naturally aspirated") << '\n';
Debug(0); // Call Debug() routine from constructor if needed
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
FGPiston::~FGPiston()
{
Debug(1); // Call Debug() routine from constructor if needed
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
double FGPiston::Calculate(void)
{
if (FuelFlow_gph > 0.0) ConsumeFuel();
Throttle = FCS->GetThrottlePos(EngineNumber);
Mixture = FCS->GetMixturePos(EngineNumber);
//
// Input values.
//
p_amb = Atmosphere->GetPressure() * 47.88; // convert from lbs/ft2 to Pa
p_amb_sea_level = Atmosphere->GetPressureSL() * 47.88;
T_amb = Atmosphere->GetTemperature() * (5.0 / 9.0); // convert from Rankine to Kelvin
RPM = Thruster->GetRPM() * Thruster->GetGearRatio();
IAS = Auxiliary->GetVcalibratedKTS();
doEngineStartup();
if(Boosted) doBoostControl();
doMAP();
doAirFlow();
doFuelFlow();
//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();
if (Thruster->GetType() == FGThruster::ttPropeller) {
((FGPropeller*)Thruster)->SetAdvance(FCS->GetPropAdvance(EngineNumber));
}
PowerAvailable = (HP * hptoftlbssec) - Thruster->GetPowerRequired();
return Thrust = Thruster->Calculate(PowerAvailable);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Start or stop the engine.
*/
void FGPiston::doEngineStartup(void)
{
// Check parameters that may alter the operating state of the engine.
// (spark, fuel, starter motor etc)
bool spark;
bool fuel;
// Check for spark
Magneto_Left = false;
Magneto_Right = false;
// Magneto positions:
// 0 -> off
// 1 -> left only
// 2 -> right only
// 3 -> both
if (Magnetos != 0) {
spark = true;
} else {
spark = false;
} // neglects battery voltage, master on switch, etc for now.
if ((Magnetos == 1) || (Magnetos > 2)) Magneto_Left = true;
if (Magnetos > 1) Magneto_Right = true;
// Assume we have fuel for now
fuel = !Starved;
// 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 > 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
}
}
// 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;
// Check for stalling (RPM = 0).
if (Running) {
if (RPM == 0) {
Running = false;
} else if ((RPM <= 480) && (Cranking)) {
Running = false;
}
}
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the Current Boost Speed
*
* This function calculates the current turbo/supercharger boost speed
* based on altitude and the (automatic) boost-speed control valve configuration.
*
* Inputs: p_amb, BoostSwitchPressure, BoostSwitchHysteresis
*
* Outputs: BoostSpeed
*/
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--;
}
}
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the manifold absolute pressure (MAP) in inches hg
*
* This function calculates manifold absolute pressure (MAP)
* from the throttle position, turbo/supercharger boost control
* system, engine speed and local ambient air density.
*
* TODO: changes in MP should not be instantaneous -- introduce
* a lag between throttle changes and MP changes, to allow pressure
* to build up or disperse.
*
* Inputs: minMAP, maxMAP, p_amb, Throttle
*
* Outputs: MAP, ManifoldPressure_inHg
*/
void FGPiston::doMAP(void)
{
if(RPM > 10) {
// Naturally aspirated
MAP = minMAP + (Throttle * (maxMAP - minMAP));
MAP *= p_amb / p_amb_sea_level;
if(Boosted) {
// If takeoff boost is fitted, we currently assume the following throttle map:
// (In throttle % - actual input is 0 -> 1)
// 99 / 100 - Takeoff boost
// 96 / 97 / 98 - Rated boost
// 0 - 95 - Idle to Rated boost (MinManifoldPressure to MaxManifoldPressure)
// In real life, most planes would be fitted with a mechanical 'gate' between
// the rated boost and takeoff boost positions.
double T = Throttle; // processed throttle value.
bool bTakeoffPos = false;
if(bTakeoffBoost) {
if(Throttle > 0.98) {
//cout << "Takeoff Boost!!!!\n";
bTakeoffPos = true;
} else if(Throttle <= 0.95) {
bTakeoffPos = false;
T *= 1.0 / 0.95;
} else {
bTakeoffPos = false;
//cout << "Rated Boost!!\n";
T = 1.0;
}
}
// Boost the manifold pressure.
MAP *= BoostMul[BoostSpeed];
// 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];
}
}
}
} else {
// rpm < 10 - effectively stopped.
// TODO - add a better variation of MAP with engine speed
MAP = Atmosphere->GetPressure() * 47.88; // psf to Pa
}
// And set the value in American units as well
ManifoldPressure_inHg = MAP / 3376.85;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the air flow through the engine.
* Also calculates ambient air density
* (used in CHT calculation for air-cooled engines).
*
* Inputs: p_amb, R_air, T_amb, MAP, Displacement,
* RPM, volumetric_efficiency
*
* TODO: Model inlet manifold air temperature.
*
* Outputs: rho_air, m_dot_air
*/
void FGPiston::doAirFlow(void)
{
rho_air = p_amb / (R_air * T_amb);
double rho_air_manifold = MAP / (R_air * T_amb);
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;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the fuel flow into the engine.
*
* Inputs: Mixture, thi_sea_level, p_amb_sea_level, p_amb, m_dot_air
*
* Outputs: equivalence_ratio, m_dot_fuel
*/
void FGPiston::doFuelFlow(void)
{
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.
*
* 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, p_amb_sea_level, RPM, T_amb,
* equivalence_ratio, Cycles, MaxHP
*
* Outputs: Percentage_Power, HP
*/
void FGPiston::doEnginePower(void)
{
if (Running) {
double T_amb_degF = KelvinToFahrenheit(T_amb);
double T_amb_sea_lev_degF = KelvinToFahrenheit(288);
// FIXME: this needs to be generalized
double ManXRPM; // Convienience term for use in the calculations
if(Boosted) {
// Currently a simple linear fit.
// The zero crossing is moved up the speed-load range to reduce the idling power.
// This will change!
double zeroOffset = (minMAP / 2.0) * (IdleRPM / 2.0);
ManXRPM = MAP * (RPM > RatedRPM[BoostSpeed] ? RatedRPM[BoostSpeed] : RPM);
// The speed clip in the line above is deliberate.
Percentage_Power = ((ManXRPM - zeroOffset) / ((RatedMAP[BoostSpeed] * RatedRPM[BoostSpeed]) - zeroOffset)) * 107.0;
Percentage_Power -= 7.0; // Another idle power reduction offset - see line above with 107.
if (Percentage_Power < 0.0) Percentage_Power = 0.0;
// Note that %power is allowed to go over 100 for boosted powerplants
// such as for the BCV-override or takeoff power settings.
// TODO - currently no altitude effect (temperature & exhaust back-pressure) modelled
// for boosted engines.
} else {
ManXRPM = ManifoldPressure_inHg * RPM; // Note that inHg must be used for the following correlation.
Percentage_Power = (6e-9 * ManXRPM * ManXRPM) + (8e-4 * ManXRPM) - 1.0;
Percentage_Power += ((T_amb_sea_lev_degF - T_amb_degF) * 7 /120);
if (Percentage_Power < 0.0) Percentage_Power = 0.0;
else if (Percentage_Power > 100.0) Percentage_Power = 100.0;
}
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(Boosted) {
HP = Percentage_Power * RatedPower[BoostSpeed] / 100.0;
} else {
HP = Percentage_Power * MaxHP / 100.0;
}
} else {
// Power output when the engine is not running
if (Cranking) {
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;
}
} else {
// Quick hack until we port the FMEP stuff
if (RPM > 0.0)
HP = -1.5;
else
HP = 0.0;
}
}
//cout << "Power = " << HP << '\n';
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the exhaust gas temperature.
*
* Inputs: equivalence_ratio, m_dot_fuel, calorific_value_fuel,
* Cp_air, m_dot_air, Cp_fuel, m_dot_fuel, T_amb, Percentage_Power
*
* Outputs: combustion_efficiency, ExhaustGasTemp_degK
*/
void FGPiston::doEGT(void)
{
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;
}
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the cylinder head temperature.
*
* Inputs: T_amb, IAS, rho_air, m_dot_fuel, calorific_value_fuel,
* combustion_efficiency, RPM
*
* Outputs: CylinderHeadTemp_degK
*/
void FGPiston::doCHT(void)
{
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;
double dqdt_forced = (h2 * m_dot_cooling_air * temperature_difference) +
(h3 * RPM * temperature_difference);
double dqdt_free = h1 * temperature_difference;
double dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;
double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
CylinderHeadTemp_degK +=
(dqdt_cylinder_head / HeatCapacityCylinderHead) * dt;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the oil temperature.
*
* Inputs: Percentage_Power, running flag.
*
* Outputs: OilTemp_degK
*/
void FGPiston::doOilTemperature(void)
{
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;
time_constant = 500; // Time constant for engine-on idling.
if (Percentage_Power > idle_percentage_power) {
time_constant /= ((Percentage_Power / idle_percentage_power) / 10.0); // adjust for power
}
} else {
target_oil_temp = 298;
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);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the oil pressure.
*
* Inputs: RPM
*
* Outputs: OilPressure_psi
*/
void FGPiston::doOilPressure(void)
{
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 = 358; // degK; FIXME: may vary by engine
double Oil_Viscosity_Index = 0.25;
OilPressure_psi = (Oil_Press_Relief_Valve / Oil_Press_RPM_Max) * RPM;
if (OilPressure_psi >= Oil_Press_Relief_Valve) {
OilPressure_psi = Oil_Press_Relief_Valve;
}
OilPressure_psi += (Design_Oil_Temp - OilTemp_degK) * Oil_Viscosity_Index;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
string FGPiston::GetEngineLabels(string delimeter)
{
std::ostringstream buf;
buf << Name << "_PwrAvail[" << EngineNumber << "]" << delimeter
<< Name << "_HP[" << EngineNumber << "]" << delimeter
<< Name << "_equiv_ratio[" << EngineNumber << "]" << delimeter
<< Name << "_MAP[" << EngineNumber << "]" << delimeter
<< Thruster->GetThrusterLabels(EngineNumber, delimeter);
return buf.str();
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
string FGPiston::GetEngineValues(string delimeter)
{
std::ostringstream buf;
buf << PowerAvailable << delimeter << HP << delimeter
<< equivalence_ratio << delimeter << MAP << delimeter
<< Thruster->GetThrusterValues(EngineNumber, delimeter);
return buf.str();
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//
// 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)
{
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 * 6 * State->Getdt() * Propulsion->GetRate();
}
} // namespace JSBSim
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