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flightgear/src/FDM/JSBSim/models/propulsion/FGPiston.cpp
Erik Hofman 1a13ecc1e9 Latest round of JSBim updates.
2011-10-30 13:30:57 +01:00

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/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Module: FGPiston.cpp
Author: Jon S. Berndt, JSBSim framework
Dave Luff, Piston engine model
Ronald Jensen, Piston engine model
Date started: 09/12/2000
Purpose: This module models a Piston engine
------------- Copyright (C) 2000 Jon S. Berndt (jon@jsbsim.org) --------------
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser 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 Lesser General Public License for more
details.
You should have received a copy of the GNU Lesser 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 Lesser 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
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
#include <iostream>
#include <sstream>
#include "FGPiston.h"
#include "FGPropeller.h"
using namespace std;
namespace JSBSim {
static const char *IdSrc = "$Id: FGPiston.cpp,v 1.68 2011/10/11 15:13:34 jentron Exp $";
static const char *IdHdr = ID_PISTON;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS IMPLEMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
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), // J/Kg
Cp_air(1005), // Specific heat (constant pressure) J/Kg/K
Cp_fuel(1700),
standard_pressure(101320.73)
{
Element *table_element;
string token;
string name="";
// Defaults and initializations
Type = etPiston;
// These items are read from the configuration file
// Defaults are from a Lycoming O-360, more or less
Cycles = 4;
IdleRPM = 600;
MaxRPM = 2800;
Displacement = 360;
SparkFailDrop = 1.0;
MaxHP = 200;
MinManifoldPressure_inHg = 6.5;
MaxManifoldPressure_inHg = 28.5;
ISFC = -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;
// These are internal program variables
Lookup_Combustion_Efficiency = 0;
Mixture_Efficiency_Correlation = 0;
crank_counter = 0;
Magnetos = 0;
minMAP = 21950;
maxMAP = 96250;
ResetToIC();
// Supercharging
BoostSpeeds = 0; // Default to no supercharging
BoostSpeed = 0;
Boosted = false;
BoostOverride = 0;
BoostManual = 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;
}
// Read inputs from engine data file where present.
if (el->FindElement("minmp")) // Should have ELSE statement telling default value used?
MinManifoldPressure_inHg = el->FindElementValueAsNumberConvertTo("minmp","INHG");
if (el->FindElement("maxmp"))
MaxManifoldPressure_inHg = el->FindElementValueAsNumberConvertTo("maxmp","INHG");
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"))
Cycles = el->FindElementValueAsNumber("cycles");
if (el->FindElement("idlerpm"))
IdleRPM = el->FindElementValueAsNumber("idlerpm");
if (el->FindElement("maxrpm"))
MaxRPM = el->FindElementValueAsNumber("maxrpm");
if (el->FindElement("maxthrottle"))
MaxThrottle = el->FindElementValueAsNumber("maxthrottle");
if (el->FindElement("minthrottle"))
MinThrottle = el->FindElementValueAsNumber("minthrottle");
if (el->FindElement("bsfc"))
ISFC = el->FindElementValueAsNumberConvertTo("bsfc", "LBS/HP*HR");
if (el->FindElement("volumetric-efficiency"))
volumetric_efficiency = el->FindElementValueAsNumber("volumetric-efficiency");
if (el->FindElement("compression-ratio"))
CompressionRatio = el->FindElementValueAsNumber("compression-ratio");
if (el->FindElement("bore"))
Bore = el->FindElementValueAsNumberConvertTo("bore","IN");
if (el->FindElement("stroke"))
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("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("ratedboost1"))
RatedBoost[0] = el->FindElementValueAsNumberConvertTo("ratedboost1", "PSI");
if (el->FindElement("ratedboost2"))
RatedBoost[1] = el->FindElementValueAsNumberConvertTo("ratedboost2", "PSI");
if (el->FindElement("ratedboost3"))
RatedBoost[2] = el->FindElementValueAsNumberConvertTo("ratedboost3", "PSI");
if (el->FindElement("ratedpower1"))
RatedPower[0] = el->FindElementValueAsNumberConvertTo("ratedpower1", "HP");
if (el->FindElement("ratedpower2"))
RatedPower[1] = el->FindElementValueAsNumberConvertTo("ratedpower2", "HP");
if (el->FindElement("ratedpower3"))
RatedPower[2] = el->FindElementValueAsNumberConvertTo("ratedpower3", "HP");
if (el->FindElement("ratedrpm1"))
RatedRPM[0] = el->FindElementValueAsNumber("ratedrpm1");
if (el->FindElement("ratedrpm2"))
RatedRPM[1] = el->FindElementValueAsNumber("ratedrpm2");
if (el->FindElement("ratedrpm3"))
RatedRPM[2] = el->FindElementValueAsNumber("ratedrpm3");
if (el->FindElement("ratedaltitude1"))
RatedAltitude[0] = el->FindElementValueAsNumberConvertTo("ratedaltitude1", "FT");
if (el->FindElement("ratedaltitude2"))
RatedAltitude[1] = el->FindElementValueAsNumberConvertTo("ratedaltitude2", "FT");
if (el->FindElement("ratedaltitude3"))
RatedAltitude[2] = el->FindElementValueAsNumberConvertTo("ratedaltitude3", "FT");
}
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);
}
}
StarterHP = sqrt(MaxHP) * 0.4;
displacement_SI = Displacement * in3tom3;
RatedMeanPistonSpeed_fps = ( MaxRPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
// Create IFSC to match the engine if not provided
if (ISFC < 0) {
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 = ( 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;
}
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 + "/bsfc-lbs_hphr";
PropertyManager->Tie(property_name, &ISFC);
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);
// 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] = 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] = 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] + ((TakeoffBoost - RatedBoost[0]) * 6895);
bTakeoffBoost = true;
} else {
TakeoffMAP[i] = RatedMAP[i];
bTakeoffBoost = false;
}
BoostMul[i] = RatedMAP[i] / (GetStdPressure100K(RatedAltitude[i]) * psftopa);
}
if (BoostSpeeds > 0) {
Boosted = true;
BoostSpeed = 0;
}
bBoostOverride = (BoostOverride == 1 ? true : false);
bBoostManual = (BoostManual == 1 ? true : false);
Debug(0); // Call Debug() routine from constructor if needed
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
FGPiston::~FGPiston()
{
delete Lookup_Combustion_Efficiency;
delete Mixture_Efficiency_Correlation;
Debug(1); // Call Debug() routine from constructor if needed
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGPiston::ResetToIC(void)
{
FGEngine::ResetToIC();
ManifoldPressure_inHg = in.Pressure * psftoinhg; // psf to in Hg
MAP = in.Pressure * psftopa;
TMAP = MAP;
double airTemperature_degK = RankineToKelvin(in.Temperature);
OilTemp_degK = airTemperature_degK;
CylinderHeadTemp_degK = airTemperature_degK;
ExhaustGasTemp_degK = airTemperature_degK;
EGT_degC = ExhaustGasTemp_degK - 273;
Thruster->SetRPM(0.0);
RPM = 0.0;
OilPressure_psi = 0.0;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGPiston::Calculate(void)
{
// Input values.
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);
RunPreFunctions();
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();
MeanPistonSpeed_fps = ( RPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
IAS = in.Vc;
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();
if (IndicatedHorsePower < 0.1250) Running = false;
doEGT();
doCHT();
doOilTemperature();
doOilPressure();
if (Thruster->GetType() == FGThruster::ttPropeller) {
((FGPropeller*)Thruster)->SetAdvance(in.PropAdvance[EngineNumber]);
((FGPropeller*)Thruster)->SetFeather(in.PropFeather[EngineNumber]);
}
LoadThrusterInputs();
Thruster->Calculate(HP * hptoftlbssec);
RunPostFunctions();
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
double FGPiston::CalcFuelNeed(void)
{
FuelExpended = FuelFlowRate * in.TotalDeltaT;
if (!Starved) FuelUsedLbs += FuelExpended;
return FuelExpended;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
int FGPiston::InitRunning(void)
{
Magnetos=3;
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;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* 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 > 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;
// Check for stalling (RPM = 0).
if (Running) {
if (RPM == 0) {
Running = false;
} else if ((RPM <= IdleRPM *0.8 ) && (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(BoostManual) {
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--;
}
}
}
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* 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.
*
* Inputs: p_amb, Throttle,
* MeanPistonSpeed_fps, dt
*
* Outputs: MAP, ManifoldPressure_inHg, TMAP
*/
void FGPiston::doMAP(void)
{
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);
// Add a one second lag to manifold pressure changes
double dMAP=0;
dMAP = (TMAP - p_ram * map_coefficient) * TotalDeltaT;
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) * volumetric_efficiency; // Fixme: p_amb should be exhaust manifold pressure
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
// In real life, most planes would be fitted with a mechanical 'gate' between
// the rated boost and takeoff boost positions.
bool bTakeoffPos = false;
if (bTakeoffBoost) {
if (in.ThrottlePos[EngineNumber] > 0.98) {
bTakeoffPos = true;
}
}
// Boost the manifold pressure.
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];
}
} else {
MAP = TMAP;
}
// And set the value in American units as well
ManifoldPressure_inHg = MAP / inhgtopa;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* 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)
{
double gamma = 1.3; // specific heat constants
// loss of volumentric efficiency due to difference between MAP and exhaust pressure
// Eq 6-10 from The Internal Combustion Engine - Charles Taylor Vol 1
double ve =((gamma-1)/gamma) +( CompressionRatio -(p_amb/MAP))/(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;
double rho_air_manifold = MAP / (R_air * T_amb);
m_dot_air = v_dot_air * rho_air_manifold;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the fuel flow into the engine.
*
* Inputs: Mixture, thi_sea_level, p_amb, m_dot_air
*
* Outputs: equivalence_ratio, m_dot_fuel
*/
void FGPiston::doFuelFlow(void)
{
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-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.
*
* Inputs: ManifoldPressure_inHg, p_amb, RPM, T_amb, ISFC,
* Mixture_Efficiency_Correlation, Cycles, MaxHP, PMEP,
* MeanPistonSpeed_fps
*
* Outputs: PctPower, HP, FMEP, IndicatedHorsePower
*/
void FGPiston::doEnginePower(void)
{
IndicatedHorsePower = 0;
FMEP = 0;
if (Running) {
// FIXME: this needs to be generalized
double ME, percent_RPM, 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 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;
} else {
// Power output when the engine is not running
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;
}
}
}
// 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 - StaticFriction_HP; //FIXME static friction should depend on oil temp and configuration
// cout << "pumping_hp " <<pumping_hp << FMEP << PMEP <<endl;
PctPower = HP / MaxHP ;
// cout << "Power = " << HP << " RPM = " << RPM << " Running = " << Running << " Cranking = " << Cranking << endl;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* 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, PctPower
*
* 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 * 0.30;
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;
} else { // Drop towards ambient - guess an appropriate time constant for now
combustion_efficiency = 0;
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, Cylinders
*
* Outputs: CylinderHeadTemp_degK
*/
void FGPiston::doCHT(void)
{
double h1 = -95.0;
double h2 = -3.95;
double h3 = -140.0; // -0.05 * 2800 (default maxrpm)
double arbitary_area = Displacement/360.0;
double CpCylinderHead = 800.0;
double MassCylinderHead = CylinderHeadMass * Cylinders;
double temperature_difference = CylinderHeadTemp_degK - T_amb;
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 * arbitary_area;
double dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;
double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
CylinderHeadTemp_degK +=
(dqdt_cylinder_head / HeatCapacityCylinderHead) * TotalDeltaT;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the oil temperature.
*
* Inputs: CylinderHeadTemp_degK, T_amb, OilPressure_psi.
*
* Outputs: OilTemp_degK
*/
void FGPiston::doOilTemperature(void)
{
double target_oil_temp; // Steady state oil temp at the current engine conditions
double time_constant; // The time constant for the differential equation
double efficiency = 0.667; // The aproximate oil cooling system efficiency // FIXME: may vary by engine
// Target oil temp is interpolated between ambient temperature and Cylinder Head Tempurature
// target_oil_temp = ( T_amb * efficiency ) + (CylinderHeadTemp_degK *(1-efficiency)) ;
target_oil_temp = CylinderHeadTemp_degK + efficiency * (T_amb - CylinderHeadTemp_degK) ;
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.
} 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 * TotalDeltaT);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* Calculate the oil pressure.
*
* Inputs: RPM, MaxRPM, OilTemp_degK
*
* Outputs: OilPressure_psi
*/
void FGPiston::doOilPressure(void)
{
double Oil_Press_Relief_Valve = 60; // FIXME: may vary by engine
double Oil_Press_RPM_Max = MaxRPM * 0.75; // 75% of max rpm 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 * 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(const string& delimiter)
{
std::ostringstream buf;
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(const string& delimiter)
{
std::ostringstream buf;
buf << (HP * hptoftlbssec) << delimiter << HP << delimiter
<< equivalence_ratio << delimiter << ManifoldPressure_inHg << delimiter
<< Thruster->GetThrusterValues(EngineNumber, delimiter);
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 << " MinMaP (Pa): " << minMAP << endl;
cout << " MaxMaP (Pa): " << maxMAP << endl;
cout << " Displacement: " << Displacement << endl;
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 << " MaxRPM: " << MaxRPM << endl;
cout << " Throttle Constant: " << Z_throttle << endl;
cout << " ISFC: " << ISFC << 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 << endl;
cout << " Combustion Efficiency table:" << endl;
Lookup_Combustion_Efficiency->Print();
cout << endl;
cout << endl;
cout << " Mixture Efficiency Correlation table:" << endl;
Mixture_Efficiency_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;
}
}
}
} // namespace JSBSim
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