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 (jsb@hal-pc.org) --------------
+ ------------- 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
#include <sstream>
#include "FGPiston.h"
-#include <models/FGPropulsion.h>
+#include "models/FGAtmosphere.h"
+#include "models/FGAuxiliary.h"
+#include "models/FGPropulsion.h"
#include "FGPropeller.h"
+#include <iostream>
+
+using namespace std;
namespace JSBSim {
-static const char *IdSrc = "$Id$";
+static const char *IdSrc = "$Id: FGPiston.cpp,v 1.54 2010/11/30 12:17:10 jberndt Exp $";
static const char *IdHdr = ID_PISTON;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
rho_fuel(800), // estimate
calorific_value_fuel(47.3e6),
Cp_air(1005), // Specific heat (constant pressure) J/Kg/K
- Cp_fuel(1700)
+ Cp_fuel(1700),
+ standard_pressure(101320.73)
{
string token;
// Defaults and initializations
Type = etPiston;
+ dt = FDMExec->GetDeltaT();
// These items are read from the configuration file
+ // Defaults are from a Lycoming O-360, more or less
- Cycles = 2;
+ 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;
// These are internal program variables
crank_counter = 0;
- OilTemp_degK = RankineToKelvin(Atmosphere->GetTemperature());
- ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
+ Magnetos = 0;
minMAP = 21950;
maxMAP = 96250;
- MAP = Atmosphere->GetPressure() * psftopa;
- CylinderHeadTemp_degK = RankineToKelvin(Atmosphere->GetTemperature());
- Magnetos = 0;
- ExhaustGasTemp_degK = RankineToKelvin(Atmosphere->GetTemperature());
- EGT_degC = ExhaustGasTemp_degK - 273;
- dt = State->Getdt();
+ 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
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 << 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;
+ 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;
+
// Read inputs from engine data file where present.
Displacement = el->FindElementValueAsNumberConvertTo("displacement","IN3");
if (el->FindElement("maxhp"))
MaxHP = el->FindElementValueAsNumberConvertTo("maxhp","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"))
if (el->FindElement("ratedaltitude3"))
RatedAltitude[2] = el->FindElementValueAsNumberConvertTo("ratedaltitude3", "FT");
}
- minMAP = MinManifoldPressure_inHg * 3386.38; // inHg to Pa
- maxMAP = MaxManifoldPressure_inHg * 3386.38;
- StarterHP = sqrt(MaxHP) * 0.2;
+
+ 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));
+// 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
+
+ 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);
// Set up and sanity-check the turbo/supercharging configuration based on the input values.
if (TakeoffBoost > RatedBoost[0]) bTakeoffBoost = 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
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-double FGPiston::Calculate(void)
+void FGPiston::ResetToIC(void)
{
+ FGEngine::ResetToIC();
+
+ ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
+ MAP = Atmosphere->GetPressure() * psftopa;
+ TMAP = MAP;
+ double airTemperature_degK = RankineToKelvin(Atmosphere->GetTemperature());
+ 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)
+{
+ RunPreFunctions();
+
if (FuelFlow_gph > 0.0) ConsumeFuel();
Throttle = FCS->GetThrottlePos(EngineNumber);
Mixture = FCS->GetMixturePos(EngineNumber);
- //
// Input values.
- //
p_amb = Atmosphere->GetPressure() * psftopa;
- p_amb_sea_level = Atmosphere->GetPressureSL() * psftopa;
+ double p = Auxiliary->GetTotalPressure() * psftopa;
+ p_ram = (p - p_amb) * Ram_Air_Factor + p_amb;
T_amb = RankineToKelvin(Atmosphere->GetTemperature());
RPM = Thruster->GetRPM() * Thruster->GetGearRatio();
+ MeanPistonSpeed_fps = ( RPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
IAS = Auxiliary->GetVcalibratedKTS();
//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;
+
+ // if (equivalence_ratio < 0.668)
+ // Running = false;
doEnginePower();
+ if (IndicatedHorsePower < 0.1250) Running = false;
+
doEGT();
doCHT();
doOilTemperature();
}
PowerAvailable = (HP * hptoftlbssec) - Thruster->GetPowerRequired();
+ Thruster->Calculate(PowerAvailable);
- return Thruster->Calculate(PowerAvailable);
+ RunPostFunctions();
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+double FGPiston::CalcFuelNeed(void)
+{
+ double dT = FDMExec->GetDeltaT() * Propulsion->GetRate();
+ FuelExpended = FuelFlowRate * dT;
+ return FuelExpended;
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+int FGPiston::InitRunning(void) {
+ Magnetos=3;
+ p_amb = Atmosphere->GetPressure() * psftopa;
+ double mix= p_amb / (101325.0*1.3);
+ FCS->SetMixturePos(EngineNumber, mix);
+ Thruster->SetRPM( 2.*IdleRPM/Thruster->GetGearRatio() );
+ //Thruster->SetRPM( 1000 );
+ Running=true;
+// cout <<"Set Running in FGPiston. RPM:" << Thruster->GetRPM()*Thruster->GetGearRatio() <<" Pressure:"<<p_amb<<" Mixture:"<< mix <<endl;
+ return 1;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// (spark, fuel, starter motor etc)
bool spark;
bool fuel;
-
// Check for spark
Magneto_Left = false;
Magneto_Right = false;
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
+ if ((RPM > IdleRPM*0.8) && (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
+ if (RPM > IdleRPM*0.8) // This allows us to in-air start
Running = true; // when windmilling
}
}
if (Running) {
if (RPM == 0) {
Running = false;
- } else if ((RPM <= 480) && (Cranking)) {
+ } else if ((RPM <= IdleRPM *0.8 ) && (Cranking)) {
Running = false;
}
}
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--;
+ 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--;
+ }
}
}
}
* 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: p_amb, Throttle,
+ * MeanPistonSpeed_fps, dt
*
- * Inputs: minMAP, maxMAP, p_amb, Throttle
- *
- * Outputs: MAP, ManifoldPressure_inHg
+ * Outputs: MAP, ManifoldPressure_inHg, TMAP
*/
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];
- }
+ double Zt = (1-Throttle)*(1-Throttle)*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 = (TMAP - p_ram * map_coefficient) * dt;
+ 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 (Throttle > 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 {
- // rpm < 10 - effectively stopped.
- // TODO - add a better variation of MAP with engine speed
- MAP = Atmosphere->GetPressure() * psftopa;
+ MAP = TMAP;
}
// And set the value in American units as well
- ManifoldPressure_inHg = MAP / 3386.38;
+ ManifoldPressure_inHg = MAP / inhgtopa;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
* (used in CHT calculation for air-cooled engines).
*
* Inputs: p_amb, R_air, T_amb, MAP, Displacement,
- * RPM, volumetric_efficiency
+ * RPM, volumetric_efficiency,
*
* TODO: Model inlet manifold air temperature.
*
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));
+// FGAtmosphere::GetDensity() * FGJSBBase::m3toft3 / FGJSBBase::kgtoslug;
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;
+ 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_sea_level, p_amb, m_dot_air
+ * 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 * 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
+ double thi_sea_level = 1.3 * Mixture; // Allows an AFR of infinity:1 to 11.3075:1
+ equivalence_ratio = thi_sea_level * 101325.0 / p_amb;
+// double AFR = 10+(12*(1-Mixture));// 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
+ FuelFlow_pph = FuelFlowRate * 3600; // seconds to hours
+ FuelFlow_gph = FuelFlow_pph / 6.0; // Assumes 6 lbs / gallon
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
/**
* 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, RPM, T_amb, ISFC,
+ * Mixture_Efficiency_Correlation, Cycles, MaxHP, PMEP,
+ * MeanPistonSpeed_fps
*
- * Inputs: ManifoldPressure_inHg, p_amb, p_amb_sea_level, RPM, T_amb,
- * equivalence_ratio, Cycles, MaxHP
- *
- * Outputs: Percentage_Power, HP
+ * Outputs: PctPower, HP, FMEP, IndicatedHorsePower
*/
void FGPiston::doEnginePower(void)
{
+ IndicatedHorsePower = 0;
+ FMEP = 0;
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);
- Percentage_Power += ((T_amb_sea_lev_degF - T_amb_degF) * 7 * dt);
- if (Percentage_Power < 0.0) Percentage_Power = 0.0;
- else if (Percentage_Power > 100.0) Percentage_Power = 100.0;
- }
+ double ME, percent_RPM, power; // Convienience term for use in the calculations
+ ME = Mixture_Efficiency_Correlation->GetValue(m_dot_fuel/m_dot_air);
- double Percentage_of_best_power_mixture_power =
- Power_Mixture_Correlation->GetValue(14.7 / equivalence_ratio);
+ percent_RPM = RPM/MaxRPM;
+// Guestimate engine friction losses from Figure 4.4 of "Engines: An Introduction", John Lumley
+ FMEP = (-FMEPDynamic * MeanPistonSpeed_fps * fttom - FMEPStatic);
- Percentage_Power *= Percentage_of_best_power_mixture_power / 100.0;
+ power = 1;
- if (Boosted) {
- HP = Percentage_Power * RatedPower[BoostSpeed] / 100.0;
- } else {
- HP = Percentage_Power * MaxHP / 100.0;
- }
+ if ( Magnetos != 3 ) power *= SparkFailDrop;
- } else {
+ IndicatedHorsePower = (FuelFlow_pph / ISFC )* ME * power;
+
+ } else {
// Power output when the engine is not running
if (Cranking) {
if (RPM < 10) {
- HP = StarterHP;
- } else if (RPM < 480) {
- HP = StarterHP + ((480 - RPM) / 10.0);
+ 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 {
- HP = StarterHP;
+ IndicatedHorsePower = StarterHP;
}
- } else {
- // Quick hack until we port the FMEP stuff
- if (RPM > 0.0)
- HP = -1.5;
- else
- HP = 0.0;
}
}
- //cout << "Power = " << HP << '\n';
+
+ // 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 - 1.5; //FIXME 1.5 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, Percentage_Power
+ * Cp_air, m_dot_air, Cp_fuel, m_dot_fuel, T_amb, PctPower
*
* Outputs: combustion_efficiency, ExhaustGasTemp_degK
*/
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);
+ ExhaustGasTemp_degK *= 0.444 + ((0.544 - 0.444) * PctPower);
} else { // Drop towards ambient - guess an appropriate time constant for now
combustion_efficiency = 0;
dEGTdt = (RankineToKelvin(Atmosphere->GetTemperature()) - ExhaustGasTemp_degK) / 100.0;
* Calculate the cylinder head temperature.
*
* Inputs: T_amb, IAS, rho_air, m_dot_fuel, calorific_value_fuel,
- * combustion_efficiency, RPM
+ * combustion_efficiency, RPM, MaxRPM, Displacement, Cylinders
*
* Outputs: CylinderHeadTemp_degK
*/
{
double h1 = -95.0;
double h2 = -3.95;
- double h3 = -0.05;
+ double h3 = -140.0; // -0.05 * 2800 (default maxrpm)
- double arbitary_area = 1.0;
+ double arbitary_area = Displacement/360.0;
double CpCylinderHead = 800.0;
- double MassCylinderHead = 8.0;
+ double MassCylinderHead = CylinderHeadMass * Cylinders;
double temperature_difference = CylinderHeadTemp_degK - T_amb;
- double v_apparent = IAS * 0.5144444;
+ 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);
- double dqdt_free = h1 * 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;
/**
* Calculate the oil temperature.
*
- * Inputs: Percentage_Power, running flag.
+ * Inputs: CylinderHeadTemp_degK, T_amb, OilPressure_psi.
*
* 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
+ double efficiency = 0.667; // The aproximate oil cooling system efficiency // FIXME: may vary by engine
- 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
- }
+// 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 {
- target_oil_temp = RankineToKelvin(Atmosphere->GetTemperature());
time_constant = 1000; // Time constant for engine-off; reflects the fact
// that oil is no longer getting circulated
}
/**
* Calculate the oil pressure.
*
- * Inputs: RPM
+ * 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 = 1800; // FIXME: may vary by engine
- double Design_Oil_Temp = 358; // degK; 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;
OilPressure_psi = Oil_Press_Relief_Valve;
}
- OilPressure_psi += (Design_Oil_Temp - OilTemp_degK) * Oil_Viscosity_Index;
+ OilPressure_psi += (Design_Oil_Temp - OilTemp_degK) * Oil_Viscosity_Index * OilPressure_psi / Oil_Press_Relief_Valve;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-string FGPiston::GetEngineLabels(string delimeter)
+string FGPiston::GetEngineLabels(const string& delimiter)
{
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);
+ buf << Name << " Power Available (engine " << EngineNumber << " in HP)" << 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(string delimeter)
+string FGPiston::GetEngineValues(const string& delimiter)
{
std::ostringstream buf;
- buf << PowerAvailable << delimeter << HP << delimeter
- << equivalence_ratio << delimeter << MAP << delimeter
- << Thruster->GetThrusterValues(EngineNumber, delimeter);
+ buf << PowerAvailable << delimiter << HP << delimiter
+ << equivalence_ratio << delimiter << ManifoldPressure_inHg << delimiter
+ << Thruster->GetThrusterValues(EngineNumber, delimiter);
return buf.str();
}
cout << " MinManifoldPressure: " << MinManifoldPressure_inHg << endl;
cout << " MaxManifoldPressure: " << MaxManifoldPressure_inHg << endl;
cout << " MinMaP (Pa): " << minMAP << endl;
- cout << " MaxMaP (Pa): " << maxMAP << 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 << " MaxThrottle: " << MaxThrottle << endl;
- cout << " MinThrottle: " << MinThrottle << 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;
cout << endl;
cout << endl;
- cout << " Power Mixture Correlation table:" << endl;
- Power_Mixture_Correlation->Print();
+ cout << " Mixture Efficiency Correlation table:" << endl;
+ Mixture_Efficiency_Correlation->Print();
cout << endl;
}
}
}
}
-
-double
-FGPiston::CalcFuelNeed(void)
-{
- return FuelFlow_gph / 3600 * 6 * State->Getdt() * Propulsion->GetRate();
-}
-
} // namespace JSBSim
projects / flightgear.git / blobdiff