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 1.58 2011/06/13 15:23:09 jentron Exp $";
static const char *IdHdr = ID_PISTON;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
: FGEngine(exec, el, engine_number),
R_air(287.3), // Gas constant for air J/Kg/K
rho_fuel(800), // estimate
- calorific_value_fuel(47.3e6),
+ calorific_value_fuel(47.3e6), // J/Kg
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 = State->Getdt();
+ 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;
MaxHP = 200;
MinManifoldPressure_inHg = 6.5;
MaxManifoldPressure_inHg = 28.5;
- BSFC = -1;
+ 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
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) << 0.780;
- *Power_Mixture_Correlation << 10 << 0.860;
- *Power_Mixture_Correlation << 11 << 0.935;
- *Power_Mixture_Correlation << 12 << 0.980;
- *Power_Mixture_Correlation << 13 << 1.000;
- *Power_Mixture_Correlation << 14 << 0.990;
- *Power_Mixture_Correlation << 15 << 0.964;
- *Power_Mixture_Correlation << 16 << 0.925;
- *Power_Mixture_Correlation << 17 << 0.880;
- *Power_Mixture_Correlation << 18 << 0.830;
- *Power_Mixture_Correlation << 19 << 0.785;
- *Power_Mixture_Correlation << 20 << 0.740;
- *Power_Mixture_Correlation << (14.7/0.6) << 0.58;
-
Mixture_Efficiency_Correlation = new FGTable(15);
*Mixture_Efficiency_Correlation << 0.05000 << 0.00000;
*Mixture_Efficiency_Correlation << 0.05137 << 0.00862;
*Mixture_Efficiency_Correlation << 0.12500 << 0.00000;
-/*
-Manifold_Pressure_Lookup = new
-
- 0 0.2 0.4 0.6 0.8 1
-0 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000
-1000 0.7778 0.8212 0.8647 0.9081 0.9516 0.9950
-2000 0.5556 0.6424 0.7293 0.8162 0.9031 0.9900
-3000 0.3333 0.4637 0.5940 0.7243 0.8547 0.9850
-4000 0.2000 0.2849 0.4587 0.6324 0.8062 0.9800
-5000 0.2000 0.2000 0.3233 0.5406 0.7578 0.9750
-6000 0.2000 0.2000 0.2000 0.4487 0.7093 0.9700
-7000 0.2000 0.2000 0.2000 0.2000 0.4570 0.7611
-8000 0.2000 0.2000 0.2000 0.2000 0.2047 0.5522
-*/
-
// Read inputs from engine data file where present.
if (el->FindElement("minmp")) // Should have ELSE statement telling default value used?
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"))
if (el->FindElement("minthrottle"))
MinThrottle = el->FindElementValueAsNumber("minthrottle");
if (el->FindElement("bsfc"))
- BSFC = el->FindElementValueAsNumber("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"))
RatedAltitude[2] = el->FindElementValueAsNumberConvertTo("ratedaltitude3", "FT");
}
- // Create a BSFC to match the engine if not provided
- // The 0.8 in the equation below is volumetric efficiency
- if (BSFC < 0) {
- BSFC = ( Displacement * MaxRPM * 0.8 ) / (9411 * MaxHP);
+ 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;
}
- char property_name[80];
- snprintf(property_name, 80, "propulsion/engine[%d]/power_hp", EngineNumber);
- PropertyManager->Tie(property_name, &HP);
- snprintf(property_name, 80, "propulsion/engine[%d]/bsfc", EngineNumber);
- PropertyManager->Tie(property_name, &BSFC);
-
minMAP = MinManifoldPressure_inHg * inhgtopa; // inHg to Pa
maxMAP = MaxManifoldPressure_inHg * inhgtopa;
- StarterHP = sqrt(MaxHP) * 0.4;
+
+// 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);
+ property_name = base_property_name + "/engine-rpm";
+ PropertyManager->Tie(property_name, this, &FGPiston::getRPM);
+ 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;
BoostSpeed = 0;
}
bBoostOverride = (BoostOverride == 1 ? true : false);
- if (MinThrottle < 0.001) MinThrottle = 0.001; //MinThrottle is a denominator in a power equation so it can't be zero
+ bBoostManual = (BoostManual == 1 ? true : false);
Debug(0); // Call Debug() routine from constructor if needed
}
FGPiston::~FGPiston()
{
delete Lookup_Combustion_Efficiency;
- delete Power_Mixture_Correlation;
delete Mixture_Efficiency_Correlation;
Debug(1); // Call Debug() routine from constructor if needed
}
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;
EGT_degC = ExhaustGasTemp_degK - 273;
Thruster->SetRPM(0.0);
RPM = 0.0;
+ OilPressure_psi = 0.0;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
-double FGPiston::Calculate(void)
+void FGPiston::Calculate(void)
{
+ RunPreFunctions();
+
if (FuelFlow_gph > 0.0) ConsumeFuel();
Throttle = FCS->GetThrottlePos(EngineNumber);
- ThrottlePos = MinThrottle+((MaxThrottle-MinThrottle)*Throttle );
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(HP<0.1250)
- Running = false;
+ if (IndicatedHorsePower < 0.1250) Running = false;
doEGT();
doCHT();
((FGPropeller*)Thruster)->SetFeather(FCS->GetPropFeather(EngineNumber));
}
- PowerAvailable = (HP * hptoftlbssec) - Thruster->GetPowerRequired();
+ Thruster->Calculate(HP * hptoftlbssec);
- return Thruster->Calculate(PowerAvailable);
+ RunPostFunctions();
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
double FGPiston::CalcFuelNeed(void)
{
- return FuelFlow_gph / 3600 * 6 * State->Getdt() * Propulsion->GetRate();
+ double dT = FDMExec->GetDeltaT() * Propulsion->GetRate();
+ FuelExpended = FuelFlowRate * dT;
+ return FuelExpended;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
int FGPiston::InitRunning(void) {
Magnetos=3;
- //Thruster->SetRPM( 1.1*IdleRPM/Thruster->GetGearRatio() );
- Thruster->SetRPM( 1000 );
+ 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;
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: minMAP, maxMAP, p_amb, Throttle
+ * Inputs: p_amb, Throttle,
+ * MeanPistonSpeed_fps, dt
*
- * Outputs: MAP, ManifoldPressure_inHg
+ * Outputs: MAP, ManifoldPressure_inHg, TMAP
*/
void FGPiston::doMAP(void)
{
- suction_loss = RPM > 0.0 ? ThrottlePos * MaxRPM / RPM : 1.0;
- if (suction_loss > 1.0) suction_loss = 1.0;
- MAP = p_amb * suction_loss;
-
- 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 += MAP * BoostMul[BoostSpeed] * suction_loss * RPM/RatedRPM[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 {
+ MAP = TMAP;
+ }
// And set the value in American units as well
ManifoldPressure_inHg = MAP / inhgtopa;
* (used in CHT calculation for air-cooled engines).
*
* Inputs: p_amb, R_air, T_amb, MAP, Displacement,
- * RPM, volumetric_efficiency, ThrottlePos
+ * RPM, volumetric_efficiency,
*
* TODO: Model inlet manifold air temperature.
*
void FGPiston::doAirFlow(void)
{
-
-rho_air = p_amb / (R_air * T_amb);
- double displacement_SI = Displacement * in3tom3;
+ 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 swept_volume = (displacement_SI * (RPM/60)) / 2;
- double v_dot_air = swept_volume * volumetric_efficiency * suction_loss;
+ 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; // Allows an AFR of infinity:1 to 11.3075:1
- equivalence_ratio = thi_sea_level; // * p_amb_sea_level / p_amb;
- double AFR = 10+(12*(1-Mixture));// mixture 10:1 to 22:1
- m_dot_fuel = m_dot_air / AFR;
- FuelFlow_gph = m_dot_fuel
- * 3600 // seconds to hours
- * 2.2046 // kg to lb
- / 6.0; // lb to gal_us of gasoline
-// / 6.6; // lb to gal_us of kerosene
+ 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,
- * Mixture_Efficiency_Correlation, Cycles, MaxHP
+ * Inputs: ManifoldPressure_inHg, p_amb, RPM, T_amb, ISFC,
+ * Mixture_Efficiency_Correlation, Cycles, MaxHP, PMEP,
+ * MeanPistonSpeed_fps
*
- * 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 ME, friction, percent_RPM, power; // Convienience term for use in the calculations
+ 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;
- friction = 1 - (percent_RPM * percent_RPM * percent_RPM * percent_RPM/10);
- if (friction < 0 ) friction = 0;
- power = friction;
+// 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;
- HP = (FuelFlow_gph * 6.0 / BSFC )* ME * suction_loss * power;
+ IndicatedHorsePower = (FuelFlow_pph / ISFC )* ME * power;
} else {
-
// Power output when the engine is not running
if (Cranking) {
if (RPM < 10) {
- HP = StarterHP;
+ IndicatedHorsePower = StarterHP;
} else if (RPM < IdleRPM*0.8) {
- HP = StarterHP + ((IdleRPM*0.8 - RPM) / 8.0);
+ 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;
}
}
- Percentage_Power = HP / MaxHP ;
+
+ // 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, Percentage_Power
+ * Cp_air, m_dot_air, Cp_fuel, m_dot_fuel, T_amb, PctPower
*
* Outputs: combustion_efficiency, ExhaustGasTemp_degK
*/
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;
+ 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;
- ExhaustGasTemp_degK *= 0.444 + ((0.544 - 0.444) * Percentage_Power);
} 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 = 0.023; // 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
*/
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-string FGPiston::GetEngineLabels(string delimeter)
+string FGPiston::GetEngineLabels(const string& delimiter)
{
std::ostringstream buf;
- buf << Name << " Power Available (engine " << EngineNumber << " in HP)" << delimeter
- << Name << " HP (engine " << EngineNumber << ")" << delimeter
- << Name << " equivalent ratio (engine " << EngineNumber << ")" << delimeter
- << Name << " MAP (engine " << EngineNumber << ")" << delimeter
- << Thruster->GetThrusterLabels(EngineNumber, delimeter);
+ 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(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 << (HP * hptoftlbssec) << 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;
Lookup_Combustion_Efficiency->Print();
cout << endl;
- cout << endl;
- cout << " Power Mixture Correlation table:" << endl;
- Power_Mixture_Correlation->Print();
- cout << endl;
-
cout << endl;
cout << " Mixture Efficiency Correlation table:" << endl;
Mixture_Efficiency_Correlation->Print();
projects / flightgear.git / blobdiff