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 1.55 2011/03/10 01:35:25 dpculp 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 = State->Getdt();
+ dt = FDMExec->GetDeltaT();
// These items are read from the configuration file
// Defaults are from a Lycoming O-360, more or less
MinManifoldPressure_inHg = 6.5;
MaxManifoldPressure_inHg = 28.5;
ISFC = -1;
- volumetric_efficiency = -0.1;
+ 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
BoostSpeed = 0;
Boosted = false;
BoostOverride = 0;
+ BoostManual = 0;
bBoostOverride = false;
bTakeoffBoost = false;
TakeoffBoost = 0.0; // Default to no extra takeoff-boost
Bore = el->FindElementValueAsNumberConvertTo("bore","IN");
if (el->FindElement("stroke"))
Stroke = el->FindElementValueAsNumberConvertTo("stroke","IN");
- if (el->FindElement("stroke"))
+ 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"))
StarterHP = sqrt(MaxHP) * 0.4;
displacement_SI = Displacement * in3tom3;
+ RatedMeanPistonSpeed_fps = ( MaxRPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
- // Create IFSC and VE to match the engine if not provided
- int calculated_ve=0;
- if (volumetric_efficiency < 0) {
- volumetric_efficiency = MaxManifoldPressure_inHg / 29.92;
- calculated_ve=1;
- }
+ // Create IFSC to match the engine if not provided
if (ISFC < 0) {
- double pmep = MaxManifoldPressure_inHg > 29.92 ? 0 : 29.92 - MaxManifoldPressure_inHg;
- pmep *= inhgtopa;
- double fmep = (18400 * (2*(Stroke/12)*(MaxRPM/60)) * fttom + 46500)/2;
+ 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 = ( Displacement * MaxRPM * volumetric_efficiency ) / (9411 * (MaxHP+hp_loss));
+ 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;
- if (calculated_ve) volumetric_efficiency = 1.0;
}
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, &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
}
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
-double FGPiston::Calculate(void)
+void FGPiston::Calculate(void)
{
+ RunPreFunctions();
+
if (FuelFlow_gph > 0.0) ConsumeFuel();
Throttle = FCS->GetThrottlePos(EngineNumber);
- // calculate the throttle plate angle. 1 unit is approx pi/2 radians.
- ThrottleAngle = MinThrottle+((MaxThrottle-MinThrottle)*Throttle );
Mixture = FCS->GetMixturePos(EngineNumber);
- //
// Input values.
- //
p_amb = Atmosphere->GetPressure() * 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();
//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;
((FGPropeller*)Thruster)->SetFeather(FCS->GetPropFeather(EngineNumber));
}
- PowerAvailable = (HP * hptoftlbssec) - Thruster->GetPowerRequired();
+ Thruster->Calculate(HP * hptoftlbssec);
- return Thruster->Calculate(PowerAvailable);
+ RunPostFunctions();
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
double FGPiston::CalcFuelNeed(void)
{
- double dT = 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.
*
- * Inputs: p_amb, Throttle, ThrottleAngle,
+ * Inputs: p_amb, Throttle,
* MeanPistonSpeed_fps, dt
*
* Outputs: MAP, ManifoldPressure_inHg, TMAP
void FGPiston::doMAP(void)
{
- // estimate throttle plate area.
- double throttle_area = ThrottleAngle*ThrottleAngle;
- // Internal Combustion Engine in Theory and Practice, Volume 2. Charles Fayette Taylor. Revised Edition, 1985 fig 6-13
- double map_coefficient = 1-((MeanPistonSpeed_fps*MeanPistonSpeed_fps)/(24978*throttle_area));
+ double Zt = (1-Throttle)*(1-Throttle)*Z_throttle; // throttle impedence
+ double Ze= MeanPistonSpeed_fps > 0 ? PeakMeanPistonSpeed_fps/MeanPistonSpeed_fps : 999999; // engine impedence
- if ( map_coefficient < 0.1 ) map_coefficient = 0.1;
+ double map_coefficient = Ze/(Ze+Z_airbox+Zt);
// Add a one second lag to manifold pressure changes
- double dMAP = (TMAP - p_amb * map_coefficient) * dt;
+ 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; // Fixme: p_amb should be exhaust manifold pressure
+ 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:
}
}
// Boost the manifold pressure.
- double boost_factor = BoostMul[BoostSpeed] * map_coefficient * RPM/RatedRPM[BoostSpeed];
- if (boost_factor < 1.0) boost_factor = 1.0; // boost will never reduce the MAP
+ 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) {
* (used in CHT calculation for air-cooled engines).
*
* Inputs: p_amb, R_air, T_amb, MAP, Displacement,
- * RPM, volumetric_efficiency, ThrottleAngle
+ * RPM, volumetric_efficiency,
*
* TODO: Model inlet manifold air temperature.
*
void FGPiston::doAirFlow(void)
{
- double gamma = 1.4; // specific heat constants
+ double gamma = 1.3; // specific heat constants
// loss of volumentric efficiency due to difference between MAP and exhaust pressure
- double ve =((gamma-1)/gamma)+( CompressionRatio -(p_amb/MAP))/(gamma*( CompressionRatio - 1));
-
+// 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 *ve;
/**
* 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,
+ * Inputs: ManifoldPressure_inHg, p_amb, RPM, T_amb, ISFC,
* Mixture_Efficiency_Correlation, Cycles, MaxHP, PMEP,
+ * MeanPistonSpeed_fps
*
- * Outputs: PctPower, HP
+ * Outputs: PctPower, HP, FMEP, IndicatedHorsePower
*/
void FGPiston::doEnginePower(void)
ME = Mixture_Efficiency_Correlation->GetValue(m_dot_fuel/m_dot_air);
percent_RPM = RPM/MaxRPM;
-// Guestimate engine friction as a percentage of rated HP + a percentage of rpm + a percentage of Indicted HP
-// friction = 1 - (percent_RPM * percent_RPM * percent_RPM/10);
- FMEP = (-18400 * MeanPistonSpeed_fps * fttom - 46500);
+// Guestimate engine friction losses from Figure 4.4 of "Engines: An Introduction", John Lumley
+ FMEP = (-FMEPDynamic * MeanPistonSpeed_fps * fttom - FMEPStatic);
power = 1;
* Calculate the cylinder head temperature.
*
* Inputs: T_amb, IAS, rho_air, m_dot_fuel, calorific_value_fuel,
- * combustion_efficiency, RPM, MaxRPM
+ * combustion_efficiency, RPM, MaxRPM, Displacement, Cylinders
*
* Outputs: CylinderHeadTemp_degK
*/
double h2 = -3.95;
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 / MaxRPM);
- double dqdt_free = h1 * temperature_difference;
+ double dqdt_free = h1 * temperature_difference * arbitary_area;
double dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;
double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
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.
+ // 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
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-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 << " 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 << " Volumentric Efficiency: " << volumetric_efficiency << 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;
projects / flightgear.git / blobdiff