JSBSim Flight Dynamics Model 1.2.2 (22 Mar 2025)
An Open Source Flight Dynamics and Control Software Library in C++
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Public Member Functions | List of all members
FGPiston Class Reference

Detailed Description

Models a Supercharged Piston engine.

Based on Dave Luff's model.

Configuration File Format:

<piston_engine name="{string}">
<minmp unit="{INHG | PA | ATM}"> {number} </minmp>
<maxmp unit="{INHG | PA | ATM}"> {number} </maxmp>
<idlerpm> {number} </idlerpm>
<maxrpm> {number} </maxrpm>
<maxhp unit="{HP | WATTS}"> {number} </maxhp>
<displacement unit="{IN3 | LTR | CC}"> {number} </displacement>
<cycles> {number} </cycles>
<bore unit="{IN | M}"> {number} </bore>
<stroke unit="{IN | M}"> {number} </stroke>
<cylinders> {number} </cylinders>
<compression-ratio> {number} </compression-ratio>
<sparkfaildrop> {number} </sparkfaildrop>
<static-friction unit="{HP | WATTS}"> {number} </static-friction>
<air-intake-impedance-factor> {number} </air-intake-impedance-factor>
<ram-air-factor> {number} </ram-air-factor>
<cooling-factor> {number} </cooling-factor>
<man-press-lag> {number} </man-press-lag>
<starter-torque> {number} </starter-torque>
<starter-rpm> {number} </starter-rpm>
<cylinder-head-mass unit="{KG | LBS}"> {number} </cylinder-head-mass>
<bsfc unit="{LBS/HP*HR | "KG/KW*HR"}"> {number} </bsfc>
<volumetric-efficiency> {number} </volumetric-efficiency>
<dynamic-fmep unit="{INHG | PA | ATM}"> {number} </dynamic-fmep>
<static-fmep unit="{INHG | PA | ATM}"> {number} </static-fmep>
<numboostspeeds> {number} </numboostspeeds>
<boostoverride> {0 | 1} </boostoverride>
<boostmanual> {0 | 1} </boostmanual>
<boost-loss-factor> {number} </boost-loss-factor>
<ratedboost1 unit="{INHG | PA | ATM}"> {number} </ratedboost1>
<ratedpower1 unit="{HP | WATTS}"> {number} </ratedpower1>
<ratedrpm1> {number} </ratedrpm1>
<ratedaltitude1 unit="{FT | M}"> {number} </ratedaltitude1>
<ratedboost2 unit="{INHG | PA | ATM}"> {number} </ratedboost2>
<ratedpower2 unit="{HP | WATTS}"> {number} </ratedpower2>
<ratedrpm2> {number} </ratedrpm2>
<ratedaltitude2 unit="{FT | M}"> {number} </ratedaltitude2>
<ratedboost3 unit="{INHG | PA | ATM}"> {number} </ratedboost3>
<ratedpower3 unit="{HP | WATTS}"> {number} </ratedpower3>
<ratedrpm3> {number} </ratedrpm3>
<ratedaltitude3 unit="{FT | M}"> {number} </ratedaltitude3>
<takeoffboost unit="{INHG | PA | ATM}"> {number} </takeoffboost>
<oil-pressure-relief-valve-psi> {number} </oil-pressure-relief-valve=psi>
<design-oil-temp-degK> {number} </design-oil-temp-degK>
<oil-pressure-rpm-max> {number} </oil-pressure-rpm-max>
<oil-viscosity-index> {number} </oil-viscosity-index>
</piston_engine>

Definition of the piston engine configuration file parameters:

Basic parameters:

  • minmp - this value is the nominal idle manifold pressure at sea-level without boost. Along with idlerpm, it determines throttle response slope.
  • maxmp - this value is the nominal maximum manifold pressure at sea-level without boost. Along with maxrpm it determines the resistance of the aircraft intake system. Overridden by air-intake-impedance-factor
  • man-press-lag - Delay in seconds for manifold pressure changes to take effect
  • starter-torque - A value specifing the zero RPM torque in lb*ft the starter motor provides. Current default value is 40% of the horse power value.
  • starter-rpm - A value specifing the maximum RPM the unloaded starter motor can achieve. Loads placed on the engine by the propeller and throttle will further limit RPM achieved in practice.
  • idlerpm - this value affects the throttle fall off and the engine stops running if it is slowed below 80% of this value. The engine starts running when it reaches 80% of this value.
  • maxrpm - this value is used to calculate air-box resistance and BSFC. It also affects oil pressure among other things.
  • maxhp - this value is the nominal power the engine creates at maxrpm. It will determine bsfc if that tag is not input. It also determines the starter motor power.
  • displacement - this value is used to determine mass air and fuel flow which impacts engine power and cooling.
  • cycles - Designate a 2 or 4 stroke engine. Currently only the 4 stroke engine is supported.
  • bore - cylinder bore is currently unused.
  • stroke - piston stroke is used to determine the mean piston speed. Longer strokes result in an engine that does not work as well at higher RPMs.
  • compression-ratio - the compression ratio affects the change in volumetric efficiency with altitude.
  • sparkfaildrop - this is the percentage drop in horsepower for single magneto operation.
  • static-friction - this value is the power required to turn an engine that is not running. Used to control and slow a windmilling propeller. Choose a small percentage of maxhp.

Advanced parameters

  • bsfc - Indicated Specific Fuel Consumption. The power produced per unit of fuel. Higher numbers give worse fuel economy. This number may need to be lowered slightly from actual BSFC numbers because some internal engine losses are modeled separately. Typically between 0.3 and 0.5
  • volumetric-efficiency - the nominal volumetric efficiency of the engine. This is the primary way to control fuel flow Boosted engines may require values above 1. Typical engines are 0.80 to 0.82
  • air-intake-impedance-factor - this number is the pressure drop across the intake system. Increasing it reduces available manifold pressure. Also a property for run-time adjustment.
  • ram-air-factor - this number creates increases manifold pressure with an increase in dynamic pressure (aircraft speed). Also a property for run-time adjustment.

Cooling control:

  • cylinders - number of cylinders scales the cylinder head mass.
  • cylinder-head-mass - the nominal mass of a cylinder head. A larger value slows changes in engine temperature
  • cooling-factor - this number models the efficiency of the aircraft cooling system. Also a property for run-time adjustment.

Supercharge parameters:

  • numboostspeed - zero (or not present) for a naturally-aspirated engine, either 1, 2 or 3 for a boosted engine. This corresponds to the number of supercharger speeds. Merlin XII had 1 speed, Merlin 61 had 2, a late Griffon engine apparently had 3. No known engine more than 3, although some German engines had continuously variable-speed superchargers.
  • boostoverride - whether or not to clip output to the wastegate value
  • boost-loss-factor - zero (or not present) for 'free' supercharging. A value entered will be used as a multiplier to the power required to compress the input air. Typical value should be 1.15 to 1.20.
  • boostmanual - whether a multispeed supercharger will manually or automatically shift boost speeds. On manual shifting the boost speeds is accomplished by controlling the property propulsion/engine/boostspeed.

  • takeoffboost - boost in psi above sea level ambient. Typically used for takeoff, and emergency situations, generally for not more than five minutes. This is a change in the boost control setting, not the actual supercharger speed, and so would only give extra power below the rated altitude. A typical takeoff boost for an early Merlin was about 12psi, compared with a rated boost of 9psi.

    When TAKEOFFBOOST is specified in the config file (and is above RATEDBOOST1), the throttle position is interpreted as:

    • 0 to 0.98 : idle manifold pressure to rated boost (where attainable)
    • 0.99, 1.0 : takeoff boost (where attainable).

The next items are all appended with either 1, 2 or 3 depending on which boostspeed they refer to:

  • ratedboost[123] - the absolute rated boost above sea level ambient (14.7 PSI, 29.92 inHg) for a given boost speed.
  • ratedpower[123] - unused
  • ratedrpm[123] - The rpm at which rated boost is developed

  • ratedaltitude[123] - The altitude up to which the rated boost can be maintained. Up to this altitude the boost is clipped to rated boost or takeoffboost. Beyond this altitude the manifold pressure must drop, since the supercharger is now at maximum unregulated output. The actual pressure multiplier of the supercharger system is calculated at initialization from this value.

    Author
    Jon S. Berndt (Engine framework code and framework-related mods)
    Dave Luff (engine operational code)
    David Megginson (initial porting and additional code)
    Ron Jensen (additional engine code)
    See also
    Taylor, Charles Fayette, "The Internal Combustion Engine in Theory and Practice"

Definition at line 223 of file FGPiston.h.

#include <FGPiston.h>

+ Inheritance diagram for FGPiston:
+ Collaboration diagram for FGPiston:

Public Member Functions

 FGPiston (FGFDMExec *exec, Element *el, int engine_number, struct Inputs &input)
 Constructor.
 
 ~FGPiston ()
 Destructor.
 
double CalcFuelNeed (void)
 The fuel need is calculated based on power levels and flow rate for that power level.
 
void Calculate (void)
 Calculates the thrust of the engine, and other engine functions.
 
double getAFR (void) const
 
double getCylinderHeadTemp_degF (void) const
 
double GetEGT (void) const
 
std::string GetEngineLabels (const std::string &delimiter)
 
std::string GetEngineValues (const std::string &delimiter)
 
double getExhaustGasTemp_degF (void) const
 
int GetMagnetos (void) const
 
double getManifoldPressure_inHg (void) const
 
double getOilPressure_psi (void) const
 
double getOilTemp_degF (void) const
 
double GetPowerAvailable (void) const
 
double getRPM (void) const
 
void ResetToIC (void)
 Resets the Engine parameters to the initial conditions.
 
void SetMagnetos (int magnetos)
 
- Public Member Functions inherited from FGEngine
 FGEngine (int engine_number, struct Inputs &input)
 
virtual double CalcOxidizerNeed (void)
 
virtual const FGColumnVector3 & GetBodyForces (void)
 
virtual bool GetCranking (void) const
 
virtual double getFuelFlow_gph () const
 
virtual double getFuelFlow_pph () const
 
virtual double GetFuelFlowRate (void) const
 
virtual double GetFuelFlowRateGPH (void) const
 
virtual double GetFuelUsedLbs (void) const
 
virtual const FGColumnVector3 & GetMoments (void)
 
virtual const std::string & GetName (void) const
 
size_t GetNumSourceTanks () const
 
virtual double GetPowerAvailable (void)
 
virtual bool GetRunning (void) const
 
unsigned int GetSourceTank (unsigned int i) const
 
virtual bool GetStarter (void) const
 
virtual bool GetStarved (void) const
 
virtual double GetThrottleMax (void) const
 
virtual double GetThrottleMin (void) const
 
virtual double GetThrust (void) const
 
FGThruster * GetThruster (void) const
 
EngineType GetType (void) const
 
void LoadThruster (FGFDMExec *exec, Element *el)
 
void LoadThrusterInputs ()
 
virtual void SetFuelDensity (double d)
 
virtual void SetFuelFreeze (bool f)
 
virtual void SetName (const std::string &name)
 
virtual void SetRunning (bool bb)
 
virtual void SetStarter (bool s)
 
virtual void SetStarved (bool tt)
 
virtual void SetStarved (void)
 
- Public Member Functions inherited from FGModelFunctions
std::string GetFunctionStrings (const std::string &delimeter) const
 Gets the strings for the current set of functions.
 
std::string GetFunctionValues (const std::string &delimeter) const
 Gets the function values.
 
std::shared_ptr< FGFunction > GetPreFunction (const std::string &name)
 Get one of the "pre" function.
 
bool Load (Element *el, FGFDMExec *fdmex, std::string prefix="")
 
void PostLoad (Element *el, FGFDMExec *fdmex, std::string prefix="")
 
void PreLoad (Element *el, FGFDMExec *fdmex, std::string prefix="")
 
void RunPostFunctions (void)
 
void RunPreFunctions (void)
 
- Public Member Functions inherited from FGJSBBase
 FGJSBBase ()
 Constructor for FGJSBBase.
 
virtual ~FGJSBBase ()
 Destructor for FGJSBBase.
 
void disableHighLighting (void)
 Disables highlighting in the console output.
 

Additional Inherited Members

- Public Types inherited from FGEngine
enum  EngineType {
  etUnknown , etRocket , etPiston , etTurbine ,
  etTurboprop , etElectric
}
 
- Public Types inherited from FGJSBBase
enum  { eL = 1 , eM , eN }
 Moments L, M, N. More...
 
enum  { eP = 1 , eQ , eR }
 Rates P, Q, R. More...
 
enum  { eU = 1 , eV , eW }
 Velocities U, V, W. More...
 
enum  { eX = 1 , eY , eZ }
 Positions X, Y, Z. More...
 
enum  { ePhi = 1 , eTht , ePsi }
 Euler angles Phi, Theta, Psi. More...
 
enum  { eDrag = 1 , eSide , eLift }
 Stability axis forces, Drag, Side force, Lift. More...
 
enum  { eRoll = 1 , ePitch , eYaw }
 Local frame orientation Roll, Pitch, Yaw. More...
 
enum  { eNorth = 1 , eEast , eDown }
 Local frame position North, East, Down. More...
 
enum  { eLat = 1 , eLong , eRad }
 Locations Radius, Latitude, Longitude. More...
 
enum  {
  inNone = 0 , inDegrees , inRadians , inMeters ,
  inFeet
}
 Conversion specifiers. More...
 
- Static Public Member Functions inherited from FGJSBBase
static const std::string & GetVersion (void)
 Returns the version number of JSBSim.
 
static constexpr double KelvinToFahrenheit (double kelvin)
 Converts from degrees Kelvin to degrees Fahrenheit.
 
static constexpr double CelsiusToRankine (double celsius)
 Converts from degrees Celsius to degrees Rankine.
 
static constexpr double RankineToCelsius (double rankine)
 Converts from degrees Rankine to degrees Celsius.
 
static constexpr double KelvinToRankine (double kelvin)
 Converts from degrees Kelvin to degrees Rankine.
 
static constexpr double RankineToKelvin (double rankine)
 Converts from degrees Rankine to degrees Kelvin.
 
static constexpr double FahrenheitToCelsius (double fahrenheit)
 Converts from degrees Fahrenheit to degrees Celsius.
 
static constexpr double CelsiusToFahrenheit (double celsius)
 Converts from degrees Celsius to degrees Fahrenheit.
 
static constexpr double CelsiusToKelvin (double celsius)
 Converts from degrees Celsius to degrees Kelvin.
 
static constexpr double KelvinToCelsius (double kelvin)
 Converts from degrees Kelvin to degrees Celsius.
 
static constexpr double FeetToMeters (double measure)
 Converts from feet to meters.
 
static bool EqualToRoundoff (double a, double b)
 Finite precision comparison.
 
static bool EqualToRoundoff (float a, float b)
 Finite precision comparison.
 
static bool EqualToRoundoff (float a, double b)
 Finite precision comparison.
 
static bool EqualToRoundoff (double a, float b)
 Finite precision comparison.
 
static constexpr double Constrain (double min, double value, double max)
 Constrain a value between a minimum and a maximum value.
 
static constexpr double sign (double num)
 
- Public Attributes inherited from FGEngine
struct Inputs & in
 
- Static Public Attributes inherited from FGJSBBase
static char highint [5] = {27, '[', '1', 'm', '\0' }
 highlights text
 
static char halfint [5] = {27, '[', '2', 'm', '\0' }
 low intensity text
 
static char normint [6] = {27, '[', '2', '2', 'm', '\0' }
 normal intensity text
 
static char reset [5] = {27, '[', '0', 'm', '\0' }
 resets text properties
 
static char underon [5] = {27, '[', '4', 'm', '\0' }
 underlines text
 
static char underoff [6] = {27, '[', '2', '4', 'm', '\0' }
 underline off
 
static char fgblue [6] = {27, '[', '3', '4', 'm', '\0' }
 blue text
 
static char fgcyan [6] = {27, '[', '3', '6', 'm', '\0' }
 cyan text
 
static char fgred [6] = {27, '[', '3', '1', 'm', '\0' }
 red text
 
static char fggreen [6] = {27, '[', '3', '2', 'm', '\0' }
 green text
 
static char fgdef [6] = {27, '[', '3', '9', 'm', '\0' }
 default text
 
static short debug_lvl = 1
 
- Protected Member Functions inherited from FGEngine
void Debug (int from)
 
bool Load (FGFDMExec *exec, Element *el)
 
- Protected Member Functions inherited from FGModelFunctions
virtual bool InitModel (void)
 
- Static Protected Member Functions inherited from FGJSBBase
static std::string CreateIndexedPropertyName (const std::string &Property, int index)
 
- Protected Attributes inherited from FGEngine
bool Cranking
 
const int EngineNumber
 
double FuelDensity
 
double FuelExpended
 
double FuelFlow_gph
 
double FuelFlow_pph
 
double FuelFlowRate
 
bool FuelFreeze
 
double FuelUsedLbs
 
double MaxThrottle
 
double MinThrottle
 
std::string Name
 
double PctPower
 
bool Running
 
double SLFuelFlowMax
 
std::vector< int > SourceTanks
 
bool Starter
 
bool Starved
 
FGThruster * Thruster
 
EngineType Type
 
- Protected Attributes inherited from FGModelFunctions
FGPropertyReader LocalProperties
 
std::vector< std::shared_ptr< FGFunction > > PostFunctions
 
std::vector< std::shared_ptr< FGFunction > > PreFunctions
 
- Static Protected Attributes inherited from FGJSBBase
static constexpr double radtodeg = 180. / M_PI
 
static constexpr double degtorad = M_PI / 180.
 
static constexpr double hptoftlbssec = 550.0
 
static constexpr double psftoinhg = 0.014138
 
static constexpr double psftopa = 47.88
 
static constexpr double fttom = 0.3048
 
static constexpr double ktstofps = 1852./(3600*fttom)
 
static constexpr double fpstokts = 1.0 / ktstofps
 
static constexpr double inchtoft = 1.0/12.0
 
static constexpr double m3toft3 = 1.0/(fttom*fttom*fttom)
 
static constexpr double in3tom3 = inchtoft*inchtoft*inchtoft/m3toft3
 
static constexpr double inhgtopa = 3386.38
 
static constexpr double slugtolb = 32.174049
 Note that definition of lbtoslug by the inverse of slugtolb and not to a different constant you can also get from some tables will make lbtoslug*slugtolb == 1 up to the magnitude of roundoff.
 
static constexpr double lbtoslug = 1.0/slugtolb
 
static constexpr double kgtolb = 2.20462
 
static constexpr double kgtoslug = 0.06852168
 
static const std::string needed_cfg_version = "2.0"
 
static const std::string JSBSim_version = JSBSIM_VERSION " " __DATE__ " " __TIME__
 

Constructor & Destructor Documentation

◆ FGPiston()

FGPiston ( FGFDMExec *  exec,
Element *  el,
int  engine_number,
struct Inputs &  input 
)

Constructor.

Definition at line 59 of file FGPiston.cpp.

60 : FGEngine(engine_number, input),
61 R_air(287.3), // Gas constant for air J/Kg/K
62 calorific_value_fuel(47.3e6), // J/Kg
63 Cp_air(1005), // Specific heat (constant pressure) J/Kg/K
64 Cp_fuel(1700),
65 standard_pressure(101320.73)
66{
67 Load(exec, el);
68
69 Element *table_element;
70 auto PropertyManager = exec->GetPropertyManager();
71
72 // Defaults and initializations
73
74 Type = etPiston;
75
76 // These items are read from the configuration file
77 // Defaults are from a Lycoming O-360, more or less
78
79 Cycles = 4;
80 IdleRPM = 600;
81 MaxRPM = 2800;
82 Displacement = 360;
83 SparkFailDrop = 1.0;
84 MaxHP = 200;
85 MinManifoldPressure_inHg = 6.5;
86 MaxManifoldPressure_inHg = 28.5;
87 ManifoldPressureLag=1.0;
88 ISFC = -1;
89 volumetric_efficiency = 0.85;
90 Bore = 5.125;
91 Stroke = 4.375;
92 Cylinders = 4;
93 CylinderHeadMass = 2; //kg
94 CompressionRatio = 8.5;
95 Z_airbox = -999;
96 Ram_Air_Factor = 1;
97 PeakMeanPistonSpeed_fps = 100;
98 FMEPDynamic= 18400;
99 FMEPStatic = 46500;
100 Cooling_Factor = 0.5144444;
101 StaticFriction_HP = 1.5;
102 StarterGain = 1.;
103 StarterTorque = -1.;
104 StarterRPM = -1.;
105
106 // These are internal program variables
107
108 Lookup_Combustion_Efficiency = 0;
109 Mixture_Efficiency_Correlation = 0;
110 crank_counter = 0;
111 Magnetos = 0;
112 minMAP = 21950;
113 maxMAP = 96250;
114
115 ResetToIC();
116
117 // Supercharging
118 BoostSpeeds = 0; // Default to no supercharging
119 BoostSpeed = 0;
120 Boosted = false;
121 BoostOverride = 0;
122 BoostManual = 0;
123 bBoostOverride = false;
124 bTakeoffBoost = false;
125 TakeoffBoost = 0.0; // Default to no extra takeoff-boost
126 BoostLossFactor = 0.0; // Default to free boost
127
128 int i;
129 for (i=0; i<FG_MAX_BOOST_SPEEDS; i++) {
130 RatedBoost[i] = 0.0;
131 RatedPower[i] = 0.0;
132 RatedAltitude[i] = 0.0;
133 BoostMul[i] = 1.0;
134 RatedMAP[i] = 100000;
135 RatedRPM[i] = 2500;
136 TakeoffMAP[i] = 100000;
137 }
138 for (i=0; i<FG_MAX_BOOST_SPEEDS-1; i++) {
139 BoostSwitchAltitude[i] = 0.0;
140 BoostSwitchPressure[i] = 0.0;
141 }
142
143 // Read inputs from engine data file where present.
144
145 if (el->FindElement("minmp"))
146 MinManifoldPressure_inHg = el->FindElementValueAsNumberConvertTo("minmp","INHG");
147 if (el->FindElement("maxmp"))
148 MaxManifoldPressure_inHg = el->FindElementValueAsNumberConvertTo("maxmp","INHG");
149 if (el->FindElement("man-press-lag"))
150 ManifoldPressureLag = el->FindElementValueAsNumber("man-press-lag");
151 if (el->FindElement("displacement"))
152 Displacement = el->FindElementValueAsNumberConvertTo("displacement","IN3");
153 if (el->FindElement("maxhp"))
154 MaxHP = el->FindElementValueAsNumberConvertTo("maxhp","HP");
155 if (el->FindElement("static-friction"))
156 StaticFriction_HP = el->FindElementValueAsNumberConvertTo("static-friction","HP");
157 if (el->FindElement("sparkfaildrop"))
158 SparkFailDrop = Constrain(0, 1 - el->FindElementValueAsNumber("sparkfaildrop"), 1);
159 if (el->FindElement("cycles"))
160 Cycles = el->FindElementValueAsNumber("cycles");
161 if (el->FindElement("idlerpm"))
162 IdleRPM = el->FindElementValueAsNumber("idlerpm");
163 if (el->FindElement("maxrpm"))
164 MaxRPM = el->FindElementValueAsNumber("maxrpm");
165 if (el->FindElement("maxthrottle"))
166 MaxThrottle = el->FindElementValueAsNumber("maxthrottle");
167 if (el->FindElement("minthrottle"))
168 MinThrottle = el->FindElementValueAsNumber("minthrottle");
169 if (el->FindElement("bsfc"))
170 ISFC = el->FindElementValueAsNumberConvertTo("bsfc", "LBS/HP*HR");
171 if (el->FindElement("volumetric-efficiency"))
172 volumetric_efficiency = el->FindElementValueAsNumber("volumetric-efficiency");
173 if (el->FindElement("compression-ratio"))
174 CompressionRatio = el->FindElementValueAsNumber("compression-ratio");
175 if (el->FindElement("bore"))
176 Bore = el->FindElementValueAsNumberConvertTo("bore","IN");
177 if (el->FindElement("stroke"))
178 Stroke = el->FindElementValueAsNumberConvertTo("stroke","IN");
179 if (el->FindElement("cylinders"))
180 Cylinders = el->FindElementValueAsNumber("cylinders");
181 if (el->FindElement("cylinder-head-mass"))
182 CylinderHeadMass = el->FindElementValueAsNumberConvertTo("cylinder-head-mass","KG");
183 if (el->FindElement("air-intake-impedance-factor"))
184 Z_airbox = el->FindElementValueAsNumber("air-intake-impedance-factor");
185 if (el->FindElement("ram-air-factor"))
186 Ram_Air_Factor = el->FindElementValueAsNumber("ram-air-factor");
187 if (el->FindElement("cooling-factor"))
188 Cooling_Factor = el->FindElementValueAsNumber("cooling-factor");
189 if (el->FindElement("starter-rpm"))
190 StarterRPM = el->FindElementValueAsNumber("starter-rpm");
191 if (el->FindElement("starter-torque"))
192 StarterTorque = el->FindElementValueAsNumber("starter-torque");
193 if (el->FindElement("dynamic-fmep"))
194 FMEPDynamic= el->FindElementValueAsNumberConvertTo("dynamic-fmep","PA");
195 if (el->FindElement("static-fmep"))
196 FMEPStatic = el->FindElementValueAsNumberConvertTo("static-fmep","PA");
197 if (el->FindElement("peak-piston-speed"))
198 PeakMeanPistonSpeed_fps = el->FindElementValueAsNumber("peak-piston-speed");
199 if (el->FindElement("numboostspeeds")) { // Turbo- and super-charging parameters
200 BoostSpeeds = (int)el->FindElementValueAsNumber("numboostspeeds");
201 if (el->FindElement("boostoverride"))
202 BoostOverride = (int)el->FindElementValueAsNumber("boostoverride");
203 if (el->FindElement("boostmanual"))
204 BoostManual = (int)el->FindElementValueAsNumber("boostmanual");
205 if (el->FindElement("takeoffboost"))
206 TakeoffBoost = el->FindElementValueAsNumberConvertTo("takeoffboost", "PSI");
207 if (el->FindElement("boost-loss-factor"))
208 BoostLossFactor = el->FindElementValueAsNumber("boost-loss-factor");
209 if (el->FindElement("ratedboost1"))
210 RatedBoost[0] = el->FindElementValueAsNumberConvertTo("ratedboost1", "PSI");
211 if (el->FindElement("ratedboost2"))
212 RatedBoost[1] = el->FindElementValueAsNumberConvertTo("ratedboost2", "PSI");
213 if (el->FindElement("ratedboost3"))
214 RatedBoost[2] = el->FindElementValueAsNumberConvertTo("ratedboost3", "PSI");
215 if (el->FindElement("ratedpower1"))
216 RatedPower[0] = el->FindElementValueAsNumberConvertTo("ratedpower1", "HP");
217 if (el->FindElement("ratedpower2"))
218 RatedPower[1] = el->FindElementValueAsNumberConvertTo("ratedpower2", "HP");
219 if (el->FindElement("ratedpower3"))
220 RatedPower[2] = el->FindElementValueAsNumberConvertTo("ratedpower3", "HP");
221 if (el->FindElement("ratedrpm1"))
222 RatedRPM[0] = el->FindElementValueAsNumber("ratedrpm1");
223 if (el->FindElement("ratedrpm2"))
224 RatedRPM[1] = el->FindElementValueAsNumber("ratedrpm2");
225 if (el->FindElement("ratedrpm3"))
226 RatedRPM[2] = el->FindElementValueAsNumber("ratedrpm3");
227 if (el->FindElement("ratedaltitude1"))
228 RatedAltitude[0] = el->FindElementValueAsNumberConvertTo("ratedaltitude1", "FT");
229 if (el->FindElement("ratedaltitude2"))
230 RatedAltitude[1] = el->FindElementValueAsNumberConvertTo("ratedaltitude2", "FT");
231 if (el->FindElement("ratedaltitude3"))
232 RatedAltitude[2] = el->FindElementValueAsNumberConvertTo("ratedaltitude3", "FT");
233 }
234
235 Design_Oil_Temp = 358; // degK;
236 Oil_Viscosity_Index = 0.25;
237 Oil_Press_Relief_Valve = 60; // psi
238 Oil_Press_RPM_Max = MaxRPM*0.75;
239 if (el->FindElement("oil-pressure-relief-valve-psi"))
240 Oil_Press_Relief_Valve = el->FindElementValueAsNumberConvertTo("oil-pressure-relief-valve-psi", "PSI");
241 if (el->FindElement("design-oil-temp-degK"))
242 Design_Oil_Temp = el->FindElementValueAsNumberConvertTo("design-oil-temp-degK", "DEGK");
243 if (el->FindElement("oil-pressure-rpm-max"))
244 Oil_Press_RPM_Max = el->FindElementValueAsNumber("oil-pressure-rpm-max");
245 if (el->FindElement("oil-viscosity-index"))
246 Oil_Viscosity_Index = el->FindElementValueAsNumber("oil-viscosity-index");
247
248 while((table_element = el->FindNextElement("table")) != 0) {
249 string name = table_element->GetAttributeValue("name");
250 try {
251 if (name == "COMBUSTION") {
252 Lookup_Combustion_Efficiency = new FGTable(PropertyManager, table_element);
253 } else if (name == "MIXTURE") {
254 Mixture_Efficiency_Correlation = new FGTable(PropertyManager, table_element);
255 } else {
256 cerr << "Unknown table type: " << name << " in piston engine definition." << endl;
257 }
258 } catch (std::string& str) {
259 // Make sure allocated resources are freed before rethrowing.
260 // (C++ standard guarantees that a null pointer deletion is no-op).
261 delete Lookup_Combustion_Efficiency;
262 delete Mixture_Efficiency_Correlation;
263 throw("Error loading piston engine table:" + name + ". " + str);
264 }
265 }
266
267
268 volumetric_efficiency_reduced = volumetric_efficiency;
269
270 if(StarterRPM < 0.) StarterRPM = 2*IdleRPM;
271 if(StarterTorque < 0)
272 StarterTorque = (MaxHP)*0.4; //just a wag.
273
274 displacement_SI = Displacement * in3tom3;
275 RatedMeanPistonSpeed_fps = ( MaxRPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
276
277 // Create IFSC to match the engine if not provided
278 if (ISFC < 0) {
279 double pmep = 29.92 - MaxManifoldPressure_inHg;
280 pmep *= inhgtopa * volumetric_efficiency;
281 double fmep = (FMEPDynamic * RatedMeanPistonSpeed_fps * fttom + FMEPStatic);
282 double hp_loss = ((pmep + fmep) * displacement_SI * MaxRPM)/(Cycles*22371);
283 ISFC = ( 1.1*Displacement * MaxRPM * volumetric_efficiency *(MaxManifoldPressure_inHg / 29.92) ) / (9411 * (MaxHP+hp_loss-StaticFriction_HP));
284// cout <<"FMEP: "<< fmep <<" PMEP: "<< pmep << " hp_loss: " <<hp_loss <<endl;
285 }
286 if ( MaxManifoldPressure_inHg > 29.9 ) { // Don't allow boosting with a bogus number
287 MaxManifoldPressure_inHg = 29.9;
288 }
289 minMAP = MinManifoldPressure_inHg * inhgtopa; // inHg to Pa
290 maxMAP = MaxManifoldPressure_inHg * inhgtopa;
291
292// For throttle
293/*
294 * Pm = ( Ze / ( Ze + Zi + Zt ) ) * Pa
295 * Where:
296 * Pm = Manifold Pressure
297 * Pa = Ambient Pressre
298 * Ze = engine impedance, Ze is effectively 1 / Mean Piston Speed
299 * Zi = airbox impedance
300 * Zt = throttle impedance
301 *
302 * For the calculation below throttle is fully open or Zt = 0
303 *
304 *
305 *
306 */
307 if(Z_airbox < 0.0){
308 double Ze=PeakMeanPistonSpeed_fps/RatedMeanPistonSpeed_fps; // engine impedence
309 Z_airbox = (standard_pressure *Ze / maxMAP) - Ze; // impedence of airbox
310 }
311 // Constant for Throttle impedence
312 Z_throttle=(PeakMeanPistonSpeed_fps/((IdleRPM * Stroke) / 360))*(standard_pressure/minMAP - 1) - Z_airbox;
313 // Z_throttle=(MaxRPM/IdleRPM )*(standard_pressure/minMAP+2); // Constant for Throttle impedence
314
315// Default tables if not provided in the configuration file
316 if(Lookup_Combustion_Efficiency == 0) {
317 // First column is thi, second is neta (combustion efficiency)
318 Lookup_Combustion_Efficiency = new FGTable(12);
319 *Lookup_Combustion_Efficiency << 0.00 << 0.980;
320 *Lookup_Combustion_Efficiency << 0.90 << 0.980;
321 *Lookup_Combustion_Efficiency << 1.00 << 0.970;
322 *Lookup_Combustion_Efficiency << 1.05 << 0.950;
323 *Lookup_Combustion_Efficiency << 1.10 << 0.900;
324 *Lookup_Combustion_Efficiency << 1.15 << 0.850;
325 *Lookup_Combustion_Efficiency << 1.20 << 0.790;
326 *Lookup_Combustion_Efficiency << 1.30 << 0.700;
327 *Lookup_Combustion_Efficiency << 1.40 << 0.630;
328 *Lookup_Combustion_Efficiency << 1.50 << 0.570;
329 *Lookup_Combustion_Efficiency << 1.60 << 0.525;
330 *Lookup_Combustion_Efficiency << 2.00 << 0.345;
331 }
332
333 // First column is Fuel/Air Ratio, second is neta (mixture efficiency)
334 if( Mixture_Efficiency_Correlation == 0) {
335 Mixture_Efficiency_Correlation = new FGTable(15);
336 *Mixture_Efficiency_Correlation << 0.05000 << 0.00000;
337 *Mixture_Efficiency_Correlation << 0.05137 << 0.00862;
338 *Mixture_Efficiency_Correlation << 0.05179 << 0.21552;
339 *Mixture_Efficiency_Correlation << 0.05430 << 0.48276;
340 *Mixture_Efficiency_Correlation << 0.05842 << 0.70690;
341 *Mixture_Efficiency_Correlation << 0.06312 << 0.83621;
342 *Mixture_Efficiency_Correlation << 0.06942 << 0.93103;
343 *Mixture_Efficiency_Correlation << 0.07786 << 1.00000;
344 *Mixture_Efficiency_Correlation << 0.08845 << 1.00000;
345 *Mixture_Efficiency_Correlation << 0.09270 << 0.98276;
346 *Mixture_Efficiency_Correlation << 0.10120 << 0.93103;
347 *Mixture_Efficiency_Correlation << 0.11455 << 0.72414;
348 *Mixture_Efficiency_Correlation << 0.12158 << 0.45690;
349 *Mixture_Efficiency_Correlation << 0.12435 << 0.23276;
350 *Mixture_Efficiency_Correlation << 0.12500 << 0.00000;
351 }
352
353 string property_name, base_property_name;
354 base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNumber);
355 property_name = base_property_name + "/power-hp";
356 PropertyManager->Tie(property_name, &HP);
357 property_name = base_property_name + "/friction-hp";
358 PropertyManager->Tie(property_name, &StaticFriction_HP);
359 property_name = base_property_name + "/bsfc-lbs_hphr";
360 PropertyManager->Tie(property_name, &ISFC);
361 property_name = base_property_name + "/starter-norm";
362 PropertyManager->Tie(property_name, &StarterGain);
363 property_name = base_property_name + "/volumetric-efficiency";
364 PropertyManager->Tie(property_name, &volumetric_efficiency);
365 property_name = base_property_name + "/map-pa";
366 PropertyManager->Tie(property_name, &MAP);
367 property_name = base_property_name + "/map-inhg";
368 PropertyManager->Tie(property_name, &ManifoldPressure_inHg);
369 property_name = base_property_name + "/air-intake-impedance-factor";
370 PropertyManager->Tie(property_name, &Z_airbox);
371 property_name = base_property_name + "/ram-air-factor";
372 PropertyManager->Tie(property_name, &Ram_Air_Factor);
373 property_name = base_property_name + "/cooling-factor";
374 PropertyManager->Tie(property_name, &Cooling_Factor);
375 property_name = base_property_name + "/boost-speed";
376 PropertyManager->Tie(property_name, &BoostSpeed);
377 property_name = base_property_name + "/cht-degF";
378 PropertyManager->Tie(property_name, this, &FGPiston::getCylinderHeadTemp_degF);
379 property_name = base_property_name + "/oil-temperature-degF";
380 PropertyManager->Tie(property_name, this, &FGPiston::getOilTemp_degF);
381 property_name = base_property_name + "/oil-pressure-psi";
382 PropertyManager->Tie(property_name, this, &FGPiston::getOilPressure_psi);
383 property_name = base_property_name + "/egt-degF";
384 PropertyManager->Tie(property_name, this, &FGPiston::getExhaustGasTemp_degF);
385 if(BoostLossFactor > 0.0) {
386 property_name = base_property_name + "/boostloss-factor";
387 PropertyManager->Tie(property_name, &BoostLossFactor);
388 property_name = base_property_name + "/boostloss-hp";
389 PropertyManager->Tie(property_name, &BoostLossHP);
390 }
391 property_name = base_property_name + "/AFR";
392 PropertyManager->Tie(property_name, this, &FGPiston::getAFR);
393
394 // Set up and sanity-check the turbo/supercharging configuration based on the input values.
395 if (TakeoffBoost > RatedBoost[0]) bTakeoffBoost = true;
396 for (i=0; i<BoostSpeeds; ++i) {
397 bool bad = false;
398 if (RatedBoost[i] <= 0.0) bad = true;
399 if (RatedPower[i] <= 0.0) bad = true;
400 if (RatedAltitude[i] < 0.0) bad = true; // 0.0 is deliberately allowed - this corresponds to unregulated supercharging.
401 if (i > 0 && RatedAltitude[i] < RatedAltitude[i - 1]) bad = true;
402 if (bad) {
403 // We can't recover from the above - don't use this supercharger speed.
404 BoostSpeeds--;
405 // TODO - put out a massive error message!
406 break;
407 }
408 // Now sanity-check stuff that is recoverable.
409 if (i < BoostSpeeds - 1) {
410 if (BoostSwitchAltitude[i] < RatedAltitude[i]) {
411 // TODO - put out an error message
412 // But we can also make a reasonable estimate, as below.
413 BoostSwitchAltitude[i] = RatedAltitude[i] + 1000;
414 }
415 BoostSwitchPressure[i] = GetStdPressure100K(BoostSwitchAltitude[i]) * psftopa;
416 //cout << "BoostSwitchAlt = " << BoostSwitchAltitude[i] << ", pressure = " << BoostSwitchPressure[i] << '\n';
417 // Assume there is some hysteresis on the supercharger gear switch, and guess the value for now
418 BoostSwitchHysteresis = 1000;
419 }
420 // Now work out the supercharger pressure multiplier of this speed from the rated boost and altitude.
421 RatedMAP[i] = standard_pressure + RatedBoost[i] * 6895; // psi*6895 = Pa.
422 // Sometimes a separate BCV setting for takeoff or extra power is fitted.
423 if (TakeoffBoost > RatedBoost[0]) {
424 // Assume that the effect on the BCV is the same whichever speed is in use.
425 TakeoffMAP[i] = RatedMAP[i] + ((TakeoffBoost - RatedBoost[0]) * 6895);
426 bTakeoffBoost = true;
427 } else {
428 TakeoffMAP[i] = RatedMAP[i];
429 bTakeoffBoost = false;
430 }
431 BoostMul[i] = RatedMAP[i] / (GetStdPressure100K(RatedAltitude[i]) * psftopa);
432
433 }
434
435 if (BoostSpeeds > 0) {
436 Boosted = true;
437 BoostSpeed = 0;
438 }
439 bBoostOverride = (BoostOverride == 1 ? true : false);
440 bBoostManual = (BoostManual == 1 ? true : false);
441 Debug(0); // Call Debug() routine from constructor if needed
442}
JSBSim::FGJSBBase::Constrain
static constexpr double Constrain(double min, double value, double max)
Constrain a value between a minimum and a maximum value.
Definition FGJSBBase.h:288
JSBSim::FGPiston::ResetToIC
void ResetToIC(void)
Resets the Engine parameters to the initial conditions.
Definition FGPiston.cpp:455
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◆ ~FGPiston()

~FGPiston ( )

Destructor.

Definition at line 446 of file FGPiston.cpp.

447{
448 delete Lookup_Combustion_Efficiency;
449 delete Mixture_Efficiency_Correlation;
450 Debug(1); // Call Debug() routine from constructor if needed
451}

Member Function Documentation

◆ CalcFuelNeed()

double CalcFuelNeed ( void  )
virtual

The fuel need is calculated based on power levels and flow rate for that power level.

It is also turned from a rate into an actual amount (pounds) by multiplying it by the delta T and the rate.

Returns
Total fuel requirement for this engine in pounds.

Reimplemented from FGEngine.

Definition at line 531 of file FGPiston.cpp.

532{
533 FuelExpended = FuelFlowRate * in.TotalDeltaT;
534 if (!Starved) FuelUsedLbs += FuelExpended;
535 return FuelExpended;
536}

◆ Calculate()

void Calculate ( void  )
virtual

Calculates the thrust of the engine, and other engine functions.

Implements FGEngine.

Definition at line 475 of file FGPiston.cpp.

476{
477 // Input values.
478
479 p_amb = in.Pressure * psftopa;
480 double p = in.TotalPressure * psftopa;
481 p_ram = (p - p_amb) * Ram_Air_Factor + p_amb;
482 T_amb = RankineToKelvin(in.Temperature);
483
484 RunPreFunctions();
485
486/* The thruster controls the engine RPM because it encapsulates the gear ratio and other transmission variables */
487 RPM = Thruster->GetEngineRPM();
488
489 MeanPistonSpeed_fps = ( RPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
490
491 IAS = in.Vc;
492
493 doEngineStartup();
494 if (Boosted) doBoostControl();
495 doMAP();
496 doAirFlow();
497 doFuelFlow();
498
499 //Now that the fuel flow is done check if the mixture is too lean to run the engine
500 //Assume lean limit at 22 AFR for now - thats a thi of 0.668
501 //This might be a bit generous, but since there's currently no audiable warning of impending
502 //cutout in the form of misfiring and/or rough running its probably reasonable for now.
503
504 // if (equivalence_ratio < 0.668)
505 // Running = false;
506
507 doEnginePower();
508 if (IndicatedHorsePower < 0.1250) Running = false;
509
510 doEGT();
511 doCHT();
512 doOilTemperature();
513 doOilPressure();
514
515 if (Thruster->GetType() == FGThruster::ttPropeller) {
516 ((FGPropeller*)Thruster)->SetAdvance(in.PropAdvance[EngineNumber]);
517 ((FGPropeller*)Thruster)->SetFeather(in.PropFeather[EngineNumber]);
518 }
519
520 LoadThrusterInputs();
521 // Filters out negative powers when the propeller is not rotating.
522 double power = HP * hptoftlbssec;
523 if (RPM <= 0.1) power = max(power, 0.0);
524 Thruster->Calculate(power);
525
526 RunPostFunctions();
527}
JSBSim::FGJSBBase::RankineToKelvin
static constexpr double RankineToKelvin(double rankine)
Converts from degrees Rankine to degrees Kelvin.
Definition FGJSBBase.h:213
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◆ getAFR()

double getAFR ( void  ) const
inline

Definition at line 250 of file FGPiston.h.

250{return m_dot_fuel > 0.0 ? m_dot_air / m_dot_fuel : INFINITY;}

◆ getCylinderHeadTemp_degF()

double getCylinderHeadTemp_degF ( void  ) const
inline

Definition at line 246 of file FGPiston.h.

246{return KelvinToFahrenheit(CylinderHeadTemp_degK);}
JSBSim::FGJSBBase::KelvinToFahrenheit
static constexpr double KelvinToFahrenheit(double kelvin)
Converts from degrees Kelvin to degrees Fahrenheit.
Definition FGJSBBase.h:185

◆ GetEGT()

double GetEGT ( void  ) const
inline

Definition at line 241 of file FGPiston.h.

241{ return EGT_degC; }

◆ GetEngineLabels()

string GetEngineLabels ( const std::string &  delimiter)
virtual

Implements FGEngine.

Definition at line 972 of file FGPiston.cpp.

973{
974 std::ostringstream buf;
975
976 buf << Name << " Power Available (engine " << EngineNumber << " in ft-lbs/sec)" << delimiter
977 << Name << " HP (engine " << EngineNumber << ")" << delimiter
978 << Name << " equivalent ratio (engine " << EngineNumber << ")" << delimiter
979 << Name << " MAP (engine " << EngineNumber << " in inHg)" << delimiter
980 << Thruster->GetThrusterLabels(EngineNumber, delimiter);
981
982 return buf.str();
983}

◆ GetEngineValues()

string GetEngineValues ( const std::string &  delimiter)
virtual

Implements FGEngine.

Definition at line 987 of file FGPiston.cpp.

988{
989 std::ostringstream buf;
990
991 buf << (HP * hptoftlbssec) << delimiter << HP << delimiter
992 << equivalence_ratio << delimiter << ManifoldPressure_inHg << delimiter
993 << Thruster->GetThrusterValues(EngineNumber, delimiter);
994
995 return buf.str();
996}

◆ getExhaustGasTemp_degF()

double getExhaustGasTemp_degF ( void  ) const
inline

Definition at line 244 of file FGPiston.h.

244{return KelvinToFahrenheit(ExhaustGasTemp_degK);}

◆ GetMagnetos()

int GetMagnetos ( void  ) const
inline

Definition at line 242 of file FGPiston.h.

242{return Magnetos;}

◆ getManifoldPressure_inHg()

double getManifoldPressure_inHg ( void  ) const
inline

Definition at line 245 of file FGPiston.h.

245{return ManifoldPressure_inHg;}

◆ getOilPressure_psi()

double getOilPressure_psi ( void  ) const
inline

Definition at line 247 of file FGPiston.h.

247{return OilPressure_psi;}

◆ getOilTemp_degF()

double getOilTemp_degF ( void  ) const
inline

Definition at line 248 of file FGPiston.h.

248{return KelvinToFahrenheit(OilTemp_degK);}

◆ GetPowerAvailable()

double GetPowerAvailable ( void  ) const
inline

Definition at line 235 of file FGPiston.h.

235{return (HP * hptoftlbssec);}

◆ getRPM()

double getRPM ( void  ) const
inline

Definition at line 249 of file FGPiston.h.

249{return RPM;}

◆ ResetToIC()

void ResetToIC ( void  )
virtual

Resets the Engine parameters to the initial conditions.

Reimplemented from FGEngine.

Definition at line 455 of file FGPiston.cpp.

456{
457 FGEngine::ResetToIC();
458
459 ManifoldPressure_inHg = in.Pressure * psftoinhg; // psf to in Hg
460 MAP = in.Pressure * psftopa;
461 TMAP = MAP;
462 double airTemperature_degK = RankineToKelvin(in.Temperature);
463 OilTemp_degK = airTemperature_degK;
464 CylinderHeadTemp_degK = airTemperature_degK;
465 ExhaustGasTemp_degK = airTemperature_degK;
466 EGT_degC = ExhaustGasTemp_degK - 273;
467 Thruster->SetRPM(0.0);
468 RPM = 0.0;
469 OilPressure_psi = 0.0;
470 BoostLossHP = 0.;
471}
JSBSim::FGEngine::ResetToIC
virtual void ResetToIC(void)
Resets the Engine parameters to the initial conditions.
Definition FGEngine.cpp:77
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◆ SetMagnetos()

void SetMagnetos ( int  magnetos)
inline

Definition at line 239 of file FGPiston.h.

239{Magnetos = magnetos;}
The documentation for this class was generated from the following files: