JSBSim Flight Dynamics Model  1.2.0 (05 Nov 2023)
An Open Source Flight Dynamics and Control Software Library in C++
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. More...
 
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. More...
 
std::string GetFunctionValues (const std::string &delimeter) const
 Gets the function values. More...
 
std::shared_ptr< FGFunction > GetPreFunction (const std::string &name)
 Get one of the "pre" function. More...
 
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.
 
enum  { eP = 1 , eQ , eR }
 Rates P, Q, R.
 
enum  { eU = 1 , eV , eW }
 Velocities U, V, W.
 
enum  { eX = 1 , eY , eZ }
 Positions X, Y, Z.
 
enum  { ePhi = 1 , eTht , ePsi }
 Euler angles Phi, Theta, Psi.
 
enum  { eDrag = 1 , eSide , eLift }
 Stability axis forces, Drag, Side force, Lift.
 
enum  { eRoll = 1 , ePitch , eYaw }
 Local frame orientation Roll, Pitch, Yaw.
 
enum  { eNorth = 1 , eEast , eDown }
 Local frame position North, East, Down.
 
enum  { eLat = 1 , eLong , eRad }
 Locations Radius, Latitude, Longitude.
 
enum  {
  inNone = 0 , inDegrees , inRadians , inMeters ,
  inFeet
}
 Conversion specifiers.
 
- Static Public Member Functions inherited from FGJSBBase
static const std::string & GetVersion (void)
 Returns the version number of JSBSim. More...
 
static constexpr double KelvinToFahrenheit (double kelvin)
 Converts from degrees Kelvin to degrees Fahrenheit. More...
 
static constexpr double CelsiusToRankine (double celsius)
 Converts from degrees Celsius to degrees Rankine. More...
 
static constexpr double RankineToCelsius (double rankine)
 Converts from degrees Rankine to degrees Celsius. More...
 
static constexpr double KelvinToRankine (double kelvin)
 Converts from degrees Kelvin to degrees Rankine. More...
 
static constexpr double RankineToKelvin (double rankine)
 Converts from degrees Rankine to degrees Kelvin. More...
 
static constexpr double FahrenheitToCelsius (double fahrenheit)
 Converts from degrees Fahrenheit to degrees Celsius. More...
 
static constexpr double CelsiusToFahrenheit (double celsius)
 Converts from degrees Celsius to degrees Fahrenheit. More...
 
static constexpr double CelsiusToKelvin (double celsius)
 Converts from degrees Celsius to degrees Kelvin. More...
 
static constexpr double KelvinToCelsius (double kelvin)
 Converts from degrees Kelvin to degrees Celsius. More...
 
static constexpr double FeetToMeters (double measure)
 Converts from feet to meters. More...
 
static bool EqualToRoundoff (double a, double b)
 Finite precision comparison. More...
 
static bool EqualToRoundoff (float a, float b)
 Finite precision comparison. More...
 
static bool EqualToRoundoff (float a, double b)
 Finite precision comparison. More...
 
static bool EqualToRoundoff (double a, float b)
 Finite precision comparison. More...
 
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. More...
 
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__
 

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 }
The documentation for this class was generated from the following files: