Models a Supercharged Piston engine. More...

#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. More...

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	SetPlacement (const FGColumnVector3 &location, const FGColumnVector3 &orientation)
	Sets engine placement information.

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...

FGFunction *	GetPreFunction (const std::string &name)
	Get one of the "pre" function. More...

bool	Load (Element el, FGPropertyManager PropertyManager, std::string prefix="")

void	PostLoad (Element el, FGPropertyManager PropertyManager, std::string prefix="")

void	PreLoad (Element el, FGPropertyManager PropertyManager, 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.

std::string	GetVersion (void)
	Returns the version number of JSBSim. More...

void	PutMessage (const Message &msg)
	Places a Message structure on the Message queue. More...

void	PutMessage (const std::string &text)
	Creates a message with the given text and places it on the queue. More...

void	PutMessage (const std::string &text, bool bVal)
	Creates a message with the given text and boolean value and places it on the queue. More...

void	PutMessage (const std::string &text, int iVal)
	Creates a message with the given text and integer value and places it on the queue. More...

void	PutMessage (const std::string &text, double dVal)
	Creates a message with the given text and double value and places it on the queue. More...

int	SomeMessages (void)
	Reads the message on the queue (but does not delete it). More...

void	ProcessMessage (void)
	Reads the message on the queue and removes it from the queue. More...

Message *	ProcessNextMessage (void)
	Reads the next message on the queue and removes it from the queue. More...

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 double	CelsiusToFahrenheit (double celsius)
	Converts from degrees Celsius to degrees Fahrenheit. More...

static double	CelsiusToKelvin (double celsius)
	Converts from degrees Celsius to degrees Kelvin. More...

static double	CelsiusToRankine (double celsius)
	Converts from degrees Celsius to degrees Rankine. More...

static double	Constrain (double min, double value, double max)
	Constrain a value between a minimum and a maximum value.

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 double	FahrenheitToCelsius (double fahrenheit)
	Converts from degrees Fahrenheit to degrees Celsius. More...

static double	FeetToMeters (double measure)
	Converts from feet to meters. More...

static double	GaussianRandomNumber (void)

static double	KelvinToCelsius (double kelvin)
	Converts from degrees Kelvin to degrees Celsius. More...

static double	KelvinToFahrenheit (double kelvin)
	Converts from degrees Kelvin to degrees Fahrenheit. More...

static double	KelvinToRankine (double kelvin)
	Converts from degrees Kelvin to degrees Rankine. More...

static double	MachFromVcalibrated (double vcas, double p, double psl, double rhosl)
	Calculate the Mach number from the calibrated airspeed. More...

static double	PitotTotalPressure (double mach, double p)
	Compute the total pressure in front of the Pitot tube. More...

static double	RankineToCelsius (double rankine)
	Converts from degrees Rankine to degrees Celsius. More...

static double	RankineToKelvin (double rankine)
	Converts from degrees Rankine to degrees Kelvin. More...

static double	sign (double num)

static double	VcalibratedFromMach (double mach, double p, double psl, double rhosl)
	Calculate the calibrated airspeed from the Mach number. More...

Public Attributes inherited from FGEngine
struct Inputs &	in

Static Public Attributes inherited from FGJSBBase
static short	debug_lvl = 1

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

Protected Member Functions inherited from FGEngine
void	Debug (int from)

virtual bool	Load (FGFDMExec exec, Element el)

Protected Member Functions inherited from FGModelFunctions
virtual bool	InitModel (void)

Protected Member Functions inherited from FGJSBBase
void	Debug (int)

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	EnginePitch

double	EngineYaw

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

double	X

double	Y

double	Z

Protected Attributes inherited from FGModelFunctions
FGPropertyReader	LocalProperties

std::vector< FGFunction * >	PostFunctions

std::vector< FGFunction * >	PreFunctions

Static Protected Attributes inherited from FGJSBBase
static const double	degtorad = 0.017453292519943295769236907684886

static const double	fpstokts = 1.0/ktstofps

static const double	fttom = 0.3048

static int	gaussian_random_number_phase = 0

static const double	hptoftlbssec = 550.0

static const double	in3tom3 = 1.638706E-5

static const double	inchtoft = 0.08333333

static const double	inhgtopa = 3386.38

static const std::string	JSBSim_version = "1.0 " __DATE__ " " __TIME__

static const double	kgtolb = 2.20462

static const double	kgtoslug = 0.06852168

static const double	ktstofps = 1.68781

static const double	lbtoslug = 1.0/slugtolb

static Message	localMsg

static const double	m3toft3 = 1.0/(fttomfttomfttom)

static double	Mair = 28.9645

static unsigned int	messageId = 0

static std::queue< Message >	Messages

static const std::string	needed_cfg_version = "2.0"

static const double	psftoinhg = 0.014138

static const double	psftopa = 47.88

static const double	radtodeg = 57.295779513082320876798154814105

static double	Reng = 1716.56

static double	Rstar = 1545.348

static const double	SHRatio = 1.40

static const double	slugtolb = 32.174049

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>
</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"

Version

Id
FGPiston.h,v 1.38 2016/01/02 17:42:53 bcoconni Exp

Definition at line 221 of file FGPiston.h.

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 515 of file FGPiston.cpp.

 {
   FuelExpended = FuelFlowRate * in.TotalDeltaT;
   if (!Starved) FuelUsedLbs += FuelExpended; 
   return FuelExpended;
 }

Here is the call graph for this function:

◆ Calculate()

void Calculate ( void )

virtual

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

Implements FGEngine.

Definition at line 462 of file FGPiston.cpp.

 {
   // Input values.
 
   p_amb = in.Pressure * psftopa;
   double p = in.TotalPressure * psftopa;
   p_ram = (p - p_amb) * Ram_Air_Factor + p_amb;
   T_amb = RankineToKelvin(in.Temperature);
 
   RunPreFunctions();
 
 /* The thruster controls the engine RPM because it encapsulates the gear ratio and other transmission variables */
   RPM = Thruster->GetEngineRPM();
 
   MeanPistonSpeed_fps =  ( RPM * Stroke) / (360); // AKA 2 * (RPM/60) * ( Stroke / 12) or 2NS
 
   IAS = in.Vc;
 
   doEngineStartup();
   if (Boosted) doBoostControl();
   doMAP();
   doAirFlow();
   doFuelFlow();
 
   //Now that the fuel flow is done check if the mixture is too lean to run the engine
   //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;
 
   doEnginePower();
   if (IndicatedHorsePower < 0.1250) Running = false;
 
   doEGT();
   doCHT();
   doOilTemperature();
   doOilPressure();
 
   if (Thruster->GetType() == FGThruster::ttPropeller) {
     ((FGPropeller*)Thruster)->SetAdvance(in.PropAdvance[EngineNumber]);
     ((FGPropeller*)Thruster)->SetFeather(in.PropFeather[EngineNumber]);
   }
 
   LoadThrusterInputs();
   Thruster->Calculate(HP * hptoftlbssec);
 
   RunPostFunctions();
 }