DEFINITIONS
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-#define ID_PISTON "$Id: FGPiston.h,v 1.26 2011/03/10 01:35:25 dpculp Exp $";
+#define ID_PISTON "$Id: FGPiston.h,v 1.29 2011/06/16 16:32:10 jentron Exp $";
#define FG_MAX_BOOST_SPEEDS 3
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS DOCUMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-/** Models Dave Luff's Turbo/Supercharged Piston engine model.
+/** Models a Supercharged Piston engine. Based on Dave Luff's model.
<h3>Configuration File Format:</h3>
<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>
- <cylinder-head-mass unit="{KG | LBS}"> {number} </cylinder-head-mass>
<compression-ratio> {number} </compression-ratio>
<sparkfaildrop> {number} </sparkfaildrop>
- <maxhp unit="{HP | WATTS}"> {number} </maxhp>
- <cycles> {number} </cycles>
- <idlerpm> {number} </idlerpm>
- <maxrpm> {number} </maxrpm>
- <maxthrottle> {number} </maxthrottle>
- <minthrottle> {number} </minthrottle>
+ <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>
+ <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>
<ratedrpm3> {number} </ratedrpm3>
<ratedaltitude3 unit="{FT | M}"> {number} </ratedaltitude3>
<takeoffboost unit="{INHG | PA | ATM}"> {number} </takeoffboost>
- <air-intake-impedance-factor> {number} </air-intake-impedance-factor>
- <ram-air-factor> {number} </ram-air-factor>
- <cooling-factor> {number} </cooling-factor>
</piston_engine>
@endcode
-<pre>
- Additional elements are required for a supercharged engine. These can be
- left off a non-supercharged engine, ie. the changes are all backward
- compatible at present.
-
- - NUMBOOSTSPEEDS - zero (or not present) for a naturally-aspirated engine,
+<h3>Definition of the piston engine configuration file parameters:</h3>
+Basic parameters:
+- \b minmp - this value is the nominal idle manifold pressure at sea-level
+ without boost. Along with idlerpm, it determines throttle response slope.
+- \b 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
+- \b 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.
+- \b maxrpm - this value is used to calculate air-box resistance and BSFC. It
+ also affects oil pressure among other things.
+- \b 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.
+- \b displacement - this value is used to determine mass air and fuel flow
+ which impacts engine power and cooling.
+- \b cycles - Designate a 2 or 4 stroke engine. Currently only the 4 stroke
+ engine is supported.
+- \b bore - cylinder bore is currently unused.
+- \b 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.
+- \b compression-ratio - the compression ratio affects the change in volumetric
+ efficiency with altitude.
+- \b sparkfaildrop - this is the percentage drop in horsepower for single
+ magneto operation.
+- \b 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
+- \b 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
+- \b 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
+- \b 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.
+- \b 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:
+- \b cylinders - number of cylinders scales the cylinder head mass.
+- \b cylinder-head-mass - the nominal mass of a cylinder head. A larger value
+ slows changes in engine temperature
+- \b cooling-factor - this number models the efficiency of the aircraft cooling
+ system. Also a property for run-time adjustment.
+
+Supercharge parameters:
+- \b 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 apparently had a continuously variable-speed
- supercharger.
-
- - BOOSTOVERRIDE - whether the boost pressure control system (either a boost
- control valve for superchargers or wastegate for turbochargers) can be
- overriden by the pilot. During wartime this was commonly possible, and
- known as "War Emergency Power" by the Brits. 1 or 0 in the config file.
- This isn't implemented in the model yet though, there would need to be
- some way of getting the boost control cutout lever position (on or off)
- from FlightGear first.
-
- - BOOSTMANUAL - whether a multispeed supercharger will manually or
- automatically shift boost speeds. On manual shifting the boost speeds
- is accomplished by controling propulsion/engine/boostspeed
-
- - The next items are all appended with either 1, 2 or 3 depending on which
- boost speed they refer to, eg RATEDBOOST1. The rated values seems to have
- been a common convention at the time to express the maximum continuously
- available power, and the conditions to attain that power.
-
- - RATEDBOOST[123] - the absolute rated boost above sea level ambient for a
- given boost speed, in psi. Eg the Merlin XII had a rated boost of 9psi,
- giving approximately 42inHg manifold pressure up to the rated altitude.
-
- - RATEDALTITUDE[123] - The altitude up to which rated boost can be
- maintained. Up to this altitude the boost is maintained constant for a
- given throttle position by the BCV or wastegate. 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 initialisation from this value.
-
- - RATEDPOWER[123] - The power developed at rated boost at rated altitude at
- rated rpm.
-
- - RATEDRPM[123] - The rpm at which rated power is developed.
-
- - TAKEOFFBOOST - Takeoff boost in psi above ambient. Many aircraft had an
- extra boost setting beyond rated boost, but not totally uncontrolled as in
- the already mentioned boost-control-cutout, typically attained by pushing
- the throttle past a mechanical 'gate' preventing its inadvertant use. This
- was 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. When TAKEOFFBOOST is specified in the
- config file (and is above RATEDBOOST1), then 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).
-
- A typical takeoff boost for an earlyish Merlin was about 12psi, compared
- with a rated boost of 9psi.
-
- It is quite possible that other boost control settings could have been used
- on some aircraft, or that takeoff/extra boost could have activated by other
- means than pushing the throttle full forward through a gate, but this will
- suffice for now.
-
- Note that MAXMP is still the non-boosted max manifold pressure even for
- boosted engines - effectively this is simply a measure of the pressure drop
- through the fully open throttle.
-</pre>
+ some German engines had continuously variable-speed superchargers.
+- \b boostoverride - unused
+- \b 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.
+- \b 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:
+- \b ratedboost[123] - the absolute rated boost above sea level ambient
+ (14.7 PSI, 29.92 inHg) for a given boost speed.
+
+- \b ratedpower[123] - unused
+- \b ratedrpm[123] - The rpm at which rated boost is developed
+- \b 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)
@author Dave Luff (engine operational code)
@author David Megginson (initial porting and additional code)
@author Ron Jensen (additional engine code)
- @version $Id: FGPiston.h,v 1.26 2011/03/10 01:35:25 dpculp Exp $
+ @see Taylor, Charles Fayette, "The Internal Combustion Engine in Theory and Practice"
+ @version $Id: FGPiston.h,v 1.29 2011/06/16 16:32:10 jentron Exp $
*/
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
const double R_air;
const double rho_fuel; // kg/m^3
- const double calorific_value_fuel; // W/Kg (approximate)
+ const double calorific_value_fuel; // J/Kg (approximate)
const double Cp_air; // J/KgK
const double Cp_fuel; // J/KgK
const double standard_pressure; //Pa
double Displacement; // cubic inches
double displacement_SI; // cubic meters
double MaxHP; // horsepower
+ double StaticFriction_HP; // horsepower: amount subtracted from final engine power
double SparkFailDrop; // drop of power due to spark failure
double Cycles; // cycles/power stroke
double IdleRPM; // revolutions per minute
double Ram_Air_Factor; // number
double StarterHP; // initial horsepower of starter motor
- int BoostSpeeds; // Number of super/turbocharger boost speeds - zero implies no turbo/supercharging.
- int BoostSpeed; // The current boost-speed (zero-based).
- bool Boosted; // Set true for boosted engine.
- int BoostManual; // The raw value read in from the config file - should be 1 or 0 - see description below.
- bool bBoostManual; // Set true if pilot must manually control the boost speed.
- int BoostOverride; // The raw value read in from the config file - should be 1 or 0 - see description below.
- bool bBoostOverride; // Set true if pilot override of the boost regulator was fitted.
+ int BoostSpeeds; // Number of super/turbocharger boost speeds - zero implies no turbo/supercharging.
+ int BoostSpeed; // The current boost-speed (zero-based).
+ bool Boosted; // Set true for boosted engine.
+ int BoostManual; // The raw value read in from the config file - should be 1 or 0 - see description below.
+ bool bBoostManual; // Set true if pilot must manually control the boost speed.
+ int BoostOverride; // The raw value read in from the config file - should be 1 or 0 - see description below.
+ bool bBoostOverride; // Set true if pilot override of the boost regulator was fitted.
// (Typically called 'war emergency power').
- bool bTakeoffBoost; // Set true if extra takeoff / emergency boost above rated boost could be attained.
+ bool bTakeoffBoost; // Set true if extra takeoff / emergency boost above rated boost could be attained.
// (Typically by extra throttle movement past a mechanical 'gate').
- double TakeoffBoost; // Sea-level takeoff boost in psi. (if fitted).
- double RatedBoost[FG_MAX_BOOST_SPEEDS]; // Sea-level rated boost in psi.
- double RatedAltitude[FG_MAX_BOOST_SPEEDS]; // Altitude at which full boost is reached (boost regulation ends)
+ double TakeoffBoost; // Sea-level takeoff boost in psi. (if fitted).
+ double RatedBoost[FG_MAX_BOOST_SPEEDS]; // Sea-level rated boost in psi.
+ double RatedAltitude[FG_MAX_BOOST_SPEEDS]; // Altitude at which full boost is reached (boost regulation ends)
// and at which power starts to fall with altitude [ft].
double RatedRPM[FG_MAX_BOOST_SPEEDS]; // Engine speed at which the rated power for each boost speed is delivered [rpm].
- double RatedPower[FG_MAX_BOOST_SPEEDS]; // Power at rated throttle position at rated altitude [HP].
- double BoostSwitchAltitude[FG_MAX_BOOST_SPEEDS - 1]; // Altitude at which switchover (currently assumed automatic)
+ double RatedPower[FG_MAX_BOOST_SPEEDS]; // Power at rated throttle position at rated altitude [HP].
+ double BoostSwitchAltitude[FG_MAX_BOOST_SPEEDS - 1]; // Altitude at which switchover (currently assumed automatic)
// from one boost speed to next occurs [ft].
double BoostSwitchPressure[FG_MAX_BOOST_SPEEDS - 1]; // Pressure at which boost speed switchover occurs [Pa]
- double BoostMul[FG_MAX_BOOST_SPEEDS]; // Pressure multipier of unregulated supercharger
- double RatedMAP[FG_MAX_BOOST_SPEEDS]; // Rated manifold absolute pressure [Pa] (BCV clamp)
- double TakeoffMAP[FG_MAX_BOOST_SPEEDS]; // Takeoff setting manifold absolute pressure [Pa] (BCV clamp)
- double BoostSwitchHysteresis; // Pa.
+ double BoostMul[FG_MAX_BOOST_SPEEDS]; // Pressure multipier of unregulated supercharger
+ double RatedMAP[FG_MAX_BOOST_SPEEDS]; // Rated manifold absolute pressure [Pa] (BCV clamp)
+ double TakeoffMAP[FG_MAX_BOOST_SPEEDS]; // Takeoff setting manifold absolute pressure [Pa] (BCV clamp)
+ double BoostSwitchHysteresis; // Pa.
double minMAP; // Pa
double maxMAP; // Pa
projects / flightgear.git / blobdiff