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5 Date started: 09/12/2000
7 ------------- Copyright (C) 2000 Jon S. Berndt (jsb@hal-pc.org) --------------
9 This program is free software; you can redistribute it and/or modify it under
10 the terms of the GNU Lesser General Public License as published by the Free Software
11 Foundation; either version 2 of the License, or (at your option) any later
14 This program is distributed in the hope that it will be useful, but WITHOUT
15 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
16 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
19 You should have received a copy of the GNU Lesser General Public License along with
20 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
21 Place - Suite 330, Boston, MA 02111-1307, USA.
23 Further information about the GNU Lesser General Public License can also be found on
24 the world wide web at http://www.gnu.org.
27 --------------------------------------------------------------------------------
28 09/12/2000 JSB Created
29 10/01/2001 DPM Modified to use equations from Dave Luff's piston model.
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43 #include <math/FGTable.h>
44 #include <input_output/FGXMLElement.h>
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50 #define ID_PISTON "$Id$";
51 #define FG_MAX_BOOST_SPEEDS 3
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63 /** Models Dave Luff's Turbo/Supercharged Piston engine model.
64 Additional elements are required for a supercharged engine. These can be
65 left off a non-supercharged engine, ie. the changes are all backward
66 compatible at present.
68 - NUMBOOSTSPEEDS - zero (or not present) for a naturally-aspirated engine,
69 either 1, 2 or 3 for a boosted engine. This corresponds to the number of
70 supercharger speeds. Merlin XII had 1 speed, Merlin 61 had 2, a late
71 Griffon engine apparently had 3. No known engine more than 3, although
72 some German engines apparently had a continuously variable-speed
75 - BOOSTOVERRIDE - whether the boost pressure control system (either a boost
76 control valve for superchargers or wastegate for turbochargers) can be
77 overriden by the pilot. During wartime this was commonly possible, and
78 known as "War Emergency Power" by the Brits. 1 or 0 in the config file.
79 This isn't implemented in the model yet though, there would need to be
80 some way of getting the boost control cutout lever position (on or off)
81 from FlightGear first.
83 - The next items are all appended with either 1, 2 or 3 depending on which
84 boost speed they refer to, eg RATEDBOOST1. The rated values seems to have
85 been a common convention at the time to express the maximum continuously
86 available power, and the conditions to attain that power.
88 - RATEDBOOST[123] - the absolute rated boost above sea level ambient for a
89 given boost speed, in psi. Eg the Merlin XII had a rated boost of 9psi,
90 giving approximately 42inHg manifold pressure up to the rated altitude.
92 - RATEDALTITUDE[123] - The altitude up to which rated boost can be
93 maintained. Up to this altitude the boost is maintained constant for a
94 given throttle position by the BCV or wastegate. Beyond this altitude the
95 manifold pressure must drop, since the supercharger is now at maximum
96 unregulated output. The actual pressure multiplier of the supercharger
97 system is calculated at initialisation from this value.
99 - RATEDPOWER[123] - The power developed at rated boost at rated altitude at
102 - RATEDRPM[123] - The rpm at which rated power is developed.
104 - TAKEOFFBOOST - Takeoff boost in psi above ambient. Many aircraft had an
105 extra boost setting beyond rated boost, but not totally uncontrolled as in
106 the already mentioned boost-control-cutout, typically attained by pushing
107 the throttle past a mechanical 'gate' preventing its inadvertant use. This
108 was typically used for takeoff, and emergency situations, generally for
109 not more than five minutes. This is a change in the boost control
110 setting, not the actual supercharger speed, and so would only give extra
111 power below the rated altitude. When TAKEOFFBOOST is specified in the
112 config file (and is above RATEDBOOST1), then the throttle position is
115 - 0 to 0.95 : idle manifold pressure to rated boost (where attainable)
116 - 0.96, 0.97, 0.98 : rated boost (where attainable).
117 - 0.99, 1.0 : takeoff boost (where attainable).
119 A typical takeoff boost for an earlyish Merlin was about 12psi, compared
120 with a rated boost of 9psi.
122 It is quite possible that other boost control settings could have been used
123 on some aircraft, or that takeoff/extra boost could have activated by other
124 means than pushing the throttle full forward through a gate, but this will
127 Note that MAXMP is still the non-boosted max manifold pressure even for
128 boosted engines - effectively this is simply a measure of the pressure drop
129 through the fully open throttle.
131 @author Jon S. Berndt (Engine framework code and framework-related mods)
132 @author Dave Luff (engine operational code)
133 @author David Megginson (initial porting and additional code)
137 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
139 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
141 class FGPiston : public FGEngine
145 FGPiston(FGFDMExec* exec, Element* el, int engine_number);
149 string GetEngineLabels(string delimeter);
150 string GetEngineValues(string delimeter);
152 double Calculate(void);
153 double GetPowerAvailable(void) {return PowerAvailable;}
154 double CalcFuelNeed(void);
156 void SetMagnetos(int magnetos) {Magnetos = magnetos;}
158 double GetEGT(void) { return EGT_degC; }
159 int GetMagnetos(void) {return Magnetos;}
161 double getExhaustGasTemp_degF(void) {return KelvinToFahrenheit(ExhaustGasTemp_degK);}
162 double getManifoldPressure_inHg(void) const {return ManifoldPressure_inHg;}
163 double getCylinderHeadTemp_degF(void) {return KelvinToFahrenheit(CylinderHeadTemp_degK);}
164 double getOilPressure_psi(void) const {return OilPressure_psi;}
165 double getOilTemp_degF (void) {return KelvinToFahrenheit(OilTemp_degK);}
166 double getRPM(void) {return RPM;}
171 double BrakeHorsePower;
173 double SpeedIntercept;
174 double AltitudeSlope;
175 double PowerAvailable;
180 void doEngineStartup(void);
181 void doBoostControl(void);
183 void doAirFlow(void);
184 void doFuelFlow(void);
185 void doEnginePower(void);
188 void doOilPressure(void);
189 void doOilTemperature(void);
196 const double rho_fuel; // kg/m^3
197 const double calorific_value_fuel; // W/Kg (approximate)
198 const double Cp_air; // J/KgK
199 const double Cp_fuel; // J/KgK
201 FGTable *Lookup_Combustion_Efficiency;
202 FGTable *Power_Mixture_Correlation;
207 double MinManifoldPressure_inHg; // Inches Hg
208 double MaxManifoldPressure_inHg; // Inches Hg
209 double Displacement; // cubic inches
210 double MaxHP; // horsepower
211 double Cycles; // cycles/power stroke
212 double IdleRPM; // revolutions per minute
213 double StarterHP; // initial horsepower of starter motor
214 int BoostSpeeds; // Number of super/turbocharger boost speeds - zero implies no turbo/supercharging.
215 int BoostSpeed; // The current boost-speed (zero-based).
216 bool Boosted; // Set true for boosted engine.
217 int BoostOverride; // The raw value read in from the config file - should be 1 or 0 - see description below.
218 bool bBoostOverride; // Set true if pilot override of the boost regulator was fitted.
219 // (Typically called 'war emergency power').
220 bool bTakeoffBoost; // Set true if extra takeoff / emergency boost above rated boost could be attained.
221 // (Typically by extra throttle movement past a mechanical 'gate').
222 double TakeoffBoost; // Sea-level takeoff boost in psi. (if fitted).
223 double RatedBoost[FG_MAX_BOOST_SPEEDS]; // Sea-level rated boost in psi.
224 double RatedAltitude[FG_MAX_BOOST_SPEEDS]; // Altitude at which full boost is reached (boost regulation ends)
225 // and at which power starts to fall with altitude [ft].
226 double RatedRPM[FG_MAX_BOOST_SPEEDS]; // Engine speed at which the rated power for each boost speed is delivered [rpm].
227 double RatedPower[FG_MAX_BOOST_SPEEDS]; // Power at rated throttle position at rated altitude [HP].
228 double BoostSwitchAltitude[FG_MAX_BOOST_SPEEDS - 1]; // Altitude at which switchover (currently assumed automatic)
229 // from one boost speed to next occurs [ft].
230 double BoostSwitchPressure[FG_MAX_BOOST_SPEEDS - 1]; // Pressure at which boost speed switchover occurs [Pa]
231 double BoostMul[FG_MAX_BOOST_SPEEDS]; // Pressure multipier of unregulated supercharger
232 double RatedMAP[FG_MAX_BOOST_SPEEDS]; // Rated manifold absolute pressure [Pa] (BCV clamp)
233 double TakeoffMAP[FG_MAX_BOOST_SPEEDS]; // Takeoff setting manifold absolute pressure [Pa] (BCV clamp)
234 double BoostSwitchHysteresis; // Pa.
241 // Inputs (in addition to those in FGEngine).
243 double p_amb; // Pascals
244 double p_amb_sea_level; // Pascals
245 double T_amb; // degrees Kelvin
246 double RPM; // revolutions per minute
253 // Outputs (in addition to those in FGEngine).
256 double volumetric_efficiency;
258 double equivalence_ratio;
260 double Percentage_Power;
262 double combustion_efficiency;
263 double ExhaustGasTemp_degK;
265 double ManifoldPressure_inHg;
266 double CylinderHeadTemp_degK;
267 double OilPressure_psi;
270 void Debug(int from);
273 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%