1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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.
31 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
38 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
40 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
43 #include <math/FGTable.h>
44 #include <input_output/FGXMLElement.h>
46 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
48 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
50 #define ID_PISTON "$Id$";
51 #define FG_MAX_BOOST_SPEEDS 3
53 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
55 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
59 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
61 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
63 /** Models Dave Luff's Turbo/Supercharged Piston engine model.
65 <h3>Configuration File Format:</h3>
68 <piston_engine name="{string}">
69 <minmp unit="{INHG | PA | ATM}"> {number} </minmp>
70 <maxmp unit="{INHG | PA | ATM}"> {number} </maxmp>
71 <displacement unit="{IN3 | LTR | CC}"> {number} </displacement>
72 <maxhp unit="{HP | WATTS}"> {number} </maxhp>
73 <cycles> {number} </cycles>
74 <idlerpm> {number} </idlerpm>
75 <maxthrottle> {number} </maxthrottle>
76 <minthrottle> {number} </minthrottle>
77 <numboostspeeds> {number} </numboostspeeds>
78 <boostoverride> {0 | 1} </boostoverride>
79 <ratedboost1 unit="{INHG | PA | ATM}"> {number} </ratedboost1>
80 <ratedpower1 unit="{HP | WATTS}"> {number} </ratedpower1>
81 <ratedrpm1> {number} </ratedrpm1>
82 <ratedaltitude1 unit="{FT | M}"> {number} </ratedaltitude1>
83 <ratedboost2 unit="{INHG | PA | ATM}"> {number} </ratedboost2>
84 <ratedpower2 unit="{HP | WATTS}"> {number} </ratedpower2>
85 <ratedrpm2> {number} </ratedrpm2>
86 <ratedaltitude2 unit="{FT | M}"> {number} </ratedaltitude2>
87 <ratedboost3 unit="{INHG | PA | ATM}"> {number} </ratedboost3>
88 <ratedpower3 unit="{HP | WATTS}"> {number} </ratedpower3>
89 <ratedrpm3> {number} </ratedrpm3>
90 <ratedaltitude3 unit="{FT | M}"> {number} </ratedaltitude3>
91 <takeoffboost unit="{INHG | PA | ATM}"> {number} </takeoffboost>
96 Additional elements are required for a supercharged engine. These can be
97 left off a non-supercharged engine, ie. the changes are all backward
98 compatible at present.
100 - NUMBOOSTSPEEDS - zero (or not present) for a naturally-aspirated engine,
101 either 1, 2 or 3 for a boosted engine. This corresponds to the number of
102 supercharger speeds. Merlin XII had 1 speed, Merlin 61 had 2, a late
103 Griffon engine apparently had 3. No known engine more than 3, although
104 some German engines apparently had a continuously variable-speed
107 - BOOSTOVERRIDE - whether the boost pressure control system (either a boost
108 control valve for superchargers or wastegate for turbochargers) can be
109 overriden by the pilot. During wartime this was commonly possible, and
110 known as "War Emergency Power" by the Brits. 1 or 0 in the config file.
111 This isn't implemented in the model yet though, there would need to be
112 some way of getting the boost control cutout lever position (on or off)
113 from FlightGear first.
115 - The next items are all appended with either 1, 2 or 3 depending on which
116 boost speed they refer to, eg RATEDBOOST1. The rated values seems to have
117 been a common convention at the time to express the maximum continuously
118 available power, and the conditions to attain that power.
120 - RATEDBOOST[123] - the absolute rated boost above sea level ambient for a
121 given boost speed, in psi. Eg the Merlin XII had a rated boost of 9psi,
122 giving approximately 42inHg manifold pressure up to the rated altitude.
124 - RATEDALTITUDE[123] - The altitude up to which rated boost can be
125 maintained. Up to this altitude the boost is maintained constant for a
126 given throttle position by the BCV or wastegate. Beyond this altitude the
127 manifold pressure must drop, since the supercharger is now at maximum
128 unregulated output. The actual pressure multiplier of the supercharger
129 system is calculated at initialisation from this value.
131 - RATEDPOWER[123] - The power developed at rated boost at rated altitude at
134 - RATEDRPM[123] - The rpm at which rated power is developed.
136 - TAKEOFFBOOST - Takeoff boost in psi above ambient. Many aircraft had an
137 extra boost setting beyond rated boost, but not totally uncontrolled as in
138 the already mentioned boost-control-cutout, typically attained by pushing
139 the throttle past a mechanical 'gate' preventing its inadvertant use. This
140 was typically used for takeoff, and emergency situations, generally for
141 not more than five minutes. This is a change in the boost control
142 setting, not the actual supercharger speed, and so would only give extra
143 power below the rated altitude. When TAKEOFFBOOST is specified in the
144 config file (and is above RATEDBOOST1), then the throttle position is
147 - 0 to 0.95 : idle manifold pressure to rated boost (where attainable)
148 - 0.96, 0.97, 0.98 : rated boost (where attainable).
149 - 0.99, 1.0 : takeoff boost (where attainable).
151 A typical takeoff boost for an earlyish Merlin was about 12psi, compared
152 with a rated boost of 9psi.
154 It is quite possible that other boost control settings could have been used
155 on some aircraft, or that takeoff/extra boost could have activated by other
156 means than pushing the throttle full forward through a gate, but this will
159 Note that MAXMP is still the non-boosted max manifold pressure even for
160 boosted engines - effectively this is simply a measure of the pressure drop
161 through the fully open throttle.
164 @author Jon S. Berndt (Engine framework code and framework-related mods)
165 @author Dave Luff (engine operational code)
166 @author David Megginson (initial porting and additional code)
170 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
172 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
174 class FGPiston : public FGEngine
178 FGPiston(FGFDMExec* exec, Element* el, int engine_number);
182 string GetEngineLabels(string delimeter);
183 string GetEngineValues(string delimeter);
185 double Calculate(void);
186 double GetPowerAvailable(void) {return PowerAvailable;}
187 double CalcFuelNeed(void);
189 void ResetToIC(void);
190 void SetMagnetos(int magnetos) {Magnetos = magnetos;}
192 double GetEGT(void) { return EGT_degC; }
193 int GetMagnetos(void) {return Magnetos;}
195 double getExhaustGasTemp_degF(void) {return KelvinToFahrenheit(ExhaustGasTemp_degK);}
196 double getManifoldPressure_inHg(void) const {return ManifoldPressure_inHg;}
197 double getCylinderHeadTemp_degF(void) {return KelvinToFahrenheit(CylinderHeadTemp_degK);}
198 double getOilPressure_psi(void) const {return OilPressure_psi;}
199 double getOilTemp_degF (void) {return KelvinToFahrenheit(OilTemp_degK);}
200 double getRPM(void) {return RPM;}
205 double BrakeHorsePower;
207 double SpeedIntercept;
208 double AltitudeSlope;
209 double PowerAvailable;
214 void doEngineStartup(void);
215 void doBoostControl(void);
217 void doAirFlow(void);
218 void doFuelFlow(void);
219 void doEnginePower(void);
222 void doOilPressure(void);
223 void doOilTemperature(void);
225 int InitRunning(void);
232 const double rho_fuel; // kg/m^3
233 const double calorific_value_fuel; // W/Kg (approximate)
234 const double Cp_air; // J/KgK
235 const double Cp_fuel; // J/KgK
237 FGTable *Lookup_Combustion_Efficiency;
238 FGTable *Power_Mixture_Correlation;
243 double MinManifoldPressure_inHg; // Inches Hg
244 double MaxManifoldPressure_inHg; // Inches Hg
245 double Displacement; // cubic inches
246 double MaxHP; // horsepower
247 double SparkFailDrop; // drop of power due to spark failure
248 double Cycles; // cycles/power stroke
249 double IdleRPM; // revolutions per minute
250 double StarterHP; // initial horsepower of starter motor
251 int BoostSpeeds; // Number of super/turbocharger boost speeds - zero implies no turbo/supercharging.
252 int BoostSpeed; // The current boost-speed (zero-based).
253 bool Boosted; // Set true for boosted engine.
254 int BoostOverride; // The raw value read in from the config file - should be 1 or 0 - see description below.
255 bool bBoostOverride; // Set true if pilot override of the boost regulator was fitted.
256 // (Typically called 'war emergency power').
257 bool bTakeoffBoost; // Set true if extra takeoff / emergency boost above rated boost could be attained.
258 // (Typically by extra throttle movement past a mechanical 'gate').
259 double TakeoffBoost; // Sea-level takeoff boost in psi. (if fitted).
260 double RatedBoost[FG_MAX_BOOST_SPEEDS]; // Sea-level rated boost in psi.
261 double RatedAltitude[FG_MAX_BOOST_SPEEDS]; // Altitude at which full boost is reached (boost regulation ends)
262 // and at which power starts to fall with altitude [ft].
263 double RatedRPM[FG_MAX_BOOST_SPEEDS]; // Engine speed at which the rated power for each boost speed is delivered [rpm].
264 double RatedPower[FG_MAX_BOOST_SPEEDS]; // Power at rated throttle position at rated altitude [HP].
265 double BoostSwitchAltitude[FG_MAX_BOOST_SPEEDS - 1]; // Altitude at which switchover (currently assumed automatic)
266 // from one boost speed to next occurs [ft].
267 double BoostSwitchPressure[FG_MAX_BOOST_SPEEDS - 1]; // Pressure at which boost speed switchover occurs [Pa]
268 double BoostMul[FG_MAX_BOOST_SPEEDS]; // Pressure multipier of unregulated supercharger
269 double RatedMAP[FG_MAX_BOOST_SPEEDS]; // Rated manifold absolute pressure [Pa] (BCV clamp)
270 double TakeoffMAP[FG_MAX_BOOST_SPEEDS]; // Takeoff setting manifold absolute pressure [Pa] (BCV clamp)
271 double BoostSwitchHysteresis; // Pa.
278 // Inputs (in addition to those in FGEngine).
280 double p_amb; // Pascals
281 double p_amb_sea_level; // Pascals
282 double T_amb; // degrees Kelvin
283 double RPM; // revolutions per minute
290 // Outputs (in addition to those in FGEngine).
293 double volumetric_efficiency;
295 double equivalence_ratio;
297 double Percentage_Power;
299 double combustion_efficiency;
300 double ExhaustGasTemp_degK;
302 double ManifoldPressure_inHg;
303 double CylinderHeadTemp_degK;
304 double OilPressure_psi;
307 void Debug(int from);
310 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%