1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
4 Author: Jon S. Berndt, JSBSim framework
5 Dave Luff, Piston engine model
6 Date started: 09/12/2000
7 Purpose: This module models a Piston engine
9 ------------- Copyright (C) 2000 Jon S. Berndt (jsb@hal-pc.org) --------------
11 This program is free software; you can redistribute it and/or modify it under
12 the terms of the GNU Lesser General Public License as published by the Free Software
13 Foundation; either version 2 of the License, or (at your option) any later
16 This program is distributed in the hope that it will be useful, but WITHOUT
17 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
18 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
21 You should have received a copy of the GNU Lesser General Public License along with
22 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
23 Place - Suite 330, Boston, MA 02111-1307, USA.
25 Further information about the GNU Lesser General Public License can also be found on
26 the world wide web at http://www.gnu.org.
28 FUNCTIONAL DESCRIPTION
29 --------------------------------------------------------------------------------
31 This class descends from the FGEngine class and models a Piston engine based on
32 parameters given in the engine config file for this class
35 --------------------------------------------------------------------------------
36 09/12/2000 JSB Created
38 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
40 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
45 #include <models/FGPropulsion.h>
46 #include "FGPropeller.h"
50 static const char *IdSrc = "$Id$";
51 static const char *IdHdr = ID_PISTON;
53 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
55 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
57 FGPiston::FGPiston(FGFDMExec* exec, Element* el, int engine_number)
58 : FGEngine(exec, el, engine_number),
59 R_air(287.3), // Gas constant for air J/Kg/K
60 rho_fuel(800), // estimate
61 calorific_value_fuel(47.3e6),
62 Cp_air(1005), // Specific heat (constant pressure) J/Kg/K
67 // Defaults and initializations
72 // These items are read from the configuration file
79 MinManifoldPressure_inHg = 6.5;
80 MaxManifoldPressure_inHg = 28.5;
82 // These are internal program variables
92 BoostSpeeds = 0; // Default to no supercharging
96 bBoostOverride = false;
97 bTakeoffBoost = false;
98 TakeoffBoost = 0.0; // Default to no extra takeoff-boost
100 for (i=0; i<FG_MAX_BOOST_SPEEDS; i++) {
103 RatedAltitude[i] = 0.0;
105 RatedMAP[i] = 100000;
107 TakeoffMAP[i] = 100000;
109 for (i=0; i<FG_MAX_BOOST_SPEEDS-1; i++) {
110 BoostSwitchAltitude[i] = 0.0;
111 BoostSwitchPressure[i] = 0.0;
114 volumetric_efficiency = 0.8; // Actually f(speed, load) but this will get us running
116 // First column is thi, second is neta (combustion efficiency)
117 Lookup_Combustion_Efficiency = new FGTable(12);
118 *Lookup_Combustion_Efficiency << 0.00 << 0.980;
119 *Lookup_Combustion_Efficiency << 0.90 << 0.980;
120 *Lookup_Combustion_Efficiency << 1.00 << 0.970;
121 *Lookup_Combustion_Efficiency << 1.05 << 0.950;
122 *Lookup_Combustion_Efficiency << 1.10 << 0.900;
123 *Lookup_Combustion_Efficiency << 1.15 << 0.850;
124 *Lookup_Combustion_Efficiency << 1.20 << 0.790;
125 *Lookup_Combustion_Efficiency << 1.30 << 0.700;
126 *Lookup_Combustion_Efficiency << 1.40 << 0.630;
127 *Lookup_Combustion_Efficiency << 1.50 << 0.570;
128 *Lookup_Combustion_Efficiency << 1.60 << 0.525;
129 *Lookup_Combustion_Efficiency << 2.00 << 0.345;
131 Power_Mixture_Correlation = new FGTable(13);
132 *Power_Mixture_Correlation << (14.7/1.6) << 78.0;
133 *Power_Mixture_Correlation << 10 << 86.0;
134 *Power_Mixture_Correlation << 11 << 93.5;
135 *Power_Mixture_Correlation << 12 << 98.0;
136 *Power_Mixture_Correlation << 13 << 100.0;
137 *Power_Mixture_Correlation << 14 << 99.0;
138 *Power_Mixture_Correlation << 15 << 96.4;
139 *Power_Mixture_Correlation << 16 << 92.5;
140 *Power_Mixture_Correlation << 17 << 88.0;
141 *Power_Mixture_Correlation << 18 << 83.0;
142 *Power_Mixture_Correlation << 19 << 78.5;
143 *Power_Mixture_Correlation << 20 << 74.0;
144 *Power_Mixture_Correlation << (14.7/0.6) << 58;
146 // Read inputs from engine data file where present.
148 if (el->FindElement("minmp")) // Should have ELSE statement telling default value used?
149 MinManifoldPressure_inHg = el->FindElementValueAsNumberConvertTo("minmp","INHG");
150 if (el->FindElement("maxmp"))
151 MaxManifoldPressure_inHg = el->FindElementValueAsNumberConvertTo("maxmp","INHG");
152 if (el->FindElement("displacement"))
153 Displacement = el->FindElementValueAsNumberConvertTo("displacement","IN3");
154 if (el->FindElement("maxhp"))
155 MaxHP = el->FindElementValueAsNumberConvertTo("maxhp","HP");
156 if (el->FindElement("sparkfaildrop"))
157 SparkFailDrop = Constrain(0, 1 - el->FindElementValueAsNumber("sparkfaildrop"), 1);
158 if (el->FindElement("cycles"))
159 Cycles = el->FindElementValueAsNumber("cycles");
160 if (el->FindElement("idlerpm"))
161 IdleRPM = el->FindElementValueAsNumber("idlerpm");
162 if (el->FindElement("maxthrottle"))
163 MaxThrottle = el->FindElementValueAsNumber("maxthrottle");
164 if (el->FindElement("minthrottle"))
165 MinThrottle = el->FindElementValueAsNumber("minthrottle");
166 if (el->FindElement("numboostspeeds")) { // Turbo- and super-charging parameters
167 BoostSpeeds = (int)el->FindElementValueAsNumber("numboostspeeds");
168 if (el->FindElement("boostoverride"))
169 BoostOverride = (int)el->FindElementValueAsNumber("boostoverride");
170 if (el->FindElement("takeoffboost"))
171 TakeoffBoost = el->FindElementValueAsNumberConvertTo("takeoffboost", "PSI");
172 if (el->FindElement("ratedboost1"))
173 RatedBoost[0] = el->FindElementValueAsNumberConvertTo("ratedboost1", "PSI");
174 if (el->FindElement("ratedboost2"))
175 RatedBoost[1] = el->FindElementValueAsNumberConvertTo("ratedboost2", "PSI");
176 if (el->FindElement("ratedboost3"))
177 RatedBoost[2] = el->FindElementValueAsNumberConvertTo("ratedboost3", "PSI");
178 if (el->FindElement("ratedpower1"))
179 RatedPower[0] = el->FindElementValueAsNumberConvertTo("ratedpower1", "HP");
180 if (el->FindElement("ratedpower2"))
181 RatedPower[1] = el->FindElementValueAsNumberConvertTo("ratedpower2", "HP");
182 if (el->FindElement("ratedpower3"))
183 RatedPower[2] = el->FindElementValueAsNumberConvertTo("ratedpower3", "HP");
184 if (el->FindElement("ratedrpm1"))
185 RatedRPM[0] = el->FindElementValueAsNumber("ratedrpm1");
186 if (el->FindElement("ratedrpm2"))
187 RatedRPM[1] = el->FindElementValueAsNumber("ratedrpm2");
188 if (el->FindElement("ratedrpm3"))
189 RatedRPM[2] = el->FindElementValueAsNumber("ratedrpm3");
190 if (el->FindElement("ratedaltitude1"))
191 RatedAltitude[0] = el->FindElementValueAsNumberConvertTo("ratedaltitude1", "FT");
192 if (el->FindElement("ratedaltitude2"))
193 RatedAltitude[1] = el->FindElementValueAsNumberConvertTo("ratedaltitude2", "FT");
194 if (el->FindElement("ratedaltitude3"))
195 RatedAltitude[2] = el->FindElementValueAsNumberConvertTo("ratedaltitude3", "FT");
197 minMAP = MinManifoldPressure_inHg * inhgtopa; // inHg to Pa
198 maxMAP = MaxManifoldPressure_inHg * inhgtopa;
199 StarterHP = sqrt(MaxHP) * 0.4;
201 // Set up and sanity-check the turbo/supercharging configuration based on the input values.
202 if (TakeoffBoost > RatedBoost[0]) bTakeoffBoost = true;
203 for (i=0; i<BoostSpeeds; ++i) {
205 if (RatedBoost[i] <= 0.0) bad = true;
206 if (RatedPower[i] <= 0.0) bad = true;
207 if (RatedAltitude[i] < 0.0) bad = true; // 0.0 is deliberately allowed - this corresponds to unregulated supercharging.
208 if (i > 0 && RatedAltitude[i] < RatedAltitude[i - 1]) bad = true;
210 // We can't recover from the above - don't use this supercharger speed.
212 // TODO - put out a massive error message!
215 // Now sanity-check stuff that is recoverable.
216 if (i < BoostSpeeds - 1) {
217 if (BoostSwitchAltitude[i] < RatedAltitude[i]) {
218 // TODO - put out an error message
219 // But we can also make a reasonable estimate, as below.
220 BoostSwitchAltitude[i] = RatedAltitude[i] + 1000;
222 BoostSwitchPressure[i] = Atmosphere->GetPressure(BoostSwitchAltitude[i]) * psftopa;
223 //cout << "BoostSwitchAlt = " << BoostSwitchAltitude[i] << ", pressure = " << BoostSwitchPressure[i] << '\n';
224 // Assume there is some hysteresis on the supercharger gear switch, and guess the value for now
225 BoostSwitchHysteresis = 1000;
227 // Now work out the supercharger pressure multiplier of this speed from the rated boost and altitude.
228 RatedMAP[i] = Atmosphere->GetPressureSL() * psftopa + RatedBoost[i] * 6895; // psi*6895 = Pa.
229 // Sometimes a separate BCV setting for takeoff or extra power is fitted.
230 if (TakeoffBoost > RatedBoost[0]) {
231 // Assume that the effect on the BCV is the same whichever speed is in use.
232 TakeoffMAP[i] = RatedMAP[i] + ((TakeoffBoost - RatedBoost[0]) * 6895);
233 bTakeoffBoost = true;
235 TakeoffMAP[i] = RatedMAP[i];
236 bTakeoffBoost = false;
238 BoostMul[i] = RatedMAP[i] / (Atmosphere->GetPressure(RatedAltitude[i]) * psftopa);
242 if (BoostSpeeds > 0) {
246 bBoostOverride = (BoostOverride == 1 ? true : false);
248 Debug(0); // Call Debug() routine from constructor if needed
251 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
253 FGPiston::~FGPiston()
255 delete Lookup_Combustion_Efficiency;
256 delete Power_Mixture_Correlation;
257 Debug(1); // Call Debug() routine from constructor if needed
260 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
262 void FGPiston::ResetToIC(void)
264 FGEngine::ResetToIC();
266 ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
267 MAP = Atmosphere->GetPressure() * psftopa;
268 double airTemperature_degK = RankineToKelvin(Atmosphere->GetTemperature());
269 OilTemp_degK = airTemperature_degK;
270 CylinderHeadTemp_degK = airTemperature_degK;
271 ExhaustGasTemp_degK = airTemperature_degK;
272 EGT_degC = ExhaustGasTemp_degK - 273;
273 Thruster->SetRPM(0.0);
277 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
279 double FGPiston::Calculate(void)
281 if (FuelFlow_gph > 0.0) ConsumeFuel();
283 Throttle = FCS->GetThrottlePos(EngineNumber);
284 Mixture = FCS->GetMixturePos(EngineNumber);
290 p_amb = Atmosphere->GetPressure() * psftopa;
291 p_amb_sea_level = Atmosphere->GetPressureSL() * psftopa;
292 T_amb = RankineToKelvin(Atmosphere->GetTemperature());
294 RPM = Thruster->GetRPM() * Thruster->GetGearRatio();
296 IAS = Auxiliary->GetVcalibratedKTS();
299 if (Boosted) doBoostControl();
304 //Now that the fuel flow is done check if the mixture is too lean to run the engine
305 //Assume lean limit at 22 AFR for now - thats a thi of 0.668
306 //This might be a bit generous, but since there's currently no audiable warning of impending
307 //cutout in the form of misfiring and/or rough running its probably reasonable for now.
308 if (equivalence_ratio < 0.668)
317 if (Thruster->GetType() == FGThruster::ttPropeller) {
318 ((FGPropeller*)Thruster)->SetAdvance(FCS->GetPropAdvance(EngineNumber));
319 ((FGPropeller*)Thruster)->SetFeather(FCS->GetPropFeather(EngineNumber));
322 PowerAvailable = (HP * hptoftlbssec) - Thruster->GetPowerRequired();
324 return Thruster->Calculate(PowerAvailable);
327 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
329 double FGPiston::CalcFuelNeed(void)
331 return FuelFlow_gph / 3600 * 6 * State->Getdt() * Propulsion->GetRate();
334 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
336 int FGPiston::InitRunning(void) {
338 //Thruster->SetRPM( 1.1*IdleRPM/Thruster->GetGearRatio() );
339 Thruster->SetRPM( 1000 );
344 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
346 * Start or stop the engine.
349 void FGPiston::doEngineStartup(void)
351 // Check parameters that may alter the operating state of the engine.
352 // (spark, fuel, starter motor etc)
357 Magneto_Left = false;
358 Magneto_Right = false;
359 // Magneto positions:
368 } // neglects battery voltage, master on switch, etc for now.
370 if ((Magnetos == 1) || (Magnetos > 2)) Magneto_Left = true;
371 if (Magnetos > 1) Magneto_Right = true;
373 // Assume we have fuel for now
376 // Check if we are turning the starter motor
377 if (Cranking != Starter) {
378 // This check saves .../cranking from getting updated every loop - they
379 // only update when changed.
384 if (Cranking) crank_counter++; //Check mode of engine operation
386 if (!Running && spark && fuel) { // start the engine if revs high enough
388 if ((RPM > 450) && (crank_counter > 175)) // Add a little delay to startup
389 Running = true; // on the starter
391 if (RPM > 450) // This allows us to in-air start
392 Running = true; // when windmilling
396 // Cut the engine *power* - Note: the engine may continue to
397 // spin if the prop is in a moving airstream
399 if ( Running && (!spark || !fuel) ) Running = false;
401 // Check for stalling (RPM = 0).
405 } else if ((RPM <= 480) && (Cranking)) {
411 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
414 * Calculate the Current Boost Speed
416 * This function calculates the current turbo/supercharger boost speed
417 * based on altitude and the (automatic) boost-speed control valve configuration.
419 * Inputs: p_amb, BoostSwitchPressure, BoostSwitchHysteresis
421 * Outputs: BoostSpeed
424 void FGPiston::doBoostControl(void)
426 if(BoostSpeed < BoostSpeeds - 1) {
427 // Check if we need to change to a higher boost speed
428 if(p_amb < BoostSwitchPressure[BoostSpeed] - BoostSwitchHysteresis) {
431 } else if(BoostSpeed > 0) {
432 // Check if we need to change to a lower boost speed
433 if(p_amb > BoostSwitchPressure[BoostSpeed - 1] + BoostSwitchHysteresis) {
439 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
442 * Calculate the manifold absolute pressure (MAP) in inches hg
444 * This function calculates manifold absolute pressure (MAP)
445 * from the throttle position, turbo/supercharger boost control
446 * system, engine speed and local ambient air density.
448 * TODO: changes in MP should not be instantaneous -- introduce
449 * a lag between throttle changes and MP changes, to allow pressure
450 * to build up or disperse.
452 * Inputs: minMAP, maxMAP, p_amb, Throttle
454 * Outputs: MAP, ManifoldPressure_inHg
457 void FGPiston::doMAP(void)
460 // Naturally aspirated
461 MAP = minMAP + (Throttle * (maxMAP - minMAP));
462 MAP *= p_amb / p_amb_sea_level;
464 // If takeoff boost is fitted, we currently assume the following throttle map:
465 // (In throttle % - actual input is 0 -> 1)
466 // 99 / 100 - Takeoff boost
467 // 96 / 97 / 98 - Rated boost
468 // 0 - 95 - Idle to Rated boost (MinManifoldPressure to MaxManifoldPressure)
469 // In real life, most planes would be fitted with a mechanical 'gate' between
470 // the rated boost and takeoff boost positions.
471 double T = Throttle; // processed throttle value.
472 bool bTakeoffPos = false;
474 if(Throttle > 0.98) {
475 //cout << "Takeoff Boost!!!!\n";
477 } else if(Throttle <= 0.95) {
482 //cout << "Rated Boost!!\n";
486 // Boost the manifold pressure.
487 MAP *= BoostMul[BoostSpeed];
488 // Now clip the manifold pressure to BCV or Wastegate setting.
490 if(MAP > TakeoffMAP[BoostSpeed]) {
491 MAP = TakeoffMAP[BoostSpeed];
494 if(MAP > RatedMAP[BoostSpeed]) {
495 MAP = RatedMAP[BoostSpeed];
500 // rpm < 10 - effectively stopped.
501 // TODO - add a better variation of MAP with engine speed
502 MAP = Atmosphere->GetPressure() * psftopa;
505 // And set the value in American units as well
506 ManifoldPressure_inHg = MAP / inhgtopa;
509 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
511 * Calculate the air flow through the engine.
512 * Also calculates ambient air density
513 * (used in CHT calculation for air-cooled engines).
515 * Inputs: p_amb, R_air, T_amb, MAP, Displacement,
516 * RPM, volumetric_efficiency
518 * TODO: Model inlet manifold air temperature.
520 * Outputs: rho_air, m_dot_air
523 void FGPiston::doAirFlow(void)
525 rho_air = p_amb / (R_air * T_amb);
526 double rho_air_manifold = MAP / (R_air * T_amb);
527 double displacement_SI = Displacement * in3tom3;
528 double swept_volume = (displacement_SI * (RPM/60)) / 2;
529 double v_dot_air = swept_volume * volumetric_efficiency;
530 m_dot_air = v_dot_air * rho_air_manifold;
533 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
535 * Calculate the fuel flow into the engine.
537 * Inputs: Mixture, thi_sea_level, p_amb_sea_level, p_amb, m_dot_air
539 * Outputs: equivalence_ratio, m_dot_fuel
542 void FGPiston::doFuelFlow(void)
544 double thi_sea_level = 1.3 * Mixture;
545 equivalence_ratio = thi_sea_level * p_amb_sea_level / p_amb;
546 m_dot_fuel = m_dot_air / 14.7 * equivalence_ratio;
547 FuelFlow_gph = m_dot_fuel
548 * 3600 // seconds to hours
550 / 6.6; // lb to gal_us of kerosene
553 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
555 * Calculate the power produced by the engine.
557 * Currently, the JSBSim propellor model does not allow the
558 * engine to produce enough RPMs to get up to a high horsepower.
559 * When tested with sufficient RPM, it has no trouble reaching
562 * Inputs: ManifoldPressure_inHg, p_amb, p_amb_sea_level, RPM, T_amb,
563 * equivalence_ratio, Cycles, MaxHP
565 * Outputs: Percentage_Power, HP
568 void FGPiston::doEnginePower(void)
571 double T_amb_degF = KelvinToFahrenheit(T_amb);
572 double T_amb_sea_lev_degF = KelvinToFahrenheit(288);
574 // FIXME: this needs to be generalized
575 double ManXRPM; // Convienience term for use in the calculations
577 // Currently a simple linear fit.
578 // The zero crossing is moved up the speed-load range to reduce the idling power.
580 double zeroOffset = (minMAP / 2.0) * (IdleRPM / 2.0);
581 ManXRPM = MAP * (RPM > RatedRPM[BoostSpeed] ? RatedRPM[BoostSpeed] : RPM);
582 // The speed clip in the line above is deliberate.
583 Percentage_Power = ((ManXRPM - zeroOffset) / ((RatedMAP[BoostSpeed] * RatedRPM[BoostSpeed]) - zeroOffset)) * 107.0;
584 Percentage_Power -= 7.0; // Another idle power reduction offset - see line above with 107.
585 if (Percentage_Power < 0.0) Percentage_Power = 0.0;
586 // Note that %power is allowed to go over 100 for boosted powerplants
587 // such as for the BCV-override or takeoff power settings.
588 // TODO - currently no altitude effect (temperature & exhaust back-pressure) modelled
589 // for boosted engines.
591 ManXRPM = ManifoldPressure_inHg * RPM; // Note that inHg must be used for the following correlation.
592 Percentage_Power = (6e-9 * ManXRPM * ManXRPM) + (8e-4 * ManXRPM) - 1.0;
593 // Percentage_Power += ((T_amb_sea_lev_degF - T_amb_degF) * 7 /120);
594 Percentage_Power += ((T_amb_sea_lev_degF - T_amb_degF) * 7 * dt);
595 if (Percentage_Power < 0.0) Percentage_Power = 0.0;
596 else if (Percentage_Power > 100.0) Percentage_Power = 100.0;
599 double Percentage_of_best_power_mixture_power =
600 Power_Mixture_Correlation->GetValue(14.7 / equivalence_ratio);
602 Percentage_Power *= Percentage_of_best_power_mixture_power / 100.0;
605 Percentage_Power *= SparkFailDrop;
608 HP = Percentage_Power * RatedPower[BoostSpeed] / 100.0;
610 HP = Percentage_Power * MaxHP / 100.0;
615 // Power output when the engine is not running
619 } else if (RPM < 480) {
620 HP = StarterHP + ((480 - RPM) / 8.0);
621 // This is a guess - would be nice to find a proper starter moter torque curve
626 // Quick hack until we port the FMEP stuff
633 // cout << "Power = " << HP << " RPM = " << RPM << " Running = " << Running << " Cranking = " << Cranking << endl;
636 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
638 * Calculate the exhaust gas temperature.
640 * Inputs: equivalence_ratio, m_dot_fuel, calorific_value_fuel,
641 * Cp_air, m_dot_air, Cp_fuel, m_dot_fuel, T_amb, Percentage_Power
643 * Outputs: combustion_efficiency, ExhaustGasTemp_degK
646 void FGPiston::doEGT(void)
648 double delta_T_exhaust;
649 double enthalpy_exhaust;
650 double heat_capacity_exhaust;
653 if ((Running) && (m_dot_air > 0.0)) { // do the energy balance
654 combustion_efficiency = Lookup_Combustion_Efficiency->GetValue(equivalence_ratio);
655 enthalpy_exhaust = m_dot_fuel * calorific_value_fuel *
656 combustion_efficiency * 0.33;
657 heat_capacity_exhaust = (Cp_air * m_dot_air) + (Cp_fuel * m_dot_fuel);
658 delta_T_exhaust = enthalpy_exhaust / heat_capacity_exhaust;
659 ExhaustGasTemp_degK = T_amb + delta_T_exhaust;
660 ExhaustGasTemp_degK *= 0.444 + ((0.544 - 0.444) * Percentage_Power / 100.0);
661 } else { // Drop towards ambient - guess an appropriate time constant for now
662 combustion_efficiency = 0;
663 dEGTdt = (RankineToKelvin(Atmosphere->GetTemperature()) - ExhaustGasTemp_degK) / 100.0;
664 delta_T_exhaust = dEGTdt * dt;
665 ExhaustGasTemp_degK += delta_T_exhaust;
669 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
671 * Calculate the cylinder head temperature.
673 * Inputs: T_amb, IAS, rho_air, m_dot_fuel, calorific_value_fuel,
674 * combustion_efficiency, RPM
676 * Outputs: CylinderHeadTemp_degK
679 void FGPiston::doCHT(void)
685 double arbitary_area = 1.0;
686 double CpCylinderHead = 800.0;
687 double MassCylinderHead = 8.0;
689 double temperature_difference = CylinderHeadTemp_degK - T_amb;
690 double v_apparent = IAS * 0.5144444;
691 double v_dot_cooling_air = arbitary_area * v_apparent;
692 double m_dot_cooling_air = v_dot_cooling_air * rho_air;
693 double dqdt_from_combustion =
694 m_dot_fuel * calorific_value_fuel * combustion_efficiency * 0.33;
695 double dqdt_forced = (h2 * m_dot_cooling_air * temperature_difference) +
696 (h3 * RPM * temperature_difference);
697 double dqdt_free = h1 * temperature_difference;
698 double dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;
700 double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
702 CylinderHeadTemp_degK +=
703 (dqdt_cylinder_head / HeatCapacityCylinderHead) * dt;
706 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
708 * Calculate the oil temperature.
710 * Inputs: Percentage_Power, running flag.
712 * Outputs: OilTemp_degK
715 void FGPiston::doOilTemperature(void)
717 double idle_percentage_power = 2.3; // approximately
718 double target_oil_temp; // Steady state oil temp at the current engine conditions
719 double time_constant; // The time constant for the differential equation
722 target_oil_temp = 363;
723 time_constant = 500; // Time constant for engine-on idling.
724 if (Percentage_Power > idle_percentage_power) {
725 time_constant /= ((Percentage_Power / idle_percentage_power) / 10.0); // adjust for power
728 target_oil_temp = RankineToKelvin(Atmosphere->GetTemperature());
729 time_constant = 1000; // Time constant for engine-off; reflects the fact
730 // that oil is no longer getting circulated
733 double dOilTempdt = (target_oil_temp - OilTemp_degK) / time_constant;
735 OilTemp_degK += (dOilTempdt * dt);
738 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
740 * Calculate the oil pressure.
744 * Outputs: OilPressure_psi
747 void FGPiston::doOilPressure(void)
749 double Oil_Press_Relief_Valve = 60; // FIXME: may vary by engine
750 double Oil_Press_RPM_Max = 1800; // FIXME: may vary by engine
751 double Design_Oil_Temp = 358; // degK; FIXME: may vary by engine
752 double Oil_Viscosity_Index = 0.25;
754 OilPressure_psi = (Oil_Press_Relief_Valve / Oil_Press_RPM_Max) * RPM;
756 if (OilPressure_psi >= Oil_Press_Relief_Valve) {
757 OilPressure_psi = Oil_Press_Relief_Valve;
760 OilPressure_psi += (Design_Oil_Temp - OilTemp_degK) * Oil_Viscosity_Index;
763 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
765 string FGPiston::GetEngineLabels(string delimeter)
767 std::ostringstream buf;
769 buf << Name << " Power Available (engine " << EngineNumber << " in HP)" << delimeter
770 << Name << " HP (engine " << EngineNumber << ")" << delimeter
771 << Name << " equivalent ratio (engine " << EngineNumber << ")" << delimeter
772 << Name << " MAP (engine " << EngineNumber << ")" << delimeter
773 << Thruster->GetThrusterLabels(EngineNumber, delimeter);
778 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
780 string FGPiston::GetEngineValues(string delimeter)
782 std::ostringstream buf;
784 buf << PowerAvailable << delimeter << HP << delimeter
785 << equivalence_ratio << delimeter << MAP << delimeter
786 << Thruster->GetThrusterValues(EngineNumber, delimeter);
791 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
793 // The bitmasked value choices are as follows:
794 // unset: In this case (the default) JSBSim would only print
795 // out the normally expected messages, essentially echoing
796 // the config files as they are read. If the environment
797 // variable is not set, debug_lvl is set to 1 internally
798 // 0: This requests JSBSim not to output any messages
800 // 1: This value explicity requests the normal JSBSim
802 // 2: This value asks for a message to be printed out when
803 // a class is instantiated
804 // 4: When this value is set, a message is displayed when a
805 // FGModel object executes its Run() method
806 // 8: When this value is set, various runtime state variables
807 // are printed out periodically
808 // 16: When set various parameters are sanity checked and
809 // a message is printed out when they go out of bounds
811 void FGPiston::Debug(int from)
813 if (debug_lvl <= 0) return;
815 if (debug_lvl & 1) { // Standard console startup message output
816 if (from == 0) { // Constructor
818 cout << "\n Engine Name: " << Name << endl;
819 cout << " MinManifoldPressure: " << MinManifoldPressure_inHg << endl;
820 cout << " MaxManifoldPressure: " << MaxManifoldPressure_inHg << endl;
821 cout << " MinMaP (Pa): " << minMAP << endl;
822 cout << " MaxMaP (Pa): " << maxMAP << endl;
823 cout << " Displacement: " << Displacement << endl;
824 cout << " MaxHP: " << MaxHP << endl;
825 cout << " Cycles: " << Cycles << endl;
826 cout << " IdleRPM: " << IdleRPM << endl;
827 cout << " MaxThrottle: " << MaxThrottle << endl;
828 cout << " MinThrottle: " << MinThrottle << endl;
831 cout << " Combustion Efficiency table:" << endl;
832 Lookup_Combustion_Efficiency->Print();
836 cout << " Power Mixture Correlation table:" << endl;
837 Power_Mixture_Correlation->Print();
842 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
843 if (from == 0) cout << "Instantiated: FGPiston" << endl;
844 if (from == 1) cout << "Destroyed: FGPiston" << endl;
846 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
848 if (debug_lvl & 8 ) { // Runtime state variables
850 if (debug_lvl & 16) { // Sanity checking
852 if (debug_lvl & 64) {
853 if (from == 0) { // Constructor
854 cout << IdSrc << endl;
855 cout << IdHdr << endl;
859 } // namespace JSBSim