Fuel consumption. Simple implementation without support for tank selection

or engine-specific feeds.

src/FDM/YASim/Airplane.cpp

@@ -62,7 +62,28 @@ void Airplane::iterate(float dt)
 
     _model.iterate();
 
-    // FIXME: Consume fuel
+    // Consume fuel.  This is a really simple implementation that
+    // assumes all engines draw equally from all tanks in proportion
+    // to the amount of fuel stored there.  Needs to be fixed, but
+    // that has to wait for a decision as to what the property
+    // interface will look like.
+    int i, outOfFuel = 0;
+    float fuelFlow = 0, totalFuel = 0.00001; // <-- overflow protection
+    for(i=0; i<_thrusters.size(); i++)
+        fuelFlow += ((ThrustRec*)_thrusters.get(i))->thruster->getFuelFlow();
+    for(i=0; i<_tanks.size(); i++)
+        totalFuel += ((Tank*)_tanks.get(i))->fill;
+    for(i=0; i<_tanks.size(); i++) {
+        Tank* t = (Tank*)_tanks.get(i);
+        t->fill -= dt * fuelFlow * (t->fill/totalFuel);
+        if(t->fill <= 0) {
+            t->fill = 0;
+            outOfFuel = 1;
+        }
+    }
+    if(outOfFuel)
+        for(int i=0; i<_thrusters.size(); i++)
+            ((ThrustRec*)_thrusters.get(i))->thruster->setFuelState(false);
 }
 
 ControlMap* Airplane::getControlMap()
@@ -189,6 +210,11 @@ float Airplane::getFuelDensity(int tank)
     return ((Tank*)_tanks.get(tank))->density;
 }
 
+float Airplane::getTankCapacity(int tank)
+{
+    return ((Tank*)_tanks.get(tank))->cap;
+}
+
 void Airplane::setWeight(float weight)
 {
     _emptyWeight = weight;
@@ -298,6 +324,7 @@ void Airplane::setFuelFraction(float frac)
     int i;
     for(i=0; i<_tanks.size(); i++) {
         Tank* t = (Tank*)_tanks.get(i);
+        t->fill = frac * t->cap;
         _model.getBody()->setMass(t->handle, t->cap * frac);
     }
 }

src/FDM/YASim/Airplane.hpp

@@ -57,6 +57,7 @@ public:
     void setFuelFraction(float frac); // 0-1, total amount of fuel
     float getFuel(int tank); // in kg!
     float getFuelDensity(int tank); // kg/m^3
+    float getTankCapacity(int tank);
 
     void compile(); // generate point masses & such, then solve
     void initEngines();

src/FDM/YASim/FGFDM.cpp

@@ -148,7 +148,7 @@ void FGFDM::startElement(const char* name, const XMLAttributes &atts)
 	float n2max = attrf(a, "n2-max", 103);
 	j->setRPMs(n1min, n1max, n2min, n2max);
 
-	if(a->hasAttribute("tsfc")) j->setTSFC(attrf(a, "tsfc"));
+	j->setTSFC(attrf(a, "tsfc", 0.8));
 	if(a->hasAttribute("egt"))  j->setEGT(attrf(a, "egt"));
 	if(a->hasAttribute("epr"))  j->setEPR(attrf(a, "epr"));
 	if(a->hasAttribute("exhaust-speed"))
@@ -328,11 +328,22 @@ void FGFDM::setOutputProperties()
         p->prop->setFloatValue(val);
     }
 
-    float fuelDensity = 718.95; // default to gasoline: ~6 lb/gal
+    float totalFuel = 0, totalCap = 0;
+    float fuelDensity = 720; // in kg/m^3, default to gasoline: ~6 lb/gal
     for(i=0; i<_airplane.numTanks(); i++) {
         fuelDensity = _airplane.getFuelDensity(i);
 	sprintf(buf, "/consumables/fuel/tank[%d]/level-gal_us", i);
 	fgSetFloat(buf, CM2GALS*_airplane.getFuel(i)/fuelDensity);
+	sprintf(buf, "/consumables/fuel/tank[%d]/level-lbs", i);
+	fgSetFloat(buf, KG2LBS*_airplane.getFuel(i));
+        totalFuel += _airplane.getFuel(i);
+        totalCap += _airplane.getTankCapacity(i);
+    }
+    if(totalCap != 0) {
+        fgSetFloat("/consumables/fuel/total-fuel-lbs", KG2LBS*totalFuel);
+        fgSetFloat("/consumables/fuel/total-fuel-gals",
+                   CM2GALS*totalFuel/fuelDensity);
+        fgSetFloat("/consumables/fuel/total-fuel-norm", totalFuel/totalCap);
     }
 
     for(i=0; i<_thrusters.size(); i++) {

src/FDM/YASim/Jet.cpp

@@ -31,6 +31,7 @@ Jet::Jet()
     // And sanify the remaining junk, just in case.
     _running = true;
     _cranking = false;
+    _fuel = true;
     _epr = 1;
     _fuelFlow = 0;
     _egt = 273;
@@ -148,6 +149,12 @@ void Jet::integrate(float dt)
     _pressureCorrect = statP/P0;
     _tempCorrect = Math::sqrt(statT/T0);
 
+    // Handle running out of fuel.  This is a hack.  What should
+    // really happen is a simulation of ram air torque on the
+    // turbine.  This just forces the engine into ground idle.
+    if(_fuel == false)
+        _throttle = 0;
+
     // Linearly taper maxThrust to zero at vMax
     float vCorr = 1 - (speed/_vMax);
 

src/FDM/YASim/PistonEngine.cpp

@@ -12,6 +12,7 @@ PistonEngine::PistonEngine(float power, float speed)
     _boost = 1;
     _running = false;
     _cranking = false;
+    _fuel = true;
 
     // Presume a BSFC (in lb/hour per HP) of 0.45.  In SI that becomes
     // (2.2 lb/kg, 745.7 W/hp, 3600 sec/hour) 7.62e-08 kg/Ws.
@@ -131,6 +132,8 @@ void PistonEngine::calc(float pressure, float temp, float speed)
 {
     if(_magnetos == 0 || speed < 200*RPM2RADPS)
 	_running = false;
+    else if(_fuel == false)
+        _running = false;
     else
 	_running = true;
 
@@ -157,6 +160,7 @@ void PistonEngine::calc(float pressure, float temp, float speed)
     // mixture setting.  Not all of this will burn with the same
     // efficiency.
     _fuelFlow = _mixture * speed * _mixCoeff;
+    if(_fuel == false) _fuelFlow = 0;
 
     // How much fuel could be burned with ideal (i.e. uncorrected!)
     // combustion.

src/FDM/YASim/PistonEngine.hpp

@@ -16,6 +16,7 @@ public:
     void setMagnetos(int magnetos);
     void setMixture(float mixture);
     void setBoost(float boost); // fraction of turbo-mul used
+    void setFuelState(bool hasFuel) { _fuel = hasFuel; }
 
     // For solver use
     void setRunning(bool r);
@@ -48,6 +49,7 @@ private:
     int _magnetos; // 0=off, 1=right, 2=left, 3=both
     float _mixture;
     float _boost;
+    bool _fuel;
 
     // Runtime state/output:
     bool _running;

src/FDM/YASim/PropEngine.cpp

@@ -15,6 +15,7 @@ PropEngine::PropEngine(Propeller* prop, PistonEngine* eng, float moment)
     _prop = prop;
     _eng = eng;
     _moment = moment;
+    _fuel = true;
 }
 
 PropEngine::~PropEngine()
@@ -140,6 +141,7 @@ void PropEngine::integrate(float dt)
     _eng->setStarter(_starter);
     _eng->setMagnetos(_magnetos);
     _eng->setMixture(_mixture);
+    _eng->setFuelState(_fuel);
     
     _prop->calc(_rho, speed, _omega, &thrust, &propTorque);
     _eng->calc(_pressure, _temp, _omega);

src/FDM/YASim/Thruster.hpp

@@ -31,6 +31,7 @@ public:
     void setThrottle(float throttle);
     void setMixture(float mixture);
     void setStarter(bool starter);
+    void setFuelState(bool hasFuel) { _fuel = hasFuel; }
 
     // Dynamic output
     virtual bool isRunning()=0;
@@ -38,7 +39,7 @@ public:
     virtual void getThrust(float* out)=0;
     virtual void getTorque(float* out)=0;
     virtual void getGyro(float* out)=0;
-    virtual float getFuelFlow()=0;
+    virtual float getFuelFlow()=0; // in kg/s
 
     // Runtime instructions
     void setWind(float* wind);
@@ -53,6 +54,7 @@ protected:
     float _throttle;
     float _mixture;
     bool _starter; // true=engaged, false=disengaged
+    bool _fuel; // true=available, false=out
 
     float _wind[3];
     float _pressure;