{
_boost = 1;
_running = false;
- _cranking = false;
_fuel = true;
+ _boostPressure = 0;
+
+ _oilTemp = Atmosphere::getStdTemperature(0);
+ _oilTempTarget = _oilTemp;
+ _dOilTempdt = 0;
// 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.
return _power0;
}
-void PistonEngine::setThrottle(float t)
-{
- _throttle = t;
-}
-
-void PistonEngine::setRunning(bool r)
-{
- _running = r;
-}
-
-void PistonEngine::setStarter(bool s)
-{
- _cranking = s;
-}
-
-void PistonEngine::setMagnetos(int m)
-{
- _magnetos = m;
-}
-
-void PistonEngine::setMixture(float m)
-{
- _mixture = m;
-}
-
-void PistonEngine::setBoost(float boost)
-{
- _boost = boost;
-}
-
-bool PistonEngine::isRunning()
-{
- return _running;
-}
-
bool PistonEngine::isCranking()
{
- return _cranking;
+ return _starter;
}
float PistonEngine::getTorque()
return _egt;
}
+void PistonEngine::stabilize()
+{
+ _oilTemp = _oilTempTarget;
+}
+
+void PistonEngine::integrate(float dt)
+{
+ _oilTemp += (_dOilTempdt * dt);
+}
+
void PistonEngine::calc(float pressure, float temp, float speed)
{
if(_magnetos == 0 || speed < 60*RPM2RADPS)
else
_running = true;
- // Calculate manifold pressure as ambient pressure modified for
- // turbocharging and reduced by the throttle setting. According
- // to Dave Luff, minimum throttle at sea level corresponds to 6"
- // manifold pressure. Assume that this means that minimum MP is
- // always 20% of ambient pressure. (But that's too much idle
- // power, so use 10% instead!) But we need to produce _zero_
- // thrust at that setting, so hold onto the "output" value
- // separately. Ick.
- _mp = pressure * (1 + _boost*(_turbo-1)); // turbocharger
- float mp = _mp * (0.1f + 0.9f * _throttle); // throttle
- _mp *= _throttle;
- if(mp > _maxMP) mp = _maxMP; // wastegate
+ // Calculate the factor required to modify supercharger output for
+ // rpm. Assume that the normalized supercharger output ~= 1 when
+ // the engine is at the nominated peak-power rpm (normalised).
+ // A power equation of the form (A * B^x * x^C) has been
+ // derived empirically from some representative supercharger data.
+ // This provides near-linear output over the normal operating range,
+ // with fall-off in the over-speed situation.
+ float rpm_norm = (speed / _omega0);
+ float A = 1.795206541;
+ float B = 0.55620178;
+ float C = 1.246708471;
+ float rpm_factor = A * Math::pow(B, rpm_norm) * Math::pow(rpm_norm, C);
+
+ // We need to adjust the minimum manifold pressure to get a
+ // reasonable idle speed (a "closed" throttle doesn't suck a total
+ // vacuum in real manifolds). This is a hack.
+ float _minMP = (-0.008 * _turbo ) + 0.1;
+
+ // Scale to throttle setting, clamp to wastegate
+ if(_running) {
+ _mp = pressure * (1 + (_boost * (_turbo-1) * rpm_factor));
+ _mp *= _minMP + (1 -_minMP) * _throttle;
+ }
+ if(_mp > _maxMP) _mp = _maxMP;
+
+ // The "boost" is the delta above ambient
+ _boostPressure = _mp - pressure;
// Air entering the manifold does so rapidly, and thus the
// pressure change can be assumed to be adiabatic. Calculate a
// temperature change, and use that to get the density.
- float T = temp * Math::pow(mp/pressure, 2.0/7.0);
- float rho = mp / (287.1f * T);
+ // Note: need to model intercoolers here...
+ float T = temp * Math::pow(_mp/pressure, 2.0/7.0);
+ float rho = _mp / (287.1f * T);
// The actual fuel flow is determined only by engine RPM and the
// mixture setting. Not all of this will burn with the same
// speed on a 160HP engine, that comes out to about 160*.15/30 ==
// 0.8 HP starter motor. Which sounds about right to me. I think
// I've finally got this tuned. :)
- if(_cranking && !_running)
+ if(_starter && !_running)
_torque += 0.15f * _power0/_omega0;
// Also, add a negative torque of 8% of cruise, to represent
// what we'd expect. And diddle the work done by the gas a bit to
// account for non-thermodynamic losses like internal friction;
// 10% should do it.
-
float massFlow = _fuelFlow + (rho * 0.5f * _displacement * speed);
float specHeat = 1300;
float corr = 1.0f/(Math::pow(_compression, 0.4f) - 1.0f);
_egt = corr * (power * 1.1f) / (massFlow * specHeat);
if(_egt < temp) _egt = temp;
+
+
+ // Oil temperature.
+ // Assume a linear variation between ~90degC at idle and ~120degC
+ // at full power. No attempt to correct for airflow over the
+ // engine is made. Make the time constant to attain target steady-
+ // state oil temp greater at engine off than on to reflect no
+ // circulation. Nothing fancy, but populates the guage with a
+ // plausible value.
+ float tau; // secs
+ if(_running) {
+ _oilTempTarget = 363.0f + (30.0f * (power/_power0));
+ tau = 600;
+ // Reduce tau linearly to 300 at max power
+ tau -= (power/_power0) * 300.0f;
+ } else {
+ _oilTempTarget = temp;
+ tau = 1500;
+ }
+ _dOilTempdt = (_oilTempTarget - _oilTemp) / tau;
}
}; // namespace yasim
projects / flightgear.git / blobdiff