virtual public void CreateEngine()
{
engineSolver = new EngineSolver();
}
/// <summary>
/// Update method for piston engine
/// </summary>
/// <param name="solver"></param>
/// <param name="shaftRPM"></param>
/// <param name="deltaTime">the current delta time for updates</param>
public void Update(EngineSolver solver, double shaftRPM, double deltaTime)
{
double pAmb = solver.p0 + _ramAir * solver.Q;
_throttle = solver.throttle;
_fuel = solver.ffFraction > 0d;
_engineThrust = 0d;
_status = "Windmilling";
bool canStart = _running = solver.running;
// in precedence order, set running = false (highest priority message last)
if (shaftRPM < 60d) // 60RPM min for engine running
{
_status = "Too Low RPM"; // status should never be seen because
_running = false; // the starter motor bit at the end will happen
// or another case will trump this.
}
if (_throttle == 0d || !canStart)
{
_status = "Magnetos Off";
_running = false;
canStart = false;
}
if (!_fuel)
{
_status = "Out of Fuel";
_running = false;
canStart = false;
}
if (!solver.oxygen || solver.rho <= 0d)
{
_status = "No Oxygen";
_running = false;
canStart = false;
}
if (_running)
{
_status = "Nominal";
shaftRPM = Math.Max(shaftRPM, 30d); // 30RPM min when running to avoid NaNs
// check if we need to switch boost modes
double power;
double MAP;
float fuelRatio = FuelAirRatio(_mixture);
double efficiency = mixtureEfficiency.Evaluate(fuelRatio);
if (_boostSwitch > 0)
{
if (pAmb < _boostSwitch - 1000d && _boostMode < 1)
{
_boostMode++;
}
if (pAmb > _boostSwitch + 1000d && _boostMode > 0)
{
_boostMode--;
}
_chargeTarget = GetChargeTarget(shaftRPM, _boostMode);
_charge = GetCharge(_chargeTarget, deltaTime);
MAP = CalcMAP(pAmb, _boostMode, _charge);
// Compute fuel flow
_airFlow = GetAirflow(pAmb, solver.t0, solver.R_c, solver.gamma_c, shaftRPM, MAP);
_fuelFlow = _airFlow * fuelRatio;
power = _fuelFlow * efficiency * _bsfcRecip - _boostCosts[_boostMode];
}
else // auto switch
{
// assume supercharger for now, so charge = target
double target0 = GetChargeTarget(shaftRPM, 0);
double target1 = GetChargeTarget(shaftRPM, 1);
double charge0 = GetCharge(target0, deltaTime);
double charge1 = GetCharge(target1, deltaTime);
double MAP0 = CalcMAP(pAmb, 0, charge0);
double MAP1 = CalcMAP(pAmb, 1, charge1);
double airflow0 = GetAirflow(pAmb, solver.t0, solver.R_c, solver.gamma_c, shaftRPM, MAP0);
double m_dot_fuel0 = airflow0 * fuelRatio;
double power0 = m_dot_fuel0 * efficiency * _bsfcRecip - _boostCosts[0];
double airflow1 = GetAirflow(pAmb, solver.t0, solver.R_c, solver.gamma_c, shaftRPM, MAP1);
double m_dot_fuel1 = airflow1 * fuelRatio;
double power1 = m_dot_fuel1 * efficiency * _bsfcRecip - _boostCosts[1];
if (power0 >= power1)
{
MAP = MAP0;
_chargeTarget = target0;
_charge = charge0;
power = power0;
_airFlow = airflow0;
_fuelFlow = m_dot_fuel0;
_boostMode = 0;
_chargeTemp = GetCAT(MAP, pAmb, solver.t0); // duplication of effort, but oh well, this needs to be done to reset _chargeTemp
}
else
{
MAP = MAP1;
_chargeTarget = target1;
_charge = charge1;
power = power1;
_airFlow = airflow1;
_fuelFlow = m_dot_fuel1;
_boostMode = 1;
}
}
_mp = MAP;
//_chargeTemp = GetCAT(MAP, pAmb, solver.t0); // duplication of effort, but oh well
// The "boost" is the delta above ambient
_boostPressure = _mp - pAmb;
_power = power;
_totalPower = _power + _boostCosts[_boostMode];
_egt = GetEGT(efficiency, solver.t0, solver.Cp_c);
// Additional thrust from engine
// FIXME now that we calculate EGT should use that.
// heat from mixture, heat hack for over-RPM, multiply by relative manifold pressure
double tmpRatio = shaftRPM / _rpm0;
if (tmpRatio > 1d)
{
tmpRatio *= tmpRatio;
}
float mixRatio = (1.5f - _mixture);
mixRatio *= mixRatio;
mixRatio = (mixRatio + 0.2f) * 1.2f;
double tempDelta = tmpRatio * mixRatio * _mp / _maxMP;
// exhaust thrust, normalized to "10% HP in lbf"
if (_exhaustThrust != 0d)
{
_netExhaustThrust = _exhaustThrust * (_totalPower * W2HP * 0.1d * LBFTON) * tempDelta;
_engineThrust += _netExhaustThrust;
}
// Meredith Effect radiator thrust, scaled by Q and by how hot the engine is running and the ambient temperature
// CTOK is there because tempdelta is expressed as a multiple of 0C-in-K (FIXME)
if (_meredithEffect != 0d)
{
_netMeredithEffect = _meredithEffect * solver.Q * (tempDelta * 273.15d / solver.t0);
_engineThrust += _netMeredithEffect;
}
//MonoBehaviour.print("Engine running: HP " + power * W2HP + "/" + _totalPower * W2HP + ", rpm " + shaftRPM + ", mp " + _mp + ", charge " + _charge + ", cat " + _chargeTemp + ", chargeRho " + _chargeDensity + ", egt " + _egt + ", fuel " + _fuelFlow + ", airflow " + _airFlow + ", effic " + efficiency);
}
else
{
_mp = solver.p0;
_boostPressure = 0d;
// assume a starter motor of 15% power
if (canStart)
{
_status = "Starter On";
_power = _totalPower = 0.2d * _power0;
_fuelFlow = _power * _bsfc * 0.2d;
_airFlow = _fuelFlow * 10d;
_mp = 0.15d * _maxMP;
_egt = GetEGT(1d, solver.t0, solver.Cp_c);
}
else
{
_fuelFlow = _airFlow = _power = _totalPower = 0d;
if (_egt > solver.t0 + 1d)
{
_egt += (solver.t0 - _egt) * 0.05d * deltaTime;
}
else
{
_egt = solver.t0;
}
}
}
// unused
/*
* // 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.
* double 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;*/
}