void CalculateNozzleCurveParameters()
{
double sqrtArea = Math.Sqrt(areaRatio);
E.y = sqrtArea;
E.x = relLength * (sqrtArea - 1) / NozzleUtils.GetConical15DegConstant();
N.x = 0.382 * Math.Cos(inflectionAngle - Math.PI / 180.0);
N.y = 0.382 * Math.Sin(inflectionAngle - Math.PI / 180.0) + 1.382;
if (shapeType == NozzleShapeType.CONICAL)
{
Q = 0.5 * (N + E);
return;
}
double slope1, slope2;
slope1 = Math.Tan(inflectionAngle);
slope2 = Math.Tan(exitAngle);
double intercept1, intercept2;
intercept1 = N.y - slope1 * N.x;
intercept2 = E.y - slope2 * E.x;
Q.x = (intercept2 - intercept1) / (slope1 - slope2);
Q.y = (intercept2 * slope1 - intercept1 * slope1) / (slope1 - slope2) + intercept1;
}
void CalcTurbineExhaustThrust()
{
double nozzleInletTemp = turbopump.GetTurbineExitTemp();
if (turbineExhaustType == TurbineExhaustEnum.DIRECT)
{
//Calc exit area, which is the throat area since this is a choked converging nozzle
exhaustArea = (gasGenPrefab.nozzleGamma + 1.0) / (gasGenPrefab.nozzleGamma - 1.0);
exhaustArea = Math.Pow(2.0 / (gasGenPrefab.nozzleGamma + 1.0), exhaustArea);
exhaustArea *= gasGenPrefab.nozzleGamma * enginePrefab.nozzleMWgMol;
exhaustArea /= (GAS_CONSTANT * nozzleInletTemp);
exhaustArea = Math.Sqrt(exhaustArea);
exhaustArea *= turbineBackPresMPa;
exhaustArea = turbineMassFlow / exhaustArea;
exhaustArea *= 0.001;
double exhaustExitTemp = nozzleInletTemp / (1.0 + (gasGenPrefab.nozzleGamma - 1.0) * 0.5);
double exhaustExitVel = Math.Sqrt(gasGenPrefab.nozzleGamma * exhaustExitTemp * GAS_CONSTANT / gasGenPrefab.nozzleMWgMol);
double exhaustThrustMomentum = exhaustExitVel * turbineMassFlow;
thrustVacAux += exhaustThrustMomentum;
thrustSLAux += exhaustThrustMomentum;
double exhaustExitPres = turbineBackPresMPa / Math.Pow((1.0 + (gasGenPrefab.nozzleGamma - 1.0) * 0.5), gasGenPrefab.nozzleGamma / (gasGenPrefab.nozzleGamma - 1.0));
thrustVacAux += exhaustExitPres * exhaustArea * 1000.0;
thrustSLAux += (exhaustExitPres - 0.1013) * exhaustArea * 1000.0;
}
else if (turbineExhaustType == TurbineExhaustEnum.INTO_NOZZLE)
{
double exhaustExpansionRatio = areaRatio / nozzleExhaustArea;
double machThroughExpansion = exhaustExpansionRatio <= 1.0 ? 1.0 : NozzleUtils.MachFromAreaRatio(exhaustExpansionRatio, gasGenPrefab.nozzleGamma);
double exhaustExitTemp = nozzleInletTemp / (1.0 + (gasGenPrefab.nozzleGamma - 1.0) * 0.5 * machThroughExpansion * machThroughExpansion);
double exhaustExitVel = Math.Sqrt(gasGenPrefab.nozzleGamma * exhaustExitTemp * GAS_CONSTANT / gasGenPrefab.nozzleMWgMol) * machThroughExpansion;
double exhaustThrustMomentum = exhaustExitVel * turbineMassFlow;
exhaustThrustMomentum *= nozzleDivEfficiency;
double relDistanceDownNozzle = nozzle.GetFracLengthAtArea(nozzleExhaustArea);
exhaustThrustMomentum *= (1.0 * relDistanceDownNozzle + nozzleFrictionEfficiency * (1.0 - relDistanceDownNozzle));
thrustVacAux += exhaustThrustMomentum;
thrustSLAux += exhaustThrustMomentum;
}
}
void CalculateExitInflectionAngles()
{
switch (shapeType)
{
case NozzleShapeType.CONICAL:
exitAngle = NozzleUtils.GetConicalExitAngle(relLength);
inflectionAngle = exitAngle;
break;
case NozzleShapeType.BELL:
Vector2d angles = NozzleUtils.GetBellExitInflectionAngles(relLength, areaRatio);
exitAngle = angles.x;
inflectionAngle = angles.y;
break;
}
exitAngleString = (exitAngle * 180.0 / Math.PI).ToString("F1");
}
void CalcTurbineExhaustBackPressure()
{
double exhaustPresMPa = 0.1013 * 1.5; //1.5 atm
if (turbineExhaustType == TurbineExhaustEnum.INTO_NOZZLE)
{
double machAtArea = NozzleUtils.MachFromAreaRatio(nozzleExhaustArea, modGamma);
double isentropicRatio = 0.5 * (modGamma - 1.0);
isentropicRatio = (1.0 + isentropicRatio * enginePrefab.nozzleMach * enginePrefab.nozzleMach) / (1.0 + isentropicRatio * machAtArea * machAtArea);
exhaustPresMPa = Math.Max(Math.Pow(isentropicRatio, modGamma / (modGamma - 1.0)) * enginePrefab.nozzlePresMPa * 1.05, exhaustPresMPa); //gets the pressure in the nozzle at this area ratio, but only if it's higher than this
}
turbineBackPresMPa = (gasGenPrefab.nozzleGamma - 1.0) * 0.5 + 1.0;
turbineBackPresMPa = Math.Pow(turbineBackPresMPa, gasGenPrefab.nozzleGamma / (gasGenPrefab.nozzleGamma - 1.0));
turbineBackPresMPa *= exhaustPresMPa;
turbineBackPresMPa = Math.Max(turbineBackPresMPa, gasGenPrefab.chamberPresMPa / 24.0);
}
protected void CalculateEngineAndNozzlePerformanceProperties()
{
effectiveFrozenAreaRatio = NozzleUtils.AreaRatioFromMach(enginePrefab.nozzleMach, enginePrefab.nozzleGamma);
effectiveExitAreaRatio = areaRatio * enginePrefab.frozenAreaRatio / effectiveFrozenAreaRatio;
modGamma = CalculateGammaModified(effectiveExitAreaRatio); //avg gamma, modified for expansion ratio
double exitMach = NozzleUtils.MachFromAreaRatio(effectiveExitAreaRatio, modGamma);
double isentropicRatio = 0.5 * (modGamma - 1.0);
isentropicRatio = (1.0 + isentropicRatio * enginePrefab.nozzleMach * enginePrefab.nozzleMach) / (1.0 + isentropicRatio * exitMach * exitMach);
double exitTemp = isentropicRatio * enginePrefab.nozzleTempK;
double exitSonicVelocity = Math.Sqrt(modGamma * GAS_CONSTANT / enginePrefab.nozzleMWgMol * exitTemp);
exhaustVelocityOpt = exitSonicVelocity * exitMach;
exitPressureMPa = Math.Pow(isentropicRatio, modGamma / (modGamma - 1.0)) * enginePrefab.nozzlePresMPa;
nozzle.UpdateNozzleStatus(areaRatio);
nozzleDivEfficiency = nozzle.GetDivergenceEff();
nozzleFrictionEfficiency = nozzle.GetFrictionEff(exhaustVelocityOpt, massFlowChamber, chamberPresMPa, enginePrefab.chamberTempK, enginePrefab.nozzleMWgMol, modGamma, throatDiameter * 0.5);
thrustVac = exhaustVelocityOpt * massFlowChamber * nozzleDivEfficiency * nozzleFrictionEfficiency * reactionEfficiency;
thrustSL = thrustVac;
thrustVac += exitPressureMPa * nozzleDivEfficiency * nozzleArea * 1000.0;
thrustSL += (exitPressureMPa * nozzleDivEfficiency - 0.1013) * nozzleArea * 1000.0;
minThrustVac = thrustVac * minThrottle;
thrustVac += thrustVacAux;
thrustSL += thrustSLAux;
specImpulseVac = thrustVac / (massFlowTotal * G0);
specImpulseSL = thrustSL / (massFlowTotal * G0);
}
double CalcExhaustVelChangeFromFriction(double massFlow, double chamberPresMPa, double chamberTempK, double molWeightGMol, double gamma, double throatRadius)
{
double delV = 0;
double gammaFactor = gamma - 1.0;
gammaFactor *= 0.5;
double gammaExp = -gamma / (gamma - 1.0);
double cumulativeDistance = throatRadius * 0.001;
Vector2d point1 = nozzlePoints[0];
double areaRat1 = point1.y * point1.y;
double mach1 = NozzleUtils.MachFromAreaRatioSubsonic(areaRat1, gamma); //should be Mach 1 here
double drag1 = mach1 * mach1 * gammaFactor + 1.0;
drag1 = Math.Pow(drag1, gammaExp);
double temp1 = chamberTempK / CalcStagTempFactor(mach1, gamma);
double visc1 = CalcApproxDynVisc(molWeightGMol, temp1);
double reynoldsScalingFactor1 = ReynoldsCalcScalingFactor(chamberPresMPa, chamberTempK, molWeightGMol, gamma);
double reynolds1 = CalcReynoldsNumber(mach1, gamma, cumulativeDistance, visc1, reynoldsScalingFactor1);
drag1 *= mach1 * mach1 * CalcCompressFriction(reynolds1);
drag1 *= point1.y;
for (int i = 1; i < nozzlePoints.Length; ++i)
{
Vector2d point2 = nozzlePoints[i];
double areaRat2 = point2.y * point2.y;
double mach2;
if (i > POINTS_CONVERGING_ARC)
{
mach2 = NozzleUtils.MachFromAreaRatio(areaRat2, gamma);
}
else if (i < POINTS_CONVERGING_ARC)
{
mach2 = NozzleUtils.MachFromAreaRatioSubsonic(areaRat2, gamma);
}
else
{
mach2 = 1.0;
}
double distanceX = point2.x - point1.x;
double distanceY = point2.y - point1.y;
double distance = Math.Sqrt(distanceX * distanceX + distanceY * distanceY);
cumulativeDistance += distance * throatRadius;
double drag2 = mach2 * mach2 * gammaFactor + 1.0;
drag2 = Math.Pow(drag2, gammaExp);
double temp2 = chamberTempK / CalcStagTempFactor(mach2, gamma);
double visc2 = CalcApproxDynVisc(molWeightGMol, temp2);
double reynoldsScalingFactor2 = ReynoldsCalcScalingFactor(chamberPresMPa, chamberTempK, molWeightGMol, gamma);
double reynolds2 = CalcReynoldsNumber(mach2, gamma, cumulativeDistance, visc2, reynoldsScalingFactor2);
drag2 *= mach2 * mach2 * CalcCompressFriction(reynolds2);
drag2 *= point2.y;
delV += (drag2 + drag1) * 0.5 * distance; //trapezoid method
point1 = point2;
drag1 = drag2;
}
delV *= chamberPresMPa;
delV *= gamma;
delV /= massFlow;
delV *= 1000.0;
delV *= throatRadius * Math.PI;
return(delV);
}
