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Clean-up: diesel spray evaporation

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This commit is contained in:
Hrvoje Jasak 2011-05-27 11:40:48 +01:00
parent c056979017
commit a79d34de50
8 changed files with 131 additions and 76 deletions
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22
src/lagrangian/dieselSpray/injector/unitInjector/unitInjector.C
View file

@ -96,7 +96,7 @@ Foam::unitInjector::unitInjector
}
// convert CA to real time
forAll(massFlowRateProfile_, i)
forAll (massFlowRateProfile_, i)
{
massFlowRateProfile_[i][0] =
t.userTimeToTime(massFlowRateProfile_[i][0]);
@ -104,14 +104,14 @@ Foam::unitInjector::unitInjector
injectionPressureProfile_[i][0] = massFlowRateProfile_[i][0];
}
forAll(TProfile_, i)
forAll (TProfile_, i)
{
TProfile_[i][0] = t.userTimeToTime(TProfile_[i][0]);
}
scalar integratedMFR = integrateTable(massFlowRateProfile_);
forAll(massFlowRateProfile_, i)
forAll (massFlowRateProfile_, i)
{
// correct the massFlowRateProfile to match the injected mass
massFlowRateProfile_[i][1] *= mass_/integratedMFR;
@ -125,9 +125,9 @@ Foam::unitInjector::unitInjector
setTangentialVectors();
// check molar fractions
// Check molar fractions
scalar Xsum = 0.0;
forAll(X_, i)
forAll (X_, i)
{
Xsum += X_[i];
}
@ -137,7 +137,7 @@ Foam::unitInjector::unitInjector
WarningIn("unitInjector::unitInjector(const time& t, Istream& is)")
<< "X does not sum to 1.0, correcting molar fractions."
<< nl << endl;
forAll(X_, i)
forAll (X_, i)
{
X_[i] /= Xsum;
}
@ -179,8 +179,14 @@ Foam::label Foam::unitInjector::nParcelsToInject
const scalar time1
) const
{
scalar mInj = mass_*(fractionOfInjection(time1)-fractionOfInjection(time0));
scalar mInj = mass_*
(
fractionOfInjection(time1)
- fractionOfInjection(time0)
);
label nParcels = label(mInj/averageParcelMass_ + 0.49);
return nParcels;
}
@ -366,7 +372,7 @@ void Foam::unitInjector::correctProfiles
scalar A = 0.25*mathematicalConstant::pi*pow(d_, 2.0);
scalar pDummy = 1.0e+5;
forAll(velocityProfile_, i)
forAll (velocityProfile_, i)
{
scalar time = velocityProfile_[i][0];
scalar rho = fuel.rho(pDummy, T(time), X_);

13
src/lagrangian/dieselSpray/injector/unitInjector/unitInjector.H
View file

@ -61,14 +61,27 @@ private:
// Private data
//- Injector properties dictionary
dictionary propsDict_;
//- Injector position
vector position_;
//- Injector direction
vector direction_;
//- Injector diameter
scalar d_;
//- Cd
scalar Cd_;
//- Parcel mass
scalar mass_;
//- Number of parcels
label nParcels_;
scalarField X_;
List<pair> massFlowRateProfile_;
List<pair> velocityProfile_;

70
src/lagrangian/dieselSpray/parcel/parcel.C
View file

@ -126,12 +126,14 @@ bool Foam::parcel::move(spray& sDB)
cpMixture += Yi[cell()]*sDB.gasProperties()[i].Cp(Tg);
}
// correct the gaseous temperature for evaporated fuel
// Correct the gaseous temperature for evaporated fuel
scalar cellV = sDB.mesh().V()[cell()];
scalar cellMass = rhog*cellV;
Tg += sDB.shs()[cell()]/(cpMixture*cellMass);
Tg = max(200.0, Tg);
// Changed cut-off temperature for evaporation. HJ, 27/Apr/2011
Tg = max(273, Tg);
scalar tauMomentum = GREAT;
scalar tauHeatTransfer = GREAT;
@ -212,7 +214,8 @@ bool Foam::parcel::move(spray& sDB)
// track parcel to face, or end of trajectory
if (keepParcel)
{
// Track and adjust the time step if the trajectory is not completed
// Track and adjust the time step if the trajectory
// is not completed
dt *= trackToFace(position() + dt*U_, sDB);
// Decrement the end-time acording to how much time the track took
@ -231,6 +234,7 @@ bool Foam::parcel::move(spray& sDB)
{
scalar z = position() & sDB.axisOfSymmetry();
vector r = position() - z*sDB.axisOfSymmetry();
if (mag(r) > SMALL)
{
correctNormal(sDB.axisOfSymmetry());
@ -299,7 +303,7 @@ bool Foam::parcel::move(spray& sDB)
sDB.shs()[celli] += oTotMass*(oH + oPE) - m()*(nH + nPE + nKE);
// Remove evaporated mass from stripped mass
ms() -= ms()*(oTotMass-m())/oTotMass;
ms() -= ms()*(oTotMass - m())/oTotMass;
// Remove parcel if it is 'small'
@ -350,7 +354,7 @@ void Foam::parcel::updateParcelProperties
// calculate mean molecular weight
scalar W = 0.0;
for(label i=0; i<Ns; i++)
for(label i = 0; i < Ns; i++)
{
W += sDB.composition().Y()[i][celli]/sDB.gasProperties()[i].W();
@ -366,7 +370,7 @@ void Foam::parcel::updateParcelProperties
// correct the gaseous temperature for evaporated fuel
scalar cpMix = 0.0;
for(label i=0; i<Ns; i++)
for (label i = 0; i < Ns; i++)
{
cpMix += sDB.composition().Y()[i][celli]
*sDB.gasProperties()[i].Cp(T());
@ -383,7 +387,9 @@ void Foam::parcel::updateParcelProperties
}
scalar Tg = Tg0 + dh/(cpMix*cellMass);
Tg = max(200.0, Tg);
// Changed cut-off temperature for evaporation. HJ, 27/Apr/2011
Tg = max(273.0, Tg);
scalarField Yfg(Nf, 0.0);
forAll(Yfg, i)
@ -494,26 +500,31 @@ void Foam::parcel::updateParcelProperties
newMass = m();
newhg = 0.0;
scalarField Ynew(fuels.Y(X()));
for(label i=0; i<Nf; i++)
for(label i = 0; i < Nf; i++)
{
label j = sDB.liquidToGasIndex()[i];
newhg += Ynew[i]*sDB.gasProperties()[j].Hs(Tnew);
}
newhv = fuels.hl(pg, Tnew, X());
scalar dm = oldMass - newMass;
scalar dhNew = oldMass*(oldhg-oldhv) - newMass*(newhg-newhv);
scalar dhNew = oldMass*(oldhg - oldhv) - newMass*(newhg - newhv);
// Prediction of new gaseous temperature and fuel mass fraction
Tg = Tg0 + (dh+dhNew)/(cpMix*cellMass);
Tg = max(200.0, Tg);
Tg = Tg0 + (dh + dhNew)/(cpMix*cellMass);
forAll(Yfg, i)
// Changed cut-off temperature for evaporation. HJ, 27/Apr/2011
Tg = max(273.0, Tg);
forAll (Yfg, i)
{
label j = sDB.liquidToGasIndex()[i];
const volScalarField& Yj = sDB.composition().Y()[j];
scalar Yfg0 = Yj[celli];
Yfg[i] =
(Yfg0*cellMass + addedMass[i] + dm)/
(addedMass[i] + cellMass + dm);
@ -543,7 +554,7 @@ void Foam::parcel::updateParcelProperties
scalar liquidcL = sDB.fuels().cp(pg, TDroplet, X());
cpMix = 0.0;
for(label i=0; i<Ns; i++)
for (label i = 0; i < Ns; i++)
{
if (sDB.isLiquidFuel()[i])
{
@ -553,6 +564,7 @@ void Foam::parcel::updateParcelProperties
else
{
scalar Y = sDB.composition().Y()[i][celli];
cpMix += Y*sDB.gasProperties()[i].Cp(Taverage);
}
}
@ -561,7 +573,7 @@ void Foam::parcel::updateParcelProperties
scalar z = 0.0;
scalar tauEvap = 0.0;
for(label i=0; i<Nf; i++)
for (label i =0 ; i < Nf; i++)
{
tauEvap += X()[i]*fuels.properties()[i].W()/tauEvaporation[i];
}
@ -571,8 +583,7 @@ void Foam::parcel::updateParcelProperties
if (sDB.evaporation().evaporation())
{
scalar hv = fuels.hl(pg, TDroplet, X());
evaporationSource =
hv/liquidcL/tauEvap;
evaporationSource = hv/liquidcL/tauEvap;
z = cpMix*tauHeatTransfer/liquidcL/tauEvap;
}
@ -582,8 +593,7 @@ void Foam::parcel::updateParcelProperties
scalar fCorrect =
sDB.heatTransfer().fCorrection(z)/tauHeatTransfer;
Tnew =
(TDroplet + dt*(fCorrect * Tg - evaporationSource))
Tnew = (TDroplet + dt*(fCorrect*Tg - evaporationSource))
/(1.0 + dt*fCorrect);
// Prevent droplet temperature to go above critial value
@ -591,19 +601,23 @@ void Foam::parcel::updateParcelProperties
// Prevent droplet temperature to go too low
// Mainly a numerical stability issue
Tnew = max(200.0, Tnew);
// Changed cut-off temperature for evaporation. HJ, 27/Apr/2011
Tnew = max(273.0, Tnew);
scalar Td = Tnew;
scalar pAtSurface = fuels.pv(pg, Td, X());
scalar pCompare = 0.999*pg;
scalar boiling = pAtSurface >= pCompare;
if (boiling)
{
// can not go above boiling temperature
scalar Terr = 1.0e-3;
label n=0;
label n = 0;
scalar dT = 1.0;
scalar pOld = pAtSurface;
while (dT > Terr)
{
n++;
@ -631,10 +645,12 @@ void Foam::parcel::updateParcelProperties
}
}
}
pOld = pAtSurface;
if (debug)
// if (debug)
{
if (n>100)
if (n > 100)
{
Info << "n = " << n << ", T = " << Td << ", pv = " << pAtSurface << endl;
}
@ -648,7 +664,7 @@ void Foam::parcel::updateParcelProperties
// if the droplet is NOT boiling use implicit scheme.
if (sDB.evaporation().evaporation())
{
for(label i=0; i<Nf; i++)
for (label i = 0; i < Nf; i++)
{
// Immediately evaporate mass that has reached
// critical condition
@ -678,6 +694,7 @@ void Foam::parcel::updateParcelProperties
}
scalar mTot = sum(mi);
if (mTot > VSMALL)
{
scalarField Ynew(mi/mTot);
@ -696,14 +713,9 @@ void Foam::parcel::updateParcelProperties
// FPK changes: avoid temperature-out-of-range errors
// in spray tracking. HJ, 13/Oct/2007
scalar temprhod;
const scalar relaxfac = sDB.sprayRelaxFactor();
if (debug)
{
temprhod = fuels.rho(pg,T(),X());
}
convergedT = mag(Tnew-T()) < 0.1 || n > sDB.sprayIterate();
convergedT = mag(Tnew - T()) < 0.1 || n > sDB.sprayIterate();
// FPK version, 13/Oct/2007
T() = T()*(1 - relaxfac) + Tnew*relaxfac;

7
src/lagrangian/dieselSpray/parcel/setRelaxationTimes.C
View file

@ -180,7 +180,9 @@ void parcel::setRelaxationTimes
for(label i=0; i<Nf; i++)
{
scalar Td = min(T(), 0.999*fuels.properties()[i].Tc());
bool boiling = fuels.properties()[i].pv(pressure, Td) >= 0.999*pressure;
bool boiling = fuels.properties()[i].pv(pressure, Td)
>= 0.999*pressure;
scalar Di = fuels.properties()[i].D(pressure, Td);
scalar Schmidt = Sc(nuf, Di);
@ -196,7 +198,8 @@ void parcel::setRelaxationTimes
{
if (!boiling)
{
// for saturation evaporation, only use 99.99% for numerical robustness
// For saturation evaporation, only use 99.99% for
// numerical robustness
scalar dm = max(SMALL, 0.9999*msat[i] - mfg[i]);
tauEvaporation[i] = sDB.evaporation().relaxationTime

5
src/lagrangian/dieselSpray/spray/spray.C
View file

@ -185,7 +185,10 @@ Foam::spray::spray
sprayIteration_(sprayProperties_.subDict("sprayIteration")),
sprayIterate_(readLabel(sprayIteration_.lookup("sprayIterate"))),
sprayRelaxFactor_(readScalar(sprayIteration_.lookup("sprayRelaxFactor"))),
minimumParcelMass_(readScalar(sprayIteration_.lookup("minimumParcelMass"))),
minimumParcelMass_
(
readScalar(sprayIteration_.lookup("minimumParcelMass"))
),
subCycles_(readLabel(sprayProperties_.lookup("subCycles"))),

11
src/lagrangian/dieselSpray/spray/spray.H
View file

@ -119,11 +119,20 @@ class spray
autoPtr<liquidMixture> fuels_;
autoPtr<injectorModel> injectorModel_;
// Iterations to avoid errors due to too small parcels causing temperature out of range
// Iterations to avoid errors due to too small parcels
// causing temperature out of range
//- Spray iteration dictionary
dictionary sprayIteration_;
//- Number of spray iterations
const label sprayIterate_;
//- Spray relaxation factor
const scalar sprayRelaxFactor_;
//- Minimum parcel mass
const scalar minimumParcelMass_;

13
src/lagrangian/dieselSpray/spraySubModels/evaporationModel/standardEvaporationModel/standardEvaporationModel.C
View file

@ -94,6 +94,7 @@ bool standardEvaporationModel::evaporation() const
return true;
}
// Correlation for the Sherwood Number
scalar standardEvaporationModel::Sh
(
@ -101,9 +102,11 @@ scalar standardEvaporationModel::Sh
const scalar SchmidtNumber
) const
{
return 2.0 + preReScFactor_*pow(ReynoldsNumber,ReExponent_)*pow(SchmidtNumber,ScExponent_);
return 2.0 + preReScFactor_*pow(ReynoldsNumber,ReExponent_)*
pow(SchmidtNumber,ScExponent_);
}
scalar standardEvaporationModel::relaxationTime
(
const scalar diameter,
@ -194,7 +197,10 @@ scalar standardEvaporationModel::boilingTime
time = liquidDensity*cpFuel*sqr(diameter)/
(
6.0 * kappa * Nusselt * log(1.0 + cpFuel * deltaT/max(SMALL, heatOfVapour))
6.0*kappa*Nusselt*log
(
1.0 + cpFuel * deltaT/max(SMALL, heatOfVapour)
)
);
time = max(VSMALL, time);
@ -202,10 +208,13 @@ scalar standardEvaporationModel::boilingTime
return time;
}
inline label standardEvaporationModel::nEvapIter() const
{
return nEvapIter_;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
} // End namespace Foam