def OFtrade(fu, ox, P, N, OFratio,
pltname): # O/F ratio trade (OFratio needs to be a vector array)
# fu: name of fuel (string, as defined in rocketcea documentation or newly added fuels)
# ox: name of ox (string, as defined in rocketcea documentation of newly added fuels)
# P: chamber pressure (either a single number, list of numbers, or range())
# N: number of desired O/F ratios to sweep over
# OFratio: values of O/F ratios (length of this list must match value of N)
# supAR: fixed nozzle expansion ratio
C = CEA_Obj(
oxName=ox, fuelName=fu, isp_units='sec',
cstar_units='m/s') # define CEA object to operate on for rocketCEA
if isinstance(P, int) == True: # if P is only one value
y = 1
else:
y = len(P)
# preallocate vars
ISP = np.zeros([y, OFratio.shape[0]]) # isp
Cstar = np.zeros([y, OFratio.shape[0]]) # cstar eff
PCPE = np.zeros([y, OFratio.shape[0]]) # pc/pe
cpcv = np.zeros([y, OFratio.shape[0]
]) # ratio of specific heats in thrust chamber
fe_pcpe = np.zeros([y, OFratio.shape[0]
]) # nozzle area ratio for fully expanded flow
for x in range(y):
if y == 1:
Pc = P # integers can't be called :(
legends = str(Pc)
else:
Pc = P[x] # chamber pressure
legends = P
pr = Pc / 14.7 # pc/pe for fully expanded flo
for i in range(N):
fe_pcpe[x, :] = C.get_eps_at_PcOvPe(Pc=Pc,
MR=OFratio[i],
PcOvPe=pr)
ISP[x, i] = C.get_Isp(Pc=Pc, MR=OFratio[i],
eps=fe_pcpe[x, i]) # ISP vacuum
Cstar[x, i] = C.get_Cstar(Pc=Pc, MR=OFratio[i]) # Cstar efficiency
fe_pcpe[x, i] = C.get_PcOvPe(Pc=Pc,
MR=OFratio[i],
eps=fe_pcpe[x, i]) # Pc/Pe
cpcv[x, i] = C.get_Chamber_Cp(Pc=Pc,
MR=OFratio[i],
eps=fe_pcpe[x, i]) # cp/cv
# generate plots for ISP, Cstar, and Pchamb/Pexit
# plots(OFratio,ISP,"O/F ratio","ISP (s)", pltname+"isp.png" , legends ) # isp plot
# plots(OFratio,Cstar,"O/F ratio","Cstar", pltname+"cstar.png" , legends ) # Cstar plot
# plots(OFratio,PCPE,"O/F ratio","Pc/Pe", pltname+"pcpe.png" , legends ) # Pc/Pe plot
return ISP, Cstar, fe_pcpe, cpcv
def ARtrade(fu, ox, P, N, OFratio, supAR, pltname): # expansion ratio trade
# fu: name of fuel (string, as defined in rocketcea documentation or newly added fuels)
# ox: name of ox (string, as defined in rocketcea documentation of newly added fuels)
# P: chamber pressure (either a single number, list of numbers, or range())
# N: number of desired supersonic area ratios (nozzle expansion ratio) to sweep over
# OFratio: fixed O/F ratio for this trade
# supAR: values of supersonic area ratios (length of this list must match value of N)
C = CEA_Obj(
oxName=ox, fuelName=fu, isp_units='sec',
cstar_units='m/s') # define CEA object to operate on for rocketCEA
if isinstance(P, int) == True: # if P is only one value
y = 1
else:
y = len(P)
# preallocate vars
ISP = np.zeros([y, supAR.shape[0]]) # isp
Cstar = np.zeros([y, supAR.shape[0]]) # cstar eff
PCPE = np.zeros([y, supAR.shape[0]]) # pc/pe
cpcv = np.zeros([y, supAR.shape[0]
]) # ratio of specific heats in thrust chamber
for x in range(y):
if y == 1:
Pc = P # integers can't be called :(
legends = str(Pc)
else:
Pc = P[x] # chamber pressure
legends = P
for i in range(N):
ISP[x, i] = C.get_Isp(Pc=Pc, MR=OFratio,
eps=supAR[i]) # ISP vacuum
Cstar[x, i] = C.get_Cstar(Pc=Pc, MR=OFratio) # Cstar efficiency
PCPE[x, i] = C.get_PcOvPe(Pc=Pc, MR=OFratio, eps=supAR[i]) # Pc/Pe
cpcv[x, i] = C.get_Chamber_Cp(Pc=Pc, MR=OFratio,
eps=supAR[i]) # cp/cv
# generate plots for ISP, Cstar, and Pchamb/Pexit. Replace the last input with the vectory array of pressures
# plots(supAR,ISP,"Ae/At","ISP (s)", pltname+"isp.png" , legends ) # isp plot
# plots(supAR,Cstar,"Ae/At","Cstar", pltname+"cstar.png" , legends ) # Cstar plot
# plots(supAR,PCPE,"Ae/At","Pc/Pe", pltname+"pcpe.png" , legends ) # Pc/Pe plot
return ISP, Cstar, PCPE, cpcv
def getPerformanceParameters(self, combustionPressure, ambientPressure, oxidizerTemperature, expansionRatio, mixtureRatio):
import CoolProp.CoolProp as CP
from rocketcea.cea_obj import CEA_Obj, add_new_fuel, add_new_oxidizer, add_new_propellant
from rocketcea.cea_obj_w_units import CEA_Obj as CEA_Obj_W_Units
from rocketcea.blends import makeCardForNewTemperature
combustionPressure = max(10, combustionPressure) # Limitation of the library...
fuelTemperature = 293
HMOLAR = CP.PropsSI('HMOLAR','T',oxidizerTemperature,'P',combustionPressure,"N2O") / 1e3
oxidizerDensity = CP.PropsSI('D','T',oxidizerTemperature,'P',combustionPressure,"N2O")
RHO = oxidizerDensity * 1e3 / (1e2 * 1e2 * 1e2)
oxid_card_str = """
oxid=NITROUS wt=1.0 t,K={:.2f} h,kj/mol={:.2f} rho,g/cc={:.2f} N 2 O 1
""".format(oxidizerTemperature, HMOLAR, RHO)
fuel_card_str = """
fuel=C(gr) wt={:.4f} t,K={:.2f}
fuel=SASOL907 wt={:.4f} t,K={:.2f} h,kj/mol={:.2f} rho,g/cc={:.3f} C 50 H 102
""".format(
assumptions.carbonBlackFraction.get(),
fuelTemperature,
1 - assumptions.carbonBlackFraction.get(),
fuelTemperature,
assumptions.fuelEnthalpyOfFormation.get(),
assumptions.fuelDensityLiquid.get() / 1e3)
problemString = "Pc={:.2f},Pa={:.2f},To={:.2f},Tf={:.2f},ER={:.2f},MR={:.2f},oxid={:},fuel={:}".format(
combustionPressure,
ambientPressure,
oxidizerTemperature,
fuelTemperature,
expansionRatio,
mixtureRatio,
oxid_card_str,
fuel_card_str
)
strHash = hashlib.md5(problemString.encode()).hexdigest()
NasaCEA.totalHits = NasaCEA.totalHits + 1
if options.enableCeaLookup and strHash in NasaCEA.inMemoryCache:
# print("Hit cache")
NasaCEA.cacheHits = NasaCEA.cacheHits + 1
return NasaCEA.inMemoryCache[strHash]
# print(HMOLAR, RHO)
add_new_oxidizer('NITROUS_COOLPROP', oxid_card_str)
add_new_fuel('SASOLWAX907_CARBONBLACK', fuel_card_str)
with hiddenPrints:
combustionPressure = round(combustionPressure, 2)
mixtureRatio = round(mixtureRatio, 2)
expansionRatio = round(expansionRatio, 2)
ambientPressure = round(ambientPressure, 2)
cea = CEA_Obj_W_Units(
oxName="NITROUS_COOLPROP",
fuelName="SASOLWAX907_CARBONBLACK",
pressure_units='Pa',
cstar_units='m/s',
temperature_units='K',
sonic_velocity_units='m/s',
enthalpy_units='J/kg',
density_units='kg/m^3',
specific_heat_units='J/kg-K',
viscosity_units='poise',
thermal_cond_units="W/cm-degC"
)
Isp,mode = cea.estimate_Ambient_Isp(Pc=combustionPressure, MR=mixtureRatio, eps=expansionRatio, Pamb=ambientPressure)
IspVac, Cstar, Tc, MW, gamma = cea.get_IvacCstrTc_ThtMwGam(Pc=combustionPressure, MR=mixtureRatio, eps=expansionRatio)
Cp = cea.get_Chamber_Cp(Pc=combustionPressure, MR=mixtureRatio, eps=expansionRatio)
rho = cea.get_Chamber_Density(Pc=combustionPressure, MR=mixtureRatio, eps=expansionRatio)
CfVac, Cf, mode = cea.get_PambCf(Pc=combustionPressure, MR=mixtureRatio, eps=expansionRatio)
PcOvPe = cea.get_PcOvPe(Pc=combustionPressure, MR=mixtureRatio, eps=expansionRatio)
exitPressure = combustionPressure / PcOvPe
result = (Isp, Cp, MW, Cstar, Tc, gamma, rho, Cf, exitPressure, oxidizerDensity)
if options.enableCeaLookup:
NasaCEA.inMemoryCache[strHash] = result
return result