def test_use_Mpa_as_input_Pc(self):
"""test use Mpa as input Pc"""
C = CEA_Obj( oxName='LOX', fuelName='LH2', fac_CR=None)
CwU = CEA_Obj_w_units( oxName='LOX', fuelName='LH2', pressure_units='MPa', fac_CR=None)
a = C.get_Isp(Pc=1000.0, MR=6.0, eps=40.0)
b = CwU.get_Isp(Pc=1000.0/145.037738, MR=6.0, eps=40.0)
self.assertAlmostEqual(a, b, delta=0.01)
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 rocket_vars(fu, ox, pcham):
C = CEA_Obj(
oxName=ox, fuelName=fu, isp_units='sec',
cstar_units='m/s') # define CEA object to operate on for rocketCEA
OFratio = np.linspace(0.1, 5., 50, endpoint=True) # OF ratio by mass
ISP = np.zeros(OFratio.shape) # isp
Cstar = np.zeros(OFratio.shape) # cstar efficiency
PCPE = np.zeros(OFratio.shape) # p_chamber / p_exit
supAR = 1 # supersonic area ratio (1 = converging nozzle only)
for i in range(50):
ISP[i] = C.get_Isp(pcham, MR=OFratio[i], eps=supAR) # ISP vacuum
Cstar[i] = C.get_Cstar(pcham, MR=OFratio[i]) # Cstar efficiency
PCPE[i] = C.get_Throat_PcOvPe(
pcham, MR=OFratio[i]
) # throat Pc/Pe (we will be using a converging nozzle)
return ISP, Cstar, PCPE
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