ispodfL = [] # list of IspODF (frozen)
mrcoreL = [] # list of MRcore (core stream tube mixture ratio)
for MRcore in np.linspace(mr_lo, mr_hi, num=60):
C.reset_attr('MRcore', MRcore)
R.scale_Rt_to_Thrust(Fvac, Pamb=0.0)
ispodeL.append(C('IspODE'))
ispodkL.append(C('IspODK'))
ispodfL.append(C('IspODF'))
mrcoreL.append(C('MRcore'))
# ========================================================
# ======= find peaks ======
mr_ode_terp = InterpProp(mrcoreL, ispodeL)
mr_ode_Peak, isp_ode_peak = gold_search_max(mr_ode_terp,
mrcoreL[0],
mrcoreL[-1],
tol=1.0e-5)
isp_ode_peak = -isp_ode_peak
print('mr_ode_Peak, isp_ode_peak', mr_ode_Peak, isp_ode_peak)
mr_odk_terp = InterpProp(mrcoreL, ispodkL)
mr_odk_Peak, isp_odk_peak = gold_search_max(mr_odk_terp,
mrcoreL[0],
mrcoreL[-1],
tol=1.0e-5)
isp_odk_peak = -isp_odk_peak
print('mr_odk_Peak, isp_odk_peak', mr_odk_Peak, isp_odk_peak)
mr_odf_terp = InterpProp(mrcoreL, ispodfL)
mr_odf_Peak, isp_odf_peak = gold_search_max(mr_odf_terp,
mrcoreL[0],
def calc_ODE_ODK_FROZ_isp(oxName='N2O4',
fuelName='MMH',
Pc=1000.0,
eps=10.0,
pcentBell=80.0,
Fvac=1000.0,
NumRuns=20,
do_show=True):
# ============ use RocketCEA to find MR range ===================
mc = MR_Temperature_Limits(oxName=oxName,
fuelName=fuelName,
PcNominal=Pc,
epsNominal=eps)
mr_peak = MR_Peak_At_EpsPc(
mc,
pc=Pc,
eps=eps,
ispType='CEAODE', # ispType can be CEAODE, CEAFROZEN
NterpSize=100)
print('Peak IspODE=%g sec at MR =' % mr_peak.ispPeak, mr_peak.mrPeak)
print()
print('MR at 97% Isp (on low side) =',
mr_peak.calc_mrLow_minus_NPcentIsp())
print('MR at 97% Isp (on high side) =',
mr_peak.calc_mrHigh_minus_NPcentIsp())
mr_lo = round(
mr_peak.mrLeftOfPeak -
(mr_peak.mrRightOfPeak - mr_peak.mrLeftOfPeak) / 10.0, 2)
mr_hi = round(mr_peak.mrRightOfPeak, 2)
delMR = (mr_hi - mr_lo) / (NumRuns - 1)
# ===============================
geomObj = Geometry(Rthrt=5.868 / 2,
CR=2.5,
eps=eps,
pcentBell=pcentBell,
RupThroat=1.5,
RdwnThroat=1.0,
RchmConv=1.0,
cham_conv_deg=30,
LchmOvrDt=3.10,
LchmMin=2.0,
LchamberInp=16)
core = CoreStream(geomObj,
oxName=oxName,
fuelName=fuelName,
MRcore=1.6,
Pc=Pc)
R = RocketThruster(name='sample', coreObj=core, injObj=None)
ispodeL = []
ispodkL = []
ispodfL = []
mrL = []
MR = mr_lo
for _ in range(NumRuns):
mrL.append(MR)
core.reset_attr('MRcore', MR, re_evaluate=True)
R.scale_Rt_to_Thrust(Fvac, Pamb=0.0, use_scipy=False)
ispodeL.append(R.coreObj.IspODE)
ispodkL.append(R.coreObj.IspODK)
ispodfL.append(R.coreObj.IspODF)
MR += delMR
# ======= find peaks ======
mr_ode_terp = InterpProp(mrL, ispodeL)
mr_ode_Peak, isp_ode_peak = gold_search_max(mr_ode_terp,
mrL[0],
mrL[-1],
tol=1.0e-5)
mr_odk_terp = InterpProp(mrL, ispodkL)
mr_odk_Peak, isp_odk_peak = gold_search_max(mr_odk_terp,
mrL[0],
mrL[-1],
tol=1.0e-5)
mr_odf_terp = InterpProp(mrL, ispodfL)
mr_odf_Peak, isp_odf_peak = gold_search_max(mr_odf_terp,
mrL[0],
mrL[-1],
tol=1.0e-5)
fig, ax = plt.subplots(figsize=(8, 6))
plt.plot(mrL, ispodeL, label='IspODE', color=COLORL[0])
plt.plot(mrL, ispodkL, label='IspODK', color=COLORL[1])
plt.plot(mrL, ispodfL, label='IspODF', color=COLORL[2])
# show ========= optimum MR difference ========
def span_mrpeak(isL):
minpt = min(isL)
maxpt = max(isL)
span = maxpt - minpt
return [maxpt - 0.8 * span, maxpt]
plt.plot([mr_ode_Peak, mr_ode_Peak],
span_mrpeak(ispodeL),
'--',
label='MRode=%.2f' % mr_ode_Peak,
linewidth=2,
color=COLORL[0])
plt.plot([mr_odk_Peak, mr_odk_Peak],
span_mrpeak(ispodkL),
'--',
label='MRodk=%.2f' % mr_odk_Peak,
linewidth=2,
color=COLORL[1])
plt.plot([mr_odf_Peak, mr_odf_Peak],
span_mrpeak(ispodfL),
'--',
label='MRodf=%.2f' % mr_odf_Peak,
linewidth=2,
color=COLORL[2])
isp_odk_peak = abs(isp_odk_peak)
plt.text(mr_odk_Peak,
isp_odk_peak,
'%i' % int(isp_odk_peak),
ha='left',
va='bottom',
transform=ax.transData,
color=COLORL[1])
plt.legend()
plt.ylabel('Isp (sec)')
plt.xlabel('Mixture Ratio')
plt.title( "%s/%s RocketIsp ODE ODK ODF\nFvac=%.0f lbf, Pc=%.0f psia, AR=%.0f:1, %%Bell=%.0f%%"%\
(oxName, fuelName, Fvac, Pc, eps, pcentBell))
png_name = 'odekf_%s_%s_Fvac%g_Pc%g_eps%g.png' % (oxName, fuelName, Fvac,
Pc, eps)
plt.savefig(png_name, dpi=120)
if do_show:
plt.show()
def __init__(
self,
mrLimitsObj,
pc=100.,
eps=10.,
ispType='CEAODE', # ispType can be CEAODE, CEAFROZEN
NterpSize=100): # size of interpolation array
self.mrLimitsObj = mrLimitsObj
self.pc = pc
self.eps = eps
self.ispType = ispType
self.mrL = [
] # build lists of non-zero isp both above and below stoich_MR
self.isL = []
stoich_MR = self.mrLimitsObj.Stoich_MR
#print( 'stoich_MR =',stoich_MR)
stoich_fox = frac_ox(stoich_MR)
#print( 'stoich_fox =',stoich_fox)
self.stoich_fox = stoich_fox
stoich_Isp = self.isp_at_mr(mr=stoich_MR)
# build mr and isp lists from the stoich point to the left and right.
# Only bother doing this because CEA frozen calc will often fail with condensed species.
# build list from stoich towards MR=0
mr_leftL = [stoich_MR]
is_leftL = [stoich_Isp]
df = 1.0 / float(NterpSize)
fox = stoich_fox - df
while fox > 0.0:
mr = mr_of_fracox(fox)
isp = self.isp_at_mr(mr=mr)
if isp > 1.0:
mr_leftL.append(mr)
is_leftL.append(isp)
fox = fox - df
if isp < stoich_Isp * 0.9:
break
else:
break
#print 'mr_leftL =',mr_leftL
#print 'is_leftL =',is_leftL
# build list from stoich towards ox fraction = 1.0
mr_rightL = []
is_rightL = []
fox = stoich_fox + df
while fox < 1.0:
mr = mr_of_fracox(fox)
isp = self.isp_at_mr(mr=mr)
if isp > 1.0:
mr_rightL.append(mr)
is_rightL.append(isp)
fox = fox + df
if isp < stoich_Isp * 0.9:
break
else:
break
#print 'mr_rightL =',mr_rightL
#print 'is_rightL =',is_rightL
# combine both lists
mr_leftL.reverse()
is_leftL.reverse()
self.mrL = mr_leftL + mr_rightL
self.isL = is_leftL + is_rightL
if len(self.mrL) < 3:
print('ERROR... len(mrL) < 3')
#print 'Optimizing pc=%g, eps=%g'%(pc, eps)
self.mr_isp_terp = InterpProp(self.mrL, self.isL)
self.mrPeak, iterp_peak = gold_search_max(self.mr_isp_terp,
self.mrL[0],
self.mrL[-1],
tol=1.0e-5)
self.ispPeak = self.isp_at_mr(mr=self.mrPeak)
self.isp_min = min(self.isL)
self.isp_max = max(self.isL)
if self.ispPeak < 0.01 or self.mrPeak < 0.0:
imin = 0
for i in range(len(self.mrL)):
if self.isL[i] < self.isL[imin]:
imin = i
imax = min(len(self.mrL) - 1, imin + 2)
imin = max(0, imin - 2)
self.mrPeak, iterp_peak = gold_search_max(self.mr_isp_terp,
self.mrL[imin],
self.mrL[imax],
tol=1.0e-5)
self.ispPeak = self.isp_at_mr(mr=self.mrPeak)
if self.ispPeak < 0.01 or self.mrPeak < 0.0:
print((
'_______________BAD OPTIMUM at pc=%g and eps=%g mrPeak=%g, ispPeak=%g'
% (pc, eps, self.ispPeak, self.mrPeak)))
# place holders for left and right of peak Isp
self._mrLeftOfPeak = None
self._mrRightOfPeak = None