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255 | # Applied Python PRISM
# (PRISM) PaRametrIc System Model
#
# Written by Charlie Taylor <cet@appliedpython.com>
# Oct,21 2005
from math import *
from prism.MassItem import MassItem
from prism.isp.cea import CEA_Isp
from prism.utils import Constants
from prism.Summary import Summary
from prism.isp import Nozzle_Eff
from prism.props import Inc_liquid
from prism.pov import POV_Items, POV_Basics
class Engine_Fixed_Design( MassItem ):
def __init__(self, name="engine", mass_lbm=10.0, oxName='N2O4', fuelName='MMH',
Pc=150.0, Dt=1.0, eps=50.0, mr=1.6, CR=2.5, xlcOxln=1.0, Lprime=4.0,
etaERE=0.97, etaNoz=0.99, isBell=1, pcentBell=80.0,
halfAngDeg=15.0, useFastCEALookup=0, Number=1, etaKinInp=1.0,
calcEtaNoz=1, inputIspDel=0, IspDel=300.0):
MassItem.__init__(self, name, type="inert")
self.Number = Number # number of engines
self.mass_lbm_inp = mass_lbm
self.oxName = oxName
self.fuelName = fuelName
self.iprop = oxName + '/' + fuelName
self.Pc = Pc
self.eps = eps
self.mr = mr
self.CR = CR
self.Dt = Dt
self.xlcOxln = xlcOxln
self.Lprime = Lprime
self.etaERE = etaERE
self.etaKinInp = etaKinInp
self.inputIspDel = inputIspDel
self.IspDel = IspDel
self.isBell = isBell
self.pcentBell = pcentBell
self.halfAngDeg = halfAngDeg
self.etaNoz = etaNoz
self.calcEtaNoz = calcEtaNoz
# assume storable liquids for the FFC engine
self.FlObj = Inc_liquid.Inc_liquid(symbol=fuelName,T=None,P=Pc*1.5)
self.OxObj = Inc_liquid.Inc_liquid(symbol=oxName,T=None,P=Pc*1.5)
self.ispObj = CEA_Isp.CEA_Isp( oxName=oxName, fuelName=fuelName, useFastLookup=useFastCEALookup ) # create isp calculating object
self.reCalc()
def getPOV_Item(self):
# be sure to include pov_h, pov_w, and pov_d calcs in reCalc
if hasattr( self, 'texture'):
texture = self.texture
else:
texture = POV_Basics.Texture( colorName="Coral" )
s = POV_Items.TCA_Bell( xlc=self.xlc , xln=self.xln, CR=self.CR,
Rt=self.Dt/2., eps=self.eps, pcentBell=self.pcentBell, texture=texture)
return s
def reCalc(self, autoCalc=1):
self.autoCalc = autoCalc
# set design variables
self.IspODE,self.CstarODE,self.Tc = \
self.ispObj.get_IvacCstrTc(Pc=self.Pc, MR=self.mr, eps=self.eps)
self.Cstar = self.CstarODE * self.etaERE
self.Rt = self.Dt / 2.0
self.At = pi * self.Rt**2
self.wdotTot = self.Pc * self.At * Constants.gc / self.Cstar
FvacEst = self.wdotTot * self.IspODE * self.etaERE * 0.98
if self.calcEtaNoz:
if self.isBell:
isConical=0
else:
isConical=1
self.etaBL,self.etaDiv,self.etaKin, etaCf = \
Nozzle_Eff.calcNozzleEfficiency(Pc=self.Pc, Fvac=FvacEst, eps=self.eps,
epsAtt=self.eps, isConical=isConical, pcentBell=self.pcentBell, halfAngleDeg=self.halfAngDeg,
iprop=self.iprop, mr=self.mr, etaKinInp=self.etaKinInp,
adjBL=1.0, adjKin=1.0, adjDiv=1.0, isRegenCham=0, isRegenNoz=0 )
self.etaNoz = etaCf
# if isp delivered is input, correct etaNoz to reflect that input
if self.inputIspDel:
self.Isp = self.IspDel
self.effIsp = self.Isp / self.IspODE
self.etaNoz = self.effIsp / self.etaERE
else:
self.effIsp = self.etaERE * self.etaNoz
self.Isp = self.IspODE * self.effIsp
self.Fvac = self.wdotTot * self.Isp
self.wdotOx = self.wdotTot * self.mr / (1.0 + self.mr)
self.wdotFl = self.wdotTot - self.wdotOx
self.volDotOx = self.wdotOx / self.OxObj.rho
self.volDotFl = self.wdotFl / self.FlObj.rho
self.Dcham = self.Dt * sqrt( self.CR )
self.Dexit = self.Dt * sqrt( self.eps )
self.xln = self.Lprime / (1.0 + self.xlcOxln)
self.xlc = self.Lprime - self.xln
self.Lcham = self.Lprime
if self.isBell:
self.Lnoz = (sqrt(self.eps)-1.0)*self.pcentBell*(self.Dt/2.0)/100.0/tan(15.0*pi/180.0)
# curve fit of ratio to minimum length rao nozzle
self.ratmlr = (self.pcentBell/100.0) * 1612.1/(self.eps + 1009.0)
self.SAnoz = self.Dt**2/4.*(3.368*(self.eps+10.875)**1.2606 + \
self.eps*(self.ratmlr-1.25)*10.75)
else:
self.Lnoz = (sqrt(self.eps)-1.0)*(self.Dt/2.0)/tan(self.halfAngDeg*pi/180.0)
r1 = self.Dt/2.0
r2 = self.Dexit/2.0
self.SAnoz = pi * sqrt((r1-r2)**2 + self.Lnoz**2) * (r1+r2)
self.Lengine = self.Lnoz + self.Lcham + self.Dcham # use Dcham as an inj face fwd length
# add up parts
self.mass_lbm = self.Number * ( self.mass_lbm_inp )
self.FtoW = self.Fvac * self.Number / self.mass_lbm
self.pov_h = self.Lengine
self.pov_w = max( self.Dexit, self.Dcham )
self.pov_d = self.pov_w
def buildSummary(self):
name = self.name
if self.Number>1:
name += ' (%i)'%self.Number
summList = []
summ = Summary( summName='Bipropellant Engine',
componentName=name, mass_lbm=self.mass_lbm, type=self.type)
summ.addAssumption( 'Propellants : ' + self.oxName + ' / ' + self.fuelName )
summ.addAssumption( 'NASA CEA Code for ODE performance ')
summ.addAssumption( 'Actual Hardware Weight ')
if self.isBell:
summ.addAssumption( 'Bell Nozzle with Percent Bell = %g'%self.pcentBell)
else:
summ.addAssumption( 'Conical Nozzle with Half Angle = %g deg'%self.halfAngDeg )
if self.Number>1:
summ.addAssumption( 'Mass is for %i engines total'%self.Number )
#summ.addInput(self, label='generic param', value=0.0, units='', format='%g')
summ.addInput('Pc', self.Pc, 'psia', '%.1f')
summ.addInput('Dt', self.Dt, 'in', '%.3f')
summ.addInput('eps', self.eps, '', '%g')
if self.isBell:
summ.addInput('%Bell', self.pcentBell, '%', '%.2f')
else:
summ.addInput('halfAngDeg', self.halfAngDeg, 'deg', '%.2f')
summ.addInput('mr', self.mr, '', '%g')
summ.addInput('CR', self.CR, '', '%g')
summ.addInput('Lprime', self.Lprime, 'in', '%.3f')
summ.addInput('xlc/xln', self.xlcOxln, '', '%g')
summ.addInput('etaERE', self.etaERE, '', '%g')
if not self.calcEtaNoz:
summ.addInput('etaNoz', self.etaNoz, '', '%g')
# outputs
summ.addOutput('Fvac', self.Fvac, 'lbf', '%g')
summ.addOutput('Isp', self.Isp, 'sec', '%g')
summ.addOutput('Cstar', self.Cstar, 'ft/sec', '%.1f')
if self.inputIspDel:
summ.addOutput('etaNoz', self.etaNoz, '', '%g')
elif self.calcEtaNoz:
summ.addOutput('etaBL', self.etaBL, '', '%g')
summ.addOutput('etaDiv', self.etaDiv, '', '%g')
summ.addOutput('etaKin', self.etaKin, '', '%g')
summ.addOutput('etaNoz', self.etaNoz, '', '%g')
summ.addOutput('effIsp', self.effIsp, '', '%g')
summ.addOutput('IspODE', self.IspODE, 'sec', '%g')
summ.addOutput('CstarODE', self.CstarODE, 'ft/sec', '%.1f')
summ.addOutput('Tc', self.Tc, 'degR', '%.1f')
summ.addOutput('wdotTot', self.wdotTot, 'lbm/sec', '%g')
summ.addOutput('wdotOx ', self.wdotOx , 'lbm/sec', '%g')
summ.addOutput('wdotFl', self.wdotFl, 'lbm/sec', '%g')
summ.addOutput('rhoFl', self.FlObj.rho, 'lbm/cuin', '%.4f')
summ.addOutput('rhoOx', self.OxObj.rho, 'lbm/cuin', '%.4f')
summ.addOutput('volDotOx ', self.volDotOx , 'cuin/sec', '%g')
summ.addOutput('volDotFl', self.volDotFl, 'cuin/sec', '%g')
summ.addOutput('At', self.At, 'sqin', '%g')
summ.addOutput('Dcham', self.Dcham, 'in', '%.3f')
summ.addOutput('Dexit', self.Dexit, 'in', '%.3f')
summ.addOutput('xlc', self.xlc, 'in', '%.3f')
summ.addOutput('xln', self.xln, 'in', '%.3f')
summ.addOutput('Lcham', self.Lcham, 'in', '%.3f')
summ.addOutput('Lnoz', self.Lnoz, 'in', '%.3f')
summ.addOutput('Lengine', self.Lengine, 'in', '%.3f')
if self.Number>1:
summ.addOutput( 'wt/Engine', self.mass_lbm/self.Number, 'lbm', '%.3f' )
summ.addOutput('F/W', self.Number * self.Fvac/self.mass_lbm, 'lbf/lbm', '%.3f')
else:
summ.addOutput('F/W', self.Fvac/self.mass_lbm, 'lbf/lbm', '%.3f')
summList.append( summ )
return summList
if __name__ == "__main__": #self test
print "Actual IR&D Style Engine =", 2.071,"lbm (1.815 w/o valves)"
h = Engine_Fixed_Design(name="Ref Axial Engine", mass_lbm=6.245, oxName='N2O4', fuelName='MMH',
Pc=500.0, Dt=1.03, eps=17.0, mr=1.08, CR=2.06, xlcOxln=1.0, Lprime=4.0,
etaERE=0.97, etaNoz=0.99, isBell=1, pcentBell=84.58,
halfAngDeg=15.0, useFastCEALookup=0, Number=1, calcEtaNoz=1)
print
print h.getSummary()
|