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#!/usr/bin/env python 

# -*- coding: ascii -*- 

 

r""" 

RocketIsp calculates delivered Isp for liquid rocket thrust chambers. 

 

RocketIsp uses a simplified JANNAF approach to calculate delivered 

specific impulse (Isp) for liquid rocket thrust chambers. 

 

RocketIsp 

Copyright (C) 2020 Applied Python 

 

This program is free software: you can redistribute it and/or modify 

it under the terms of the GNU General Public License as published by 

the Free Software Foundation, either version 3 of the License, or 

(at your option) any later version. 

 

This program is distributed in the hope that it will be useful, 

but WITHOUT ANY WARRANTY; without even the implied warranty of 

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

GNU General Public License for more details. 

 

You should have received a copy of the GNU General Public License 

along with this program. If not, see <http://www.gnu.org/licenses/>. 

""" 

import os 

here = os.path.abspath(os.path.dirname(__file__)) 

 

__author__ = 'Charlie Taylor' 

__copyright__ = 'Copyright (c) 2020 Charlie Taylor' 

__license__ = 'GPL-3' 

exec( open(os.path.join( here,'_version.py' )).read() ) # creates local __version__ variable 

__email__ = "cet@appliedpython.com" 

__status__ = "4 - Beta" # "3 - Alpha", "4 - Beta", "5 - Production/Stable" 

 

from math import pi 

from scipy import optimize 

 

from rocketprops.rocket_prop import get_prop 

from rocketprops.unit_conv_data import get_value # for any units conversions 

from rocketisp.efficiency.eff_pulsing import eff_pulse 

from rocketisp.efficiency.eff_divergence import eff_div 

from rocketisp.efficiency.effBL_NASA_SP8120 import eff_bl_NASA, regen_corrected_bl 

 

from rocketisp.efficiency.calc_full_pcentLossBL import calc_pcentLossBL 

 

from rocketisp.efficiency.calc_noz_kinetics import calc_IspODK 

 

#from rocketisp.nozzle.cd_throat import get_Cd 

from rocketisp.nozzle.calc_full_Cd import calc_Cd 

 

from rocketisp.stream_tubes import CoreStream 

 

AVAIL_EFF_MODEL_D = {} # index=eff name, value=list of recognized model names 

AVAIL_EFF_MODEL_D['Pulse'] = ['rough estimate'] 

AVAIL_EFF_MODEL_D['Div'] = ['simple fit', 'MLP fit'] 

AVAIL_EFF_MODEL_D['BL'] = ['MLP fit', 'NASA-SP8120'] 

AVAIL_EFF_MODEL_D['Kin'] = ['MLP fit'] 

AVAIL_EFF_MODEL_D['Em'] = ['Rupe'] 

AVAIL_EFF_MODEL_D['Mix'] = ['mixAngle'] 

AVAIL_EFF_MODEL_D['Vap'] = ['Lgen'] 

 

 

selected_eff_modelD = {}# index=eff name, value= name of selected efficiency model 

selected_eff_modelD['Pulse'] = 'rough estimate' 

selected_eff_modelD['Div'] = 'simple fit' 

selected_eff_modelD['BL'] = 'MLP fit' 

selected_eff_modelD['Kin'] = 'MLP fit' 

selected_eff_modelD['Em'] = 'Rupe' 

selected_eff_modelD['Mix'] = 'mixAngle' 

selected_eff_modelD['Vap'] = 'Lgen' 

 

class RocketThruster(object): 

""" 

RocketIsp calculates delivered Isp for liquid rocket thrust chambers by 

simplified JANNAF method. 

 

:param name: name of RocketThruster 

:param coreObj: CoreStream object 

:param injObj: Injector object (optional) 

:param noz_regen_eps: regen cooled nozzle area ratio 

:param pulse_sec: duration of pulsing engine (default = infinity) 

:param pulse_quality: on a scale of 0.0 to 1.0, how good is engine at pulsing 

:param isRegenCham: flag to indicate chamber is regen cooled 

:param calc_CdThroat: flag to trigger calc_CdThroat 

:type name: str 

:type coreObj: CoreStream 

:type injObj: Injector 

:type noz_regen_eps: float 

:type pulse_sec: float 

:type pulse_quality: float 

:type isRegenCham: bool 

:type calc_CdThroat: bool 

:return: RocketThruster object 

:rtype: RocketThruster 

""" 

 

def set_eff_model(self, eff_name='Div', model_name='MLP fit'): 

""" 

Change the named efficiency model from the default model to a different model. 

For example, change from the simple nozzle divergence model (Div) to the  

Multi-Layer Perceptron (MLP) divergence model. 

 

:param eff_name: name of efficiency (e.g. Div, BL, Kin) 

:param model_name: name of model to be used (must be in AVAIL_EFF_MODEL_D) 

:type eff_name: str 

:type model_name: str 

:return: None 

:rtype: None  

""" 

if eff_name in AVAIL_EFF_MODEL_D: 

if model_name in AVAIL_EFF_MODEL_D[ eff_name ]: 

selected_eff_modelD[ eff_name ] = model_name 

else: 

raise Exception('in set_eff_model, "%s" is not a recognized model name for %s.'%(model_name, eff_name) ) 

 

else: 

raise Exception('in set_eff_model, "%s" is not a recognized efficiency name'%eff_name) 

 

 

def __call__(self, name): 

return getattr(self, name ) # let it raise exception if no name attr. 

 

def __init__(self, name='Rocket Thruster', 

coreObj=CoreStream(), injObj=None, noz_regen_eps=1.0, 

pulse_sec=float('inf'), pulse_quality=0.8, 

isRegenCham=0, calc_CdThroat=True): 

""" 

Calculate delivered thrust chamber Isp by simplified JANNAF method. 

""" 

self.name = name 

self.coreObj = coreObj 

self.geomObj = coreObj.geomObj 

self.ceaObj = coreObj.ceaObj 

self.injObj = injObj 

 

self.iprop = coreObj.oxName + '/' + coreObj.fuelName 

self.pulse_sec = pulse_sec 

self.pulse_quality = pulse_quality 

 

self.noz_regen_eps = noz_regen_eps 

self.isRegenCham = isRegenCham 

 

self.calc_CdThroat = calc_CdThroat 

 

 

self.calc_all_eff() 

 

def scale_Rt_to_Thrust(self, ThrustLbf=500.0, Pamb=0.0, use_scipy=False): 

""" 

Adjust throat size in order to get total thrust at specified ambient pressure exactly 

 

:param ThrustLbf: lbf, desired thrust at specified ambient pressure (Pamb) 

:param Pamb: psia, ambient pressure 

:param use_scipy: flag to indicate the need for more sophisticated root finder 

:type ThrustLbf: float 

:type Pamb: float 

:type use_scipy: bool 

:return: None 

:rtype: None """ 

 

Pamb_save = Pamb 

self.coreObj.reset_attr( 'Pamb', Pamb, re_evaluate=True) 

 

def f_diff( Rt ): 

self.geomObj.reset_attr( 'Rthrt', Rt, re_evaluate=True) 

#self.coreObj.evaluate() 

self.calc_all_eff() 

return ThrustLbf - self.coreObj.Fambient 

 

At_guess = self.geomObj.At * ThrustLbf / self.coreObj.Fambient 

Rt_guess = (At_guess/pi)**0.5 

 

if use_scipy: 

# demand convergence to a tolerance with a root solver. 

Rt_min = Rt_guess/1.4 

Rt_max = Rt_guess*1.4 

 

sol = optimize.root_scalar(f_diff, x0=Rt_guess, bracket=[Rt_min, Rt_max], 

xtol=ThrustLbf/1.0E8, method='brentq') 

#print('sol.root=%g, sol.iterations=%g, sol.function_calls=%g'%(sol.root, sol.iterations, sol.function_calls)) 

f_diff( sol.root ) 

else: 

# often converges in just a few iterations. 

xtol=ThrustLbf/1.0E8 

 

#print( 'self.coreObj.Fambient',self.coreObj.Fambient ) 

f_diff( Rt_guess ) 

#print( 'self.coreObj.Fambient',self.coreObj.Fambient ) 

for _ in range( 10 ): 

At_guess = self.geomObj.At * ThrustLbf / self.coreObj.Fambient 

Rt_guess = (At_guess/pi)**0.5 

err = f_diff( Rt_guess ) 

#print( 'self.coreObj.Fambient',self.coreObj.Fambient ) 

if abs(err) < xtol: 

self.coreObj.reset_attr( 'Pamb', Pamb_save, re_evaluate=True) 

return 

self.coreObj.reset_attr( 'Pamb', Pamb_save, re_evaluate=True) 

 

 

def calc_all_eff(self): 

""" 

Looks at the efficiency object (effObj) and calculates those efficiencies 

that have not been set as constants by the user. 

 

see: self.calc_CdThroat or effObj['XXX'].is_const for individual efficiencies 

""" 

DOREVAL = False 

made_a_change = False 

effObj = self.coreObj.effObj 

 

if self.calc_CdThroat: 

#CdThroat = get_Cd( RWTU=self.geomObj.RupThroat, gamma=self.coreObj.gammaChm ) 

CdThroat = calc_Cd( Pc=self.coreObj.Pc, Rthrt=self.geomObj.Rthrt, RWTU=self.geomObj.RupThroat ) 

 

self.coreObj.reset_CdThroat( CdThroat, method_name='MLP fit', re_evaluate=DOREVAL) 

made_a_change = True 

 

#if self.calc_effPulse: 

if not effObj['Pulse'].is_const: 

effPulse = eff_pulse( pulse_sec=self.pulse_sec, pulse_quality=self.pulse_quality) 

msg = 'rough estimate (%g sec, Q=%g)'%(self.pulse_sec, self.pulse_quality) 

self.coreObj.effObj.set_value( 'Pulse', effPulse, value_src=msg, re_evaluate=DOREVAL) 

made_a_change = True 

 

#if self.calc_effDiv: 

if not effObj['Div'].is_const: 

 

# AVAIL_EFF_MODEL_D['Div'] = ['simple fit', 'MLP fit'] 

if selected_eff_modelD['Div'] == 'simple fit': 

effDiv = eff_div( eps=self.geomObj.eps, pcBell=self.geomObj.pcentBell) 

msg = selected_eff_modelD['Div'] + ' eps=%g, %%bell=%g'%(self.geomObj.eps, self.geomObj.pcentBell) 

 

elif selected_eff_modelD['Div'] == 'MLP fit': 

raise Exception('MLP fit not yet implemented for eff Div') 

 

 

self.coreObj.effObj.set_value( 'Div', effDiv, value_src=msg, re_evaluate=DOREVAL) 

made_a_change = True 

 

#if self.calc_effBL: 

if not effObj['BL'].is_const: 

 

# AVAIL_EFF_MODEL_D['BL'] = ['MLP fit', 'NASA-SP8120'] 

if selected_eff_modelD['BL'] == 'NASA-SP8120': 

effBL = eff_bl_NASA( Dt=self.geomObj.Rthrt*2.0, Pc=self.coreObj.Pc, eps=self.geomObj.eps) 

elif selected_eff_modelD['BL'] == 'MLP fit': 

 

pclossBL = calc_pcentLossBL( Pc=self.coreObj.Pc, eps=self.geomObj.eps, 

Rthrt=self.geomObj.Rthrt, pcentBell=self.geomObj.pcentBell, 

TcCham=self.coreObj.TcODE ) 

 

effBL = (100.0 - pclossBL)/100.0 

 

msg = selected_eff_modelD['BL'] 

 

if self.noz_regen_eps > 1.0: 

msg += 'regen-corrected' 

effBL = regen_corrected_bl( eff_bl=effBL, eps=self.geomObj.eps, noz_regen_eps=self.noz_regen_eps ) 

 

self.coreObj.effObj.set_value( 'BL', effBL, value_src=msg, re_evaluate=DOREVAL) 

made_a_change = True 

 

#if self.calc_effKin: 

if not effObj['Kin'].is_const: 

IspODK = calc_IspODK(self.ceaObj, Pc=self.coreObj.Pc, eps=self.geomObj.eps, 

Rthrt=self.geomObj.Rthrt, pcentBell=self.geomObj.pcentBell, 

MR=self.coreObj.MRcore) 

 

# coreObj has made IspODE calc already 

effKin = IspODK / self.coreObj.IspODE 

msg = selected_eff_modelD['Kin'] 

 

self.coreObj.effObj.set_value( 'Kin', effKin, value_src=msg, re_evaluate=DOREVAL) 

made_a_change = True 

 

if self.injObj is not None: 

#if self.calc_effEm: 

if not effObj['Em'].is_const: 

effEm = self.injObj.calculate_effEm() 

msg = 'Rupe Em=%g'%self.injObj.Em 

self.coreObj.effObj.set_value( 'Em', effEm, value_src=msg, re_evaluate=DOREVAL) 

made_a_change = True 

 

#if self.calc_effMix: 

if not effObj['Mix'].is_const: 

effMix = self.injObj.calculate_effMix() # calc inter-element mixing efficiency (2 deg estimate) 

msg = 'mixAngle=%.2f deg'%self.injObj.mixAngle 

self.coreObj.effObj.set_value( 'Mix', effMix, value_src=msg, re_evaluate=DOREVAL) 

made_a_change = True 

 

#if self.calc_effVap: 

if not effObj['Vap'].is_const: 

effVap = self.injObj.calculate_effVap() 

msg = 'gen vaporized length' 

self.coreObj.effObj.set_value( 'Vap', effVap, value_src=msg, re_evaluate=DOREVAL) 

made_a_change = True 

 

# after all updates, re_evaluate 

if made_a_change: 

self.coreObj.evaluate() 

 

def summ_print(self): 

""" 

print to standard output, the current state of RocketThruster instance. 

""" 

print('='*30, ' %s '%self.name, '='*30) 

 

self.coreObj.summ_print() 

 

if self.injObj is not None: 

self.injObj.summ_print(show_core_stream=False) 

 

 

if __name__ == '__main__': 

from rocketisp.geometry import Geometry 

 

from rocketisp.injector import Injector 

from rocketisp.efficiencies import Efficiencies 

 

geomObj = Geometry(Rthrt=5.868/2, 

CR=2.5, eps=150, pcentBell=80, 

RupThroat=1.5, RdwnThroat=1.0, RchmConv=1.0, cham_conv_deg=30, 

LchmOvrDt=3.10, LchmMin=2.0, LchamberInp=16) 

 

effObj = Efficiencies() 

#effObj.set_const('ERE', 0.98) 

 

core = CoreStream( geomObj, effObj, oxName='N2O4', fuelName='MMH', MRcore=1.85, 

Pc=150, CdThroat=0.995, 

pcentFFC=14.0, ko=0.035) 

 

inj = Injector(core, Tox=None, Tfuel=None, Em=0.9, 

fdPinjOx=0.25, fdPinjFuel=0.25, 

elemDensInp=None, NelementsInp=None, 

setNelementsBy='acoustics', # can be "acoustics", "density", "input" 

setAcousticFreqBy='mode', # can be "mode" or "freq" 

desAcousMode=0.8*4.2012, desFreqInp=2000, 

OxOrfPerEl=1.0, FuelOrfPerEl=1.0, 

lolFuelElem=True, 

CdOxOrf=0.75, CdFuelOrf=0.75, dropCorrOx=0.33, dropCorrFuel=0.33, 

DorfMin=0.008, 

LfanOvDorfOx=20.0, LfanOvDorfFuel=20.0) 

 

C = RocketThruster(name='Sample Thruster',coreObj=core, injObj=inj, pulse_sec=float('inf'), pulse_quality=0.8) 

 

#C.scale_Rt_to_Thrust( 10000.0, Pamb=0.0, use_scipy=False ) 

C.summ_print()