gekko - 如何解决 Gekko 中的简单混合操作？

Question

我正在尝试解决 gekko 中的一个简单混合操作。 blender mx采用两个入口流 Feed1和 Feed2 .预期结果是导出流的质量流量mx.outlet应该是入口流的质量流量的总和。
这是我尝试过的。

from gekko import GEKKO, chemical
m = GEKKO(remote=False)    

f = chemical.Flowsheet(m)
P = chemical.Properties(m)

c1 = P.compound('Butane')
c2 = P.compound('Propane')

feed1 = f.stream()
m_feed1 = f.massflows(sn= feed1.name)
m_feed1.mdot = 200
m_feed1.mdoti = [50,150]

feed2= f.stream()
m_feed2 = f.massflows(sn= feed2.name)
m_feed2.mdot = 200
m_feed2.mdoti = [50,150]      

mx = f.mixer(ni=2)
mx.inlet = [feed1.name,feed2.name]
m.options.SOLVER = 1

mf = f.massflows(sn = mx.outlet)
m.solve()

代码运行成功。但是，在 mf.mdot似乎输出不正确的值 [-1.8220132454e-06]。预期值为 400。任何帮助，我的代码有什么问题？

Answer 1

这是适用于此混合应用程序的源代码:

from gekko import GEKKO, chemical
import json

m = GEKKO(remote=False)    

f = chemical.Flowsheet(m)
P = chemical.Properties(m)

# define compounds
c1 = P.compound('Butane')
c2 = P.compound('Propane')

# create feed streams
feed1 = f.stream(fixed=False)
feed2 = f.stream(fixed=False)

# create massflows objects
m_feed1 = f.massflows(sn=feed1.name)
m_feed2 = f.massflows(sn=feed2.name)

# create mixer
mx = f.mixer(ni=2)

# connect feed streams to massflows objects
f.connect(feed1,mx.inlet[0])
f.connect(feed2,mx.inlet[1])
m.options.SOLVER = 1

mf = f.massflows(sn = mx.outlet)

# specify mass inlet flows
mi = [50,150]
for i in range(2):
    m.fix(m_feed1.mdoti[i],val=mi[i])
    m.fix(m_feed2.mdoti[i],val=mi[i])
# fix pressure and temperature
m.fix(feed1.P,val=101325)
m.fix(feed2.P,val=101325)
m.fix(feed1.T,val=300)
m.fix(feed2.T,val=305)

m.solve(disp=True)

# print results
print(f'The total massflow out is {mf.mdot.value}')

print('')

# get additional solution information
with open(m.path+'//results.json') as f:
    r = json.load(f)
for name, val in r.items():
    print(f'{name}={val[0]}')

下面是求解器输出。这仅适用于 APM 0.9.1 和 Gekko v0.2.3(将于 2019 年 8 月发布)。 Thermo 和 Flowsheet 对象库随 v0.2.2 一起发布，并且有几个功能仍在开发中。下一个版本应该解决其中的许多问题。

 ----------------------------------------------------------------
 APMonitor, Version 0.9.1
 APMonitor Optimization Suite
 ----------------------------------------------------------------


 --------- APM Model Size ------------
 Each time step contains
   Objects      :  6
   Constants    :  0
   Variables    :  19
   Intermediates:  0
   Connections  :  44
   Equations    :  2
   Residuals    :  2

 Number of state variables:    14
 Number of total equations: -  14
 Number of slack variables: -  0
 ---------------------------------------
 Degrees of freedom       :    0

 ----------------------------------------------
 Steady State Optimization with APOPT Solver
 ----------------------------------------------

 Iter    Objective  Convergence
    0  3.86642E-16  1.99000E+02
    1  4.39087E-18  1.11937E+01
    2  8.33448E-19  6.05819E-01
    3  1.84640E-19  1.62783E-01
    4  2.91981E-20  7.21250E-02
    5  1.55439E-21  2.28110E-02
    6  5.51232E-24  1.21437E-03
    7  7.03139E-29  4.30650E-06
    8  7.03139E-29  4.30650E-06
 Successful solution

 ---------------------------------------------------
 Solver         :  APOPT (v1.0)
 Solution time  :  0.0469 sec
 Objective      :  0.
 Successful solution
 ---------------------------------------------------


v1 not found in results file
The total massflow out is [400.0]

time=0.0
feed1.h=44154989.486
feed1.x[2]=0.79815448476
feed1.vdot=104.9180373
feed1.dens=0.040621756423
feed1.c[1]=0.0081993193551
feed1.c[2]=0.032422437068
feed1.mdot=200.0
feed1.y[1]=0.25
feed1.y[2]=0.75
feed1.sfrc=0.0
feed1.lfrc=0.0
feed1.vfrc=1.0
feed2.h=44552246.421
feed2.x[2]=0.79815448476
feed2.vdot=106.66667125
feed2.dens=0.03995582599
feed2.c[1]=0.0080649042837
feed2.c[2]=0.031890921707
feed2.mdot=200.0
feed2.y[1]=0.25
feed2.y[2]=0.75
feed2.sfrc=0.0
feed2.lfrc=0.0
feed2.vfrc=1.0
mixer5.outlet.t=381.10062836
mixer5.outlet.h=44353617.96
mixer5.outlet.ndot=8.5239099109
mixer5.outlet.x[1]=0.20184551524
mixer5.outlet.x[2]=0.79815448476
mixer5.outlet.vdot=1.5797241143
mixer5.outlet.dens=5.5635215396
mixer5.outlet.c[1]=1.0891224437
mixer5.outlet.c[2]=4.3066994177
mixer5.outlet.mdot=400.0
mixer5.outlet.y[1]=0.25
mixer5.outlet.y[2]=0.75
mixer5.outlet.sfrc=0.0
mixer5.outlet.lfrc=1.0
mixer5.outlet.vfrc=0.0
v2=300.0
v3=4.2619549555
v4=0.20184551524
v5=0.79815448476
v6=101325.0
v7=305.0
v8=4.2619549555
v9=0.20184551524
v10=0.79815448476
v11=200.0
v12=50.0
v13=150.0
v14=200.0
v15=50.0
v16=150.0
v17=400.0
v18=100.0
v19=300.0