Numeric solver runaway using ReactorNet.advance_to_steady_state

Open
  • Is something wrong?
#989 6 comments 0 reactions 0 assignees View on GitHub

@hasin4 is already working on this.

Since Oct 11, 2026.

Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
backend

Research direction

Start by running the supplied Python example with Cantera 2.5 and focus on ReactorNet.advance_to_steady_state with IdealGasConstPressureReactor. Compare the failing cases with ConstPressureReactor and IdealGasReactor, recording reactor mass and volume; done means the reproduced cases no longer generate invalid values or CanteraErrors, or the limitation is clearly documented.

Written by the indexing model from the issue text.

Description

documentation enhancement Reactors

I want to simulate burning methane in an IdealGasConstPressureReactor. I use different mass-flows and equivalence-ratios using two vectors you can see in my example code below. However, using ReactorNet.advance_to_steady_state breaks the solver at certain points, leading to huge reactor masses and volumes and therefore CanteraErrors. If I varying the equivalence-ratio leads to different combustors failing, varying the mass-flows to each reactor has no effect on this. Using a ConstPressureReactor also leads to the same results, using an IdealGasReactor eliminates the error while the pressure before and after the reactor stays about the same (0.1% differences).

Steps to reproduce

My example code:

import cantera as ct
import numpy as np

# Initial constants
inlet_temperature = 712 # K
inlet_pressure = 2171756.0738435777 # Pa
inlet_density = 10.529 # kg/m³
phi_mean = 0.3
phi_std = 0.25
mdot = 350 # kg/s

# Vectors for phi and mass flow ratio
x=[0.1125, 0.1375, 0.1625, 0.1875, 0.2125, 0.2375, 0.2625, 0.2875, 0.3125, 0.3375,
 0.3625, 0.3875, 0.4125, 0.4375, 0.4625, 0.4875]
y_norm=[0.05223705, 0.05602466, 0.05948904, 0.0625391,  0.06509137, 0.0670737,
 0.06842868, 0.0691164,  0.0691164,  0.06842868, 0.0670737,  0.06509137,
 0.0625391,  0.05948904, 0.05602466, 0.05223705]

psr_exhaust_gases = []


# Run Combustors for each Massflow/Phi
n = 0
for phi, ratio in zip(x,y_norm):
    gas = ct.Solution("gri30.xml")
    gas.TP = inlet_temperature, inlet_pressure
    print(f"{n} Combustor using phi={phi} and mass flow {ratio*mdot}")
    gas.set_equivalence_ratio(phi, 'CH4:1.0', 'O2:1.0, N2:3.76')
    gas.equilibrate("HP")
    inlet = ct.Reservoir(gas)
    exhaust = ct.Reservoir(gas)
    reactor = ct.IdealGasConstPressureReactor(gas)
    reactor.volume = 1
    inlet_mfc = ct.MassFlowController(inlet, reactor, mdot=mdot*ratio)
    outlet_mfc = ct.PressureController(reactor, exhaust, master=inlet_mfc, K=0.98)  
    
    # Perform simulation
    sim = ct.ReactorNet([reactor])
    try:
        sim.advance_to_steady_state()
    except Exception:
        print(f"Reactor {n} failed")
    print(f"Reactor Mass: {reactor.mass}")
    psr_exhaust_gases.append(gas)
    n+=1

Behavior

0 Combustor using phi=0.1125 and mass flow 18.2829675
Reactor Mass: 7.509287323526787
1 Combustor using phi=0.1375 and mass flow 19.608631
Reactor 1 failed
Reactor Mass: -31989052.24073112
2 Combustor using phi=0.1625 and mass flow 20.821164
Reactor Mass: 6.698140629935816
3 Combustor using phi=0.1875 and mass flow 21.888685
Reactor Mass: 6.363181017677751
4 Combustor using phi=0.2125 and mass flow 22.7819795
Reactor 4 failed
Reactor Mass: 5706937067178.77
5 Combustor using phi=0.2375 and mass flow 23.475795
Reactor 5 failed
Reactor Mass: -503360543931.0006
6 Combustor using phi=0.2625 and mass flow 23.950038000000003
Reactor Mass: 5.5565265127696755
7 Combustor using phi=0.2875 and mass flow 24.190739999999998
Reactor 7 failed
Reactor Mass: -1743850606.9494267
8 Combustor using phi=0.3125 and mass flow 24.190739999999998
Reactor Mass: 5.139242033695134
9 Combustor using phi=0.3375 and mass flow 23.950038000000003
Reactor Mass: 4.957399144199033
10 Combustor using phi=0.3625 and mass flow 23.475795
Reactor 10 failed
Reactor Mass: -1583462983.9286568
11 Combustor using phi=0.3875 and mass flow 22.7819795
Reactor 11 failed
Reactor Mass: -1327952461.4260874
12 Combustor using phi=0.4125 and mass flow 21.888685
Reactor Mass: 4.4945519221887915
13 Combustor using phi=0.4375 and mass flow 20.821164
Reactor 13 failed
Reactor Mass: 1025354594.860802
14 Combustor using phi=0.4625 and mass flow 19.608631
Reactor 14 failed
Reactor Mass: -6298273.947422755
15 Combustor using phi=0.4875 and mass flow 18.2829675
Reactor 15 failed
Reactor Mass: -2568280.108493603

System information

  • Cantera version: 2.5
  • OS: Windows 10
  • Python software version: 3.8.5
Dominant language
C++
Stars
883
Forks
436
Avg merge
3h 41m
Merged PRs (30d)
1

Getting set up

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from Cantera/cantera

All issues in Cantera/cantera

Similar issues

More C++ issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.