Cantera Lecture

Cantera Overview

Cantera is a code written in C++ that can be used to perform chemical kinetic and thermodynamic calculations.

The way it does this is by providing the user with a set of building blocks, and allowing the user to piece these building blocks together to form complex kinetic/thermodynamic systems or networks

Users can interface with Cantera through C++, or through the other interfaces:

• Matlab toolbox
• Python
• Fortran

Visit the Cantera (software) page for a Cantera installation guide for either Mac, Linux, or Windows.

Cantera Objects

Reservoir - fixed state

• the state of the reservoir never changes
• used to impose fixed upstream/inlet conditions
• chemistry is frozen - so no reactions will take place

Reactor - canonical chemical reactor

• contains some mixture of species
• has a set of characteristics
• e.g. T, V, P, composition, enthalpy, density, MW, etc...

Fluids - gases or liquids

Chemical Mechanisms - external files "fed" to Cantera

• chemical mechanisms specify two things:
  • species
  • reactions
• all thermodynamic data for species is specified (e.g. heat capacity as a polynomial function - "NASA coefficients")
• all thermodynamic data for chemical reactions (pre-exponential factors, activation energies, etc.)

Walls - separate reactors

• can have heat transfer via the usual mechanisms - convection, conduction, radiation
• can have a set heating rate (a constant, or a function of time)
• can move - due to a pressure difference, a displacement rate expression, etc.)

Flow controllers - control flow... 3 types

Mass flow controller - maintains a fixed mass flowrate

Valves - the mass flowrate is a function of $ \Delta P $

Pressure flow controller - maintains a fixed $ P $ in the reactor (think of this as a pressure relief valve)

Matlab Examples

Batch Reactor Example

How might we combine the above Cantera objects to make a batch reactor?

e.g. where would the reactor go? Where would the flow controllers go?

Any reservoirs needed? No

Any flow controllers needed? No

We want to know what happens when the reactor is changing from state 1 to state 2

For a constant volume reactor:

What is going into our reactor?

% Import a phase to fill the reactor with
% (The H2 combustion mechanism is contained in the file h2o2.cti, which comes with Cantera)
gas = importPhase('h2o2.cti');

What is the thermodynamic state of the material going into the reactor?

% Set the gas temperature at 1500 K
% Set the pressure at 1 atm
% Set the composition to be 2 parts hydrogen, 1 part oxygen, and 20 parts dilute, inert Argon
set(gas, 'T',1500, 'P',oneatm, 'X','H2:2, O2:1, AR:20')

How to create a batch reactor? Create a Cantera Reactor object

% We have already set the thermodynamic state of the "gas" object
% But if we wanted to, we could set it when we create the Reactor
batch = Reactor(gas);

What is the volume of the reactor if we don't specify it?

How do we specify a volume for the reactor?