Cantera simulation of H2 + NH3 mixture in a constant vol combustion chamber

[Nikita Lahoti]

I am trying to do Cantera simulation of H2+NH3 mixture in a control vol combustion chamber. My main aim is to plot pressure rise curves and heat release rates. The problem I am facing is in finding an appropriate code for this problem. I got a code in Cantera Documentation- "Adiabatic Combustion of a ideal gas" but in that code if I am giving an initial temperature of 300 K , the mixture doesn't ignite at all ; it only ignites at T=1000K but that is not my mixture's initial temp. I don't want to introduce radicals for the ignition as that will change the chemistry. I want a way to introduce spark in this combustion at the beginning to ignite the mixture. Can someone help me modify the code for that?

Regards 

Nikita Lahoti

[Ray Speth]

Hi Nikita,

I think there's a significant conceptual mismatch between a homogeneous reactor model and a spark ignition engine. The combustion process in such an engine is inherently inhomogeneous. The spark creates a small flame kernel in one location, and the flame then propagates through the unburned mixture. That can't be represented as a homogenous process. To compute pressure rise curves and heat release rates, you need an unsteady model with at least one spatial dimension.

What Cantera can do for you, given its focus on the chemistry rather than the fluid mechanics, is to model (a) steady laminar flame speeds, which inform the rate at which the flame would propagate through the cylinder (though this is coupled to the fluid mechanics since the actual combustion process is turbulent) and (b) model ignition delays for the end gas to evaluate knocking, for example by applying a time varying volume profile to represent the compression process that this gas experiences as the flame propagates.

Regards,

Ray