CO and NOx calculation 1

[RBC557CG]

I am tuning a rich burn combustion engine that runs on waste gas. This engine has a PVC circuit. We are trying to target 17:1 air fuel ratio to 16.7:1. With an emissions analyzer we can monitor CO and NOX. If the CO is high, it is rich, if the NOx is high, it is lean. My question is tuning this engine with an o2 sensor, how can I calculate proper balance between Nox and CO?

 

[franzh]

The O2 sensor cannot detect the presence of HC, CO, or NOx, only the relative comparison of the oxygen present in the exhaust manifold to the ambient air.

Ideally, you should tune for the middle of the resolution range of your sensor, but most normal band sensors have a flat spot in that range, relying on switching of ratios to establish an average AF ratio. A wide band sensor is more practical but there are no hard and fast numbers to tell you what voltage equates to which residual emission balance.

You say you are tuning a rich burn engine, but 16.7:1 to 17.1:1 is relatively lean (assuming you are using Methane as a base gas). You will need a NOx sampler with a stationary gas analyzer. You might do ok using a production 5 gas automotive base analyzer. Units made by Blanke and one by Bridge are very nice and portable, but there are many others too.

Franz

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.