A Fast-Response Flame Ionization Detector for Exhaust Hydrocarbons 660117
A hydrogen flame ionization detector with a specially designed sample inlet system has been developed which makes it possible to monitor continuously and accurately the total hydrocarbon content of exhaust gases from a cyclically operating engine. The apparatus has a sample delay time (that is, the time required for the exhaust sample to travel from the sampling point to the detector) of about 1 sec, enabling it to follow rapidly changing engine operating conditions.
Hydrocarbon emission (HCE) measurements with the fast-response detector are shown to be substantially higher and more indicative of absolute hydrocarbon concentration than values obtained using nondispersive infrared equipment according to the California test procedure. In addition, sample delay time is shown to affect apparent HCE values.
By using high ratios of hydrogen-to-sample gas flow rates to the detector, errors in hydrocarbon measurement resulting from oxygen interference can be held to less than 10%, thereby making the device suitable for monitoring HCE from cars employing exhaust air injection for emission control.