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A fast response NO detector has been developed to study fast transient emissions from internal combustion engines. The device combines the standard ChemiLuminescence Detector (CLD) measurement technique used in conventional NO detectors with the rapid sampling system of an existing Fast Flame Ionisation Detector (FFID) hydrocarbon detector. The 10-90% response time of the fast NO detector is approximately 3 milliseconds and enables resolution of transient NO concentration within individual engine cycles. Both the fast NO and fast HC detectors were fitted in the exhaust port of a firing SI engine. With the probe tips at the same position, simultaneous fast transient NO and HC concentration data have been recorded during steady state and transient engine load conditions. Cycle-by-cycle NO concentration, HC concentration, and cylinder pressure are compared and features of the transient NO and HC concentration are discussed.

Hydrocarbon wall quenching has been studied using a 19mm diameter, 1m long combustion tube, open at one end. Mixtures of propane, heptane, iso-octane and gasoline, initially quiescent, were burnt with the ignition source at the closed end. The post-flame HC levels were measured at a series of axial locations using a fast FID. The results indicate that the effective quench layer thickness increases significantly as the molecular weight of the fuel is increased. The diffusion/mixing time constant of the quench layer was found to be approximately 0.1s for propane, 0.4s for iso-octane and 1.0s for gasoline. The axial variation of residual HC levels suggests that flame stretch is a factor influencing the extent of the quench layer.