Abstract
A combined experimental and phenomenological modelling approach for upgrading a slow response, automotive, chemiluminescent analyser for transient nitric oxide (NO) measurement is studied. The approach adopts two physical models, viz diffusion and perfect gas-mixing models, as the basis for analysis such that the behaviour of gas transport through the chemiluminescent analyser can be characterised and formulated. This is done by simulating the behaviour of gas transportation using a series of alternately arranged pipes and control volumes such that the distortion of the transient NO emission signal due to gas diffusion and mixing in any pipes and surge volumes within the analyser can be physically explained and modelled. A computer-controlled transient NO emission simulator is developed which controls the ONs and OFFs status of a fast response solenoid valve in order to generate a known concentration of NO emission pulse to the analyser. This simulator is able to generate a square pulse-train of NO emission continuously with random or user defined pulse width and dwell. Characterisation of analyser is possible only when both the input reference NO emission signal and the output response signal of the analyser are logged simultaneously. Signal inference technique is employed when the characteristic constants of the analyser are determined by matching the input and response signals using the phenomenological models.