Characterization and Signal Inference of a NDIR Automotive Emission Analyzer Used for Dynamic Measurement

Conventional gases emission analyzers based upon non-dispersive infra-red measuring technique are of limited use in transient engine testing due to the dynamic response of these analyzers cause distortion of emission signal measured during transient engine operation. A phenomenological modelling approach is proposed which simulates the behaviour of gas transportation through an emission analyzer by a series of alternately arranged pipes and surge volumes such that the distortion of the emission signal can be physically explained and modelled.

Characterization of emission analyzer using two physical models, viz diffusion and perfect gas-mixing models, is adopted as the basis for analysis so that physical interpretation can be made to account for the resulting distortion and variation of measured emission signal. The actual emission signal before distorted by the slow response emission analyzer can be inferred by solving these models numerically.

A computer program has been developed which provides a continuous signal inference from a series of distorted emission pulses measured during transient engine operation.