Search Results

In a recent paper, a novel fast-response NDIR-based CO2 (fCO2) sensor was described, with applications to automotive engine gas analysis. Certain shortcomings were identified with the sensor. The present paper is concerned with the evolution of the sensor towards a mature instrument and an important application: the measurement of Exhaust Gas Recirculation (EGR) rates during rapid transients. The application described concerns transient EGR measurements at unprecedented bandwidths. Essentially, the technique is based on comparing the inlet manifold CO2 concentration with that in the exhaust. Sampling complications caused by the wide range of inlet pressures encountered in the inlet manifold are discussed. A comparison of EGR from the present test is made with those deduced by the engine controller and a standard slow bench instrument. EGR calibration errors are then identified and related to legislated emissions measured with a similar frequency response.

A semi-empirical model of fuel transport in the intake manifold of spark ignition engines, which assumes a fraction of injected fuel deposits onto the port walls and describes the detailed fuel film phenomena, is proposed. The model is applied in the throttle ramp transients during which both the air and the fuel flow change significantly. The predicted air fuel ratio excursions, engine torque etc, are in good agreement with the experimental data. Also simulated is another kind of transience, which has only an air flow jump, i.e. with fuelling rate constant, when the engine jumps between stoichiometric and lean running. The results are again in satisfactory agreement with experiment.