Improved In-Cylinder Local CAD-Resolved Equivalence Ratio Measurement Probe for SI Engines

A new tool able to deliver the local in-cylinder equivalence air fuel ratio with high temporal CA resolution is presented for SI engines. Although non-intrusive laser techniques have considerable advantages, they are inappropriate for series engines application and other measurement techniques do not have a fast enough time response. The probe presented fullfills the demand for fast local air-fuel ratio measurement with a simpler device than fast FID. Mounted at the spark plug location, it allows a completely normal running of the engine as it is integrated in a spark plug. The probe is based on hot wire anemometry technique involving catalytic oxidation of hydrocarbons on the wire. A parametric study giving the major characteristics of the measurement sensitivity, confidence, response time and some applications of the probe to in-cylinder engine measurements are presented which confirm the ability of the technique to characterize, quantitatively, the homogeneity or in-homogeneity of air-fuel mixture, especially during the compression stroke with a CA resolution.