Vortex shedding device for use in measuring air flow rate into an internal combustion engine

Claim 1

A vortex shedding device for use in measuring the rate at which air flows into the air intake of an internal combustion engine, said device comprising: a conduit having a passage within it through which air whose flow rate is to be measured may flow, said passage having a venturi section formed in it, said venturi section being of rectangular cross-section throughout and having width and height dimensions, the width dimension being the greater of said dimensions, said venturi section including an inlet portion a throat portion having a cross-sectional area in the range from about one-third to about one-half of the cross-sectional area of said inlet portion, a converging portion between said inlet and throat portions, and a diverging portion extending away from said throat portion toward the end of said passage remote from said inlet portion, said converging and diverging portions being formed by variation of said height dimension, said width dimension being constant over the length of said venturi section, an elongated element for generating vortices in air flowing in said passage in a direction from said inlet portion toward said diverging portion, said elongated element being located in said throat portion of said passage and extending transverse to said direction of air flow and parallel to said width dimension, said elongated element being of circular or semi-circular cross-section and having a diameter in the range from about 1.5 mm to 3.5 mm, a honeycomb structure positioned in said inlet portion of said passage venturi section, said honeycomb structure having a plurality of flow channels extending in said direction of said air flow to impart stratified characteristics to such air flow, said honeycomb structure being spaced from said converging portion of said venturi section, and said cross-sectional area of said throat portion being sized, relative to said internal combustion engine, to achieve a maximum flow velocity in said throat portion in the range from about 76 to about 92 m/sec.