Apparatus for the preparation of fuel mixtures for carburetors

A device for the preparation of liquid fuels for mixture compressing internal combustion engines by supplying supplementary air into an induction system downstream of a main butterfly valve of a carburetor comprising:

• a manifold downstream of the main butterfly valve and having first and second opposed air admitting arcuate slits extending part way around the manifold, supplementary air flowing from the first slit at idling speed at nearly the speed of sound, a passageway for supplying air to the second arcuate slit, and a control member coupled to the butterfly valve for controlling the supply of air through the passageway and to the second arcuate slit within a predetermined load range and in relation to the butterfly valve opening;
• the second slit being designed as a Laval jet having an arcuate slit which gradually converges in a radially inward direction to supply supplementary air at very high speed in the transition range of engine operation and to supply supplementary air at a speed near the speed of sound in the part-load range of engine operation so that the cross-section which limits the air flow from the second arcuate slit changes from that determined by the control member to that of the second slit from the medium power range onward with the supplementary air flowing from the second slit at about the speed of sound.

A carbureted mixture compressing internal combustion engine having apparatus for the preparation of liquid fuels by feeding supplementary air into the engine induction system downstream of a main butterfly valve of a recirculated air carburetor by way of first and second opposed openings in the induction system where supplementary air flows from the openings depending upon a supplementary air control member,

• means including the control member, and effective only in the transition range, for limiting the air flowing from the openings;
• and
• means including the openings for limiting the air flow from the openings at about the speed of sound in the part load range with the air flow rate remaining relatively constant from the part-load range on into the higher power ranges.