Ricardo UK Limited

Stephen Brian Glover

Stephen Morris

The carburetor () includes a flow duct including rich () and lean () flow passage in parallel, through which, in use, air flows in a flow direction and which are separated by a substantially planar partition (), at least one fuel jetcommunicating with the rich passage (), the partition () including an aperture () towards which the fuel jet () is directed, and a substantially planar butterfly valve () being received in the aperture () so as to be pivotable between a first position, in which the flow duct is substantially closed and the aperture () is substantially open, and a second position, in which the flow duct is substantially open and the aperture () is substantially closed, the upstream half of the aperture () being defined by an upstream semi-annular seating ledge () affording an upstream seating surface which is engaged by one of the surfaces of the butterfly valve () when it is in the second position and a first end surface which extends between the upstream seating surface and that surface of the partition () which is directed towards the lean passage (), the downstream half of the aperture () being defined by a down-stream semi-annular seating ledge () affording a downstream seating surface which is engaged by the other surface of the butterfly valve () when it is in the second position and a second end surface, which extends between the downstream seating surface and that surface of the partition () which is directed towards the rich passage.

Carburettor

A carburettor for a two stroke engine includes a flow duct including rich and lean flow passages () in parallel, through which, in use, air flows in a flow direction and which are separated by substantially planar partition (). At least one fuel jet () communicates with the rich passage () and the partition includes an aperture () towards which the fuel jet is directed. A substantially planar butterfly valve () is received in the aperture so as to be pivotable between a first position, in which the flow duct is substantially closed and the aperture is substantially open, and a second position, in which the flow duct is substantially open and the aperture is substantially closed. The upstream half of the aperture () is defined by upstream semi-annular seating ledge () affording an upstream seating surface (), which is engaged by one of the surfaces of the butterfly valve (), when it is in the second position, and a first end surface (), which extends between the upstream seating surface and that surface of the partition which is directed towards the lean passage. The downstream half of the aperture () is defined by a downstream semi annular seating ledge () affording a downstream seating surface (), which is engaged by the upper surface of the butterfly valve, when it is in the second position, and a second end surface (), which extends between the downstream seating surface and that surface of the partition which is directed towards the rich passage. At least one of the upstream semi annular seating ledge, the downstream semi-annular seating and the valve are so shaped that, in use, a pressure differential is created between the rich and lean passages at the upstream and/or downstream edges of the valve, the pressure in the lean passage being higher than that in the rich passage.

A carburettor is connected into the inlet duct () of an internal combustion engine. The inlet duct is divided by a dividing wall () into a rich passage () and a lean passage (). The carburettor includes a fuel chamber () and defines a flow duct divided by a planar partition () into a rich duct () and a lean duct () which communicate with the rich and lean passages, respectively. The partition () defines an aperture () in which a planar butterfly valve () is pivotably mounted. A number of fuel supply orifices () communicate with the fuel chamber () and with the duct () at a position opposite to the aperture (). The butterfly valve () is pivotable between an open position, in which the flow duct is substantially open and the aperture () is substantially closed and all of the fuel flowing out of the fuel supply orifices () flows into the rich duct (), and a closed position, in which the flow duct is substantially closed and the aperture () is substantially open and the fuel flowing out of the fuel supply orifices flows into to both the rich and lean ducts. An idle fuel supply orifice () is provided in the dividing wall () and communicates with the rich and lean passages () and with the fuel chamber () and with the atmosphere. Under idling operation of the engine, an air/fuel mixture is induced into the rich and lean passages not only through one of the fuel supply orifices () but also through the idle fuel supply orifice ().

Carburettors

A reciprocating piston engine ( ) includes an exhaust system comprising an exhaust pipe ( ) which communicates with a silencer ( ), whose upstream portion ( ) is divergent in the direction of gas flow through it, an oxidising catalyst ( ) and an air supply pipe ( ) communicating with the exhaust pipe at a position upstream of the catalyst and silencer. The air supply pipe ( ) includes a Reed valve ( ) which is adapted to open under a pressure differential to permit air to flow into the exhaust pipe. In order to maximise the air flow into the exhaust pipe the effect of pressure pulses within the exhaust pipe is utilised and for this purpose 3L &minus;(2L &plus;L ) is equal to &plusmn;0.25 to 0.5 m, wherein is the distance from the junction of the exhaust pipe ( ) measured from a first intersection point at which the axes of the exhaust pipe ( ) and the air supply pipe ( ) intersect, to a point midway along the length in the flow direction of the said upstream portion ( ) of the silencer ( ) and L is the length of the air supply pipe ( ) from the Reed valve ( ) to the said first intersection point.

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Killarney, Ireland

Stephen Brian Glover