Internal combustion engines

Details Internal combustion engines Internal combustion engines

1990-04-11

1991-02-26

Cross, E. Rollins

Internal-combustion engines

Valve

Valve head cooperates with manifold

123197AC, 123 9043, F01L 300

Patent

active

049953583

DESCRIPTION:

BRIEF SUMMARY
This invention relates to internal combustion engines, and, more particularly, to inlet porting systems thereof.
In conventional engines, whether one or two inlet valves are provided and even at the present state of the art efficiency, the inlet airflow is required to turn through between 120.degree. and 160.degree. tending to concentrate the flow on one side of the valve head and is further impeded by the valve stem and its guide. The result is that only an average of 200.degree. of the periphery of the valve head is able to pass efficiently the incoming fuel laden air.
GB-A-371,211 describes a cylinder porting system comprising a pair of outer gas supply ducts which merge into a single inner supply duct that encircles the stem of a poppet valve controlling a cylinder port to provide a gas stream which is parallel to the axis of the valve stem. Such a system is hereinafter referred to as "a dual duct porting system". This system provides an improved volumetric efficiency over a single gas supply duct; it is at least comparable with a twin inlet valve system and has other technical advantages thereover, e.g. easier production since the valve operating mechanism is only required for one valve rather than a pair of valves. Ideally, it is desired to have the gas stream distributed around the entire periphery of the valve head so that eddies of gas are shed into the combustion chamber from all around the valve head periphery which provides a particularly effective preparation of the combustible fuel mixture which is evenly spread around the valve head. This is known as torroidal vortex induction and can only be achieved effectively by a dual or multiple duct portion system.
However when applying such a porting system to a cylinder head where side entry into the pair of outer supply ducts is required, the individual streams in the respective outer supply ducts, which are bent for the side entry, tend to break away from the insides of the bends and flow towards the outside portions of the bends and thereafter form a merged stream which is distributed over about 200.degree. of the periphery of the valve head. This prevents the formation of an evenly distributed torroidal vortex shed from the valve head into the combustion chamber.
The object of the invention is to provide a dual duct porting system adapted for side entry in which the gas flow therethrough is such as to provide a relatively evenly distributed flow over the associated valve head.
The invention provides a dual duct porting system for an internal combustion engine, which system comprises a pair of juxtaposed bent, side entry supply ducts which merge into a single supply passage formed to define a venturi section and communicating with a valve port with the single supply passage surrounding the stem of a poppet valve associated with the valve port, wherein each bent side entry supply duct is provided with means for creating eddies in the gas flow at a specific position along the radially inner region of the duct bend and an outwardly bulging portion at a radially outer region of the duct bend.
In use, the eddy creating means produce a controlled breakaway of the boundary layer of the gas flow on the inside of the duct bend to produce a low pressure region which, together with the direction of swirl of the eddies, tends to pull the gas flow, in a controlled manner, back into contact with the radially inner wall of the duct, while the outward bulging on the outside of the duct bend tends to turn back the gas flow in that region. The combination of these effects tends to straighten the gas flow in the respective duct downstream of the bend therein so that it is nearer to an evenly distributed axial flow in that downstream section of the duct. In this way the gas streams issuing from outer supply ducts merge to form a stream flowing generally axially through the single supply passage to spread substantially evenly over the poppet valve head and to shed therefrom as evenly distributed torroidal vortices.
Said eddy creating means may take various forms. For

REFERENCES:
patent: 287284 (1939-07-01), Schmidt
patent: 1898119 (1933-02-01), Edwards

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