Internal-combustion engines – Means to whirl fluid before – upon – or after entry into... – Having multiple oxidant inlet means
Utility Patent
1999-06-10
2001-01-02
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Means to whirl fluid before, upon, or after entry into...
Having multiple oxidant inlet means
C123S184420, C123S184590, C123S306000, C123S430000, C123S518000, C123S568170
Utility Patent
active
06167865
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an intake system of an internal combustion engine having a plurality of cylinders, at least one intake valve per cylinder and an intake port leading to the intake valve, the intake system comprising an intake manifold having a plenum connected to ambient air by way of a main throttle and having a plurality of branches each leading from the plenum to an intake port of a respective one of the engine cylinders.
BACKGROUND OF THE INVENTION
In exhaust gas recirculation (EGR) systems, it is known to achieve improved dynamic response to sudden changes in EGR flow by delivering the EGR gases directly to each intake port and avoiding the transport delay through the plenum chamber and branches of the intake manifold as experienced in conventional EGR. Such systems are sometimes termed “ported EGR” systems. A disadvantage of ported EGR is increased risk of unstable combustion because a substantial segment of the intake manifold branch is back-filled with EGR gases during a large part of the engine cycle, forming a stratified column within the branch caused by gases being drawn continuously by the prevailing manifold vacuum and stored along the length of the branch during the period when the associated intake valve is closed. During the intake period, this column containing a long segment of EGR gases followed by intake air is drawn sequentially into the engine cylinder and unless the charge is well mixed within the combustion chamber, isolated pockets of EGR gases may persist causing combustion instability.
It has also been proposed to improve combustion stability by controlling the stratification of the air and EGR gases. WO95/22687 achieves charge stratification by storing EGR gases as a column in a branch of the intake manifold. The EGR gases and the air enter the combustion chamber consecutively and as a result the charge is vertically stratified with the EGR gases that enter the cylinder first concentrated at the bottom of the cylinder and the air that enters last concentrated at the top.
The present invention is also concerned with an engine in which a stream of gases, such as EGR or fuel vapour, is stored as a column in the intake manifold to be drawn into the cylinder separately from the main air charge to form a stratified charge within the engine combustion chamber.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an intake system of an internal combustion engine having a plurality of cylinders, at least one intake valve per cylinder and an intake port leading to the intake valve, the intake system comprising an intake manifold having a plenum connected to ambient air by way of a main throttle and having a plurality of branches each leading from the plenum) to an intake port of a respective one of the engine cylinders, a plurality of storage pipes each connected in parallel with a respective one of the branches of the intake manifold, each storage pipe opening at one end into the plenum and opening at the other end into the associated intake port, and a plurality of auxiliary pipes connecting an auxiliary gas supply to a point along the storage pipe, wherein the position along the storage pipe of the connection with the auxiliary pipe is such that when the associated intake valve is closed, gases from the auxiliary supply are drawn by intake manifold vacuum only into the storage pipe, whereby, when the associated intake valve is subsequently opened, air from the branch of the intake manifold and gases from the auxiliary supply stored in the storage pipe enter the cylinder as parallel streams to form within the cylinder stratified regions of air and gases from the auxiliary supply.
The auxiliary supply may either be a pipe connected to the exhaust system to supply EGR gases to the cylinders or it may be a vapour source deriving fuel vapours from the fuel storage tank for the engine, a vapour storage canister communicating with the ullage space of the fuel storage tank or a vapour extraction system acting to separate the fuel supply to the engine into a liquid fraction and a vapour fraction.
In its application to recirculating exhaust gases, the present invention may be regarded as a variation on that in WO95/22687 and differs from it in that the EGR gases are stored in separate pipes from the intake branches and enter the cylinders at the same time as and in parallel with the air in the branches of the intake manifold. This allows a superior form of stratification that better survives the compression stroke of the piston. In the prior art, though the gases are vertically (or axially) stratified at the end of the intake stroke, they tend to mix by the end of the compression stroke. The present invention on the other hand allows radial or lateral stratification of the charge in which the swirling gases can remain in the same relative position even after compression.
The same considerations of maintaining improved stratification even during the compression stroke applies to engines in which the auxiliary supply of gases is a fuel vapour supply intended to provide an easily ignitable cloud that resides in the vicinity of the spark plug gap at the time of ignition.
REFERENCES:
patent: 4174686 (1979-11-01), Shimizu et al.
patent: 5329912 (1994-07-01), Matsumoto et al.
patent: 5653202 (1997-08-01), Ma
patent: 473931 (1991-07-01), None
Argenbright Tony M.
Drouillard Jerome R.
Ford Global Technologies Inc.
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